With this article, we are opening a new direction for our site: testing batteries and galvanic cells (or, in simple terms, batteries).

Despite the fact that lithium-ion batteries, specific to each specific device model, are becoming increasingly popular, the market for standard batteries general purpose is still very large - a lot of different products are powered by them, ranging from children's toys to inexpensive cameras and professional flashlights. The range of these elements is also great - batteries and accumulators of various types, capacities, sizes, brands, workmanship...

At first, we do not set ourselves the goal of embracing all the wealth of batteries - we will limit ourselves to only the most standard and common of them: cylindrical batteries and nickel batteries.

This article is intended to introduce you to some basic concepts regarding the batteries we are studying, as well as the testing methodology and the equipment we use. However, we will discuss many theoretical and practical issues in subsequent articles devoted to specific batteries - especially since it is much more convenient and clearer to do this on "live examples".

Types of batteries and galvanic cells

Salt electrolyte batteries

Batteries with saline electrolyte, they are also zinc-carbon (however, unlike alkaline batteries, manufacturers usually simply do not indicate their chemistry on packages of salt electrolytes) - the cheapest chemical current sources available on the market: the cost of one battery ranges from four to five to eight to ten rubles, depending on the brand.

Such a battery is a zinc cylindrical container (serving at the same time as the body and the “minus” of the battery), in the center of which there is a carbon electrode (“plus”). A layer of manganese dioxide is placed around the anode, and the remaining space between it and the walls of the container is filled with a paste of ammonium chloride and zinc chloride diluted in water. The composition of this paste can vary: in low-power batteries, it is dominated by ammonium chloride, and in more capacious batteries (commonly referred to as "Heavy Duty" by manufacturers) - zinc chloride.

During battery operation, the zinc from which its case is made gradually oxidizes, as a result of which holes may appear in it - then the electrolyte will leak out of the battery, which can lead to damage to the device in which it is installed. However, such problems were typical mainly for domestic batteries from the times of the existence of the USSR, while modern batteries are securely packed in an additional outer shell and "leak" very rarely. However, you should not leave dead batteries in the device for a long time.

As mentioned above, the chemical composition of the salt battery electrolyte may vary slightly - the "powerful" version uses an electrolyte with a predominance of zinc chloride. However, the word "powerful" in relation to them can only be written in quotation marks - none of the varieties of salt batteries is designed for any serious load: in a flashlight they will last for a quarter of an hour, and in a camera they may not even be enough to extend the lens. The fate of salt batteries is remote controls, watches and electronic thermometers, that is, devices whose energy consumption is within units, in extreme cases, tens of milliamps.

Alkaline batteries

The next type of batteries are alkaline or manganese batteries. Some not very literate sellers and even manufacturers call them "alkaline" - this is a slightly distorted tracing paper from the English "alkaline", that is, "alkaline".

Prices for alkaline batteries vary from ten to forty-fifty rubles (however, most of their types fall within the range of up to 25 rubles, only individual models increased power), and they can be distinguished from salt ones by the inscription "Alkaline" usually present in one form or another on the package (and sometimes right in the name, for example, "GP Super Alkaline" or "TDK Power Alkaline").

The negative pole of an alkaline battery consists of zinc powder - compared to the zinc case of salt cells, the use of powder allows you to increase the speed of chemical reactions, and hence the current given off by the battery. The positive pole is made of manganese dioxide. The main difference from salt batteries is the type of electrolyte: in alkaline batteries, potassium hydroxide is used as it.

Alkaline batteries are well suited for devices with energy consumption from tens to several hundred milliamps - with a capacity of about 2 ... 3 Ah, they provide quite a reasonable operating time. Unfortunately, they also have a significant disadvantage: a large internal resistance. If you load a battery with a really high current, its voltage will drop a lot, and a significant part of the energy will be spent on heating the battery itself - as a result, the effective capacity of alkaline batteries is highly dependent on the load. Let's say, if when discharging with a current of 0.025 A, we manage to get 3 A * h from the battery, then at a current of 0.25 A, the real capacity will drop to 2 A * h, and at a current of 1 A - completely below 1 A * h.

However, for some time, an alkaline battery can work under heavy load, it's just that this time is relatively short. For example, if a modern digital camera may not even turn on on saline batteries, then one set of alkaline batteries will last for half an hour of work.

By the way, if you are forced to use alkaline batteries in your camera, buy two sets at once and periodically swap them, this will allow you to slightly extend their life: if you let a battery discharged with a high current “lie down” for a while, it will partially restore the charge and will be able to work a little more. Five minutes.

Lithium batteries

The last of the widely used types of batteries is lithium. As a rule, they are rated at a voltage that is a multiple of 3 V, so most types of lithium batteries with 1.5 volt salt and alkaline batteries are not interchangeable. Such batteries are widely used in watches, and also - less often - in photographic equipment.

However, there are also 1.5 V lithium batteries, made in standard AA and AAA form factors - they can be used in any technique designed for conventional saline or alkaline batteries. The main advantage of lithium batteries is their lower internal resistance compared to alkaline batteries: their capacity depends little on the load current. Therefore, although at low current both alkaline and lithium batteries have the same capacity of 3 A * h, if you put them in a digital camera that consumes 1 A, then alkaline ones will “die” in thirty minutes, but lithium ones will live almost three hours.

The disadvantage of lithium batteries is their high cost: not only is lithium itself expensive, but also due to the danger of its ignition when water enters, the design of the battery turns out to be noticeably more complicated than alkaline ones. As a result, one lithium battery costs 100-150 rubles, that is, three to five times more expensive than a very good alkaline one. About the same price is a Ni-MH battery, which has discharge characteristics similar to lithium batteries, but can survive several hundred charge-discharge cycles - therefore, buying lithium batteries is justified only when you have nowhere, no time or nothing to charge conventional batteries.

Yes, since we are talking about charge cycles, it must be said that it is absolutely impossible to try to charge lithium batteries! If an ordinary alkaline or saline battery, when trying to charge it, can, at most, simply leak out, then sealed lithium batteries explode when charged.

Also, in addition to good discharge characteristics, lithium batteries have two more advantages, as a rule, not very significant: durability (the permissible shelf life reaches 15 years, while the battery will lose only 10% of its capacity) and the ability to operate at low temperatures, when salt and alkaline batteries, the electrolyte simply freezes.

Nickel-cadmium (Ni-Cd) batteries

The main alternative to batteries are batteries - current sources, the chemical processes in which are reversible: when the battery is connected to the load, they go in one direction, and when voltage is applied to it, they go in the opposite direction. Thus, if the battery after use has to be thrown away and a new one purchased, then the battery can be charged to its full (or almost full) original capacity.

We will consider batteries used in light consumer electronic equipment - therefore, heavy (both literally and figuratively) lead-acid batteries found in cars, uninterruptible power supplies and other devices with high power consumption and without special restrictions on weight and dimensions , are immediately left out of our today's article. But we will pay much more attention to various types of nickel batteries ...

The first nickel - more precisely, nickel-cadmium - batteries were created by the Swedish scientist Waldemar Junger (Waldmar Jungner) already in 1899, but at that time they were relatively expensive, and besides, they were not sealed: when charging, the battery emitted gas. Only in the middle of the last century was it possible to create a nickel-cadmium battery with a closed cycle: the gases released during charging were absorbed by the battery itself.

Nickel-cadmium batteries are reliable and durable (they can be stored for up to five years, and charged - with proper use - up to 1000 times), they work well at low temperatures and easily withstand large discharge currents, can be charged with both small and large currents.

They also have a lot of downsides, though. Firstly, the relatively low energy density (that is, the ratio of the capacity of the element to its volume), secondly, a noticeable self-discharge current (after several months of storage, the battery will need to be recharged before use), thirdly, the use of poisonous cadmium in the design, and Fourth, the memory effect.

