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 a 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're talking about about the two-stage charge profile of 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's 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.

To date maximum capacity 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 one 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's another option printed circuit board with SMD LED and micro USB connector:

LTC4054 (STC4054)

Very simple circuit, 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:

1. Monitoring the voltage of the connected battery (this happens all the time).
2. 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.
3. Charging with a maximum constant current (1000 mA at R prog = 1.2 kOhm);
4. 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.
5. 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.
6. 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 the temperature sensor built into the lithium-ion battery (usually the middle terminal of the battery cell phone). 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).

A transistor will do just fine any p-n-p, 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). On its basis it turns out very a budget option charging (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:

1. Minimum number of body parts.
2. Possibility of charging a completely discharged battery (precharge current 30 mA);
3. Determining the end of charging.
4. Programmable charging current - up to 1000 mA.
5. Charge and error indication (capable of detecting non-chargeable batteries and signaling this).
6. 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.

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 valid values for this 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.

At first, when the battery is still discharged, laboratory block 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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The cordless tool is more mobile and easier to use compared to its networked counterparts. But we must not forget about the significant disadvantage of cordless tools; as you yourself understand, the fragility of batteries. Buying new batteries separately is comparable in price to purchasing a new tool.

After four years of service, my first screwdriver, or rather the batteries, began to lose capacity. To begin with, I assembled one from two batteries by choosing working “banks,” but this modernization did not last long. I converted my screwdriver to a corded one - it turned out to be very inconvenient. I had to buy the same, but new 12 volt “Interskol DA-12ER”. The batteries in the new screwdriver lasted even less. As a result, two working screwdrivers and more than one working battery.

There is a lot written on the Internet about how to solve this problem. It is proposed to convert used Ni-Cd batteries into Li-ion batteries standard size 18650. At first glance, there is nothing complicated about this. You remove the old Ni-Cd batteries from the case and install new Li-ion ones. But it turned out that not everything is so simple. The following describes what you should pay attention to when upgrading your cordless tool.

For the remodel you will need:

I'll start with 18650 lithium-ion batteries. Purchased at.

The nominal voltage of the elements is 18650 - 3.7 V. According to the seller, the capacity is 2600 mAh, marking ICR18650 26F, dimensions 18 by 65 mm.

The advantages of Li-ion batteries over Ni-Cd are smaller dimensions and weight, with a higher capacity, as well as the absence of the so-called “memory effect”. But lithium-ion batteries have serious disadvantages, namely:

1. Negative temperatures sharply reduce capacity, which cannot be said about nickel-cadmium batteries. Hence the conclusion - if the tool is often used at subzero temperatures, then replacing it with Li-ion will not solve the problem.

2. Discharge below 2.9 - 2.5V and overcharge above 4.2V can be critical, and complete failure is possible. Therefore, a BMS board is needed to control charge and discharge; if it is not installed, the new batteries will quickly fail.

The Internet mainly describes how to convert a 14-volt screwdriver - it is ideal for modernization. At serial connection four 18650 cells and rated voltage 3.7V. we get 14.8V. - just what you need, even with a full charge plus another 2V, this is not dangerous for the electric motor. What about a 12V instrument? There are two options: install 3 or 4 18650 elements, if three then seem to be not enough, especially with partial discharge, and if four - a bit too much. I chose four and in my opinion I made the right choice.

And now about the BMS board, it is also from AliExpress.

This is the so-called battery charge and discharge control board, specifically in my case CF-4S30A-A. As you can see from the markings, it is designed for a battery of four 18650 “cans” and a discharge current of up to 30A. It also has a built-in so-called “balancer”, which controls the charge of each element separately and eliminates uneven charging. For proper operation of the board, batteries for assembly are taken from the same capacity and preferably from the same batch.

In general, there are a great variety of BMS boards on sale with different characteristics. I don’t recommend taking it for a current lower than 30A - the board will constantly go into protection and to restore operation, some boards need to be briefly supplied with charging current, and to do this you need to remove the battery and connect it to a charger. The board we are considering does not have such a drawback; you just release the trigger of the screwdriver and in the absence of short circuit currents, the board will turn on itself.

