Converting a screwdriver battery to lithium cells

Many owners of screwdrivers want to convert their batteries to lithium battery cells. Many articles have been written on this topic and in this material I would like to summarize the information on this issue. First of all, let's look at the arguments in favor of converting a screwdriver to lithium batteries and against it. We will also consider individual aspects of the battery replacement process itself.

First you need to think, do I need this alteration? After all, this will be an outright “homemade” and in some cases can lead to failure of both the battery and the screwdriver itself. Therefore, let's look at the pros and cons of this procedure. It is possible that after this some of you will decide to abandon the conversion of Ni─Cd to lithium cells.

Pros

Let's start with the advantages:

The energy density of lithium-ion elements is significantly higher than that of nickel-cadmium elements, which are used by default in screwdrivers. That is, a lithium battery will have less weight than a cadmium battery with the same capacity and output voltage;
Charging of lithium battery cells occurs much faster than in the case of Ni─Cd. It will take about an hour to charge them safely;
Lithium-ion batteries do not have a “memory effect”. This means that they do not have to be completely discharged before charging them..

Now about the shortcomings and difficulties.

Cons

Lithium battery cells cannot be charged above 4.2 volts and discharged below 2.7 volts. In real conditions, this interval is even narrower. If you go beyond these limits, the battery can be damaged. Therefore, in addition to the lithium cans themselves, you will need to connect and install a charge-discharge controller in the screwdriver;
The voltage of one Li─Ion element is 3.6─3.7 volts, and for Ni─Cd and Ni─MH this value is 1.2 volts. That is, problems arise with assembling a battery for screwdrivers with a voltage rating of 12 volts. From three lithium cans connected in series, you can assemble a battery with a nominal value of 11.1 volts. Out of four ─ 14.8, out of five ─ 18.5 volts and so on. Naturally, the voltage limits during charge-discharge will also be different. That is, there may be problems with the compatibility of the converted battery with the screwdriver;
In most cases, 18650 standard banks are used as lithium cells for conversion. They differ in size from Ni─Cd and Ni─MH cans. In addition, you will need a place for the charge-discharge controller and wires. All this will need to fit into a standard screwdriver battery case. Otherwise, it will be extremely inconvenient for them to work;
A charger for cadmium batteries may not be suitable for charging the battery after it has been rebuilt. It may be necessary to modify the memory or use universal chargers;
Lithium batteries lose their functionality at low temperatures. This is critical for those who use a screwdriver outdoors;
The price of lithium batteries is higher than cadmium batteries.

Replacing batteries in a screwdriver with lithium ones

What do you need to consider before starting work?

You need to decide on the number of elements in the battery, which ultimately decides the voltage value. For three elements the ceiling will be 12.6, and for four ─ 16.8 volts. We are talking about converting widely used batteries with a nominal value of 14.4 volts. It is better to choose 4 elements, since during operation the voltage will drop quite quickly to 14.8. A difference of a few volts will not affect the operation of the screwdriver.

In addition, more lithium cells will give greater capacity. This means more operating time for the screwdriver.

Next, you need to choose the right lithium cells themselves. The form factor without options is 18650. The main thing you need to look at is the discharge current and capacity. According to statistics, during normal operation of a screwdriver, the current consumption is in the range of 5-10 amperes. If you press the start button sharply, the current may jump to 25 amperes for a few seconds. That is, you need to choose lithium ones with a maximum discharge current of 20-30 amperes. Then, with a short-term increase in current to these values, the battery will not be damaged.

The nominal voltage of lithium cells is 3.6-3.7 volts, and the capacity in most cases is 2000-3000 mAh. If the battery case allows, you can take not 4, but 8 cells. Connect them two by two into 4 parallel assemblies, and then connect them in series. As a result, you can increase the battery capacity. But not every case will be able to pack 8 18650 cans.

And the last preparatory stage is the choice of controller. According to its characteristics, it must correspond to the rated voltage and discharge current. That is, if you decide to assemble a 14.4 volt battery, then choose a controller with this voltage. The operating discharge current is usually selected to be two times less than the maximum permissible current.

Above, we established that the maximum permissible short-term discharge current for lithium cells is 25-30 amperes. This means that the charge-discharge controller should be designed for 12-15 amperes. Then the protection will operate when the current increases to 25-30 amperes. Don't forget also about the dimensions of the protection board. It, along with the elements, will need to be placed in the battery case of the screwdriver.

From native nickel-cadmium NI-CD to lithium-ion Li-ion size 18650.

A little theory.

Powerful portable power devices use special batteries with increased current output. In a screwdriver, under increased load, a high current is created, and to cope with it, reinforced Ni-CD and NiMH batteries (usually wrapped in paper) are used. The average operating current of a twelve-volt screwdriver is 3-7 amperes, with a load it can reach up to 15A, and in a pulse up to 30A.

It follows from this first recommendation– When replacing cadmium with lithium, it is necessary to use only high-current lithium-ion batteries. Now these batteries are produced by Samsung, LG, SONY and a number of other manufacturers.

Using 4 Li Ion Batteries in a 12 Volt Screwdriver destructive for the power switch PWM speed controller, located in the button. The voltage of a fully charged Li Ion battery is 4.2 volts, the voltage of a fully charged assembly of four batteries will be 16.8 volts, which is a third higher than the recommended voltage, according to Ohm’s law - “the current is directly proportional to the voltage in the circuit”, tells us that the current will also increase by a third , and in a pulse it can reach 40A, not a single key can withstand such an overload and will fail. We recommend using only 3 lithium-ion batteries for a 12 Volt battery, 4 batteries will do an excellent job with a 14.4 Volt battery, and 5 batteries are enough for an 18 Volt battery.

During operation of a lithium-ion battery, it is necessary to control its charge and discharge voltage, since due to its physical and chemical characteristics, the voltage must be kept within a strictly defined range of 2.5-4.2 volts. Only under these conditions can maximum battery life and safe operation be guaranteed.