It is worth dwelling on the latter in more detail, since when talking about batteries, we will remember it more than once. The memory effect is a consequence of a violation of the internal structure of the battery: crystals begin to grow in it, reducing the effective surface and, accordingly, the capacity of the battery. The effect got its name due to the fact that crystals grow especially quickly when the battery is not completely discharged: it seems to remember to what level it was discharged last time - if the battery was discharged, say, only by 25%, then the next charge will restore it capacity is not up to 100%, but less. To combat the memory effect, it is recommended to completely discharge the battery before charging - this destroys the resulting crystals and restores the battery capacity. Among the available types of batteries, it is nickel-cadmium that is most susceptible to the memory effect.

However, in some cases, the use of nickel-cadmium batteries is justified even now - due to low cost, durability and the ability to charge at low temperatures without negative consequences for the battery.

Nickel Metal Hydride (Ni-MH) Batteries

Despite the close proximity on store shelves, historically there is an abyss between Ni-Cd and Ni-MH batteries: the latter were developed only in the 1980s. Interestingly, the possibility of storing hydrogen for nickel-hydrogen batteries used in space technology was initially studied, but as a result, we also got one of the most common types of batteries in everyday life.

Unlike nickel cadmium batteries, nickel-metal hydride do not contain heavy metals, which means that they are harmless to environment and do not require special processing for disposal. However, this is far from their only plus: from the point of view of consumers, that is, you and I, it is much more important that, with the same dimensions, Ni-MH batteries have two to three times the capacity - for the most common AA batteries, it already reaches up to 2500-2700 mAh versus 800-1000 mAh for nickel-cadmium.

Moreover, Ni-MH batteries also practically do not suffer from the memory effect. More precisely, manufacturers reduce its influence year after year - and therefore, although theoretically the effect is present in Ni-MH batteries, in practice, modern models he is insignificant. However, we will not rely on manufacturers for everything and in one of our next articles we will try to evaluate the influence of the memory effect ourselves.

Unfortunately, Ni-MH batteries have their own problems. Firstly, they have a higher self-discharge current (however, we will talk about this again a little later) compared to Ni-Cd, and secondly, although the number of recharge cycles can also reach 1000, a drop in battery capacity can be observed after 200- 300 cycles, thirdly, too high discharge currents and charging at low temperatures significantly reduce the life of the battery.

However, in terms of the totality of characteristics - cost, reliability, capacity, ease of maintenance - on this moment Ni-MH batteries are among the best, which led to their use in a huge mass of household devices.

Recently, so-called "Ready To Use" Ni-MH batteries have also appeared on the market. They differ from ordinary ones in a low self-discharge current - the manufacturer claims that in six months the battery will lose no more than 10% of its capacity, and in a year - no more than 15% (for comparison, a regular Ni-MH battery will sit down by 20 ... 30% in a month, and for a year - to zero). Hence the name: being charged by the manufacturer, these batteries will not have time to fully discharge before you buy them in the store, which means that they can be used without pre-charging, immediately after purchase. The downside of such batteries is a lower capacity - an AA cell has a capacity of 2000 ... 2100 mAh versus 2600 ... 2700 mAh for conventional Ni-MH batteries.

Chargers for Ni-Cd and Ni-MH batteries

The principles of charging Ni-Cd and Ni-MH batteries are largely similar - for this reason, modern charging device, as a rule, support both types at once. Charging methods and, accordingly, types of chargers can be divided into four groups. In all cases, we will indicate the charging current through the battery capacity: for example, the recommendation to charge with a current of "0.1C" means that a battery with a capacity of 2700 mAh in such a circuit corresponds to a current of 270 mA (0.1 * 2700 = 270) , and a battery with a capacity of 1400 mAh - 140 mA.

Slow charge current 0.1C

This method is based on the fact that modern batteries easily withstand overcharging (that is, an attempt to "fill" them with more energy than the battery can store), if the charging current does not exceed 0.1C. If the current exceeds this value, the battery may fail during overcharging.

Accordingly, a low-current charger does not need any control over the end of the charge: there is nothing wrong with its excessive duration, the battery will simply dissipate excess energy in the form of heat. Appropriate chargers are cheap and widely available. To charge the battery, it is enough to leave it in such a charger for at least 1.6 * C / I, where C is the battery capacity, I is the charging current. Say, if we take a charger with a current of 200 mA, then a battery with a capacity of 2700 mAh is guaranteed to be charged in 1.6 * 2700/200 = 21 hours 36 minutes. Almost a day ... in general, the main drawback of such memory is obvious - the charging time often exceeds reasonable values.

However, if you are not in a hurry, such a charger has the right to life. The main thing is that if you use low-capacity batteries paired with a modern charger, check that the charging current (and it must be indicated in the characteristics of the charger) does not exceed 0.1C. It is also worth considering that a slow charge contributes to the manifestation of the memory effect in batteries.

Charging current 0.2 ... 0.5C without control of the end of the charge

Such chargers, although rare, are still found - mainly among cheap Chinese products. At a current of 0.2 ... 0.5C, they either do not have charge termination control at all, or they only have a built-in timer that turns off the batteries after a specified time.

Use similar memory absolutely not recommended: since there is no end-of-charge control, in most cases the battery will be under- or overcharged, which will significantly reduce its life. If you save on a charger, you will lose money on batteries.

Charging current up to 1C with control of the end of the charge

This class of chargers is the most versatile for everyday use: on the one hand, they charge the batteries in a reasonable time (from one and a half to four to six hours, depending on the specific charger and batteries), on the other hand, they clearly control the end of the charge in automatic mode. .

The most commonly used end-of-charge control method is voltage droop, commonly referred to as the "dV/dt method", "negative delta method" or "-ΔV method". It consists in the fact that during the entire charge, the voltage on the battery slowly increases - but when the battery reaches full capacity, it briefly decreases. This change is very small, but it is quite possible to detect it - and, having detected it, stop the charge.

Many charger manufacturers also list "microprocessor control" in their specifications - but, in fact, this is the same as negative delta control: if it is, then it is carried out by a specialized microprocessor.

However, voltage control is not the only one available: at the moment the battery reaches its full capacity, the pressure and temperature of the case sharply increase in it, which can also be controlled. In practice, however, it is technically easiest to measure the voltage, so other methods for monitoring the end of the charge are rare.

Also, many high-quality chargers have two protective mechanisms: battery temperature control and a built-in timer. The first stops charging if the temperature exceeds the allowable limit, the second - if the negative delta charge stop did not work in a reasonable time. Both can happen if we use old or simply low-quality batteries.

Having finished charging the batteries with a high current, the most "reasonable" chargers recharge them with a low current (less than 0.1C) for some time - this allows you to get the maximum possible capacity from the batteries. The charge indicator on the device usually turns off, indicating that the main stage of charging is completed.

There are two problems with such devices. Firstly, not all of them are able to "catch" the moment of voltage drop with sufficient accuracy - but, alas, this can only be verified empirically. Secondly, although such devices are usually designed for 2 or 4 batteries, most of them do not know how to charge these batteries independently of each other.

For example, if the instructions for the charger indicate that it can only charge 2 or 4 batteries at the same time (but not 1 or 3), this means that it has only two independent charge channels. Each of the channels provides a voltage of about 3 V, and the batteries are connected in pairs in series. There are two consequences of this. The obvious thing is that you will not be able to charge a single battery in such a charger (and, say, your humble servant daily uses an mp3 player powered by just one AAA battery). Less obvious is that the control of the end of the charge is also carried out only for a couple batteries. If you are using batteries that are not too new, then simply due to technological variation, some of them will grow old a little earlier than others - and if two batteries with different degrees of aging are caught in a pair, then such a charger will either undercharge one of them or recharge the second. Of course, this will only exacerbate the rate of aging of the worst of the pair.