The original universal charger was perfect for charging the converted battery. In recent years, Interskol has begun to equip its tools with universal chargers.

The photo shows to what voltage the BMS board charges my battery together with the standard charger. The voltage on the battery after charging is 14.95V, slightly higher than what is needed for a 12-volt screwdriver, but this is probably even better. My old screwdriver became faster and more powerful, and the fears that it would burn out gradually dissipated after four months of use. That seems to be all the main nuances, you can start remaking.

We disassemble the old battery.

We solder the old cans and leave the terminals along with the temperature sensor. If you also remove the sensor, it will not turn on when using the standard charger.

According to the diagram in the photo, we solder 18650 cells into one battery. The jumpers between the “banks” must be made with a thick wire of at least 2.5 square meters. mm, since the currents when operating a screwdriver are large, and with a small cross-section, the power of the tool will sharply drop. They write online that Li-ion batteries cannot be soldered because they are afraid of overheating, and they recommend connecting them using spot welding. You can only solder by needing a soldering iron with at least 60 watts of power. The most important thing is to solder quickly so as not to overheat the element itself.

It should be approximately so that it fits into the battery case.

Inventions and the use of tools with autonomous power sources have become one of the business cards our time. New active components are being developed and introduced to improve the performance of battery assemblies. Unfortunately, batteries cannot work without recharging. And if on devices that have constant access to the power grid, the issue is solved by built-in sources, then for powerful power sources, for example, a screwdriver, separate chargers for lithium batteries are necessary, taking into account the peculiarities various types batteries.

In recent years, products based on lithium-ion active components have been increasingly used. And this is quite understandable, since these power supplies have proven themselves to be very good:

• they have no memory effect;
• Self-discharge has been almost completely eliminated;
• can work at sub-zero temperatures;
• hold the discharge well.
• the number was increased to 700 cycles.

But, each type of battery has its own characteristics. Thus, the lithium-ion component requires the design of elementary batteries with a voltage of 3.6V, which requires some individual features for such products.

Recovery Features

With all the advantages of lithium-ion batteries, they have their drawbacks - this is the possibility of internal short-circuiting of elements during charging overvoltage due to active crystallization of lithium in the active component. There is also a limitation on minimum value voltage, which makes it impossible for the active component to accept electrons. To eliminate the consequences, the battery is equipped with an internal controller that breaks the circuit of elements with the load when critical values ​​are reached. Such cells are stored best when charged to 50% at +5 - 15° C. Another feature lithium-ion batteries is that the service life of a battery depends on the time of its manufacture, regardless of whether it has been in use or not, or in other words, it is subject to the “aging effect”, which limits its service life to five years.

Charging lithium-ion batteries

The simplest single cell charging device

In order to understand more complex charging schemes for lithium-ion batteries, let's consider a simple charger for lithium batteries, more precisely for one battery.

The basis of the circuit is control: a TL 431 microcircuit (acts as an adjustable zener diode) and one reverse conduction transistor.
As can be seen from the diagram, the control electrode TL431 is included in the base of the transistor. Setting up the device comes down to the following: you need to set the voltage at the output of the device to 4.2V - this is set by adjusting the zener diode by connecting resistance R4 - R3 with a nominal value of 2.2 kOhm and 3 kOhm to the first leg. This circuit is responsible for adjusting the output voltage, the voltage adjustment is only set once and is stable.

Next, the charge current is regulated, the adjustment is made by resistance R1 (in the diagram with a nominal value of 3 Ohms) if the emitter of the transistor is turned on without resistance, then the input voltage will also be at the charging terminals, that is, it is 5V, which may not meet the requirements.