The use of a charge and discharge controller is mandatory and, based on the first recommendation, the controller must support operation at currents from 12 to 30 amperes, otherwise under increased load the controller will “go into protection” and normal operation of the device will not work.

For charging, you can use your own charger, do not forget to leave the temperature and overheating sensor in place, otherwise it will not charge. If for some reason the charger “does not want” to work, then the following two Options are for you.

You can take a ready-to-use one, designed for the number of elements in your assembly, and select it based on the optimal charge current. In this case, a hole is drilled in the block for a 5.5 * 2.1 mm socket, and further charging will be carried out through it. This solution is especially helpful when there is very little space in the battery pack. In our case, we did just that, but we left all the sensors in their places, in case they came in handy.

An excellent charging solution is the use of a universal DC-DC voltage conversion module with the ability to adjust current and voltage, the so-called CC CV. Step-down modules based on XL4015 and LM2596 chips are very popular. You set the charge voltage at the module output to 12.6-13.6 V and the charge current in the range of 500-900 mAh and the module will do the rest itself. The use of these modules makes it possible to charge the screwdriver from any power source with a voltage above 13 volts. It is especially justified if your screwdriver has a power supply separate from the charging unit, then the old power supply will do an excellent job of charging new batteries.

Well, general recommendations - it is advisable to use a wire cross-section of at least 4 mm2, be careful when installing, any short circuits lead to instant heating of the conductors and you can get burned, all connections and soldering points must be as reliable and durable as possible, since high currents Well, there is vibration.

We decided to use batteries for our screwdriver; they meet all the necessary parameters. It was also used - this is a miniature 50 * 22 mm high-current controller with short-circuit and overload protection. We made all connections with silicone wire 6 mm.kv (we recommend using a smaller cross-section, it is difficult to work with such a cross-section).

From the beginning, we thought for a long time about how to place the batteries with the board. Then we thought about where to put the charging connector. Well, once we decided, we began to slowly solder everything together. It turned out to be most convenient to place two batteries in the main body, and place the BMS board and the third battery in the pin of the case.

During the assembly process, the idea arose to supply our battery, no sooner said than done. There is a place to screw it on, and they didn’t forget the button so that you can press it and see how much capacity is left. The module is customizable, so essentially it can be screwed onto any battery.

As a conclusion.

Everyone was satisfied with the process and the result. The weight of the battery has been halved. The battery passed all the tests without any complaints.

From wishes for the future.

There is an AEG screwdriver lying around, also with a 12-volt battery, we hope you can get your hands on it and there will be more space in it and we are thinking of installing batteries.

The problem facing everyone who has any kind of electric tool at home that runs on batteries is increasing their service life. Basically, all household models of screwdrivers are equipped with metal hydride (NiMH) or nickel-cadmium (NiCd) batteries. And this is primarily due to their lower price compared to lithium-ion (Li-ion) counterparts.

Despite the high cost, the latter are preferable in many respects. It is enough to indicate only two - the almost complete absence of self-discharge and a longer shelf life. You don’t have to use a screwdriver in everyday life, but only occasionally, so it makes sense to convert the screwdriver battery from NiCd (or NiMH) to a lithium-ion battery yourself, without spending money on an industrial sample. This article is about how to do this.

All voltage values indicated below are only for one of the screwdriver models, as an example of calculations.

Algorithm for converting a battery to a lithium-ion battery

Selection of batteries

Here it is useful to remember high school - when batteries are connected in series, their voltage ratings are summed up. For example, if a screwdriver needs 14.4 V for normal operation, then instead of one (standard) battery it is enough to purchase 4 pieces of 3.3 V each. This is quite enough, since the lithium-ion elements do not “sag” too much when the tool is turned on.

What to consider:

Once the decision has been made to remake the screwdriver battery, then to achieve the expected effect you should buy mini-batteries from a well-known manufacturer. For example, LiFePO4 batteries from Sistem A123. Their capacity (in mAh) is 2,300, which is quite enough for the normal operation of the electric tool. If you focus on cheap elements “made in China”, then remodeling loses its meaning - these products will not last long.
Purchasing mini lithium-ion batteries through an online store will allow you to save a lot. They will cost about 900 rubles, while at a retail outlet you will have to pay at least 1,700 - 2,000 for them. The same applies to the charger. This approach will solve the problem at minimal cost, otherwise it’s easier to buy a ready-made Li-ion battery for a screwdriver for 6,800 - 7,150 rubles and not waste time on rework. About, .
When purchasing batteries, you should pay attention to the presence of copper strips on their terminals. This will greatly facilitate the process of assembling the battery from individual elements (soldering stage).

Selection of tools and materials

The soldering process is distinguished by its specifics. The soldering iron tip heats up to a high temperature, and prolonged thermal exposure is detrimental to the battery. Therefore, it is necessary to keep the heating time to a minimum. This can be achieved if, instead of the traditional flux - pine rosin or alcohol-containing compounds based on it - you use soldering acid. You can purchase it at any point where radio installation tools and parts are sold, or at a car store (spare parts department). The cost of a 20 g soldering bottle is about 35 rubles.

Based on the above, and so that its power is enough to quickly melt the solder. The author used the most common one in everyday life - 65 W/220. It is more difficult to work with a tool of higher power - 100 W - since overheating is difficult to avoid. This requires experience and accuracy. The same applies to a 40 W soldering iron. You will have to increase the heating time, so you can “overdo it”. Although this is a recommendation based on personal experience and the author has no right to impose his opinion.

Lithium-ion battery installation

Preparing the “assembly”

Before you start soldering, you should decide on the layout of the battery compartment. That is, arrange all the elements so that they fit comfortably into it. After this, the purchased batteries are secured with adhesive tape (PVC, tape).

Processing of mini-battery contacts

They gradually oxidize. This means they need to be cleaned up a bit. Just lightly, using fine-grained (sanding) sandpaper.

