After turning on the device in the network, a certain voltage appears on the resistor R2, which is transmitted to the transistor VT2. Then, the current flows further, as a result of which the VD7 LED begins to burn intensively.

A story about a homemade device

USB charging

You can make a charger for nickel-cadmium batteries based on regular USB port. At the same time, they will be charged with a current with a capacity of approximately 100 mA. The scheme, in this case, will be as follows:

At the moment, there are quite a few different chargers sold in stores, but their cost can be quite high. Given that the main point of various homemade products is precisely to save money, then self-assembly is even more appropriate in this case.

This circuit can be improved by adding an additional circuit to charge a pair of AA batteries. Here's what happened in the end:

To make it more clear, here are the components that were used in the assembly process:

It is clear that we cannot do without elementary tools, so before starting the assembly, you need to make sure that you have everything you need:

• soldering iron;
• solder;
• flux;
• tester;
• tweezers;
• various screwdrivers and a knife.

Read also: Consider which voltage stabilizer to choose?

Interesting material about making your own hands, we recommend viewing

A tester is necessary in order to check the performance of our radio components. To do this, you need to compare their resistance, and then check with the nominal value.

For assembly, we also need a case and a battery compartment. The latter can be taken from the children's Tetris simulator, and the case can be made from a regular plastic case (6.5cm/4.5cm/2cm).

We fix the battery compartment on the case using screws. As a basis for the circuit, the board from the Dandy prefix, which needs to be cut out, is perfect. We remove all unnecessary components, leaving only the power socket. The next step is to solder all the parts based on our scheme.

The power cord for the device You can take a regular cord from computer mouse, which has a USB input, as well as part of the power cord with a plug. When soldering, polarity must be strictly observed, i.e. solder plus to plus, etc. We connect the cable to USB, checking the voltage that is supplied to the plug. The tester should show 5V.

Evaluating the characteristics of a particular charger is difficult without understanding how the exemplary charge should actually flow. li-ion battery A. Therefore, before proceeding directly to the circuits, let's recall 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 of them:

• with lithium cobaltate cathode;
• with 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 sizes and form factors. They can be either in a case version (for example, the 18650 batteries that are popular today) or in a laminated or prismatic version (gel-polymer batteries). The latter are hermetically sealed bags made of a special film, in which the electrodes and the electrode mass are located.

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

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

How to properly charge lithium-ion batteries

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

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

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

1. At the first stage a constant charge current must be provided. The current value is 0.2-0.5C. For accelerated charging, it is allowed to increase the current up 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 in 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 (charger) must be able to raise the voltage at the battery terminals. In fact, at the first stage, the memory works like 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 must make sure that the open-circuit voltage of the circuit can never exceed 6-7 volts. Otherwise, the protection board may fail.

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 capacity value will depend on the charge current: with an accelerated charge it will be slightly less, with a nominal charge - a little more). This moment is the end of the first stage of the charge and serves as a signal for the transition to the second (and last) stage.

2. Second charge stage- this is the charge of the battery with a 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 0.05-0.01С, the charging process is considered completed.

An important nuance in the operation of the correct charger is its complete shutdown from the battery after charging is completed. This is due to the fact that it is extremely undesirable for lithium batteries to be 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 result, a decrease in its capacity. Long stay means tens of hours or more.

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

We have considered 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 to normal operating mode.

At this stage, the charge is provided direct current reduced value 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, which, for example, have 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 how lucky.

Another benefit of pre-charging is the pre-heating of 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, to conclude that the battery is faulty.

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

Exceeding the rated charging voltage by 0.15V can cut the battery life in half. Reducing the charge voltage by 0.1 volts 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 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 fast you would like to charge it and can range from 0.2C to 1C.

For example, for a 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 charge time directly depends on the charge current and is calculated by the formula:

T \u003d C / I charge.

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

3. How to properly charge a lithium polymer battery?

Any lithium batteries charged 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 overdischarge 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 if they do not have a built-in protection board. Therefore, 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 mikrukh (JW01, JW11, K091, G2J, G3J, S8210, S8261, NE57600, etc. 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, then they can be produced both with and without a protection board. The protection module is located in the area of ​​​​the negative terminal of the battery.

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

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

Any battery with protection can easily be converted into an unprotected battery by simply gutting it.

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

Do not confuse PCB-board with PCM-module (PCM - power charge module). If the former serve only to protect 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 a 18650 battery or any other lithium battery? Then we turn to a small selection of ready-made circuit 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 element base.

LM317

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

The circuit is simple, the whole setting comes down to setting the output voltage to 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 completed (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 chip 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 cases:

Pin assignment (pinout):

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

Charging current can be increased up to 3A if you take LM350 instead of LM317. True, it will 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.

The disadvantage of the circuit: the supply voltage must be in the range of 8-12V. This is due to the fact that for the normal operation of the LM317 microcircuit, 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 that can work from USB or from a separate power adapter (for example, a phone charger).

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

A detailed description of these chips from the manufacturer -.

Maximum input voltage from the DC adapter - 7 V, when powered from USB - 6 V. When the supply voltage drops to 3.52 V, the microcircuit turns 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 USB bus, then the maximum charge 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 280mA.

The chips have built-in overheating protection. But even in this case, the circuit continues to work, reducing the charge current by 17mA for every 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 wiring diagram:

If there is a guarantee that the voltage at the output of your adapter cannot exceed 7 volts under any circumstances, 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 any external diodes or external transistors. In general, of course, chic mikruhi! Only they are too small, it is inconvenient to solder. And they are still expensive ().