The "correct" charger should allow you to charge an arbitrary number of batteries - one, two, three or four - and ideally, also have a separate indicator for the end of charging for each of them (otherwise the indicator goes out when the last of the batteries is charged). Only in this case will you have some guarantee that each of the batteries will be charged to full capacity, regardless of the condition of the other batteries. Separate charge indicators also make it possible to catch prematurely failed batteries: if one of the four cells used together charges much longer or much faster than the others, then it will be the weak link of the entire battery.

Multi-channel chargers have another nice feature: in many of them, when charging half the number of batteries, you can choose the charge rate. For example, the Sanyo NC-MQR02 charger, designed for four AA batteries, when charging one or two batteries, allows you to choose the charging current between 1275 mA (when batteries are installed in the outer slots) and 565 mA (when they are installed in the central slots). When three or four batteries are installed, they are charged with a current of 565 mA.

In addition to ease of use, chargers of this type are also the most "useful" for batteries: medium size with end-of-charge control by negative delta is optimal in terms of increasing battery life.

A separate subclass of fast chargers is a charger with a preliminary discharge of batteries. This was done to combat the memory effect and can be very useful for Ni-Cd batteries: the charger will make sure that they are completely discharged first, and only after that it will start charging. For modern Ni-MHs, this training is no longer necessary.

Charging with a current of more than 1C with control of the end of the charge

And finally, the last method is an ultra-fast charge, lasting from 15 minutes to an hour, with charge control, again by negative voltage delta. Such memory has two advantages: firstly, you almost instantly get charged batteries, and secondly, an ultra-fast charge allows you to largely avoid the memory effect.

There are, however, also disadvantages. Firstly, not all batteries can withstand a fast charge well: low-quality models with high internal resistance can overheat in this mode until they fail. Secondly, a very fast (15-minute) charge can negatively affect the life of the batteries - again, due to their excessive heating during charging. Thirdly, such a charge "fills" the battery only up to 90 ... 95% of the capacity - after which, in order to achieve 100% capacity, additional recharging with a small current is required (however, most fast chargers carry it out).

However, if you are in need of ultra-fast battery charging, purchasing a "15-minute" or "half-hour" charger will be a good option. Of course, only high-quality batteries from large manufacturers should be used with it, as well as timely exclusion of outdated copies from batteries.

If you are satisfied with a charge duration of several hours, then the memory devices described in the previous section with a charging current of less than 1C and control of the end of the charge by a negative voltage delta are still optimal.

A separate issue is the compatibility of chargers with different types of batteries. Chargers for Ni-MH and Ni-Cd are usually universal: any of them can charge batteries of each of these two types. Chargers for Ni-MH batteries with a negative delta voltage charge termination, even if this is not directly stated for them, can also work with Ni-Cd batteries, but vice versa - alas. The point here is that the voltage surge, that same negative delta, is noticeably smaller for Ni-MH than for Ni-Cd, so not every memory device configured to work with Ni-Cd will be able to "feel" this surge on Ni-MH .

For other types of batteries, including lithium-ion and lead-acid, these chargers are unsuitable in principle - such batteries have a completely different charge scheme.

Test Methodology

In the process of testing batteries and electrochemical cells in our laboratory, we measure the following parameters, which are most important for determining both the quality of the cells (that is, their compliance with the manufacturer's promises) and a reasonable area of ​​\u200b\u200buse:

capacity at various discharge modes;
the value of internal resistance;
self-discharge value (only for batteries);
the presence of a memory effect (only for batteries).

The main part of the test bench is, of course, an adjustable load that allows you to discharge up to four batteries or batteries at a given current at the same time.

To control the voltage of all four elements, a Velleman PCS10 digital recorder is used, which is connected to a computer via a USB interface. The measurement error is no more than 1% (the recorder's own error is 3%, but we additionally calibrate each of its channels, making appropriate corrections to the final data), the voltage measurement discreteness is 12 mV, the measurement frequency is 250 ms.

The installation scheme is quite simple: these are four separate current stabilizers made on the LM324 operational amplifier (this microcircuit just consists of four op-amps in one package) and IRL3502 field-effect transistors. All stabilizers are controlled by one multi-turn variable resistor, so the current is set on them simultaneously - this simplifies setting up the installation for a specific test and minimizes the error in manually setting the current. Possible limits of load change are from 0 to 3 A for each battery.

To measure the voltage on another LM324 chip, four differential amplifiers are assembled, the inputs of which are connected directly to the contacts of the block in which the batteries are installed - this completely eliminates the error introduced by losses on the connecting wires. From the outputs of the differential amplifiers, the signal is fed to the recorder.

In addition, the circuit contains a rectangular pulse generator not shown in the figure above, which periodically turns on and off the load completely. The duration of "zero" at the output of the generator is 6.0 s, the duration of "one" is 2.25 s. The generator allows you to test the batteries in the mode of operation with a pulsed load and, in particular, to determine their internal resistance.

Also, the figure above does not show the power supply circuit of the installation: it is connected to the computer power supply, its output voltage (+12 V) is reduced to +9 V by a stabilizer on the 78L09 microcircuit, and the -9 V voltage necessary for bipolar power supply of the op-amp is formed by a capacitive converter on the microcircuit ICL7660. However, these are already unimportant nuances, which we discuss only in order to prevent in advance questions about the correctness of measurements that may arise from readers who are knowledgeable in electronics.

To cool the power transistors, feedback shunts and the actual batteries under test, the entire installation is blown by a standard 12-volt fan with a size of 80x80x20 mm.

A special program was written to receive and automatically process data from the recorder - fortunately, Velleman supplies very easy-to-use SDKs and libraries for many of its devices. The program allows you to plot voltage graphs on batteries in real time depending on the time elapsed since the beginning of the test, as well as calculate - at the end of the test - their capacity. The latter, obviously, is equal to the product of the discharge current and the time during which the element reached the lower voltage limit.

The boundary is selected depending on the type of element and discharge conditions. For batteries at low currents, this is 1.0 V - it is simply impossible to discharge them below, as this can lead to irreversible damage to the cell; at high currents, the lower limit is reduced to 0.9 V in order to properly take into account the internal resistance of the battery.

for batteries practical sense have two discharge boundaries. On the one hand, the element is considered completely empty if the voltage on it has dropped to 0.7 V - therefore it is logical to measure the capacitance precisely upon reaching this level. On the other hand, not all battery-powered devices are capable of operating at voltages below 0.9 V, so when the battery is discharged to this level is of practical importance. In our tests, we will give both of these values ​​- although many cells, having reached the level of 1.0 V, then discharge very quickly, there are some that last for a relatively long time between 0.7 V and 0.9 V.

So, having installed the batteries, set the desired current and turned on the recorder, we begin testing. For each type of battery, several discharge modes were selected in order to obtain the most interesting and characteristic results.

For batteries it is:

discharge with a small direct current: 250 mA for AA format elements, 100 mA for AAA format elements;
discharge with a large direct current: 750 mA for AA format elements, 300 mA for AAA format elements;

For Ni-MH batteries, these are:

discharge with a small direct current: 500 mA for AA format elements, 200 mA for AAA format elements;
discharge with a large direct current: 2500 mA for AA format elements, 1000 mA for AAA format elements;
discharge by pulsed current: pulse duration 2.25 s, pause duration 6.0 s, current amplitude 2500 mA for AA format elements and 1000 mA for AAA format elements.

For Ni-Cd batteries in AA format, the discharge modes are the same as for Ni-MH batteries in AAA format - taking into account the similar nameplate capacity of the first and second.