It begins with degreasing the “contact” part of the battery and briefly heating the applied solder. It is better to tin with easily melting ones, for example, POS-40. The soldering iron should come into contact with the metal of the battery for no more than 1.2 - 2 seconds. Pay special attention when soldering the positive terminal.
It is advisable to use copper wires as connecting wires, with a cross-section of at least 2.5 square meters. They must be insulated with thermo-cambric.
All mini-batteries are connected by jumpers according to the diagram. As such, wire or “tires” made of strips of thin metal are used.
The final step is to connect the wires to the terminals of the battery compartment. If laying the assembly into it is difficult, the stiffening ribs should be removed. They are made of plastic, so using side cutters to get rid of them is easy.

Additionally

It's up to you, the reader, to decide whether to do it or not. But the peculiarity of Li-ion batteries is that they are sensitive to overcharging. Therefore, it is advisable to control the voltage rating not only on the entire assembly, but also on each element separately. This means that in addition to 2 wires “+” and “–”, you need to output 5 more. To limit yourself to just one connector (for both charging and balancing), you can use this one.

Contact wiring diagram

“+” – 5 and 9.
“–” – 1 and 6.
Balancing contacts (ascending) – 2, 7, 3, 8 and 4.

Connectors for connecting to the charger are selected depending on its model. Both connecting cables are soldered according to the diagram.

Despite the fact that the use of lithium-ion batteries provides many advantages - the absence of battery “memory”, extremely low self-discharge, the ability to work as a screwdriver in subzero temperatures, a long shelf life (up to 8 years) - they are more sensitive to compliance with charging technology. If you do not control the voltage rating, then Li-ion batteries are quickly destroyed. Consequently, you will have to purchase a special, more expensive charger. The one that was originally equipped with the screwdriver is not suitable for lithium-ion batteries.

On the Internet there are recommendations for reusing Li-ion batteries that were previously installed in other technical devices. For example, to ensure autonomous operation of a laptop or telephone (cell phone). There are many options. The author suggests asking a simple question - Is such savings rational if used products do not ensure the normal functioning of the screwdriver, taking into account the specific use of this electric tool? Perhaps it will perform its task for some time, but how effectively and for how long is a completely logical question. Therefore, such advice from various “homemade” people is hardly worthy of attention.

To monitor the condition of the battery cells, you can purchase a voltage indicator. The radio shop will tell you which board is best to use. It is inexpensive - around 180 rubles.

Before reworking the battery, you should look at the screwdriver's data sheet. What is the rated voltage indicated? Depending on this, the required number of elements is selected.

The author draws attention to the fact that without sufficient knowledge of radio engineering, it is not advisable to independently manufacture electronic boards. The slightest mistake, for example, in selecting parts for a balancing circuit will lead to the elements starting to “fly out” one after another, and they will have to be replaced regularly with new mini-batteries.

If you are not sure that the work will be completed efficiently, you should not waste time on remodeling and purchase a lithium-ion battery for the screwdriver in the store. Despite its price, in the long run it will be cheaper than constant resuscitation of a homemade battery. Or it’s easier to do it - buy the appropriate model of charger. Then you won't have to mount the boards.

2016-06-02

Has the meaning. The advantage is that they have a high electrical density. As a result, by installing such a device in the screwdriver body, we can achieve an increase in the operating time of the tool many times over. The charging current for high-power lithium batteries, especially for new modifications, can reach 1-2 C. Such a device can be recharged in 1 hour, without exceeding the parameters recommended by the manufacturer and without spoiling the quality of the product.

What do lithium batteries look like?

Most lithium devices are housed in a prismatic body, but some models are cylindrical. These batteries use roll electrodes and separators. The body is made of aluminum or steel. The positive pole goes to the housing cover.

In prismatic configurations, the electrodes are in the form of rectangular plates. To ensure safety, the battery is equipped with a device that acts as a regulator of all processes and opens the electrical circuit in critical situations. Increased sealing of the housing prevents electrolyte from leaking out and oxygen and moisture from penetrating inside.

What precautions should be taken to avoid damaging the lithium battery?

Due to technology limitations, the charge level of lithium batteries should not be higher than 4.25-4.35 V. The discharge should not reach 2.5-2.7. This condition is indicated in the technical data sheet for each specific model. If these values are too high, you may damage the device. Special charge and discharge controllers are used that keep the voltage on the lithium cell within normal limits. Converting the screwdriver to a lithium battery with a controller will protect the device from malfunction.
The voltage of lithium batteries is a multiple of 3.7 V (3.6 V). For Ni-Mh models this figure is 1.2 V. This phenomenon is understandable. in lithium devices it is stored in a separate cell. The 12 volt lithium battery will never be assembled. The rating will be 11.1V (three cells in series) or 14.8V (four cells in series). In addition, the voltage indicator of the lithium cell changes when operating when fully charged by 4.25 V, and when fully discharged - by 2.5 V. The voltage indicator 3S (3 serial - three serial connections) will change when the device is operating from 12.6 V (4.2x3) to 7.5 V (2.5x3). For the 4S configuration, this figure ranges from 16.8 to 10 V.
Converting a screwdriver to 18650 lithium batteries (the vast majority of products have this exact size) requires taking into account the difference in dimensions with Ni-Mh cells. The cell diameter 18650 is 18 mm and the height is 65 mm. It is very important to calculate how many cells will fit in the case. It should be remembered that for a model with a power of 11.1 V you will need a number of cells that is a multiple of three. For a model with a power of 14.8 V - four. The controller and patching wires must also fit.
The charging device for a lithium-based battery differs from the device for Ni-Mh modifications.

The article will discuss how to convert a screwdriver to lithium. The tool is equipped with a pair of Ni-Mh rechargeable batteries with a voltage of 12 V and a capacity of 2.6 Ah. Hitachi screwdriver conversion will be considered. Lithium batteries will provide the device with long-term service.

Selecting the nominal voltage

First of all, you should decide on the choice of voltage rating for a lithium-based device. The choice should be made between the 3S model (its voltage range is from 12.6 to 7.5 V) and the 4S-Li-Ion battery (voltage range is from 16.8 to 10 V).