Also, in this case, the LED will not light up, but it signals the current saturation process. The resistor can be rated from 3 to 8 ohms.
To quickly adjust the voltage across the load, resistance R3 can be set adjustable (potentiometer). The voltage is adjusted without load, that is, without element resistance, with a nominal value of 4.2 - 4.5V. After reaching the required value, it is enough to measure the resistance value of the variable resistor and install the main part of the required value in its place. If the required value is not available, it can be assembled from several pieces using a parallel or serial connection.

Resistance R4 is designed to open the base of the transistor, its nominal value should be 220 Ohms. As the battery charge increases, the voltage will increase, the control electrode of the transistor base will increase the emitter-collector contact resistance, reducing the charging current.

The transistor can be used KT819, KT817 or KT815, but then you will have to install a radiator for cooling. Also, a radiator will be required if currents exceed 1000mA. In general, this classic scheme simplest charging.

Improvement of the charger for lithium li-ion batteries

When it becomes necessary to charge lithium-ion batteries connected from several soldered unit cells, it is best to charge the cells separately using a monitoring circuit that will monitor the charging of each individual battery individually. Without this circuit, a significant deviation in the characteristics of one element in a series-soldered battery will lead to a malfunction of all batteries, and the unit itself will even be dangerous due to its possible overheating or even fire.

Charger for 12 volt lithium batteries. Balancer device

The term balancing in electrical engineering means a charging mode that controls each individual element involved in the process, preventing the voltage from increasing or decreasing below the required level. The need for such solutions arises from the features of assemblies with li-ion. If, due to the internal design, one of the elements charges faster than the others, which is very dangerous for the condition of the remaining elements, and as a result of the entire battery. The balancer circuit design is designed in such a way that the circuit elements absorb excess energy, thereby regulating the charging process of an individual cell.

If we compare the principles of charging nickel-cadmium batteries, they differ from lithium-ion batteries, primarily for Ca - Ni, the end of the process is indicated by an increase in the voltage of the polar electrodes and a decrease in the current to 0.01 mA. Also, before charging, this source must be discharged to at least 30% of the original capacity; if this condition is not maintained, a “memory effect” occurs in the battery, which reduces the battery capacity.

With the Li-Ion active component the opposite is true. Completely discharging these cells can lead to irreversible consequences and dramatically reduce the ability to charge. Often, low-quality controllers may not provide control over the level of battery discharge, which can lead to malfunctions of the entire assembly due to one cell.

A way out of the situation may be to use the above-discussed circuit on an adjustable zener diode TL431. A load of 1000 mA or more can be achieved by installing more powerful transistor. Such cells connected directly to each cell will protect against incorrect charging.

The transistor should be selected based on power. Power is calculated using the formula P = U*I, where U is voltage, I is charging current.

For example, with a charging current of 0.45 A, the transistor must have a power dissipation of at least 3.65 V * 0.45 A = 1.8 W. and this is large for internal transitions current load, so it is better to install the output transistors in radiators.

Below is an approximate calculation of the values ​​of resistors R1 and R2 for different charge voltages:

22.1k + 33k => 4.16 V

15.1k + 22k => 4.20 V

47.1k + 68k => 4.22 V

27.1k + 39k => 4.23 V

39.1k + 56k => 4.24 V

33k + 47k => 4.25 V

Resistance R3 is the load based on the transistor. Its resistance can be 471 Ohm - 1.1 kOhm.

But, when implementing these circuit solutions, a problem arose: how to charge a separate cell in a battery pack? And such a solution was found. If you look at the contacts on the charging leg, then on the recently produced cases with lithium-ion batteries there are as many contacts as there are individual cells in the battery; naturally, on the charger, each such element is connected to a separate controller circuit.

In terms of cost, such a charger is slightly more expensive than a linear device with two contacts, but it is worth it, especially when you consider that assemblies with high-quality lithium-ion components cost up to half the cost of the product itself.

Pulse charger for lithium li-ion batteries

Recently, many leading companies producing hand tools with self-powered, widely advertises fast chargers. For these purposes, pulse converters based on pulse-width modulated signals (PWM) were developed to restore power supplies for screwdrivers based on a PWM generator on the UC3842 chip; a flyback AS-DS converter with a load of pulse transformer.

