Thanks to improvements in manufacturing, Ni-Cd batteries are now used in most portable electronic devices. Acceptable cost and high performance indicators made the presented variety of batteries popular. Such devices are widely used today in instruments, cameras, players, etc. In order for the battery to last a long time, you need to learn how to charge Ni-Cd batteries. By adhering to the rules of operation of such devices, you can significantly extend their service life.
Main characteristics
To understand how to charge Ni-Cd batteries, you need to familiarize yourself with the features of such devices. They were invented by V. Jungner back in 1899. However, their production was then too expensive. Technologies have improved. Today, easy-to-use and relatively inexpensive nickel-cadmium batteries are available for sale.
The devices presented require that charging occurs quickly and discharging slowly. Moreover, the battery capacity must be completely drained. Recharging is carried out using pulsed currents. These parameters should be adhered to throughout the entire life of the device. Knowing Ni-Cd, you can extend its service life by several years. Moreover, such batteries are used even in the most harsh conditions. A feature of the presented batteries is the “memory effect”. If the battery is not completely discharged periodically, large crystals will form on the plates of its cells. They reduce battery capacity.
Advantages
To understand how to properly charge Ni-Cd batteries for a screwdriver, camera, camera and other portable devices, you need to familiarize yourself with the technology of this process. It is simple and does not require special knowledge and skills from the user. Even after storing the battery for a long time, it can be quickly recharged. This is one of the advantages of the presented devices that makes them popular.
Nickel-cadmium batteries have a large number of charge and discharge cycles. Depending on the manufacturer and operating conditions, this figure can reach more than 1 thousand cycles. The advantage of the Ni-Cd battery is its endurance and ability to work under heavy-duty conditions. Even when operating in cold weather, the equipment will work properly. Its capacity does not change under such conditions. At any charge level, the battery can be stored for a long time. Its important advantage is its low cost.
Flaws
One of the disadvantages of the presented devices is the fact that the user must study how to charge correctly Ni-Cd batteries.
The presented batteries, as mentioned above, are characterized by a “memory effect”. Therefore, the user must periodically carry out preventive measures to eliminate it.
The energy density of the presented batteries will be slightly lower than that of other types of autonomous power sources. In addition, in the manufacture of these devices, toxic materials that are unsafe for the environment and human health are used. Disposal of such substances requires additional costs. Therefore, in some countries the use of such batteries is limited. After long-term storage, Ni-Cd batteries require a charge cycle. It's connected with high speed how to charge correctly self-discharge. This is also a disadvantage of their design. However, knowing
Ni-Cd batteries, if used correctly, can provide your equipment with an autonomous power source for many years.
Types of chargers To properly charge a nickel-cadmium battery, you need to use special equipment. Most often it comes complete with a battery. If for some reason you don’t have a charger, you can purchase it separately. Automatic and reversible pulse varieties are on sale today. When using the first type of device, the user does not need to know to what voltage should I charge?
Using a special switch, the device is set to discharge mode. In this case, the color indicator will glow yellow. When this procedure is completed, the device automatically switches to charging mode. The red indicator will light up. When the battery reaches the required capacity, the device will stop supplying current to the battery. The indicator will light up green light. Reversible ones belong to the group of professional equipment. They are capable of performing several charge and discharge cycles with different durations.
Special and universal chargers
Many users are interested in the question of how to charge a screwdriver battery Ni-Cd type. In this case not regular will do device designed for AA batteries. A special charger is most often supplied with the screwdriver. This is what should be used when servicing the battery. If there is no charger, you should purchase equipment for batteries of the presented type. In this case, only the screwdriver battery can be charged. If batteries are in use various types, worth purchasing universal equipment. It will allow you to service autonomous energy sources for almost all devices (cameras, screwdrivers, and even batteries). For example, it will be able to charge Ni-Cd batteries iMAX B6. This is a simple and useful device in the household.
Discharging pressed battery
Pressed Ni- are characterized by a special design and the discharge performance of the presented devices depends on their internal resistance. This indicator is influenced by some design features. For long work equipment, disk type batteries are used. They have flat electrodes of sufficient thickness. During the discharge process, their voltage slowly drops to 1.1 V. This can be checked by plotting a curve graph.