If everything is simple when testing batteries - I unpacked the package, inserted the battery into the installation, started the test - then the batteries must first be prepared, because all of them, except for the "Ready To Use" series mentioned above, are completely discharged at the time of purchase. Therefore, testing of batteries was carried out strictly according to the following scheme;

measurement of residual capacitance at low current (only for "Ready To Use" models);
charger;
discharging with high current without capacitance measurement (training);
charger;
high current discharge with capacitance measurement;
charger;
discharge by pulsed current with capacitance measurement;
charger;
low current discharge with capacitance measurement;
charger;
exposure for 7 days;
low current discharge with capacity measurement - then the result is compared with that obtained in the previous step and the percentage of capacity loss due to self-discharge for 1 week is calculated;

In battery tests, we use one cell of each brand at each stage. In battery tests - at least two cells of each brand.

To charge the batteries, we use the Sanyo NC-MQR02 charger.

This is a fast charger with negative delta voltage and battery temperature control that allows you to charge from one to four (in arbitrary combinations) AA batteries, as well as one or two AAA batteries. The former can be charged with both a current of 565 mA and 1275 mA (if there are no more than two batteries), the latter with a current of 310 mA per cell. For several years of regular use, this charger has convincingly proved its high efficiency and compatibility with any batteries, which led to its choice for testing. To avoid loss of capacity due to self-discharge, in all tests, except for the self-discharge test itself, the batteries are charged immediately before the start of measurements.

Measurements at direct current give a logical picture (an example is shown in the graph above): the voltage on the cells quickly decreases in the first minutes of the test, then it reaches a more or less constant level, and at the very end of the test, at the last percentage of the charge, it quickly drops again.

Somewhat less commonplace are measurements on a pulsed current. The figure above shows a greatly enlarged section of the graph obtained in such a test: voltage dips on it correspond to turning on the load, rises to turn off. From this graph, it is easy to calculate the internal resistance of the battery: as you can see, with a current amplitude of 2.5 A, the voltage sags by 0.1 V - respectively, the internal resistance is 0.1 / 2.5 \u003d 0.04 Ohm \u003d 40 mOhm. The importance of this parameter will become clearer in our subsequent articles, in which we will compare different types of batteries and accumulators with each other - but for now, we will only note that a large internal resistance causes not only a “drawdown” of voltage under load, but also a loss of energy stored in batteries to heat themselves.

On a full scale, the pulses merge with each other into a continuous band, the upper limit of which corresponds to the voltage on the battery without load, the lower one - with the load. By the shape of this strip, one can estimate not only the operating time of the element under a heavy impulse load, but also the dependence of its internal resistance on the depth of discharge: for example, as you can see, the resistance of a Sony Ni-MH battery is almost constant and begins to grow only when it is completely discharged . Good result.

As many of our readers will surely notice, we have chosen very hard discharge modes: a current of 2.5 A is very large, and a 6-second pause between pulses does not allow the element to "rest" properly (as we mentioned above, batteries, having "rested" a little , can partially restore their capacity). Nevertheless, this was done on purpose in order to show the differences between batteries of different types and different qualities as clearly and clearly as possible. In order to get closer to milder real-world operating conditions, as well as the conditions in which battery manufacturers measure their capacity, we added discharge modes with a relatively small direct current to the test.

By the way, the manufacturers themselves usually indicate the discharge modes in the same way as the charging ones - in proportion to the capacity of the element. Let's say, regular measurements of battery capacity are supposed to be carried out at a current of 0.2C - that is, 540 mA for a 2700 mAh battery, 500 mA for a 2500 mAh battery, and so on. However, since batteries of the same form factor in our tests are quite close in characteristics, we decided to test them at fixed currents that do not depend on the nameplate capacity of a particular instance - this greatly simplifies the presentation and comparison of results.

And since we are talking about capacity, it is worth mentioning some deceptiveness of such a generally accepted unit as the ampere-hour. The fact is that the energy stored in the battery is determined not only by how long it held a given current, but also by what voltage it had at the same time - so, it is quite obvious that a lithium battery with a capacity of 3 A * h and a voltage of 3 B is able to store twice as much energy as a battery with the same capacity of 3 A * h, but with a voltage of 1.5 V. Therefore, it is more correct to indicate the capacity not in ampere-hours, but in watt-hours, getting them through the integral of the dependence of the battery voltage on time discharge at its direct current. In addition to naturally taking into account the different operating voltages of different elements, this technique also allows you to take into account how well this particular element kept the voltage under load. Let's say if two batteries were discharged to 0.7 V in 60 minutes, but the first battery was at 1.1 V for most of that time, and the second at 0.9 V, it is clear that the first has a large real capacity - despite the fact that the total time of their discharge is the same. This is especially important in light of the fact that most modern electronic devices consume not constant current, and a constant power- and elements with high voltage in them will work in more favorable modes.

Closer to practice: examples of energy consumption

Of course, in addition to abstract testing of batteries on a controlled load, we were interested in how real devices consume current. To clarify this issue, we, having looked around the surrounding space, randomly selected a set of objects powered by various batteries.

Only part of this set

If the device consumed more or less direct current, the measurements were carried out with a conventional Uni-Trend UT70D digital multimeter in ammeter mode. If the consumption current changed greatly, then we measured it by connecting a low-resistance shunt between the device and the batteries that powered it, the voltage drop across which was recorded by the Velleman PCSU1000 oscilloscope.

The results are presented in the table below:

Well, among our devices there were also quite "gluttonous" ones - a flashlight, a camera and a flashlight with an incandescent lamp. If the latter consumed the 700 mA assigned to it constantly and continuously, then the nature of the energy consumption of the first two turned out to be more interesting.

The value of the vertical division on the oscillograms below is 200 mA, zero corresponds to the first division from the bottom.

Camera
Waveform division value - 200 mA

In normal mode, the Canon PowerShot A510, powered by two AA cells, consumed about 800 mA - a lot, but not a record high. However, when turning on (the first group of narrow peaks on the oscillogram), moving the lens (the second group of peaks) and focusing (the third group), the current could increase by more than one and a half times, up to 1.2 ... 1.4 A. Interestingly, immediately after pressing the "shutter" the power consumption of the camera has dropped - when you record the frame just taken on a flash drive, it automatically turns off the screen. However, as soon as the frame was recorded, the consumption rose back to 800 mA.

photo flash
Waveform division value - 100 mA

The Pentax AF-500FTZ flash (four AA format elements) consumed current even more interesting: it was almost zero in the periods between firings, instantly increased to 700 mA immediately after firing (such a moment was captured on the oscillogram above), after which for 10. ..15 seconds smoothly decreased back to zero (the torn line of the oscillogram was due to the fact that the flash consumes current at a frequency of about 6 kHz). At the same time, the flash showed a clear relationship between the current decay time and the voltage of the elements that feed it: since it had to accumulate a certain amount of energy each time, the more the supply voltage sagged under load, the more time it took to accumulate the required reserve. This, by the way, well illustrates one of the roles of the internal resistance of batteries - the smaller it is, the less, all other things being equal, the voltage will drop and the faster you can take the next frame with a flash.

In our next articles, where we will consider specific types and instances of batteries and accumulators, a rough idea of ​​​​energy needs different devices will help us determine which batteries are suitable for them.

At the present stage, there are many batteries that have a different chemical composition and, due to the presence of certain elements in them, their own characteristics and operational benefits. Nickel-cadmium batteries have been around for a long time. But they are still popular and necessary in various spheres of human activity.

From the history of creation

The first alkaline Ni-Cd batteries appeared at the end of the 20th century. They were invented by the Swedish scientist Waldmar Jungner, using nickel as a positive charge, and cadmium as a negative one. Despite the obvious benefits of this invention, at that time the mass production of such batteries was very expensive and energy intensive. Therefore, it was postponed for a period of almost 50 years.