Advantages of the second option

The second option is more suitable because the voltage in the battery drops quite quickly from maximum to minimum (from 16.8 to 14.8 V). For an electric motor, which, strictly speaking, is a screwdriver, exceeding 2.8 V is not a critical level.

The lowest voltage indicator is for the 3S-Li-Ion modification. It is equal to 7.5 V, which is insufficient for the normal functioning of the electrical device. By mounting four configurations, we will increase the battery capacity.

How to decide on the choice of lithium cells?

To select lithium-based cells, limiting factors must be identified. Currently, lithium devices are produced with a permissible current load value of 20-25 A.

Pulse current values (short, up to 1-2 seconds) reach 30-35 A. The battery configuration will not be damaged.

How many cells will fit in the case?

It will not be possible to assemble 4S2P (four serial connections and two parallel ones). Converting a screwdriver to 18650 lithium batteries assumes the presence of eight cells. How can they make it to four? Each cell will bear the maximum current load.

How to determine the maximum current in a screwdriver?

Converting a 12V screwdriver to lithium batteries involves connecting the device to a laboratory power source with a maximum current of 30 A. The limiter regulator is set to the maximum value. Having created the voltage level of the power source close to the nominal value of the future battery, we begin to smoothly pull the trigger. The current consumed by the screwdriver will rise to 5 A. Now you should sharply pull the trigger. This will short out the power circuit. The current will reach a power of 20-30 A. Perhaps its indicator would be much higher, but the power of the power source will not allow this to be recorded. This will be a short-term load current when the screwdriver trigger is pressed sharply. Any model of such a device will react similarly.

Next, you should clamp the tip of the screwdriver with a vice and observe to what value the current consumption will increase during the operating mode when the ratchet in the screwdriver is activated. The current indicator in this case increases to 10-12 A.

This way you can determine the value of the load current. In this case, it will be equal to 5 A at idle and 30 A at a sharp start, and at maximum load it will be 12 A. The manufacturer must select lithium cells whose nominal load current will be 10-20 A, and the pulse current - 25-30 A.

How to choose a controller?

So, the screwdriver is being converted to lithium batteries. Regular charging for the device is required. When choosing a controller, please note that the device must meet two parameters:

rated operating voltage indicator;
rated operating current.

With voltage, everything is very clear: if the battery is 11.1 V, then the controller will have the same voltage.

The term “rated operating current” refers to the protection capacity of the board. Thus, a 4 A controller is designed for a current mark of 4 A, and at 8 A an additional load is placed on it. In this case, the protective device will operate. All these technical data are presented in the passport of each controller modification. In this case, one modification may have a limiting current indicator of 30 A, and another - 50 A. And both of these devices will formally be suitable for operation. Also, when creating a lithium battery, there is a limitation in size. Therefore, you should purchase a controller that will fit in the body of an old battery.

Disassembly and assembly

Converting a screwdriver to lithium batteries includes the following steps:

You should open the old battery by unscrewing five screws.
Remove the Ni-Mh battery from the housing. It will be noticeable that the contact pad that engages with the contact group of the screwdriver is welded to the negative contact of one of the Ni-Mh cells. Welding points should be cut using a tool with a cutting stone built into it
Wires are soldered to the contacts, the cross-section of which is at least 2 mm 2 for power terminals and 0.2 mm 2 for the thermistor. The contact pad is glued into the battery case using hot-melt adhesive.
Based on the internal resistance indicator, four cells are selected on the meter. The value must be the same for all four devices.
Lithium cells are glued together with hot glue so that they are compactly located in the housing.
Cells are welded on a resistance welding machine using a nickel welding tape (its cross-section should be 2X10 mm).

Installing the protection board

This stage can show how lightweight the lithium battery design is. The weight of the Ni-Mh device was 536 g. The weight of the new lithium device is 199 g, which will be quite noticeable. We managed to win 337 g in weight. At the same time, an increase in energy capacity is observed.

The battery is mounted in the housing. The voids are filled with soft material from the packaging.

Connection to a screwdriver

A sharp pull on the trigger triggers the current protection mechanism. But in reality, such a protective mode is unlikely to be needed when using the tool. If you do not specifically provoke the defense, the operation of the screwdriver will be stable.
The tip should be clamped in a vice. The battery power freely activates the ratchet, which limits the increase in rotation speed.
The screwdriver is discharged by The discharge current indicator should be 5 A.
The battery is inserted into the standard charger. The measured charge current is 3 A, which is acceptable for lithium cells. For the LG INR18650HG2 configuration, the maximum charge current will be 4 A, which is indicated in the technical specifications.

How long does it take to replace batteries?

Converting a screwdriver to lithium batteries will take approximately 2 hours. If all parameters are checked, then it will take 4 hours.

You can do everything yourself, without the help of another person. But resistance welding and selection of batteries cannot be carried out without specialized equipment.

How else can you test the degree of charge besides the controller?

The screwdriver has been converted to use lithium batteries. The standard charger built into the case is an ideal option. But the cost of the controller is quite high. The device will cost $30, which is the same as the cost of the battery itself.

To test the charge level of a lithium battery on the go, without using a charger, you can use a special indicator RC helicopter lipo battery AKKU portable voltage meter tester alarm 2-6S AOK. The cost of the device is very low. It has a balancing and charging connector similar to the iMax6 device. The device is connected to the battery using an adapter. This voltage level control device is very convenient. It can measure from two to six lithium cells connected in series, and also provide the total value or voltage of each element separately with extreme accuracy.

How much will it cost to replace a Ni-Mh with a lithium device?

What financial costs will it require to convert a screwdriver to a lithium battery?

The price of such a device consists of the cost of several components:

the lithium-based 4S battery configuration costs RUB 2,200;
purchasing a controller for charging and discharging plus a balancer costs 1,240 rubles;
the cost of welding and assembly is 800 rubles.

