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

What are lithium batteries

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

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

All 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 standard sizes and form factors. They can be both in a case design (for example, the popular 18650 today) and in a laminated or prismatic design (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 (they all have a nominal voltage of 3.7 volts):

Designation	Standard size	Similar size
XXYY0, Where XX - indication of the diameter in mm, YY - length value in mm, 0 - reflects execution 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 (like AA), but shorter
	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	FROM
	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, therefore 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 used by Sony in all its chargers. Despite the more sophisticated charge controller, this provides a fuller charge for li-ion batteries without compromising their lifespan.

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

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

1. At the first stage 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 mA / h, 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 provide a constant charging current of a given value, the charger circuit (charger) must be able to raise the voltage at the battery terminals. In fact, at the first stage, the charger works like a classical current stabilizer.

Important: if you plan to charge batteries with a built-in protection board (PCB), then when designing the memory circuit, you must 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 a value of 4.2 volts, the battery will gain approximately 70-80% of its capacity (the specific value of the capacity will depend on the charging current: with accelerated charging it will be slightly less, with nominal - slightly more) This moment is the end of the first stage of charging and serves as a signal to go to the second (and last) stage.

2. Second stage of charging - this is a battery charge with constant voltage, but 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. This is due to the fact that for lithium batteries it is extremely undesirable for them to stay under increased voltage for a long time, which usually provides a 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. A long stay means tens of hours or more.

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

We have covered two main stages of charging. However, coverage of the issue of charging lithium batteries would be incomplete if one more stage of charging was not mentioned - the so-called. precharge.

Pre-charge stage (pre-charge) - this stage is used only for deeply discharged batteries (below 2.5 V) to bring them back to normal operating conditions.

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

A preliminary stage is necessary to prevent swelling and depressurization (or even explosion with fire) of damaged batteries, for example, having 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 warming up, and then how lucky.

Another benefit of precharge is to preheat 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 stage of charging and, if the voltage does not rise for a long time, conclude that the battery is faulty.

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

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

To summarize the above, we will outline the main theses:

1. What current 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 an 18650 battery 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 rechargeable batteries?

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

T \u003d 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 the lithium polymer battery?

All lithium batteries charge the same way. It doesn't matter if 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 over discharge of the lithium battery. As a rule, overheating protection is also built into the protection modules.

For safety reasons, it is forbidden to use lithium batteries in household appliances unless they have a built-in protection board. Therefore, all batteries from cell phones always have a PCB board. Output terminals of the battery are located directly on the board:

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

For example, here is a diagram of the BP-6M battery protection board, which were supplied with old Nokia phones:

If we talk about 18650, then they can be produced with or without a protection board. The protection module is located in the area of \u200b\u200bthe negative terminal of the battery.

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

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

Any protected battery easily turns into an unprotected battery, you just need to gut it.

To date, the maximum capacity of the 18650 battery is 3400mAh. Protected batteries must be marked on the case ("Protected").

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

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

Charging schemes for li-ion batteries

All circuits are suitable for charging any lithium battery, it remains only to decide on the charging current and the element base.

LM317

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

The circuit is simple, the whole setup is reduced to setting the output voltage of 4.2 volts using the trimmer resistor R8 (without a connected battery!) And setting the charge current by selecting resistors R4, R6. The power of the resistor R1 is at least 1 Watt.

As soon as the LED goes out, the charging process can be considered complete (the charging current will never decrease to zero). It is not recommended to keep the battery in 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 switching circuit). It is sold on every corner and costs a penny in general (you can take 10 pieces for only 55 rubles).

LM317 comes in different housings:

Pin assignment (pinout):

Analogs of the LM317 microcircuit are: GL317, SG31, SG317, UC317T, ECG1900, LM31MDT, SP900, KR142EN12, KR1157EN1 (the last two are of domestic production).

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

The printed circuit board and assembly are shown below:

The old Soviet transistor KT361 can be replaced with a similar p-n-p 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 within 8-12V. This is due to the fact that for normal operation of the LM317 microcircuit, the difference between the voltage on the battery and the supply voltage must be at least 4.25 volts. Thus, it will not work from the USB port.

MAX1555 or MAX1551

The MAX1551 / MAX1555 are dedicated Li + battery chargers that can be powered by USB or a separate power adapter (such as a phone charger).

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

A detailed description of these microcircuits from the manufacturer -.