LP2951

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

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

The charge current is 150 - 300mA, this value is limited by the internal circuits of the LP2951 chip (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 get. The diode is used as a blocking diode to prevent reverse current from the battery to the LP2951 chip when the input voltage is turned off.

This charger produces a fairly low charging current, so any 18650 battery can be charged all night.

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 chip allows you to create the right chargers, besides, it is cheaper than the hyped MAX1555.

A typical switching circuit 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 output of the microcircuit. Its resistance should be in the range of 2-10 kOhm.

The charger assembly looks like this:

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

Here is 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 overheat 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 (agree, there is nowhere easier: a pair of resistors and one conder):

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

I=1000/R. You should not set a large current right away, first see how much the microcircuit will heat up. For my purposes, I took a 2.7 kOhm resistor, while the charge current turned out to be about 360 mA.

It is unlikely that a radiator can be adapted to this microcircuit, 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 leads" - making the tracks as thick as possible and leaving the foil under the microcircuit case. And in general, the more "earth" foil left, the better.

By the way, most of the heat is removed through the 3rd leg, so you can make this track 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 one can lift a very dead battery (on which the voltage is less than 2.9 volts), while the second one cannot (you need to swing it separately).

Микросхема вышла очень удачной, поэтому имеет кучу аналогов: STC4054, MCP73831, TB4054, QX4054, TP4054, SGM4054, ACE4054, LP4054, U4054, BL4054, WPM4054, IT4504, Y1880, PT6102, PT6181, VS6102, HX6001, LC6000, LN5060, CX9058, EC49016, CYT5026, Q7051. Before using any of the analogues, check the datasheets.

TP4056

The microcircuit is made in the SOP-8 package (see), it has a metal heat sink on its belly that is not connected to the contacts, which makes it possible to more efficiently remove heat. 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 attachments:

The circuit implements the classic charge process - first charge 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 all the time).
2. Pre-charge stage (if the battery is discharged below 2.9 V). Charging current 1/10 from the programmed R prog resistor (100mA at R prog = 1.2 kOhm) to the level of 2.9 V.
3. Charging with a maximum constant current (1000mA at R prog = 1.2 kOhm);
4. When the battery reaches 4.2 V, the battery voltage is fixed at this level. A gradual decrease in the charging current begins.
5. When the current reaches 1/10 of the R prog programmed by the resistor (100mA at R prog = 1.2 kOhm), the charger turns off.
6. After charging is completed, 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 turns on again. And so in a circle.

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

A real test of charging 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 only 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 once every few seconds.

The supply voltage of the circuit must lie 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 this is the average output of the battery cell phone). 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 put that foot on the ground.

Attention! This circuit has one significant drawback: the absence of a battery reverse 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 falls on the battery, which is very dangerous.

The seal is simple, done in an hour on the knee. If time suffers, you can order ready-made modules. Some manufacturers of finished 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 multiple TP4056 chips in parallel to increase the charging current and with reverse polarity protection (example).

LTC1734

It's also a very simple design. 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).

Transistor will fit any p-n-p, the main thing is that it be designed for a given charging current.

There is no charge indicator on this 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 end-of-charge control using an 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 from more accessible components. Here the most difficult thing is to find the source of the reference voltage TL431. But they are so common that they are found almost everywhere (rarely what power source does without this microcircuit).

Well, the TIP41 transistor can be replaced by any other 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 trimmer at a level of 4.2 volts. Resistor R1 sets the maximum value of the charging current.

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

MCP73812

There is another undeservedly neglected microchip from Microchip - MCP73812 (see). On its basis it turns out very a budget option charging (and inexpensive!). The whole 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 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 small size (DFN-10 package, size 3x3 mm). Not everyone is able to 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. Ability to charge a completely discharged battery (pre-charge current 30mA);
3. Definition 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 this).
6. Long-term charge protection (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 not so large (~ $ 1) to refuse to use it. If you are friends with a soldering iron, I would recommend opting for this option.

More detailed description is in .

Is it possible to charge a lithium-ion battery without a controller?

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

In general, it will not work to charge the battery, for example, our 18650 without a charger at all. You still need to somehow limit the maximum charge current, so at least the most primitive memory, but 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 depend on the voltage of the power supply that will be used for charging.

Let's, as an example, calculate a resistor for a 5 volt power supply. 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 minimal 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 = U / I = 2.2 / 1 = 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 un - 4.2) / R \u003d (5 - 4.2) / 2.2 \u003d 0.3 A

That is, as we can see, all values ​​do not go beyond the allowable limits 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 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 do not tolerate even a short-term overvoltage very well - 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 higher, then everything is simplified. Upon reaching a certain voltage on the battery, the board itself will disconnect it from the charger. However, this method of charging 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 allowable values ​​for this battery (protection boards cannot limit the charge current, unfortunately).

Charging with a laboratory power supply

If you have a power supply with current protection (limitation) at your disposal, then you are saved! Such a power supply 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 to 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 fall.

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

As you can see, the laboratory PSU is an almost perfect 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 trifle, which is not even worth paying 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 the anode from reacting chemically 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 the CR2032 non-rechargeable battery, that is, the LIR2032, which is very similar to it, is already a full-fledged battery. It can and should be recharged. Only her voltage is not 3, but 3.6V.

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