It turns out that a do-it-yourself lithium battery costs 4,240 rubles.

For comparison, let's take a similar configuration from factory-produced lithium. For example, the Makita 194065-3 device is designed for a screwdriver. It has similar parameters. The cost of such a device is 6500 rubles. It turns out that converting a screwdriver to lithium batteries saves 2,300 rubles.

Assessing the characteristics of a particular charger is difficult without understanding how an exemplary charge of a li-ion battery should actually proceed. Therefore, before moving directly to the diagrams, let's remember a little theory.

What are lithium batteries?

Depending on what material the positive electrode of a lithium battery is made of, there are several varieties:

with lithium cobaltate cathode;
with a cathode based on lithiated iron phosphate;
based on nickel-cobalt-aluminium;
based on nickel-cobalt-manganese.

All of these batteries have their own characteristics, but since these nuances are not of fundamental importance for the general consumer, they will not be considered in this article.

Also, all li-ion batteries are produced in various sizes and form factors. They can be either cased (for example, the popular 18650 today) or laminated or prismatic (gel-polymer batteries). The latter are hermetically sealed bags made of a special film, which contain electrodes and electrode mass.

The most common sizes of li-ion batteries are shown in the table below (all of them have a nominal voltage of 3.7 volts):

Designation	Standard size	Similar size
XXYY0, Where XX- indication of diameter in mm, YY- length value in mm, 0 - reflects the design in the form of a cylinder	10180	2/5 AAA
	10220	1/2 AAA (Ø corresponds to AAA, but half the length)
	10280
	10430	AAA
	10440	AAA
	14250	1/2 AA
	14270	Ø AA, length CR2
	14430	Ø 14 mm (same as AA), but shorter length
	14500	AA
	14670
	15266, 15270	CR2
	16340	CR123
	17500	150S/300S
	17670	2xCR123 (or 168S/600S)
	18350
	18490
	18500	2xCR123 (or 150A/300P)
	18650	2xCR123 (or 168A/600P)
	18700
	22650
	25500
	26500	WITH
	26650
	32650
	33600	D
	42120

Internal electrochemical processes proceed in the same way and do not depend on the form factor and design of the battery, so everything said below applies equally to all lithium batteries.

How to properly charge lithium-ion batteries

The most correct way to charge lithium batteries is to charge in two stages. This is the method Sony uses in all of its chargers. Despite a more complex charge controller, this ensures a more complete charge of li-ion batteries without reducing their service life.

Here we are talking about a two-stage charge profile for lithium batteries, abbreviated as CC/CV (constant current, constant voltage). There are also options with pulse and step currents, but they are not discussed in this article. You can read more about charging with pulsed current.

So, let's look at both stages of charging in more detail.

1. At the first stage A constant charging current must be ensured. The current value is 0.2-0.5C. For accelerated charging, it is allowed to increase the current to 0.5-1.0C (where C is the battery capacity).

For example, for a battery with a capacity of 3000 mAh, the nominal charge current at the first stage is 600-1500 mA, and the accelerated charge current can be in the range of 1.5-3A.

To ensure a constant charging current of a given value, the charger circuit must be able to increase the voltage at the battery terminals. In fact, at the first stage the charger works as a classic current stabilizer.

Important: If you plan to charge batteries with a built-in protection board (PCB), then when designing the charger circuit you need to make sure that the open circuit voltage of the circuit can never exceed 6-7 volts. Otherwise, the protection board may be damaged.

At the moment when the voltage on the battery rises to 4.2 volts, the battery will gain approximately 70-80% of its capacity (the specific capacity value will depend on the charging current: with accelerated charging it will be a little less, with a nominal charge - a little more). This moment marks the end of the first stage of charging and serves as a signal for the transition to the second (and final) stage.

2. Second charge stage- this is charging the battery with a constant voltage, but a gradually decreasing (falling) current.

At this stage, the charger maintains a voltage of 4.15-4.25 volts on the battery and controls the current value.

As the capacity increases, the charging current will decrease. As soon as its value decreases to 0.05-0.01C, the charging process is considered complete.

An important nuance of the correct charger operation is its complete disconnection from the battery after charging is complete. This is due to the fact that for lithium batteries it is extremely undesirable for them to remain under high voltage for a long time, which is usually provided by the charger (i.e. 4.18-4.24 volts). This leads to accelerated degradation of the chemical composition of the battery and, as a consequence, a decrease in its capacity. Long-term stay means tens of hours or more.

During the second stage of charging, the battery manages to gain approximately 0.1-0.15 more of its capacity. The total battery charge thus reaches 90-95%, which is an excellent indicator.

We looked at two main stages of charging. However, coverage of the issue of charging lithium batteries would be incomplete if another charging stage were not mentioned - the so-called. precharge.

Preliminary charge stage (precharge)- this stage is used only for deeply discharged batteries (below 2.5 V) to bring them to normal operating mode.

At this stage, the charge is provided with a reduced constant current until the battery voltage reaches 2.8 V.

The preliminary stage is necessary to prevent swelling and depressurization (or even explosion with fire) of damaged batteries that have, for example, an internal short circuit between the electrodes. If a large charge current is immediately passed through such a battery, this will inevitably lead to its heating, and then it depends.

Another benefit of precharging is pre-heating the battery, which is important when charging at low ambient temperatures (in an unheated room during the cold season).

Intelligent charging should be able to monitor the voltage on the battery during the preliminary charging stage and, if the voltage does not rise for a long time, draw a conclusion that the battery is faulty.

All stages of charging a lithium-ion battery (including the pre-charge stage) are schematically depicted in this graph:

Exceeding the rated charging voltage by 0.15V can reduce the battery life by half. Lowering the charge voltage by 0.1 volt reduces the capacity of a charged battery by about 10%, but significantly extends its service life. The voltage of a fully charged battery after removing it from the charger is 4.1-4.15 volts.