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

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

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

The microcircuits have built-in overheating protection. Even so, the circuit continues to operate, decreasing the charge current by 17mA for every degree above 110 ° C.

There is a precharge function (see above): as long as the voltage on the battery 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 under no circumstances can 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 need external diodes or external transistors. In general, of course, gorgeous mikruhi! Only they are too small, it is inconvenient to solder. And they are also expensive ().

LP2951

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

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

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

Use a 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 microcircuit when the input voltage is disconnected.

This charging provides a fairly low charging current, so any 18650 battery can be charged overnight.

The microcircuit can be bought both in a DIP package and in a SOIC package (the cost is about 10 rubles per piece).

MCP73831

The microcircuit allows you to create the right chargers, and it is also cheaper than the hyped MAX1555.

A typical wiring diagram is taken from:

An important advantage of the circuit is the absence of low-resistance power resistors limiting 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 kΩ.

Charging assembly looks like this:

The microcircuit heats up quite well during operation, but this does not seem to interfere with it. Performs its function.

Here is another PCB option 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 greatly simplified by throwing out one or even both LEDs with a transistor. Then it will look like this (you must admit, it's nowhere easier: a pair of resistors and one condenser):

One of the PCB options is available from. The board is designed for elements of standard size 0805.

I \u003d 1000 / R... It is not worth setting a large current right away, first look at how much the microcircuit will heat up. For my own purposes, I took a 2.7 kOhm resistor, while the charge current turned out to be about 360 mA.

A radiator for this microcircuit is unlikely to be able to adapt, and it is not a fact that it will be effective due to the high thermal resistance of the crystal-case transition. The manufacturer recommends making the heat sink "through the pins" - making the tracks as thick as possible and leaving the foil under the microcircuit case. In general, the more "earthy" foil is left, the better.

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

The package for the LTC4054 can be labeled LTH7 or LTADY.

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

The microcircuit came out very successful, therefore it has a bunch of analogues: STC4054, MCP73831, TB4054, QX4054, TP4054, SGM4054, ACE4054, LP4054, U4054, BL4054, WPM4054, IT4504, Y1880, PT6102, PT6181, VS6102, CX6001, LC9050, EC49016, CYT5026, Q7051. Before using any of the analogs, check the datasheet.

TP4056

The microcircuit is made in the SOP-8 case (see), has a metal heat collector on its belly that is not connected to the contacts, which allows for more efficient heat dissipation. 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 very minimum of hinged elements:

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

1. Monitoring the voltage of the connected battery (this happens constantly).
2. Precharge stage (if the battery is discharged below 2.9 V). Charge with a current of 1/10 from the programmed resistor R prog (100mA at R prog \u003d 1.2 kOhm) to the level of 2.9 V.
3. Charging with maximum constant current (1000mA at R prog \u003d 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 that programmed by the R prog resistor (100mA at R prog \u003d 1.2kOhm), the charger turns off.
6. After the end of charging, the controller continues monitoring the battery voltage (see item 1). The current consumed by the monitoring circuit is 2-3 μA. After the voltage drops to 4.0V, the charging turns on again. And so in a circle.

The charge current (in amperes) is calculated by the formula I \u003d 1200 / R prog... The allowed maximum is 1000 mA.

The real charging test with a 18650 battery at 3400 mAh 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 (this way the chip heats up less).

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

Attention! This circuit has one significant drawback: the lack 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 goes directly to the battery, which is very dangerous.

The sign is simple, done in an hour on the knee. If time is running out, 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 lead-out contact for the temperature sensor. Or even a charging module with several paralleled TP4056 chips to increase the charging current and with reverse polarity protection (example).

LTC1734

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

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

The transistor will do any p-n-p in general, the main thing is that it is designed for a given charging current.

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

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

TL431 + transistor

Probably, it is difficult to come up with more affordable components. The tricky part here is finding the TL431 voltage reference. But they are so widespread that they are found almost everywhere (rarely any power supply does without this microcircuit).

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

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

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

MCP73812

There is another undeservedly neglected microcircuit from Microchip - MCP73812 (see). On its basis, a very budgetary charging option (and inexpensive!) Is obtained. The whole body kit is just one resistor!

By the way, the microcircuit is made in a case convenient for soldering - SOT23-5.