If the battery continues to be discharged to 1 V, its discharge capacity will be 5-10% of the original value. If the current is increased to 0.2 C, the voltage decreases significantly. This also applies to battery capacity. This is explained by the impossibility of discharging the mass evenly over the entire surface of the electrode. Therefore, today their thickness is being reduced. At the same time, the design of the disk battery contains 4 electrodes. In this case, they can be discharged with a current of 0.6 C.
Cylindrical batteries
Today, batteries with metal-ceramic electrodes are widely used. They have low resistance and provide high energy performance of the device. Charged voltage This type of Ni-Cd battery is kept at 1.2 V until 90% of its specified capacity is lost. About 3% of it is lost during a subsequent discharge from 1.1 to 1 V. The presented type of battery can be discharged with a current of 3-5 C.
Roll-type electrodes are installed in cylindrical batteries. They can be discharged with current over high performance, which is at the level of 7-10 C. The capacity indicator will be maximum at a temperature of +20 ºC. As it increases, this value changes insignificantly. If the temperature drops to 0 ºС and below, the discharge capacity decreases in direct proportion to the increase in discharge current. How to charge Ni- CD batteries, types which are presented for sale, need to be considered in detail.
General charging rules
When charging a nickel-cadmium battery, it is extremely important to limit the excess current flowing to the electrodes. This is necessary due to the pressure build-up inside the device during this process. When charging, oxygen will be released. This affects the current utilization factor, which will decrease. There are certain requirements that explain how to charge Ni- CD batteries. Parameters The process is taken into account by manufacturers of special equipment. Chargers, during their operation, report 160% of the nominal capacity to the battery. The temperature range throughout the entire process must remain between 0 and +40 ºС.
Standard charging mode
Manufacturers must indicate in the instructions how much to charge Ni-Cd battery and what current should be used. Most often, the mode of performing this process is standard for most types of batteries. If the battery has a voltage of 1 V, it should be charged within 14-16 hours. In this case, the current should be 0.1 C.
In some cases, process characteristics may vary slightly. This is influenced by the design features of the device, as well as the increased loading of the active mass. This is necessary to increase the battery capacity.
The user may also be interested in what current to charge the battery with? Ni-Cd. In this case, there are two options. In the first case, the current will be constant throughout the entire process. The second option allows you to charge the battery for a long time without the risk of damaging it. The circuit involves the use of a stepwise or smooth reduction in current. At the first stage it will significantly exceed 0.1 C.
Fast charging
There are other methods that accept Ni- CD batteries. How to charge battery of this type accelerated mode? There is a whole system here. Manufacturers increase the speed of this process by releasing special devices. They can be charged at higher current levels. In this case, the device has a special control system. It prevents the battery from overcharging. Such a system can be either the battery itself or its charger.
Cylindrical types of devices are charged with a constant current, the value of which is 0.2 C. The process will last only 6-7 hours. In some cases, it is possible to charge the battery with a current of 0.3 C for 3-4 hours. In this case, process control is essential. With an accelerated procedure, the recharge rate should be no more than 120-140% of the capacity. There are even batteries that can be fully charged in just 1 hour.
Stop charging
When learning how to charge Ni-Cd batteries, it is necessary to consider the completion of the process. After the current stops flowing to the electrodes, the pressure inside the battery still continues to increase. This process occurs due to the oxidation of hydroxyl ions at the electrodes.
Over some time, there is a gradual equalization of the rate of oxygen release and absorption at both electrodes. It leads to gradual decrease pressure inside the battery. If the recharge was significant, this process will be performed more slowly.
Mode setting
To charge correctly Ni-Cd battery, you need to know the rules for setting up the equipment (if they are provided by the manufacturer). The nominal capacity of the battery must have a charge current of up to 2 C. It is necessary to select the type of pulse. It can be Normal, Re-Flex or Flex. The sensitivity threshold (pressure reduction) should be 7-10 mV. It is also called Delta Peak. It's better to put it on minimum level. The pumping current needs to be set in the range of 50-100 mAh. To be able to fully utilize the battery power, you need to charge with a high current. If it is required maximum power, the battery is charged with low current at normal mode. By looking at how to charge Ni-Cd batteries, every user will be able to complete this process correctly.
Basics Ni-Cd difference batteries and Ni-Mh batteries - this is the composition. The base of the battery is the same - it is nickel, it is the cathode, but the anodes are different. For a Ni-Cd battery, the anode is cadmium metal; for a Ni-Mh battery, the anode is a hydrogen metal hydride electrode.