Let me summarize the above and outline the main points:

1. What current should I use to charge a li-ion battery (for example, 18650 or any other)?

The current will depend on how quickly you would like to charge it and can range from 0.2C to 1C.

For example, for a battery size 18650 with a capacity of 3400 mAh, the minimum charge current is 680 mA, and the maximum is 3400 mA.

2. How long does it take to charge, for example, the same 18650 batteries?

The charging time directly depends on the charging current and is calculated using the formula:

T = C / I charge.

For example, the charging time of our 3400 mAh battery with a current of 1A will be about 3.5 hours.

3. How to properly charge a lithium polymer battery?

All lithium batteries charge the same way. It doesn't matter whether it is lithium polymer or lithium ion. For us, consumers, there is no difference.

What is a protection board?

The protection board (or PCB - power control board) is designed to protect against short circuit, overcharge and overdischarge of the lithium battery. As a rule, overheating protection is also built into the protection modules.

For safety reasons, it is prohibited to use lithium batteries in household appliances unless they have a built-in protection board. That's why all cell phone batteries always have a PCB board. The battery output terminals are located directly on the board:

These boards use a six-legged charge controller on a specialized device (JW01, JW11, K091, G2J, G3J, S8210, S8261, NE57600 and other analogues). The task of this controller is to disconnect the battery from the load when the battery is completely discharged and disconnect the battery from charging when it reaches 4.25V.

Here, for example, is a diagram of the BP-6M battery protection board that was supplied with old Nokia phones:

If we talk about 18650, they can be produced either with or without a protection board. The protection module is located near the negative terminal of the battery.

The board increases the length of the battery by 2-3 mm.

Batteries without a PCB module are usually included in batteries that come with their own protection circuits.

Any battery with protection can easily turn into a battery without protection; you just need to gut it.

Today, the maximum capacity of the 18650 battery is 3400 mAh. Batteries with protection must have a corresponding designation on the case ("Protected").

Do not confuse the PCB board with the PCM module (PCM - power charge module). If the former serve only the purpose of protecting the battery, then the latter are designed to control the charging process - they limit the charge current at a given level, control the temperature and, in general, ensure the entire process. The PCM board is what we call a charge controller.

I hope now there are no questions left: how to charge an 18650 battery or any other lithium battery? Then we move on to a small selection of ready-made circuit solutions for chargers (the same charge controllers).

Charging schemes for li-ion batteries

All circuits are suitable for charging any lithium battery; all that remains is to decide on the charging current and the element base.

LM317

Diagram of a simple charger based on the LM317 chip with a charge indicator:

The circuit is the simplest, the whole setup comes down to setting the output voltage to 4.2 volts using trimming resistor R8 (without a connected battery!) and setting the charging current by selecting resistors R4, R6. The power of resistor R1 is at least 1 Watt.

As soon as the LED goes out, the charging process can be considered completed (the charging current will never decrease to zero). It is not recommended to keep the battery on this charge for a long time after it is fully charged.

The lm317 microcircuit is widely used in various voltage and current stabilizers (depending on the connection circuit). It is sold on every corner and costs pennies (you can take 10 pieces for only 55 rubles).

LM317 comes in different housings:

Pin assignment (pinout):

Analogues of the LM317 chip are: GL317, SG31, SG317, UC317T, ECG1900, LM31MDT, SP900, KR142EN12, KR1157EN1 (the last two are domestically produced).

The charging current can be increased to 3A if you take LM350 instead of LM317. It will, however, be more expensive - 11 rubles/piece.

The printed circuit board and circuit assembly are shown below:

The old Soviet transistor KT361 can be replaced with a similar pnp transistor (for example, KT3107, KT3108 or bourgeois 2N5086, 2SA733, BC308A). It can be removed altogether if the charge indicator is not needed.

Disadvantage of the circuit: the supply voltage must be in the range of 8-12V. This is due to the fact that for normal operation of the LM317 chip, the difference between the battery voltage and the supply voltage must be at least 4.25 Volts. Thus, it will not be possible to power it from the USB port.

MAX1555 or MAX1551

MAX1551/MAX1555 are specialized chargers for Li+ batteries, capable of operating from USB or from a separate power adapter (for example, a phone charger).

The only difference between these microcircuits is that MAX1555 produces a signal to indicate the charging process, and MAX1551 produces a signal that the power is on. Those. 1555 is still preferable in most cases, so 1551 is now difficult to find on sale.

A detailed description of these microcircuits from the manufacturer is.

The maximum input voltage from the DC adapter is 7 V, when powered by USB - 6 V. When the supply voltage drops to 3.52 V, the microcircuit turns off and charging stops.

The microcircuit itself detects at which input the supply voltage is present and connects to it. If the power is supplied via the USB bus, then the maximum charging current is limited to 100 mA - this allows you to plug the charger into the USB port of any computer without fear of burning the south bridge.

When powered by a separate power supply, the typical charging current is 280 mA.

The chips have built-in overheating protection. But even in this case, the circuit continues to operate, reducing the charge current by 17 mA for each degree above 110 ° C.

There is a pre-charge function (see above): as long as the battery voltage is below 3V, the microcircuit limits the charge current to 40 mA.

The microcircuit has 5 pins. Here is a typical connection diagram:

If there is a guarantee that the voltage at the output of your adapter cannot under any circumstances exceed 7 volts, then you can do without the 7805 stabilizer.

The USB charging option can be assembled, for example, on this one.

The microcircuit does not require either external diodes or external transistors. In general, of course, gorgeous little things! Only they are too small and inconvenient to solder. And they are also expensive ().

LP2951

The LP2951 stabilizer is manufactured by National Semiconductors (). It provides the implementation of a built-in current limiting function and allows you to generate a stable charge voltage level for a lithium-ion battery at the output of the circuit.

The charge voltage is 4.08 - 4.26 volts and is set by resistor R3 when the battery is disconnected. The voltage is kept very precisely.

The charge current is 150 - 300mA, this value is limited by the internal circuits of the LP2951 chip (depending on the manufacturer).

Use the diode with a small reverse current. For example, it can be any of the 1N400X series that you can purchase. The diode is used as a blocking diode to prevent reverse current from the battery into the LP2951 chip when the input voltage is turned off.

This charger produces a fairly low charging current, so any 18650 battery can charge overnight.

The microcircuit can be purchased both in a DIP package and in a SOIC package (costs about 10 rubles per piece).

MCP73831

The chip allows you to create the right chargers, and it’s also cheaper than the much-hyped MAX1555.

A typical connection diagram is taken from:

An important advantage of the circuit is the absence of low-resistance powerful resistors that limit the charge current. Here the current is set by a resistor connected to the 5th pin of the microcircuit. Its resistance should be in the range of 2-10 kOhm.

The assembled charger looks like this:

The microcircuit heats up quite well during operation, but this does not seem to bother it. It fulfills its function.

Here is another version of a printed circuit board with an SMD LED and a micro-USB connector:

LTC4054 (STC4054)

Very simple scheme, great option! Allows charging with current up to 800 mA (see). True, it tends to get very hot, but in this case the built-in overheating protection reduces the current.

The circuit can be significantly simplified by throwing out one or even both LEDs with a transistor. Then it will look like this (you must admit, it couldn’t be simpler: a pair of resistors and one condenser):

One of the printed circuit board options is available at . The board is designed for elements of standard size 0805.

I=1000/R. You shouldn’t set a high current right away; first see how hot the microcircuit gets. For my purposes, I took a 2.7 kOhm resistor, and the charge current turned out to be about 360 mA.

It is unlikely that it will be possible to adapt a radiator to this microcircuit, and it is not a fact that it will be effective due to the high thermal resistance of the crystal-case junction. The manufacturer recommends making the heat sink “through the leads” - making the traces as thick as possible and leaving the foil under the chip body. In general, the more “earth” foil left, the better.

By the way, most of the heat is dissipated through the 3rd leg, so you can make this trace very wide and thick (fill it with excess solder).

The LTC4054 chip package may be labeled LTH7 or LTADY.

LTH7 differs from LTADY in that the first can lift a very low battery (on which the voltage is less than 2.9 volts), while the second cannot (you need to swing it separately).

The chip turned out to be very successful, so it has a bunch of analogues: STC4054, MCP73831, TB4054, QX4054, TP4054, SGM4054, ACE4054, LP4054, U4054, BL4054, WPM4054, IT4504, Y1880, PT6102, PT6181, 2, HX6001, LC6000, LN5060, CX9058, EC49016, CYT5026, Q7051. Before using any of the analogues, check the datasheets.

TP4056

The microcircuit is made in a SOP-8 housing (see), it has a metal heat sink on its belly that is not connected to the contacts, which allows for more efficient heat removal. Allows you to charge the battery with a current of up to 1A (the current depends on the current-setting resistor).

The connection diagram requires the bare minimum of hanging elements:

The circuit implements the classical charging process - first charging with a constant current, then with a constant voltage and a falling current. Everything is scientific. If you look at charging step by step, you can distinguish several stages:

Monitoring the voltage of the connected battery (this happens all the time).
Precharge phase (if the battery is discharged below 2.9 V). Charge with a current of 1/10 from the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm) to a level of 2.9 V.
Charging with a maximum constant current (1000 mA at R prog = 1.2 kOhm);
When the battery reaches 4.2 V, the voltage on the battery is fixed at this level. A gradual decrease in the charging current begins.
When the current reaches 1/10 of the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm), the charger turns off.
After charging is complete, the controller continues monitoring the battery voltage (see point 1). The current consumed by the monitoring circuit is 2-3 µA. After the voltage drops to 4.0V, charging starts again. And so on in a circle.

The charge current (in amperes) is calculated by the formula I=1200/R prog. The permissible maximum is 1000 mA.

A real charging test with a 3400 mAh 18650 battery is shown in the graph:

The advantage of the microcircuit is that the charge current is set by just one resistor. Powerful low-resistance resistors are not required. Plus there is an indicator of the charging process, as well as an indication of the end of charging. When the battery is not connected, the indicator blinks every few seconds.

The supply voltage of the circuit should be within 4.5...8 volts. The closer to 4.5V, the better (so the chip heats up less).

The first leg is used to connect a temperature sensor built into the lithium-ion battery (usually the middle terminal of a cell phone battery). If the output voltage is below 45% or above 80% of the supply voltage, charging is suspended. If you don't need temperature control, just plant that foot on the ground.

Attention! This circuit has one significant drawback: the absence of a battery reverse polarity protection circuit. In this case, the controller is guaranteed to burn out due to exceeding the maximum current. In this case, the supply voltage of the circuit directly goes to the battery, which is very dangerous.

The signet is simple and can be done in an hour on your knee. If time is of the essence, you can order ready-made modules. Some manufacturers of ready-made modules add protection against overcurrent and overdischarge (for example, you can choose which board you need - with or without protection, and with which connector).

You can also find ready-made boards with a contact for a temperature sensor. Or even a charging module with several parallel TP4056 microcircuits to increase the charging current and with reverse polarity protection (example).

LTC1734

Also a very simple scheme. The charging current is set by resistor R prog (for example, if you install a 3 kOhm resistor, the current will be 500 mA).

Microcircuits are usually marked on the case: LTRG (they can often be found in old Samsung phones).

Any pnp transistor is suitable, the main thing is that it is designed for a given charging current.

There is no charge indicator on the indicated diagram, but on the LTC1734 it is said that pin “4” (Prog) has two functions - setting the current and monitoring the end of the battery charge. For example, a circuit with control of the end of charge using the LT1716 comparator is shown.

The LT1716 comparator in this case can be replaced with a cheap LM358.

TL431 + transistor

It is probably difficult to come up with a circuit using more affordable components. The most difficult thing here is to find the TL431 reference voltage source. But they are so common that they are found almost everywhere (rarely does a power source do without this microcircuit).

Well, the TIP41 transistor can be replaced with any other one with a suitable collector current. Even the old Soviet KT819, KT805 (or less powerful KT815, KT817) will do.

Setting up the circuit comes down to setting the output voltage (without a battery!!!) using a trim resistor at 4.2 volts. Resistor R1 sets the maximum value of the charging current.

This circuit fully implements the two-stage process of charging lithium batteries - first charging with direct current, then moving to the voltage stabilization phase and smoothly reducing the current to almost zero. The only drawback is the poor repeatability of the circuit (it is capricious in setup and demanding on the components used).

MCP73812

There is another undeservedly neglected microcircuit from Microchip - MCP73812 (see). Based on it, a very budget charging option is obtained (and inexpensive!). The whole body kit is just one resistor!

By the way, the microcircuit is made in a solder-friendly package - SOT23-5.

The only negative is that it gets very hot and there is no charge indication. It also somehow doesn’t work very reliably if you have a low-power power source (which causes a voltage drop).

In general, if the charge indication is not important for you, and a current of 500 mA suits you, then the MCP73812 is a very good option.

NCP1835

A fully integrated solution is offered - NCP1835B, providing high stability of the charging voltage (4.2 ±0.05 V).

Perhaps the only drawback of this microcircuit is its too miniature size (DFN-10 case, size 3x3 mm). Not everyone can provide high-quality soldering of such miniature elements.

Among the undeniable advantages I would like to note the following:

Minimum number of body parts.
Possibility of charging a completely discharged battery (precharge current 30 mA);
Determining the end of charging.
Programmable charging current - up to 1000 mA.
Charge and error indication (capable of detecting non-chargeable batteries and signaling this).
Protection against long-term charging (by changing the capacitance of the capacitor C t, you can set the maximum charging time from 6.6 to 784 minutes).

The cost of the microcircuit is not exactly cheap, but also not so high (~$1) that you can refuse to use it. If you are comfortable with a soldering iron, I would recommend choosing this option.

A more detailed description is in.

Can I charge a lithium-ion battery without a controller?

Yes, you can. However, this will require close control of the charging current and voltage.

In general, it will not be possible to charge a battery, for example, our 18650, without a charger. You still need to somehow limit the maximum charge current, so at least the most primitive memory will still be required.

The simplest charger for any lithium battery is a resistor connected in series with the battery:

The resistance and power dissipation of the resistor depend on the voltage of the power source that will be used for charging.

As an example, let's calculate a resistor for a 5 Volt power supply. We will charge an 18650 battery with a capacity of 2400 mAh.

So, at the very beginning of charging, the voltage drop across the resistor will be:

U r = 5 - 2.8 = 2.2 Volts

Let's say our 5V power supply is rated for a maximum current of 1A. The circuit will consume the highest current at the very beginning of the charge, when the voltage on the battery is minimal and amounts to 2.7-2.8 Volts.

Attention: these calculations do not take into account the possibility that the battery may be very deeply discharged and the voltage on it may be much lower, even to zero.

Thus, the resistor resistance required to limit the current at the very beginning of the charge at 1 Ampere should be:

R = U / I = 2.2 / 1 = 2.2 Ohm

Resistor power dissipation:

P r = I 2 R = 1*1*2.2 = 2.2 W

At the very end of the battery charge, when the voltage on it approaches 4.2 V, the charge current will be:

I charge = (U ip - 4.2) / R = (5 - 4.2) / 2.2 = 0.3 A

That is, as we see, all values do not go beyond the permissible limits for a given battery: the initial current does not exceed the maximum permissible charging current for a given battery (2.4 A), and the final current exceeds the current at which the battery no longer gains capacity ( 0.24 A).

The main disadvantage of such charging is the need to constantly monitor the voltage on the battery. And manually turn off the charge as soon as the voltage reaches 4.2 Volts. The fact is that lithium batteries tolerate even short-term overvoltage very poorly - the electrode masses begin to quickly degrade, which inevitably leads to loss of capacity. At the same time, all the prerequisites for overheating and depressurization are created.

If your battery has a built-in protection board, which was discussed just above, then everything becomes simpler. When a certain voltage is reached on the battery, the board itself will disconnect it from the charger. However, this charging method has significant disadvantages, which we discussed in.

The protection built into the battery will not allow it to be overcharged under any circumstances. All you have to do is control the charge current so that it does not exceed the permissible values for a given battery (protection boards cannot limit the charge current, unfortunately).

Charging using a laboratory power supply

If you have a power supply with current protection (limitation), then you are saved! Such a power source is already a full-fledged charger that implements the correct charge profile, which we wrote about above (CC/CV).

All you need to do to charge li-ion is set the power supply to 4.2 volts and set the desired current limit. And you can connect the battery.

Initially, when the battery is still discharged, the laboratory power supply will operate in current protection mode (i.e., it will stabilize the output current at a given level). Then, when the voltage on the bank rises to the set 4.2V, the power supply will switch to voltage stabilization mode, and the current will begin to drop.

When the current drops to 0.05-0.1C, the battery can be considered fully charged.

As you can see, the laboratory power supply is an almost ideal charger! The only thing it can’t do automatically is make a decision to fully charge the battery and turn off. But this is a small thing that you shouldn’t even pay attention to.

How to charge lithium batteries?

And if we are talking about a disposable battery that is not intended for recharging, then the correct (and only correct) answer to this question is NO.

The fact is that any lithium battery (for example, the common CR2032 in the form of a flat tablet) is characterized by the presence of an internal passivating layer that covers the lithium anode. This layer prevents a chemical reaction between the anode and the electrolyte. And the supply of external current destroys the above protective layer, leading to damage to the battery.

By the way, if we talk about the non-rechargeable CR2032 battery, then the LIR2032, which is very similar to it, is already a full-fledged battery. It can and should be charged. Only its voltage is not 3, but 3.6V.

How to charge lithium batteries (be it a phone battery, 18650 or any other li-ion battery) was discussed at the beginning of the article.

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