The only negative is that it gets very hot and there is no charge indication. It also somehow does not work very reliably if you have a low-power power supply (which gives a voltage drop).

In general, if the charge indication is not important for you, and the 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.

Of the indisputable advantages, I would like to note the following:

1. The minimum number of body kit parts.
2. The ability to charge a fully discharged battery (precharge with a current of 30mA);
3. Determination of the end of charging.
4. Programmable charging current - up to 1000 mA.
5. Charge and error indication (capable of detecting non-rechargeable batteries and signaling about it).
6. Protection against continuous charge (by changing the capacitance of the capacitor C t, you can set the maximum charge time from 6.6 to 784 minutes).

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

A more detailed description is in.

Can a lithium-ion battery be charged without a controller?

Yes, you can. However, this will require tight control over the charging current and voltage.

In general, charging a battery, for example, our 18650 without a charger, will not work. All the same, you need to somehow limit the maximum charge current, so at least the most primitive charger is still required.

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

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

Let's calculate the resistor for a 5 volt power supply as an example. We will charge a 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 \u003d 5 - 2.8 \u003d 2.2 Volts

Suppose our 5V power supply is rated for a maximum current of 1A. The circuit will consume the largest current at the very beginning of the charge, when the voltage on the battery is minimum and is 2.7-2.8 Volts.

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

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

R \u003d U / I \u003d 2.2 / 1 \u003d 2.2 Ohm

Resistor Dissipation Power:

P r \u003d I 2 R \u003d 1 * 1 * 2.2 \u003d 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 \u003d (U ip - 4.2) / R \u003d (5 - 4.2) / 2.2 \u003d 0.3 A

That is, as we can see, all the values \u200b\u200bdo not go beyond the permissible for a given battery: the initial current does not exceed the maximum allowable charge current for a given battery (2.4 A), and the final current exceeds the current at which the battery stops gaining capacity ( 0.24 A).

The main disadvantage of such charging is the need to constantly monitor the voltage on the battery. And manually disconnect the charge as soon as the voltage reaches 4.2 Volts. The fact is that lithium batteries very poorly tolerate even a short-term overvoltage - the electrode masses begin to degrade quickly, which inevitably leads to a 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 a little above, then everything is simplified. Upon reaching a certain voltage on the battery, the board will automatically disconnect it from the charger. However, this charging method has significant disadvantages, which we talked about in.

The protection built into the battery will not allow it to be recharged under any circumstances. All that remains for you to do is to control the charge current so that it does not exceed the permissible values \u200b\u200bfor a given battery (unfortunately, protection boards do not know how to limit the charge current).

Charging with a laboratory power supply

If you have a power supply with current limiting protection, 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 the li-ion is to set 4.2 volts on the power supply 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, a laboratory PSU is almost an ideal charger! The only thing that he does not know how to do automatically is to make the decision to fully charge the battery and turn off. But this is a trifle that is not even worth paying attention to.

How do I charge lithium batteries?

And if we are talking about a disposable battery that is not intended to be recharged, then the correct (and only correct) answer to this question is NONE.

The fact is that any lithium battery (for example, the widespread 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 the anode from chemically reacting with 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 a non-rechargeable CR2032 battery, that is, the LIR2032, which is very similar to it, is already a full-fledged battery. It can and should be charged. Only her voltage is not 3, but 3.6V.

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

85 kopecks / pcs. Buy MCP73812 Rub 65 / pc. Buy NCP1835 Rub 83 / pc. Buy * All ICs with free shipping

Li-ion accumulators of the 18650 type of various capacities are now very widespread. With their purchase, the problem of charging arises and it is necessary in accordance with the technical requirements for the charging process. Some of these requirements are:
- charging with a stable current;
- voltage stabilization mode;
- indication of the end of charging;
- not exceeding the permissible temperature while charging the battery.

We bring to your attention an easy-to-manufacture and commissioning scheme for the storage device of Li-ion batteries, which has proven itself in operation.

The circuit is a current and voltage stabilizer. Until the voltage on the battery during charging reaches the level Ustab. \u003d (R7 / R5 + 1) * Uref (Uref-reference voltage TL431 \u003d 2.5V), TL431 is in the closed state, and the circuit works as a current stabilizer. Istab. \u003d 0.6 / R2 (0.6 is the opening voltage of the KT816V transistor). As soon as the voltage on the battery reaches Ustab., The circuit switches to the voltage stabilization mode. For a Li-ion battery, this value is 4.2V. When the voltage on the battery reaches 4.2V, a yellow LED starts to glow, signaling that the battery is 80-90% charged. The charging current drops to 7… 8mA. Leave the battery in this state for 10-15 hours to reach full capacity.