Each type of battery has its pros and cons, knowing them you can more accurately select the battery you need.
| pros | Minuses | |
| Ni-Cd |
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| Ni-Mh |
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Will the old charger fit the new battery if I change the Ni-Cd to a Ni-Mh battery or vice versa?
The charging principle for both batteries is absolutely the same, so the charger can be used from the previous battery. The basic rule for charging these batteries is that they can only be charged after they are completely discharged. This requirement is a consequence of the fact that both types of batteries are subject to the “memory effect”, although with Ni-Mh batteries this problem is minimized.
How to properly store Ni-Cd and Ni-Mh batteries?
The best place to store a battery is in a cool, dry room, since the higher the storage temperature, the faster the battery self-discharges. The battery can be stored in any condition other than completely discharged or fully charged. The optimal charge is 40-60%%. Once every 2-3 months, you should recharge (due to the presence of self-discharge), discharge and charge again to 40-60% of the capacity. Storage for up to five years is acceptable. After storage, the battery should be discharged, charged and then used normally.
Can I use batteries with a larger or smaller capacity than the battery from the original kit?
Battery capacity is the operating time of your power tool on battery power. Accordingly, there is absolutely no difference in battery capacity for a power tool. The actual difference will only be in the charging time of the battery and the operating time of the power tool from the battery. When choosing a battery capacity, you should proceed from your requirements; if you need to work longer using one battery, choose more capacious batteries; if the included batteries are completely satisfactory, then you should choose batteries of equal or similar capacity.
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.
Contents
What is Nickel Cadmium Battery
Nickel-cadmium batteries are galvanic rechargeable current sources that were invented in 1899 in Sweden by Waldmar Jungner. Before 1932, their practical use was very limited due to the high cost of the metals used compared to lead-acid batteries.
Improvements in their production technology led to a significant improvement in their performance characteristics and made it possible in 1947 to create a sealed maintenance-free battery with excellent parameters.
Operating principle and design of Ni-Cd battery
These batteries produce electrical energy through 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 available in sealed enclosures, which house electrodes separated by a neutral separator containing nickel and cadmium in a solution of a jelly-like alkaline electrolyte (usually potassium hydroxide, KOH).
The positive electrode is a steel mesh or foil coated with nickel oxide-hydroxide paste mixed with conductive material
The negative electrode is a steel mesh (foil) with pressed porous cadmium.
One nickel cadmium element is capable of producing a voltage of about 1.2 volts, therefore, to increase the voltage and power of batteries, their design uses many parallel-connected electrodes separated by separators.
Technical characteristics and types of Ni-Cd batteries
Ni-Cd batteries have the following technical characteristics:
- the discharge voltage of one element is about 0.9-1 volts;
- the rated 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;
- 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*hour/kg;
- service life is about 10 years.
Ni-Cd batteries are produced in various cases of standard sizes and in non-standard designs, including disk and sealed form.
Where are nickel cadmium batteries used?
These batteries are used in devices that consume high current and also experience high loads when used 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 equipment;
- portable radios;
- in radio-controlled toys;
- in diving lights.
Currently, due to tightening 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 NiCd batteries of various sizes in use that were released several years ago.
Ni-Cd cells have a long service life, which sometimes exceeds 10 years, and therefore this type of battery can still be found in many 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 number of charge-discharge cycles;
- long service life and storage;
- fast charging capability;
- ability to withstand heavy loads and low temperatures;
- maintaining performance in the most unfavorable conditions operation;
- low cost;
- the ability to store these batteries in a discharged state for up to 5 years;
- average overcharge resistance.
At the same time, nickel-cadmium power supplies have a number of disadvantages:
- the presence of a memory effect, manifested in loss of capacity when charging the battery without waiting for complete discharge;
- the need for preventive maintenance (several charge-discharge cycles) to reach the full capacity;
- complete restoration of the battery after long-term storage requires three to four full charge-discharge cycles;
- high self-discharge (about 10% in the first month of storage), leading to almost complete discharge of the battery within a year of storage;
- low energy density compared to other batteries;
- the 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;
- greater weight compared to modern batteries.