The 30s of the last century are remarkable in that it was then that the technique for introducing chemically active materials of plates onto a porous nickel-coated electrode was created. Mass production of Ni-Cd batteries began after the 50s.

Key features and benefits

Nickel-cadmium batteries, in most cases, have a cylindrical shape. Therefore, in the common people they are often called "banks". There are also flat Ni batteries - for example, for watches. All charging cells of this type have a relatively small capacity when compared with (Ni-MH), which appeared much later in order to improve Ni-Cd batteries.

However, the lower capacity is not a disadvantage that could be the reason for the good old cadmium battery to be completely phased out. One of its undoubted advantages is that during operation it does not heat up as quickly as MH. This greatly reduces the risk of overheating and premature failure.

The slower heating process of Ni-Cd is due to the fact that the chemical reactions occurring inside them are endothermic. In other words, the heat released during the reactions is absorbed internally. As for MH, they differ from cadmium ones in exothermic reactions with the release of a large amount of heat. In this regard, MH heat up much faster and can "burn out" if not stopped in time.

Ni-Cd batteries have a dense metal case, which is characterized by increased strength and good tightness. They are able to withstand any chemical reactions inside and withstand high gas pressure even in the worst conditions. Until the temperature drops to -40°C. Nickel-cadmium batteries are not subject to the risk of spontaneous combustion, unlike modern ones.

Among them there are powerful and reliable industrial Ni batteries that can fully operate for 20-25 years. And, despite the fact that this battery has long been replaced by MH and lithium larger capacity, Ni-Cd batteries continue to be actively used to this day.

If we talk about the price category, the cost of Ni-Cd is significantly lower than other batteries. This is also one of their main pluses.

Scope of application

Small Ni-Cd batteries are widely used to power various household appliances and equipment, mainly in cases where a particular device consumes a large amount of current. Standard "banks" still ensure the operation of electric drills and screwdrivers. Elements large sizes indispensable in public transport. For example, in trolleybuses or trams to power their control circuits, in shipping and especially in aviation as on-board secondary current sources.

Operation features

Since Ni-Cd batteries only noticeably heat up when they are fully charged, most devices "understand" this as a signal to stop charging. In order for them to work longer, it is recommended to charge them quickly, and use them until they are completely discharged: unlike MH, deep-discharge nickel-cadmium batteries are not afraid.

This type of battery is the only battery that is recommended to be stored fully discharged, while MH batteries should be stored fully charged, and they need to periodically check the voltage at the output. Such a difference, with a significant difference in operation, is certainly another obvious point in favor of Ni-Cd.

When stored for a long time without use in a discharged form, nothing terrible will happen to the batteries. But to bring them in working condition, you need to carry out a full charge-discharge cycle with them two or three times. It is better to do this shortly before use, it is possible for a day, and then nickel-cadmium batteries will work with optimal current output.

Any Ni-Cd used in everyday life, when fed with a small amount of current and periodically incompletely discharged, can significantly lose capacity, which gives the impression full output Battery out of order. If Ni-Cd has been on charge for a long time, for example, in a device with constant food, it will also lose a certain capacitance indicator, although its voltage level, at the same time, will be correct.

This means that it is not worth using Ni-Cd in the mode of constant replenishment and “under-discharge”, and if this nevertheless happened to the battery, one deep discharge cycle followed by a full charge will be enough for the capacity to be restored.

This effect is called the “memory effect” and occurs when a partially discharged battery is recharged before it is fully discharged. The fact is that the so-called pressed electrodes are used in the production of nickel-cadmium batteries. This is very convenient, since "pressing" is high-tech and cheaper. But it is precisely its chemical composition that is prone to the "memory effect" - in other words, to the appearance in the electrochemical composition of the battery of an "extra" double electric layer in the form of large crystals, which causes a decrease in voltage.

That is why Ni-Cd cells “love” a full and deep discharge so much, after which, having “cleared the memory”, they can work fully for a long time.

Recovery of a nickel-cadmium battery

Water recovery

You can try to restore the performance of Ni-Cd batteries using the most common electrolyte in the form of distilled water.

To do this, you need a few simple tools and devices:

• soldering acid ;
• disposable syringe ;
  soldering iron;
• some distilled water .

Usually, the battery pack inside a drill or screwdriver looks like a bunch of several metal "cans" wrapped in thick paper. In order to understand which “bank” in the bundle is the weakest, you must first measure the voltage at the poles of each element. How to check voltage? Very simple, using a multimeter or tester. Most often, the voltage indicator for the weakest "cans" is close to or equal to zero.

In order to start the recovery process, you need to drill a small hole in the battery, after releasing it from the paper or label. This can be done with a screwdriver using a sharp No. 16 self-tapping screw. It is important to take care not to damage the inside of the battery, but to drill only its outer shell.

In this case, it is worth noting one more undeniable advantage: in such batteries, due to their design, increased tightness and features of ongoing chemical reactions, spontaneous combustion does not occur. Therefore, amateur return methods nickel-cadmium cells to life are safe, unlike carrying out this kind of manipulation with modern lithium batteries, which are prone to explosions and swelling.

1 ml of distilled water is drawn into a disposable syringe, and the battery is gradually filled with it. In this case, it is important not to rush, to ensure that water gradually penetrates into the battery. Distilled water is needed to return and create the necessary electrolyte density inside the battery. After the water is filled, the hole is closed with soldering acid, which is taken on a match, and sealed with a well-heated soldering iron.

Some craftsmen argue that if instead of distilled water, electrolyte from mining flashlights is poured into the battery, the battery will work much better and longer.

In conclusion, you need to again measure the voltage with a multimeter and put the battery on charge. Of course, a soldered battery will not last long, but it can help buy some time before purchasing a new one.

Zapping recovery

For nickel-cadmium batteries, there is a proven, but very risky, recovery method called zapping. Its essence lies in the fact that the batteries are subjected to short discharges of very high currents, ten times higher than the norm. Each element is literally "burned" by short-second current pulses of 10, 20 amperes and above.

Zapping requires a good electronics hobbyist and safety precautions in the form of goggles and, preferably, overalls. It is claimed to restore elements that have not been used for 20 years or more. Keep in mind that zapping only applies to nickel-cadmium batteries. Recovery of Ni-MH batteries in this way is not recommended.

Discharge-charge cycle

To eliminate the "memory effect" , need discharge the battery to 0.8-1 volt, then fully charge it again . If the battery has not been restored for a long time, several such cycles can be carried out, and to minimize the “memory effect”, it is advisable to train the battery in this way once a month.

As for the popular "school" method, which involves freezing NiCd or NiMH batteries in the freezer - despite the fact that the effectiveness of this method is very doubtful, you can find a lot of information on the network about the "recovery" of batteries by placing them in the refrigerator. In fact, it is better to use the method of restoring elements with distilled water - at least in this case, there will be much more chances to reanimate them.

So, nickel-cadmium batteries are not inferior to modern batteries in a number of advantages of their technical characteristics. They are still reliable, durable, inexpensive and extremely safe to use.

The main types of batteries:

Ni-Cd Nickel Cadmium Batteries

For cordless tools, nickel-cadmium batteries are the de facto standard. Engineers are well aware of their advantages and disadvantages, in particular Ni-Cd Nickel-cadmium batteries contain cadmium - a heavy metal of increased toxicity.

Nickel-cadmium batteries have a so-called "memory effect", the essence of which boils down to the fact that when charging an incompletely discharged battery, its new discharge is possible only to the level from which it was charged. In other words, the battery "remembers" the level of residual charge from which it was fully charged.

So, when charging an incompletely discharged Ni-Cd battery, its capacity decreases.

There are several ways to deal with this phenomenon. We will describe only the simplest and most reliable way.

When using a cordless tool with Ni-Cd rechargeable batteries should be adhered to simple rule: Charge only fully discharged batteries.

It is recommended to store Ni-Cd Nickel Cadmium batteries in a discharged state, preferably not deep discharge, otherwise it may cause irreversible processes in the battery.

Pros of Ni-Cd Nickel Cadmium Batteries

• Low Price Ni-Cd Nickel Cadmium Batteries
• Ability to deliver the highest load current
• Ability to quickly charge the battery
• Maintain high battery capacity down to -20°C
• A large number of charge-discharge cycles. With proper operation, such batteries work perfectly and allow up to 1000 charge-discharge cycles or more.

Cons of Ni-Cd Nickel Cadmium Batteries

• Relatively high level of self-discharge - Ni-Cd Nickel-cadmium battery loses about 8-10% of its capacity in the first day after a full charge.
• During Ni-Cd storage A nickel-cadmium battery loses about 8-10% of its charge every month
• After long-term storage, the capacity of the Ni-Cd Nickel-Cadmium battery is restored after 5 charge-discharge cycles.
• To prolong the life of the Ni-Cd Ni-Cd battery, it is recommended to completely discharge it each time to prevent the “memory effect”

Ni-MH Nickel-metal hydride batteries

These batteries are offered on the market as less toxic (compared to Ni-Cd Nickel Cadmium batteries) and are more environmentally friendly, both in production and disposal.

In practice, Ni-MH Nickel-Metal Hydride batteries do show a very large capacity with dimensions and weight somewhat smaller than standard Ni-Cd Nickel-Cadmium batteries.

Due to the almost complete elimination of the use of toxic heavy metals in the design of Ni-MH Nickel-Metal Hydride batteries, the latter after use can be disposed of quite safely and without environmental consequences.

Nickel-metal hydride batteries have a slightly reduced "memory effect". In practice, the "memory effect" is almost invisible due to the high self-discharge of these batteries.

When using Ni-MH Nickel-Metal Hydride batteries, it is desirable to not fully discharge them during operation.

Store Ni-MH NiMH batteries in a charged state. For long (more than a month) interruptions in operation, the batteries should be recharged.

Pros of Ni-MH Nickel-Metal Hydride Batteries

• Non-toxic batteries
• Less "memory effect"
• Good performance at low temperature
  
• Large capacity compared to Ni-Cd Ni-Cad batteries

Cons of Ni-MH Nickel-Metal Hydride Batteries

• More expensive battery type
• The self-discharge rate is about 1.5 times higher than Ni-Cd Ni-Cad batteries
• After 200-300 charge-discharge cycles, the working capacity of Ni-MH Ni-MH batteries decreases slightly
• Ni-MH Nickel-Metal Hydride batteries have a limited lifespan

Li-Ion Lithium-ion batteries

The undoubted advantage of lithium-ion batteries is the almost imperceptible "memory effect".

Thanks to this remarkable property, the Li-Ion battery can be charged or recharged as needed, based on needs. For example, you can recharge a partially discharged lithium-ion battery before important, demanding or long work.

Unfortunately, these batteries are the most expensive batteries. In addition, lithium-ion batteries have a limited service life, independent of the number of charge-discharge cycles.

In summary, we can assume that lithium-ion batteries are best suited for cases of constant intensive use of cordless tools.

Pros of Li-Ion Lithium-Ion Batteries

• There is no "memory effect" and therefore it is possible to charge and recharge the battery as needed
• High Capacity Li-Ion Lithium Ion Batteries
• Light Weight Li-Ion Lithium-Ion Batteries
• Record low level of self-discharge - no more than 5% per month
• Ability to quickly charge Li-Ion Lithium-ion batteries

Cons of Li-Ion Lithium-Ion Batteries

• The high cost of Li-Ion Li-ion batteries
• Reduced operating time at temperatures below zero degrees Celsius
  
• Limited service life

Note

From the practice of operating Li-Ion Lithium-ion batteries in phones, cameras, etc. it can be noted that these batteries serve an average of 4 to 6 years and withstand about 250-300 discharge-charge cycles during this time. At the same time, it was absolutely definitely noticed: more discharge-charge cycles - shorter service life of Li-Ion Lithium-ion batteries!

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For a full fifty years, portable devices could rely solely on nickel-cadmium power supplies for battery life. But cadmium is a very toxic material, and in the 1990s nickel-cadmium technology was replaced by a more environmentally friendly nickel-metal hydride technology. In fact, these technologies are very similar, and most of the characteristics of nickel-cadmium batteries were inherited by nickel-metal hydride. But nevertheless, for some applications, nickel-cadmium batteries remain indispensable and are used to this day.

1. Nickel-cadmium batteries (NiCd)

Invented by Waldmar Jungner in 1899, the nickel-cadmium battery had several advantages over the only lead-acid battery available at the time, but was more expensive due to the cost of materials. The development of this technology was rather slow, but in 1932 a significant breakthrough was made - a porous material with an active substance inside was used as an electrode. A further improvement was made in 1947 and solved the problem of gas absorption, which made it possible to create a modern sealed maintenance-free nickel-cadmium battery.

For many years, NiCd batteries have served as power sources for two-way radios, emergency medical equipment, professional video cameras and power tools. In the late 1980s, ultra high-capacity NiCd batteries were developed, which shocked the world with their capacity, 60% higher than that of a standard battery. This was achieved by placing a larger amount of active substance in the battery, but there were also disadvantages - internal resistance increased and the number of charge / discharge cycles decreased.

The NiCd standard remains one of the most reliable and unassuming of batteries, and the aviation industry remains true to this system. However, the longevity of these batteries depends on proper maintenance. NiCd, and to some extent NiMH batteries, are subject to the “memory” effect, which leads to a loss of capacity if the battery is not cycled through periodically. If the recommended charging mode is violated, the battery seems to remember that in the previous cycles of operation its capacity was not fully used, and when discharged, it gives off electricity only to a certain level. ( See: How to repair a nickel battery). Table 1 lists the advantages and disadvantages of a standard nickel-cadmium battery.

Advantages

Reliable; high number of cycles with proper maintenance The only battery capable of ultra-fast charging with minimal stress Good load characteristics, forgive their exaggeration Long shelf life; possibility of storage in a discharged state No special requirements for storage and transportation Good performance at low temperatures Lowest cost per cycle of any battery Available in a wide range of sizes and designs

Flaws

Relatively low energy density compared to newer systems "Memory" effect; the need for periodic maintenance to avoid it Cadmium is a toxic material, special disposal is required High self-discharge; needs recharging after storage Low cell voltage of 1.2 volts, requires building multi-cell systems to provide high voltage

Table 1: Advantages and disadvantages of nickel-cadmium batteries.

2. Nickel-metal hydride batteries (NiMH)

Research into nickel-metal hydride technology began as early as 1967. However, the instability of the metal hydride hampered development, which in turn led to the development of the nickel-hydrogen (NiH) system. New hydride alloys, discovered in the 1980s, solved the safety concerns and made it possible to create a battery with a specific energy content 40% higher than that of standard nickel-cadmium.

Nickel-metal hydride batteries are not without drawbacks. For example, their charging process is more complicated than that of NiCd. With a self-discharge of 20% for the first day and then a monthly rate of 10%, NiMH is one of the leaders in its class. By modifying the hydride alloy, it is possible to achieve a reduction in self-discharge and corrosion, but this will add the disadvantage of reducing the specific energy consumption. But in the case of use in electric vehicles, these modifications are very useful, as they increase reliability and increase battery life.

3. Use in the consumer segment

NiMH batteries are currently among the most readily available. Industry giants such as Panasonic, Energizer, Duracell and Rayovac have recognized the need for low cost and long-lasting battery, and offer nickel-metal hydride power supplies in a variety of sizes, including AA and AAA. Manufacturers are working hard to win back some of the market from alkaline batteries.

In this market segment, nickel-metal hydride batteries are an alternative to rechargeable alkaline batteries, which appeared back in 1990, but due to the limited life cycle and weak load characteristics, did not gain success.

Table 2 compares the specific energy intensity, voltage, self-discharge and operating time of batteries and accumulators in the consumer segment. Available in AA, AAA and other sizes, these power supplies can be used in portable devices. Even if they may have slightly different nominal voltages, the state of discharge usually occurs at the same actual voltage value of 1 V for everyone. This voltage range is acceptable, since portable devices have some flexibility in terms of voltage range. The main thing is that it is necessary to use only the same type together. electrical elements. Safety concerns and voltage incompatibilities have hindered the development of AA and AAA Li-Ion batteries.

Table 2: Comparison of different AA batteries.

* Eneloop is a trademark of Sanyo Corporation based on the NiMH system.

The high self-discharge rate of NiMH is a continuing consumer concern. Lantern or portable device with a NiMH battery will run out if left unused for several weeks. The proposal to charge the device before each use is unlikely to find understanding, especially in the case of flashlights, which are positioned as backup lighting sources. The advantage of an alkaline battery with a shelf life of 10 years seems undeniable here.

The nickel-metal hydride battery from Panasonic and Sanyo under the brand name Eneloop has been able to significantly reduce self-discharge. Eneloop can be stored without recharging six times longer than conventional NiMH. But the disadvantage of such an improved battery is a slightly lower energy density.

Table 3 lists the advantages and disadvantages of the nickel-metal hydride electrochemical system. The table does not take into account the characteristics of Eneloop and other consumer brands.

Advantages	30-40 percent higher capacity than NiCd Less prone to "memory" effect, can be recovered Simple requirements for storage and transportation; lack of regulation of these processes Environmentally friendly; contain only moderately toxic materials Nickel content makes recycling self-sustaining Wide operating temperature range
Flaws	Limited service life; deep discharges contribute to its reduction Sophisticated charging algorithm; sensitive to overcharging Special requirements for recharge mode Generate heat during fast charging and discharging with powerful loads High self-discharge Coulomb efficiency at the level of 65% (for comparison, for lithium-ion - 99%)

Table 3: Advantages and disadvantages of NiMH batteries.

4. Iron-nickel batteries (NiFe)

After the invention of the nickel-cadmium battery in 1899, the Swedish engineer Waldmar Jungner continued his research and tried to replace expensive cadmium with cheaper iron. But the low charge efficiency and excessive hydrogen gassing forced him to abandon further development of the NiFe battery. He didn't even patent the technology.

An iron-nickel battery (NiFe) uses nickel oxide as a cathode, iron as an anode, and electrolyte as water solution potassium hydroxide. The cell of such a battery generates a voltage of 1.2 V. NiFe is resistant to overcharging and deep discharge; can be used as a backup power source for more than 20 years. Vibration resistance and high temperatures made this accumulator the most used in the mining industry in Europe; also it has found its use to provide power to railway signaling, also used as traction battery for loaders. It can be noted that during the Second World War, it was iron-nickel batteries that were used in the German V-2 rocket.

NiFe has a low specific power of about 50 W/kg. Also, the disadvantages include poor performance at low temperatures and high rate self-discharge (20-40 percent per month). It is this, together with high cost production, encourages manufacturers to stay true to lead-acid batteries.

But the iron-nickel electrochemical system is actively developing and in the near future can become an alternative to lead-acid in some industries. The experimental model of the lamella design looks promising, it managed to reduce the self-discharge of the battery, it became practically immune to the harmful effects of over- and undercharging, and its service life is expected to be 50 years, which is comparable to the 12-year service life of a lead-acid battery in the mode work with deep cyclic discharges. The expected price of such a NiFe battery would be comparable to that of a lithium-ion battery, and only four times the price of a lead-acid battery.

NiFe batteries, as well as NiCd and NiMH, require special charging rules - the voltage curve has a sinusoidal shape. Accordingly, use the charger for lead acid or lithium ion the battery will not come out, it can even harm. Like all nickel-based batteries, NiFe is afraid of overcharging - it causes the decomposition of water in the electrolyte and leads to its loss.

The capacity of such a battery, reduced as a result of improper use, can be restored by applying high discharge currents (commensurate with the value of the battery capacity). This procedure must be carried out up to three times with a discharge period of 30 minutes. You should also monitor the temperature of the electrolyte - it should not exceed 46 ° C.

5. Nickel-zinc batteries (NiZn)

A nickel-zinc battery is similar to a nickel-cadmium battery in that it uses an alkaline electrolyte and a nickel electrode, but differs in voltage - NiZn provides 1.65 volts per cell, while NiCd and NiMH have 1.20 volts per cell. It is necessary to charge a NiZn battery with a constant current with a voltage value of 1.9 V per cell, it is also worth remembering that this type of battery is not designed to work in recharge mode. The specific energy consumption is 100W/kg, and the number of possible cycles is 200-300 times. NiZn does not contain toxic materials and can be easily recycled. Available in various sizes, including AA.

In 1901, Thomas Edison received a US patent for a rechargeable nickel-zinc battery. Later, his designs were perfected by the Irish chemist James Drumm, who installed these batteries on railcars that ran along the Dublin Brae route from 1932 to 1948. NiZn was not well developed due to its strong self-discharge and short life cycle caused by dendritic formation, which also often led to short circuits. But the improvement of the electrolyte composition has reduced this problem, which gave rise to consider NiZn again for commercial use. Low cost, high power output and wide range operating temperatures make this electrochemical system extremely attractive.

6. Nickel-hydrogen batteries (NiH)

When the development of nickel-metal hydride batteries began in 1967, researchers were faced with the instability of metal hydrites, which caused a shift towards the development of a nickel-hydrogen (NiH) battery. The cell of such a battery includes an electrolyte encapsulated in a vessel, nickel and hydrogen (hydrogen is enclosed in a steel cylinder under a pressure of 8207 bar) electrodes.

In the second half of the twentieth century, some of the best rechargeable chemical sources current were rechargeable batteries manufactured using nickel-cadmium technology. They are still widely used in various fields due to their reliability and unpretentiousness.

Maintenance

What is a nickel cadmium battery

Nickel-cadmium batteries are galvanic rechargeable current sources that were invented in 1899 in Sweden by Waldmar Jungner. Until 1932, their practical use was very limited due to the high cost of the metals used in comparison with lead-acid batteries.

Improvement in the technology of their production led to a significant improvement in their performance and made it possible in 1947 to create a sealed maintenance-free battery with excellent settings.

The principle of operation and the device of the Ni-Cd battery

These batteries produce electrical energy due to the reversible process of interaction of cadmium (Cd) with nickel oxide-hydroxide (NiOOH) and water, which results in the formation of nickel hydroxide Ni (OH) 2 and cadmium hydroxide Cd (OH) 2, causing the appearance electromotive force.

Ni-Cd batteries are produced in sealed cases, which contain electrodes separated by a neutral separator containing nickel and cadmium, which are in a solution of a jelly-like alkaline electrolyte (usually potassium hydroxide, KOH).

The positive electrode is a steel mesh or foil coated with a nickel oxide hydroxide paste mixed with a conductive material.

The negative electrode is a steel mesh (foil) with pressed porous cadmium.

One nickel-cadmium cell is capable of delivering a voltage of about 1.2 volts, therefore, to increase the voltage and power of the batteries, many parallel-connected electrodes separated by separators are used in their design.

Specifications and what are Ni-Cd batteries

Ni-Cd batteries have the following specifications:

• the discharge voltage of one element is about 0.9-1 volts;
• the nominal voltage of the element is 1.2 v, to obtain voltages of 12v and 24v, a series connection of several elements is used;
• full charge voltage - 1.5-1.8 volts;
• operating temperature: from -50 to +40 degrees;
• the number of charge-discharge cycles: from 100 to 1000 (in the most modern batteries - up to 2000), depending on the technology used;
• self-discharge level: from 8 to 30% in the first month after a full charge;
• specific energy intensity - up to 65 W*h/kilogram;
• service life is about 10 years.

Ni-Cd batteries are produced in various cases of standard sizes and in non-standard versions, including disc-shaped, hermetic ones.

Where are nickel cadmium batteries used?

These batteries are used in devices that draw a lot of current and also experience high loads during operation in the following cases:

• on trolleybuses and trams;
• on electric cars;
• on sea and river transport;
• in helicopters and airplanes;
• in power tools (screwdrivers, drills, electric screwdrivers and others);
• electric shavers;
• in military technology;
• portable radio stations;
• in radio-controlled toys;
• diving lights.

Currently, due to the tightening of environmental requirements, most batteries of popular sizes (, and others) are produced using nickel-metal hydride and lithium-ion technologies. At the same time, there are still many Ni Cd batteries of various sizes, released a few years ago, in operation.

Ni-Cd cells have a long service life, sometimes exceeding 10 years, and therefore you can still find this type of battery in a variety of electronic devices, in addition to those listed above.

Pros and cons of Ni-Cd battery

This type of battery has the following positive characteristics:

• long service life and the number of charge-discharge cycles;
• long service life and storage;
• the possibility of fast charging;
• ability to withstand heavy loads and low temperatures;
• maintaining performance in the most adverse operating conditions;
• low cost;
• the ability to store these batteries in a discharged state for up to 5 years;
• average resistance to overcharging.

At the same time, nickel-cadmium power supplies have a number of disadvantages:

• the presence of a memory effect, manifested in the loss of capacity when charging the battery, without waiting for a full discharge;
• the need for preventive work (several charge-discharge cycles) to reach full capacity;
• full recovery of the battery after long-term storage requires three to four full charge-discharge cycles;
• large self-discharge (about 10% in the first month of storage), leading to an almost complete discharge of the battery for a year of storage;
• low energy density compared to other batteries;
• high toxicity of cadmium, due to which they are banned in a number of countries, including the EU, the need to dispose of such batteries using special equipment;
• more weight than modern batteries.

The difference between Ni-Cd and Li-Ion or Ni-Mh sources

Batteries with active components, including nickel and cadmium, have a number of differences from more modern lithium-ion and nickel-metal hydride sources of electricity:

• Ni-Cd elements, in contrast to the variants, have a memory effect, have a lower specific capacity with the same dimensions;
• NiCd sources are more unpretentious, remain operational at very low temperatures, are many times more resistant to overcharging and strong discharge;
• Li-Ion and Ni-Mh batteries are more expensive, they are afraid of overcharging and strong discharge, but they have a lower self-discharge;
• the service life and storage life of Li-Ion batteries (2-3 years) is several times less than Ni Cd products (8-10 years);
• nickel-cadmium sources quickly lose capacity when used in buffer mode (for example, in UPS). Although they can then be completely restored by deep discharge and charge, it is better not to use Ni Cd products in devices where they are constantly recharged;
• the same charge mode for Ni-Cd and Ni-Mh batteries allows you to use the same chargers, but you need to take into account the fact that nickel-cadmium batteries have a more pronounced memory effect.

Based on the existing differences, it is impossible to draw an unambiguous conclusion about which batteries are better, since all elements have both strengths and weaknesses.

Operating rules

During operation, a number of changes occur in Ni Cd power supplies, which lead to a gradual deterioration in performance and, ultimately, to a loss of performance:

• the useful area and weight of the electrodes are reduced;
• the composition and volume of the electrolyte changes;
• there is a decomposition of the separator and organic impurities;
• loss of water and oxygen;
• there are current leaks associated with the growth of cadmium dendrites on the plates.

In order to minimize damage to the battery during its operation and storage, it is necessary to avoid adverse effects on the battery, which are associated with the following factors:

• the charge of an incompletely charged battery leads to a reversible loss of its capacity due to a decrease in the total area of ​​the active substance as a result of crystal formation;
• regular strong overcharging, which leads to overheating, increased gas formation, loss of water in the electrolyte and destroys the electrodes (especially the anode) and the separator;
• undercharging, leading to premature battery depletion;
• long-term operation at very low temperatures leads to a change in the composition and volume of the electrolyte, the internal resistance of the battery increases and its performance deteriorates, in particular, the capacity drops.

With a strong increase in pressure inside the battery as a result of fast charging with high current and severe degradation of the cadmium cathode, excess hydrogen can be released into the battery, which leads to a sharp increase in pressure, which can deform the case, violate the assembly density, increase internal resistance and reduce operating voltage.

In batteries equipped with an emergency pressure relief valve, the risk of deformation can be prevented, but irreversible changes chemical composition batteries cannot be avoided.

Charging Ni Cd batteries should be done with a current of 10% (if you need a quick charge in special batteries - with a current of up to 100% in 1 hour) of their capacity (for example, 100 mA with a capacity of 1000 mAh) for 14-16 hours. Most best mode their discharge - with a current equal to 20% of the battery capacity.

How to restore Ni Cd battery

Nickel-cadmium power supplies in the event of loss of capacity can be almost completely restored using a complete discharge (up to 1 volt per cell) and subsequent charge in standard mode. This battery training can be repeated several times for the most complete restoration of their capacity.

If it is impossible to restore the battery by discharging and charging, you can try to restore them by exposure to short current pulses (tens of times greater than the capacity of the restored element) for several seconds. This effect eliminates the internal circuit in the battery cells, which occurs due to the growth of dendrites by burning them out with a strong current. There are special industrial activators that carry out such an impact.

Full restoration of the original capacity of such batteries is impossible due to irreversible changes in the composition and properties of the electrolyte, as well as degradation of the plates, but it makes it possible to extend the service life.

The method of recovery at home is to carry out the following actions:

• a wire with a cross section of at least 1.5 square millimeters is connected to the minus of the restored element with the cathode of a powerful battery, for example, a car battery or from a UPS;
• a second wire is securely attached to the anode (plus) of one of the batteries;
• for 3-4 seconds, the free end of the second wire quickly touches the free positive terminal (with a frequency of 2-3 touches per second). In this case, it is necessary to prevent welding of wires at the junction;
• a voltmeter checks the voltage at the source being restored, if it is absent, another recovery cycle is made ;;
• when an electromotive force appears on the battery, it is put on charge;

In addition, you can try to destroy the dendrites in the battery by freezing them for 2-3 hours, followed by their sharp tapping. When frozen, the dendrites become brittle and are destroyed by impact, which theoretically can help get rid of them.

There are also more extreme restoration methods associated with adding distilled water to old elements by drilling out their case. But the full-fledged provision of the tightness of such elements in the future is very problematic. Therefore, it is not worth saving and putting your health at risk of poisoning with cadmium compounds due to the gain of several work cycles.

Storage and disposal

It is better to store nickel-cadmium batteries in a discharged state at a low temperature in a dry place. The lower the storage temperature of such batteries, the less self-discharge they have. High-quality models can be stored for up to 5 years without significant damage to technical characteristics. To put them into operation, it is enough to charge them.

Harmful substances contained in one AA battery can pollute about 20 square meters of territory. For the safe disposal of Ni Cd batteries, they must be taken to recycling centers, from where they are transported to factories, where they must be destroyed in special sealed ovens equipped with filters that trap toxic substances.

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