A little about the purpose of the circuit elements.
LED1 - blue, lights up when the battery (AK) is installed in the charging box with the charger not powered. When the AC voltage is less than 3V, LED1 does not light up.
LED2 is yellow. Serves to indicate the end of the AK charging process. When an uncharged AK is installed in the box, LED2 does not light up. If it is lit, it means that a charged AK is inserted into the box (when the charger is not powered).
R2 - limits the charging current of the AK.
R5, R7 - are used to set a voltage of 4.2V at the contacts of the charging box before installing a battery in it (you can use any one).

All parts of the charger, except for the transistor, are installed on the printed circuit board from the side of the printed conductors:

Board option for those who are not lazy to drill holes in fiberglass:

The transistor is equipped with a small heat sink. During charging, the transistor heats up to 40 ° C. Resistor R2 also heats up, so it is better to install two 10 ohms in parallel to reduce heating.
The voltage of the power supply for charging a single battery is approximately 5V DC. If it is necessary to charge several batteries at once, the power supply voltage is selected so that on each unit it is 4.2V. The power supply is selected from the charging current for each battery. You can use a switching power supply. The dimensions of the charger will be smaller.
Setting up the charger is simple. Without inserting the battery, we supply power to the circuit. Both LEDs should be on. Next, we measure the voltage at the contacts of the charging box. If it is 4.2V, you are in luck and the setup is almost complete. If the voltage is more or less than 4.2V, turn off the power, instead of resistor R5 or R7, we solder a variable multiturn resistor 10k and precisely set the voltage to 4.2V at the box contacts. Having measured the value of the resulting resistance of the tuning resistor, we select the same constant and solder it into the circuit. Once again we check the voltage at the contacts of the charging box. We check the value of the charging current with an ammeter at the contacts of the charging box, without inserting the battery. By selecting the value of the resistor R2, you can set the desired charging current. We are not carried away with large currents, the battery may warm up, which is categorically unacceptable. Due to overheating, the capacity of Li-ion batteries decreases and does not recover.
It is best to charge the batteries one at a time. If you need to charge several batteries at the same time, you can connect the blocks in series according to this scheme.

In this scheme, each battery is charged separately. The voltage at the end of charging on each AK will be 4.2V, and the charging current will be 0.5A. When charging seven batteries simultaneously, for example, the voltage of the power source should be 4.2V * 7 \u003d 29.5V. The power source power is determined by the size of the charging current 0.5A for each AK, i.e. approximately 40W.

Photo of the finished device.

First you need to decide on the terminology.

As such discharge-charge controllers do not exist... This is nonsense. There is no point in controlling the discharge. The discharge current depends on the load - how much it needs, it will take as much. The only thing to do when discharging is to monitor the voltage on the battery to prevent over-discharge. For this they apply.

At the same time, separate controllers charge not only exist, but are absolutely necessary for the implementation of the process of charging li-ion batteries. It is they who set the required current, determine the end of the charge, monitor the temperature, etc. A charge controller is an essential part of anyone.

Based on my experience, I can say that a charge / discharge controller is actually understood as a circuit for protecting the battery from too deep discharge and, conversely, overcharge.

In other words, when we talk about a charge / discharge controller, we are talking about protection built into almost all lithium-ion batteries (PCB or PCM modules). Here she is:

And here they are too:

It is obvious that protection boards are available in different form factors and are assembled using various electronic components. In this article, we will just look at the options for protection schemes for Li-ion batteries (or, if you prefer, discharge / charge controllers).

Charge-discharge controllers

Since this name is so well entrenched in society, we will use it too. Let's start with the most common variant on the DW01 (Plus) chip.

DW01-Plus

Such a protective board for li-ion batteries is found in every second battery from a mobile phone. To get to it, you just need to tear off the self-adhesive with inscriptions, which is pasted over the battery.

The DW01 microcircuit itself is six-legged, and two field-effect transistors are structurally made in one case in the form of an 8-legged assembly.