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 power sources:
- Ni-Cd elements, in contrast to the variants, have a memory effect and have a lower specific capacity with the same dimensions;
- NiCd sources are more unpretentious, remain operational at very low temperatures, and 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 less self-discharge;
- the service life and storage life of Li-Ion batteries (2-3 years) is several times less than that of 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 fully restored by deep discharging and charging, it is better not to use Ni Cd products in devices where they are constantly recharged;
- The identical charging mode of 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 make 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 loss of performance:
- the useful area and mass of the electrodes decreases;
- the composition and volume of the electrolyte changes;
- the separator and organic impurities decompose;
- water and oxygen are lost;
- Current leaks appear due to the growth of cadmium dendrites on the plates.
In order to minimize damage to the battery that occurs during its operation and storage, it is necessary to avoid adverse effects on the battery that are associated with the following factors:
- charging an incompletely charged battery leads to a reversible loss of its capacity due to a decrease in the total area 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 changes in the composition and volume of the electrolyte, increasing internal resistance battery and deteriorate performance characteristics, in particular, the capacity drops.
With a strong increase in pressure inside the battery as a result of rapid charging with a 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 that can deform the case, disrupt 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 in the chemical composition of the battery cannot be avoided.
Ni Cd batteries must be charged with a current of 10% (if fast charging in special batteries is necessary - 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 discharging them with a current equal to 20% of the battery capacity.
How to restore Ni Cd battery
Nickel-cadmium power supplies in case of loss of capacity can be almost completely restored using a complete discharge (up to 1 volt per element) and subsequent charging in standard mode. This battery training can be repeated several times to fully restore their capacity.
If it is impossible to restore the battery by discharging and charging, you can try to restore them using short current pulses (tens of magnitude more capacity element being restored) for several seconds. This effect eliminates the internal short circuit in the battery cells that 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 effect.
Complete 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 recovery method at home consists of the following steps:
- a wire with a cross-section of at least 1.5 square millimeters connects the minus of the element being restored to the cathode of a powerful battery, for example a car battery or one from 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 is quickly touched to the free positive terminal (with a frequency of 2-3 touches per second). In this case, it is necessary to prevent welding of the wires at the connection point;
- a voltmeter is used to check the voltage on the source being restored; if it is absent, another restoration cycle is performed;;
- when an electromotive force appears on the battery, it is charged;
In addition, you can try to destroy the dendrites in the battery by freezing them for 2-3 hours and then sharply tapping them. When frozen, dendrites become brittle and are destroyed by impact, which could theoretically help get rid of them.
There are also more extreme restoration methods that involve adding distilled water to old elements by drilling out their housing. But fully ensuring the tightness of such elements in the future is very problematic. Therefore, you should not save money and expose your health to the 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 lower their self-discharge. 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.
The harmful substances contained in one AA battery can pollute about 20 square meters of territory. To safely dispose of NiCd batteries, they must be taken to recycling points, 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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I bought a new screwdriver and decided to take a deeper look at how to properly operate its nickel-cadmium batteries.
Target - active work a screwdriver with changing batteries without the risk of damaging the batteries ahead of time.
Reference:
This screwdriver has:
- Accumulator battery- 12V.
- Number of elements - 10.
- Battery capacity - 1.2 Ah.
- EMF of a charged battery - 13.6V.
Peculiarities:
- It is believed that the maximum EMF of a completely discharged battery is 10V.
- All Ni Cd batteries have a “memory” effect, i.e. If they are not fully discharged, they lose their capacity.
- Ni-Cd batteries have a high self-discharge.
- The number of charge-discharge cycles for any battery is limited.
- It is believed that the only criterion for the full charge of Ni Cd batteries (at currents greater than 0.1 C) is their temperature, which is approximately 40 * C.
What I've done:
1. First, I studied math. part (file attached).
2. Secondly, I carried out a series of measurements.
3. Thirdly, I designed and made a charger-discharge device for ultra-fast charging and automatic shutdown at rated discharge.
So, point by point:
1. Read the theory (file).
2. I measured the charging currents and battery temperatures at two strong different currents and compared them with the “theory”.
I charged the completely discharged battery using a charger taken from an old laptop with an EMF of 15 Volts without additional current/voltage limiters, i.e. - directly. Actually, this is called "constant voltage charging".
Result:
In the first 15 minutes, the battery took 50% of its capacity, while charging current decreased to 1.4A. The battery temperature remained almost unchanged.
Then, over the next 45 minutes, the current asymptotically approached 0.22A (increased to 30*C). Then for almost 1 hour the current remained at the level of 0.22A (at the end - 34 * C) and after another 30 minutes I turned off the charge with an explicit automatic equalization of the charge of the elements (in accordance with the “theory”) - when the current increased to 0. 35A and temperatures up to 38*C.
Conclusion: a full charge with high current can be done in 2.5 hours. And up to 50% - in 15 minutes. I haven't read anywhere about problems with undercharging. The only problems are with the under once near. Well, and, of course, - with re behind nearby (or rather, with overheating due to overcharging).
2B. Slow charge with low current (0.1C, i.e. - 120mA). The mode is close to “drip”.
I charged a completely discharged battery using a charger from another screwdriver (less powerful than the standard one) without additional current/voltage limiters, i.e. also directly.
In the first 15 minutes, the charging current dropped from 310mA to 120mA and then remained more or less stable, and the temperature rose to 37*C after 15 hours of charging.
At the same time, the temperature of 36-37*C stabilized after 10.5 hours of charging.
Conclusion: Charging with a current close to, but not more than 0.1 C can be carried out without a time limit, i.e. - do not be afraid of overheating/overcharging the battery. Roughly speaking, I turned it on “for the night” and then when I woke up, I scratched myself and turned it off. This is useful if the battery does not have a shut-off thermocouple.
3. From charging block I made a charge-discharge device (CDD) from an old screwdriver.
Well, the charge there is direct from any of the two described above chargers, and the discharge is through a powerful resistor (24 Ohms) with a relay circuit. Relay - automatically turns off the discharge when the voltage reaches 9-10 Volts.
Why forced discharge? It is needed so that the battery capacity does not decrease, i.e., to eliminate the “memory” effect (see “theory” in the file). That is, when the user thinks that the battery needs to be changed, he inserts the half-discharged battery into the discharge mode and, minding his own business, waits for the LED to go out. After this, it turns the toggle switch to the charge position and, if this battery has a thermoelement that turns off the charge when the temperature rises to 40-45*C, it “forgets” about it. Moreover, it can use a rechargeable battery in just 15 minutes (with fast charging). If there is no thermoelement, then you can use a daily electromechanical timer to turn it off.
Note 1. In principle, you can discharge the battery with the screwdriver itself, but I didn’t like it. Control of the level of the nominal discharge is approximately the following: if a cartridge that is already barely rotating without load is stopped by hand and after that it no longer begins to rotate, then the discharge is close to the nominal one.
Note 2. At any real charge current, the end of charging of Ni Cd batteries can and should be judged by the temperature of the battery - preferably about 40*C (at room ambient temperature!).
Note 3. Based on the above, recommendations can be made for battery storage. The purpose of the recommendations is to maximize battery life.
I would highlight two different modes screwdriver operation:
- Rarely. Let one battery remain in the same condition as left after last work, and keep the other unloaded. When starting work, use it first (before once dress while working), and the second one can be charged at this time.
- Often. Store one in a charged state, and the other in whatever state remains after the last work. Well, if it happens very often (every day), then you can store both in a charged state.
***
I understand that not everyone has a charger for fast charging, as well as for slow charging (standard ones usually give an average current between them). However, they are still easy to make/find. In any case, I hope that what is written here will help someone understand a little about such “peculiar” Ni Cd batteries.
At the present stage, there are many batteries that have different chemical composition and, due to the presence of certain elements in them, their characteristics and operational advantages. 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 twentieth century. They were invented by the Swedish scientist Waldmar Jungner, using nickel as a positive charge and cadmium as a negative charge. Despite the obvious benefits of this invention, at that time 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 because it was then that the technique of introducing chemically active plate materials onto a porous electrode coated with nickel 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 common parlance they are often called “banks”. There are also flat Ni batteries - for example, for watches. All charging elements 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, lower capacity ratings are not a drawback that would cause the good old cadmium battery was finally discontinued. One of its undoubted advantages is that during operation it does not heat up as quickly as MH. This significantly 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 reactions is absorbed internally. As for MH, they differ from cadmium in exothermic reactions with the release of large amounts of heat. In this regard, MHs heat up much faster and can “burn out” if their use is not stopped in time.
Ni-Сd batteries have a dense metal case, characterized by increased strength and good sealing. 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 at risk of spontaneous combustion, unlike modern ones.
Among them are powerful and reliable industrial Ni batteries that can fully operate for 20-25 years. And, despite the fact that these batteries have long been replaced by MH and lithium batteries with a higher capacity, Ni-Cd batteries continue to be actively used to this day.
If speak about price category, the cost of Ni-Cd is significantly lower than other batteries. This is also one of their main advantages.
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 “cans” still provide operation for 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.
Features of operation
Since Ni-Cd batteries noticeably heat up only if they are fully charged, most devices “understand” this as a signal to stop the charging process. In order for them to work longer, it is recommended to charge them quickly and use them until they are completely discharged: unlike MH, nickel-cadmium batteries are not afraid of deep discharge.
This type of battery is the only battery that is recommended to be stored completely discharged, while MH batteries should be stored fully charged, and they periodically need to check the output voltage. Such a difference, with a significant difference in operation, is certainly another obvious point in favor of Ni-Cd.
If stored for a long time without use in a discharged state, nothing bad will happen to the batteries. But to bring them to working condition, you need to swipe it two or three times full cycle"charge-discharge". It is better to do this shortly before use, maybe a day before, and then the nickel-cadmium batteries will work with optimal current output.
Any Ni-Cd used in everyday life, when powered by a small current and periodically incompletely discharging, can significantly lose capacity, which creates the impression full exit The battery is out of order. If Ni-Cd has been recharging for a long time, for example, in a device with constant nutrition, it will also lose a certain capacity indicator, although its voltage level will be correct.
This means that it is not worth using Ni-Cd in the mode of constant replenishment and “underdischarge”, and if this does happen to the battery, one cycle of deep discharge followed by a full charge will be enough for the capacity to be restored.
This effect is called the “memory effect” and occurs when an incompletely discharged battery is recharged before it is completely discharged. The fact is that in the production of nickel-cadmium batteries, so-called pressed electrodes are used. This is very convenient, since “pressing” is high-tech and cheaper. But it is 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 electrical layer in the form of large crystals, which causes a decrease in voltage.
This is why Ni-Cd elements “love” full and deep discharge, after which, having “cleared the memory”, they can work fully for a long time.
Nickel-cadmium battery refurbishment
Restoration with water
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 will need a few simple tools and devices:
- soldering acid ;
- disposable syringe
;
soldering iron; - some distilled water .
Usually battery pack, located 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 bunch is the weakest, you must first measure the voltage at the poles of each element. How to check the 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 begin the recovery process, you need to drill a small hole in the battery, after first freeing it from 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 only drill through its outer shell.
IN in this case It is worth noting one more undoubted advantage: in such batteries, due to their design, increased tightness and the characteristics of leaking chemical reactions, spontaneous combustion does not occur. Therefore, amateur methods of bringing nickel-cadmium cells back 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 taken into a disposable syringe, and the battery is gradually filled with it. It is important to take your time and ensure that the water gradually penetrates inside the battery. Distilled water is needed to return and create the required density of the electrolyte inside the battery. After the water has been poured in, the hole is closed with soldering acid, which is taken on a match, and sealed with a well-heated soldering iron.
Some craftsmen claim that if instead of distilled water you pour electrolyte from miners' flashlights into the battery, the battery will work much better and longer.
Finally, you need to measure the voltage again with a multimeter and charge the battery. Of course, a soldered battery will not last long, but this can help buy you some time before purchasing a new one.
Restoration using zapping method
For nickel-cadmium batteries, there is a proven, but very risky recovery method called zapping. Its essence lies in the fact that batteries are subjected to short discharges of very high currents, tens of times higher than normal. Each element is literally “burned through” by short-second current pulses of 10, 20 amperes and higher.
Zapping requires good training as an electronics enthusiast and compliance with safety precautions in the form of safety glasses and, preferably, overalls. It claims to restore elements that have not been used for 20 years or more. It should be remembered that zapping is applicable exclusively to nickel-cadmium batteries. Reconditioning Ni-MH batteries in this way is not recommended.
Discharge-charge cycle
To eliminate the "memory effect" , need to discharge the battery to 0.8-1 volts, then fully charge it again . If the battery has not been restored for a long time, several such cycles can be performed, 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 NiСd or NiMH batteries in the freezer - despite the fact that the effectiveness of this method is very questionable, you can find a lot of information on the Internet about “restoring” 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 a much greater chance of resuscitating them.
So, nickel-cadmium batteries are not inferior to modern batteries in a number of their advantages technical characteristics. They are still reliable, durable, inexpensive and extremely safe to use.