Next, we will consider the operation of the circuit of the most common source (see the attached circuit): mains voltage 220V is supplied to the diode assembly D1-D4, for these purposes any diodes with a power of up to 2A are used. Ripple smoothing occurs on capacitor C1, where a voltage of about 300V is concentrated. This voltage is the power supply for a pulse generator with transformer T1 at the output.

The initial power to start the integrated circuit A1 is supplied through resistor R1, after which the pulse generator of the microcircuit is turned on, which outputs them to pin 6. Next, the pulses are supplied to the gate of the powerful field effect transistor VT1 opening it. The drain circuit of the transistor supplies power to the primary winding of the pulse transformer T1. After which the transformer is switched on and the transmission of pulses to the secondary winding begins. The pulses of the secondary winding 7 - 11 after rectification by the VT6 diode are used to stabilize the operation of the A1 microcircuit, which in full generation mode consumes much more current than it receives through the circuit from resistor R1.

In the event of a malfunction of the D6 diodes, the source switches to pulsation mode, alternately starting the transformer and stopping it, while a characteristic pulsating “squeak” is heard; let’s see how the circuit works in this mode.

Power through R1 and capacitor C4 start the chip's oscillator. After startup, higher current is required for normal operation. If D6 malfunctions, no additional power is supplied to the microcircuit and generation stops, then the process is repeated. If diode D6 is working properly, it immediately turns on the pulse transformer under full load. During normal startup of the generator, a pulse current of 12 - 14V appears on winding 14-18 (at idle 15V). After rectification by diode V7 and smoothing of the pulses by capacitor C7, the pulse current is supplied to the battery terminals.

A current of 100 mA does not harm the active component, but increases the recovery time by 3-4 times, reducing its time from 30 minutes to 1 hour. ( source - magazine online edition Radioconstructor 03-2013)

Fast charger G4-1H RYOBI ONE+ BCL14181H

Pulse device for 18 volt lithium batteries produced by the German company Ryobi, manufactured in the People's Republic of China. The pulse device is suitable for lithium-ion, nickel-cadmium 18V. Designed for normal operation at temperatures from 0 to 50 C. The circuit design provides two power supply modes for voltage and current stabilization. Pulse current supply ensures optimal recharge of each individual battery.

The device is made in an original case made of impact-resistant plastic. Forced cooling from a built-in fan is used, with automatic switching on upon reaching 40° C.

Characteristics:

• Minimum charge time 18V at 1.5 A/h - 60 minutes, weight 0.9 kg, dimensions: 210 x 86 x 174 mm. The charging process is indicated by a blue LED; when completed, the red LED lights up. There is a fault diagnosis, which lights up when there is a fault in the assembly with a separate light on the case.
• Power supply single phase 50Hz. 220V. The length of the network cable is 1.5 meters.

Charging station repair

If it happens that the product has ceased to perform its functions, it is best to contact specialized workshops, but basic faults can be eliminated with your own hands. What to do if the power indicator is not on, let’s look at some simple faults using the station as an example.

This product is designed to operate with 12V, 1.8A lithium-ion batteries. The product is made with a step-down transformer; the conversion of reduced alternating current is performed by a four-diode bridge circuit. Installed to smooth out pulsation electrolytic capacitor. The indication includes LEDs for mains power, start and end of saturation.

So, if the network indicator does not light up. First of all, it is necessary to verify the integrity of the circuit of the primary winding of the transformer through the power plug. To do this, you need to test the integrity of the primary winding of the transformer through the pins of the mains power plug with an ohmmeter by touching the probes of the device to the pins of the mains plug; if the circuit shows an open circuit, then you need to inspect the parts inside the housing.

The fuse may break; usually it is a thin wire, stretched in a porcelain or glass case, which burns out when overloaded. But some companies, for example, Interskol, in order to protect the transformer windings from overheating, install a thermal fuse between the turns of the primary winding, the purpose of which, when the temperature reaches 120 - 130 ° C, is to break the power supply circuit of the network and, unfortunately, after the break does not restore.