Pin 1 and 3 are the management of the discharge protection keys (FET1) and overcharge (FET2) respectively. Threshold voltages: 2.4 and 4.25 Volts. Conclusion 2 - a sensor that measures the voltage drop across the field-effect transistors, due to which overcurrent protection is implemented. The contact resistance of the transistors acts as a measuring shunt, therefore the response threshold has a very large spread from product to product.

The whole scheme looks something like this:

The right microcircuit labeled 8205A is the field-effect transistors that play the role of keys in the circuit.

S-8241 Series

SEIKO has developed specialized microcircuits to protect lithium-ion and lithium-polymer batteries from overdischarge / overcharge. S-8241 integrated circuits are used to protect one can.

Overdischarge and overcharge protection keys operate at 2.3V and 4.35V, respectively. The overcurrent protection is activated when the voltage across FET1-FET2 is 200 mV.

AAT8660 Series

LV51140T

A similar protection scheme for lithium single-cell batteries with protection against overdischarge, overcharge, excess charge and discharge currents. Implemented using the LV51140T microcircuit.

Threshold voltages: 2.5 and 4.25 Volts. The second leg of the microcircuit is the input of the overcurrent detector (limit values: 0.2V when discharging and -0.7V when charging). Pin 4 is not used.

R5421N Series

The schematic solution is similar to the previous ones. In operating mode, the microcircuit consumes about 3 μA, in blocking mode - about 0.3 μA (letter C in the designation) and 1 μA (letter F in the designation).

The R5421N series contains several modifications that differ in the magnitude of the trigger voltage during recharge. Details are given in the table:

SA57608

Another version of the charge / discharge controller, only on the SA57608 microcircuit.

The voltages at which the microcircuit disconnects the bank from external circuits depends on the letter index. See table for details:

The SA57608 consumes a fairly large current in sleep mode - about 300 μA, which distinguishes it from the above analogs for the worse (there, the consumed currents are of the order of fractions of a microampere).

LC05111CMT

And finally, we offer an interesting solution from one of the world leaders in the production of electronic components On Semiconductor - a charge-discharge controller on the LC05111CMT microcircuit.

The solution is interesting because the key MOSFETs are built into the microcircuit itself, so only a couple of resistors and one capacitor remained from the attachments.

The contact resistance of the built-in transistors is ~ 11 milliohm (0.011 Ohm). The maximum charge / discharge current is 10A. The maximum voltage between the terminals S1 and S2 is 24 Volts (this is important when combining batteries into batteries).

The microcircuit is produced in the WDFN6 2.6x4.0, 0.65P, Dual Flag package.

The circuit, as expected, provides protection against overcharge / discharge, overcurrent in the load, and overcharging.

Charge controllers and protection circuits - what's the difference?

It is important to understand that protection module and charge controllers are not the same thing. Yes, their functions overlap to some extent, but it would be a mistake to call the protection module built into the battery a charge controller. Now I will explain the difference.

The most important role of any charge controller is to implement the correct charge profile (typically CC / CV - constant current / constant voltage). That is, the charge controller must be able to limit the charging current at a given level, thereby controlling the amount of energy "poured" into the battery per unit of time. Excess energy is released in the form of heat, so any charge controller heats up quite a lot during operation.

For this reason, charge controllers are never built into the battery (unlike protection cards). The controllers are just part of the right charger and nothing more.

In addition, no protection board (or protection module, call it what you will) is capable of limiting the charge current. The board only controls the voltage on the bank itself and, if it goes beyond the predetermined limits, opens the output keys, thereby disconnecting the bank from the outside world. By the way, protection against short-circuit also works on the same principle - in case of a short circuit, the voltage on the bank drops sharply and the protection circuit against deep discharge is triggered.

The confusion between the protection circuits of lithium batteries and charge controllers arose due to the similarity of the response threshold (~ 4.2V). Only in the case of the protection module, the can is completely disconnected from the external terminals, and in the case of the charge controller, it switches to the voltage stabilization mode and a gradual decrease in the charging current.

Modern electronic devices (such as cell phones, laptop computers or tablets) are powered by lithium-ion batteries, which have replaced alkaline counterparts. Nickel-cadmium and nickel-metal hydride batteries gave way to Li─Ion batteries due to the best technical and consumer qualities of the latter. The charge available from the moment of production in such batteries is from four to six percent, after which it begins to decrease with use. During the first 12 months, the capacity of the batteries decreases by 10 to 20%.

Original chargers

Chargers for an ion battery are very similar to similar devices for lead-acid ones, however, they have a higher voltage on the batteries, called "banks" for their external similarity, therefore there are more stringent requirements for tolerance (for example, the permissible voltage difference is only 0, 05 c). The most common format for a can of ionic batteries is 18650, which means that it has a diameter of 1.8 cm and a height of 6.5 cm.

On a note. A standard lithium-ion battery takes up to three hours to charge, and more precisely, the time is determined by its original capacity.

Manufacturers of Li-ion batteries recommend using only original chargers for charging, which are guaranteed to provide the required voltage for the battery and will not destroy part of its capacity by recharging the cell and disrupting the chemical system; full charging of the battery is also undesirable.

Note! During long-term storage, lithium batteries should optimally have a small (no more than 50%) charge; it is also necessary to remove them from the units.

If lithium batteries have a protection board, they are not in danger of overcharging.

A built-in protection board cuts off excessive voltage (more than 3.7 volts per cell) during charging and disconnects the battery if the charge level drops to minimum, usually 2.4 volts. The charge controller detects when the voltage on the bank reaches 3.7 volts and disconnects the charger from the battery. It also monitors the temperature of the battery to prevent overheating and overcurrent. The protection is assembled on the basis of the DV01-P microcircuit. After the circuit is interrupted by the controller, it is restored automatically when the parameters are normalized.

On the microcircuit, a red indicator means a charge, and a green or blue indicator indicates that the battery is charged.

How to properly charge lithium batteries

Well-known manufacturers of li-ion batteries (for example, such as Sony) use a two or three stage charging principle in their chargers, which significantly extends the battery life.

At the output, the charger has a voltage of five volts, and the current value ranges from 0.5 to 1.0 of the nominal battery capacity (for example, for a cell with a capacity of 2200 milliampere-hours, the charger current should be from 1.1 amperes.)

At the initial stage, after connecting the charging for lithium batteries, the current value is from 0.2 to 1.0 of the nominal capacity, while the voltage is 4.1 volts (per cell). Under these conditions, the batteries are charged for 40 to 50 minutes.

To achieve a constant current, the charger circuit must be able to raise the voltage at the battery terminals, at which time the charger for most lithium-ion batteries operates as a conventional voltage regulator.

Important! If it is necessary to charge lithium-ion batteries, which have a built-in protection board, then the open circuit voltage should not exceed six to seven volts, otherwise it will deteriorate.

When the voltage reaches 4.2 volts, the battery capacity will be 70 to 80 percent, signaling the end of the initial charging phase.

The next stage is carried out in the presence of constant voltage.

Additional Information. Some units use a pulse method for faster charging. If the lithium-ion battery has a graphite system, then a voltage limit of 4.1 volts per cell must be observed for them. If this parameter is exceeded, the energy density of the battery will increase and initiate oxidative reactions that shorten the battery life. In modern battery models, special additives are used that allow you to increase the voltage when connecting a charger for li ion batteries up to 4.2 volts plus / minus 0.05 volts.

In simple lithium batteries, the chargers keep the voltage level at 3.9 volts, which is a reliable guarantee of a long service for them.

When delivering current to 1 value of battery capacity, the time to obtain an optimally charged battery will be from 2 to 3 hours. As soon as the charge becomes full, the voltage reaches the cut-off rate, the current value drops rapidly and remains at the level of a couple of percent of the initial value.

If the charging current is artificially increased, the time of using the charger to power the lithium-ion batteries will hardly decrease. In this case, the voltage initially rises faster, but at the same time the duration of the second stage increases.

Some chargers can fully charge the battery in 60-70 minutes, during such charging the second stage is excluded, and the battery can be used after the initial stage (the charge level will also be at 70 percent capacity).

In the third final stage of charging, a compensating charge is carried out. It is carried out not every time, but only once every 3 weeks, when storing (and not using) the batteries. It is not possible to use trickle charging under storage conditions because lithium metallization occurs. However, short-term recharges with constant voltage help avoid charge losses. The termination of charging ends as soon as the voltage reaches 4.2 volts.

Lithium metallization is dangerous by the release of oxygen and sudden pressure build-up, which can lead to fire and even explosion.

DIY battery charger

A charger for lithium-ion batteries is inexpensive, but if you have a little knowledge of electronics, you can make one yourself. If there is no exact information about the origin of the battery elements, and there are doubts about the accuracy of the measuring devices, the charge threshold should be set in the region from 4.1 to 4.15 volts. This is especially true if the battery does not have a protective board.

To assemble a charger for lithium batteries with your own hands, one simplified circuit is enough, of which there are a lot of freely available on the Internet.

For the indicator, you can use a charging type LED, which lights up when the battery charge is significantly reduced, and goes out when it is discharged to zero.

The charger is assembled in the following order:

• there is a suitable case;
• a five-volt power supply and other circuit details are mounted (strictly follow the sequence!);
• a pair of brass strips are cut out and attached to the socket holes;
• using a nut, the distance between the contacts and the connected battery is determined;
• a switch is installed to change the polarity (optional).

If the task is to assemble a charger for 18650 batteries with your own hands, then a more complex circuit and more technical skills will be required.

All lithium-ion batteries need to be recharged from time to time, however, overcharging and over-discharge should be avoided. Maintaining the performance of batteries and maintaining their working capacity for a long time is possible with the help of special chargers. It is advisable to use original chargers, but you can assemble them yourself.

Video

Lithium-ion batteries are the most efficient batteries available today. They are compact, have a high power consumption, and have no memory effect. With all the advantages, they have one significant drawback, their work and the charging process must be carefully controlled. If the battery is discharged below a certain limit or overcharged, it quickly loses its properties, swells and even explodes. The same is the case in the case of overload and short circuits - heating, gas formation and eventually an explosion.

Some lithium-ion batteries have a safety valve to prevent the battery from exploding, but most high-power polymer batteries do not.

In other words, when using lithium-ion batteries, a protection system is required.

Many have probably noticed small boards in mobile phone batteries, and this board is the protection. It protects against deep discharge, overcharge and short circuits or overcurrent.

The scheme of this protection is very simple, on the board there is a pair of microcircuits with small things.

All processes are monitored by the DW01 microcircuit. The second microcircuit is an assembly of two field-effect transistors.The first transistor controls the discharge process, the second is responsible for charging the battery.

During discharge, the microcircuit monitors the voltage drop at the field switch junctions, if it reaches a critical value (150-200mV), the microcircuit closes the transistors, disconnecting the battery from the load. The circuit recovers in less than a second after the load is removed.

The microcircuit monitors the voltage drop at the transitions of the transistors through the second pin.

Depending on the battery capacity, these controllers can radically differ in appearance, short-circuit current and circuit topology, but their function is always the same - to protect the battery from overcharge, deep discharge and overcurrent. Many controllers also provide protection against overheating of the jar, temperature control is carried out by a temperature sensor.

I have accumulated a lot of protection cards from mobile phone batteries and just for one of my projects in which a lithium-ion battery is involved, a protection system was needed. The problem is that these boards are designed for a maximum current of 1 Ampere, and I needed a board with a current of at least 6-7 Amps. Boards with the current needed for my purposes cost less than half a dollar, but I could not wait a month or two. After examining the Chinese boards for aliexpress, I realized that they are not much different from mine. The schematic is the same, only the protection current is higher due to the parallel connection of power transistors.

When field-effect transistors are connected in parallel, the resistance of their channels will be much less, therefore, the voltage drop across them will be less, and the protection operation current will be greater. Parallel connection of keys will make it possible to commute high currents, the more keys, the greater the total commutation current.

The circuit uses standard assemblies of two field workers in one case. They are often used on smart phone battery protection boards and not only.

Assemblies 8205A have a lot of analogs, as well as control ICs DW01.

After assembling the board, I tested it. It turned out exactly what I need for the project:

• The board charges the battery to a voltage of 4.2V and disconnects it from the charger;
• When the battery is discharged below 2.5V, the battery is disconnected from the load;
• At currents above 12-13 Amperes, the battery is disconnected.

Lithium-ion batteries have low self-discharge, but a battery supplemented with such a board will discharge faster than a battery without protection. The current consumption of the protection circuit is scanty, and is about 2.5 MICROamperes.

More on how the protection board works

(youtube) lXKELGFo79o (/ youtube)

Putting together a powerful control board

(youtube) _w-AUCG4k_0 (/ youtube)

Protection board for one bank LI-ION http://ali.pub/28463y

Protection board for two cans