Usually the fuse is located under the cover paper insulation of the primary winding, after opening which, this part can be easily found. To bring the circuit back into working condition, you can simply solder the ends of the winding into one whole, but you need to remember that the transformer remains without short circuit protection and it is best to install a regular mains fuse instead of a thermal fuse.

If the primary winding circuit is intact, the secondary winding and bridge diodes ring. To check the continuity of the diodes, it is better to unsolder one end from the circuit and check the diode with an ohmmeter. When connecting the ends to the terminals of the probes alternately in one direction, the diode should show an open circuit, in the other, a short circuit.

Thus, it is necessary to check all four diodes. And, if, indeed, we got into the circuit, then it is best to immediately change the capacitor, because diodes are usually overloaded due to high electrolyte in the capacitor.

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I made myself a charger for four lithium-ion batteries. Someone will now think: well, he did it and did it, there are plenty of them on the Internet. And I want to say right away that my design is capable of charging either one battery or four at once. All batteries are charged independently of each other.
This makes it possible to simultaneously charge batteries from different devices and with different initial charges.
I made a charger for 18650 batteries, which I use in a flashlight, powerbanks, laptop, etc.
The circuit consists of ready-made modules and is assembled very quickly and simply.

Will need

• - 4 things.
• - 4 things.
• Stationery clips.

Manufacturing a charger for different numbers of batteries

First we'll make the battery compartment. To do this, take a universal circuit board with big amount holes and regular paper clips.

We bite off these corners from the paper clips.

We insert it into the board, having previously tried on the length of the batteries you need. Because such a charger can be made not only for 18650 batteries.

We solder parts of the paper clips to the bottom of the board.

Then we take the charging controllers and place them on the remaining space on the board, preferably opposite each battery.

The charging controller will be mounted on these legs, made from a PLS connector.

Solder the module on top and to the board below. These legs will carry the power current to the module and the charging current to the batteries.

Four sections are ready.

Next, to switch charging points, we will install buttons or toggle switches.

The whole thing connects like this:

You may ask - why are there only three buttons and not four? And I will answer - since one module will always work, because one battery will always be charged, otherwise there is no point in plugging in a charger at all.
We solder the conductive tracks.

The result is that with buttons you can connect a place to charge from 1 to 4 batteries.

An LED is installed on the charge module, which indicates that the battery that is being charged from it is charged or not.
I assembled the entire device in half an hour. It is powered by a 5-volt power supply (adapter), which, by the way, also needs to be chosen wisely so that it charges all four batteries at once. The entire circuit can also be powered from a USB computer.
We connect the adapter to the first module, and then turn on the necessary buttons and the voltage from the first module will go to other places, depending on the switches that are turned on.

Hi all! Today I’ll tell you and show you charging circuit for lithium-ion batteries from 12 volts. Such a charger can be useful when fishing, on a hike to charge flashlights, or at home when using a 12-volt power source.

So, a charger assembled according to this scheme is suitable for lithium-ion batteries with a capacity of 900 mAh or more. The charger can be powered from any 12 V power source or from a car cigarette lighter. The maximum charge current will be about 650 mA.

This is what the finished assembled device looks like:

The scheme is quite simple. Initially, it can be seen that the output voltage of 8.4v is intended for charging a pair (2) of cans. But it is not so. The fact is that the variable resistor in the circuit (R4) is responsible for the voltage. With its help, you can adjust the output voltage for both one 4.2V element and a pair of elements with a total voltage of 8.4V.

To create such a charge you will need:

• Regulator with adjustable output voltage LM317
• 2N2222A or any transistor that handles 800mA
• 2 Capacitors 0.1 µF
• Resistor 1 ohm 1Watt
• Variable resistor 1K
• Not a big heatsink for LM317

Resistor R4 sets the required output voltage
R1 controls the output current

Photo of the board after etching and in assembled condition: