Li ion discharge circuit. Charger for Li-ion for free
Many people probably have a problem with charging a Li-Ion battery without a controller; I had this situation. I received a dead laptop, and there were 4 SANYO UR18650A cans in the battery that were alive.
I decided to replace LED flashlight, instead of three AAA batteries. The question arose about charging them.
After digging around on the Internet I found a bunch of diagrams, but details are a little tight in our city.
I tried charging from a cell phone charger, the problem is in charge control, you need to constantly monitor the heating, it just starts to heat up, you need to disconnect from charging, otherwise the battery will be damaged in the best case, otherwise you can start a fire.
I decided to do it myself. I bought a bed for the battery in the store. I bought a charger at a flea market. To make it easier to track the end of the charge, it is advisable to find one with a two-color LED that signals the end of the charge. It switches from red to green when charging is complete.
But you can also use a regular one. The charger can be replaced with a USB cord and charged from a computer or charger with a USB output.
My charger is only for batteries without a controller. I took the controller from an old cell phone battery. It ensures that the battery is not overcharged above a voltage of 4.2 V, or discharged below 2...3 V. Also, the protection circuit saves from short circuits by disconnecting the bank itself from the consumer at the moment of a short circuit.
It contains the DW01 chip and an assembly of two SM8502A MOSFET transistors (M1, M2). There are also other markings, but the circuits are similar to this one and work similarly.
Cell phone battery charge controller.
Controller circuit.
Another controller circuit.
The main thing is not to confuse the polarity of soldering the controller to the bed and the controller to the charger. The controller board has “+” and “-” contacts.
It is advisable to make a clearly visible indicator in the bed near the positive contact, using red paint or self-adhesive film, to avoid polarity reversal.
I put everything together and this is what happened.
Charges great. When the voltage reaches 4.2 volts, the controller disconnects the battery from charging and the LED switches from red to green. Charging is complete. You can charge other Li-Ion batteries, just use a different bed. Good luck to all.
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 are 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 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
Most the right way Lithium batteries are charged in two stages. This is the method used Sony company in all of its chargers. Despite a more complex charge controller, this ensures a more complete charge of li-ion batteries without reducing their service life.
Here we are talking about a two-stage charge profile for lithium batteries, abbreviated as CC/CV (constant current, constant voltage). There are also options with pulse and step currents, but they are not discussed in this article. You can read more about charging with pulsed current.
So, let's look at both stages of charging in more detail.
1. At the first stage A constant charging current must be ensured. The current value is 0.2-0.5C. For accelerated charging, it is allowed to increase the current to 0.5-1.0C (where C is the battery capacity).
For example, for a battery with a capacity of 3000 mAh, the nominal charge current at the first stage is 600-1500 mA, and the accelerated charge current can be in the range of 1.5-3A.
To ensure a constant charging current of a given value, the charger circuit must be able to increase the voltage at the battery terminals. In fact, at the first stage the charger works as a classic current stabilizer.
Important: If you plan to charge batteries with a built-in protection board (PCB), then when designing the charger circuit you need to make sure that the open circuit voltage of the circuit can never exceed 6-7 volts. IN otherwise The protection board may fail.
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 operation of a proper charger is its complete shutdown from the battery after charging is completed. 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 ensured DC 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 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 must be able to monitor the voltage on the battery during the preliminary charging phase and, in case the voltage for a long time does not rise, conclude that the battery is faulty.
All stages of charging a lithium-ion battery (including the pre-charge stage) are schematically depicted in this graph: 
Exceeding the rated charging voltage by 0.15V can reduce the battery life by half. Lowering the charge voltage by 0.1 volt reduces the capacity of a charged battery by about 10%, but significantly extends its service life. The voltage of a fully charged battery after removing it from the charger is 4.1-4.15 volts.
Let me summarize the above and outline the main points:
1. What current should I use to charge a li-ion battery (for example, 18650 or any other)?
The current will depend on how quickly you would like to charge it and can range from 0.2C to 1C.
For example, for a battery size 18650 with a capacity of 3400 mAh, the minimum charge current is 680 mA, and the maximum is 3400 mA.
2. How long does it take to charge, for example, the same 18650 batteries?
The charging time directly depends on the charging current and is calculated using the formula:
T = C / I charge.
For example, the charging time of our 3400 mAh battery with a current of 1A will be about 3.5 hours.
3. How to properly charge a lithium polymer battery?
All lithium batteries charge the same way. It doesn't matter whether it is lithium polymer or lithium ion. For us, consumers, there is no difference.
What is a protection board?
The protection board (or PCB - power control board) is designed to protect against short circuit, overcharge and overdischarge of the lithium battery. As a rule, overheating protection is also built into the protection modules.
For safety reasons, the use of lithium batteries in household appliances, if they do not have a built-in protection board. Therefore, in all batteries from cell phones There is always a PCB board. The battery output terminals are located directly on the board: 
These boards use a six-legged charge controller on a specialized device (JW01, JW11, K091, G2J, G3J, S8210, S8261, NE57600 and other analogues). The task of this controller is to disconnect the battery from the load when the battery is completely discharged and disconnect the battery from charging when it reaches 4.25V.
Here, for example, is a diagram of the BP-6M battery protection board that was supplied with old Nokia phones: 
If we talk about 18650, they can be produced either with or without a protection board. The protection module is located near the negative terminal of the battery. 
The board increases the length of the battery by 2-3 mm. 
Batteries without a PCB module are usually included in batteries that come with their own protection circuits.
Any battery with protection can easily turn into a battery without protection; you just need to gut it. 
Today, the maximum capacity of the 18650 battery is 3400 mAh. Batteries with protection must have a corresponding designation on the case ("Protected"). 
Do not confuse the PCB board with the PCM module (PCM - power charge module). If the former serve only the purpose of protecting the battery, then the latter are designed to control the charging process - they limit the charge current at a given level, control the temperature and, in general, ensure the entire process. The PCM board is what we call a charge controller.
I hope now there are no questions left, how to charge an 18650 battery or any other lithium battery? Then we move on to a small selection of ready-made circuit solutions for chargers (the same charge controllers).
Charging schemes for li-ion batteries
All circuits are suitable for charging any lithium battery; all that remains is to decide on the charging current and the element base.
LM317
Diagram of a simple charger based on the LM317 chip with a charge indicator: 
The circuit is the simplest, the whole setup comes down to setting the output voltage to 4.2 volts using trimming resistor R8 (without a connected battery!) and setting the charging current by selecting resistors R4, R6. The power of resistor R1 is at least 1 Watt.
As soon as the LED goes out, the charging process can be considered completed (the charging current will never decrease to zero). It is not recommended to keep the battery on this charge for a long time after it is fully charged.
The lm317 microcircuit is widely used in various voltage and current stabilizers (depending on the connection circuit). It is sold on every corner and costs pennies (you can take 10 pieces for only 55 rubles).
LM317 comes in different housings: 
Pin assignment (pinout): 
Analogues of the LM317 chip are: GL317, SG31, SG317, UC317T, ECG1900, LM31MDT, SP900, KR142EN12, KR1157EN1 (the last two are domestically produced).
The charging current can be increased to 3A if you take LM350 instead of LM317. It will, however, be more expensive - 11 rubles/piece.
The printed circuit board and circuit assembly are shown below: 
The old Soviet transistor KT361 can be replaced with a similar 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 accurately.
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 to the LP2951 chip when the input voltage is turned off. 
This charger produces a fairly low charging current, so any 18650 battery can charge overnight.
The microcircuit can be purchased both in a DIP package and in a SOIC package (costs about 10 rubles per piece).
MCP73831
The chip allows you to create the right chargers, and it’s also cheaper than the much-hyped MAX1555. 
A typical connection diagram is taken from: 
An important advantage of the circuit is the absence of low-resistance powerful resistors that limit the charge current. Here the current is set by a resistor connected to the 5th pin of the microcircuit. Its resistance should be in the range of 2-10 kOhm.
The assembled charger looks like this: 
The microcircuit heats up quite well during operation, but this does not seem to bother it. It fulfills its function.
Here is another version of a printed circuit board with an SMD LED and a micro-USB connector: 
LTC4054 (STC4054)
Very simple 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 couple 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, VS61 02, HX6001, LC6000, LN5060, CX9058, EC49016, CYT5026, Q7051. Before using any of the analogues, check the datasheets.
TP4056
The microcircuit is made in a SOP-8 housing (see), it has a metal heat sink on its belly that is not connected to the contacts, which allows for more efficient heat removal. Allows you to charge the battery with a current of up to 1A (the current depends on the current-setting resistor). 
The connection diagram requires the bare minimum of hanging elements: 
The circuit implements the classical charging process - first charging with a constant current, then with a constant voltage and a falling current. Everything is scientific. If you look at charging step by step, you can distinguish several stages:
- Monitoring the voltage of the connected battery (this happens all the time).
- Precharge phase (if the battery is discharged below 2.9 V). Charge with a current of 1/10 from the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm) to a level of 2.9 V.
- Charging with a maximum constant current (1000 mA at R prog = 1.2 kOhm);
- When the battery reaches 4.2 V, the voltage on the battery is fixed at this level. A gradual decrease in the charging current begins.
- When the current reaches 1/10 of the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm), the charger turns off.
- After charging is complete, the controller continues monitoring the battery voltage (see point 1). The current consumed by the monitoring circuit is 2-3 µA. After the voltage drops to 4.0V, charging starts again. And so on in a circle.
The charge current (in amperes) is calculated by the formula I=1200/R prog. The permissible maximum is 1000 mA.
A real charging test with a 3400 mAh 18650 battery is shown in the graph: 
The advantage of the microcircuit is that the charge current is set by just one resistor. Powerful low-resistance resistors are not required. Plus there is an indicator of the charging process, as well as an indication of the end of charging. When the battery is not connected, the indicator blinks every few seconds.
The supply voltage of the circuit should be within 4.5...8 volts. The closer to 4.5V, the better (so the chip heats up less).
The first leg is used to connect a temperature sensor built into the lithium-ion battery (usually the middle terminal of a cell phone battery). If the output voltage is below 45% or above 80% of the supply voltage, charging is suspended. If you don't need temperature control, just plant that foot on the ground.
Attention! This circuit has one significant drawback: the absence of a battery reverse polarity protection circuit. In this case, the controller is guaranteed to burn out due to exceeding the maximum current. In this case, the supply voltage of the circuit directly goes to the battery, which is very dangerous.
The signet is simple and can be done in an hour on your knee. If time is of the essence, you can order ready-made modules. Some manufacturers of ready-made modules add protection against overcurrent and overdischarge (for example, you can choose which board you need - with or without protection, and with which connector). 
You can also find ready-made boards with a contact for the 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 hardest part here is finding 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:
- Minimum number of body parts.
- Possibility of charging a completely discharged battery (precharge current 30 mA);
- Determining the end of charging.
- Programmable charging current - up to 1000 mA.
- Charge and error indication (capable of detecting non-chargeable batteries and signaling this).
- Protection against long-term charging (by changing the capacitance of the capacitor C t, you can set the maximum charging time from 6.6 to 784 minutes).
The cost of the microcircuit is not exactly cheap, but also not so high (~$1) that you can refuse to use it. If you are comfortable with a soldering iron, I would recommend choosing this option.
More detailed description is in .
Can I charge a lithium-ion battery without a controller?
Yes, you can. However, this will require close control of the charging current and voltage.
In general, it will not be possible to charge a battery, for example, our 18650, without a charger. You still need to somehow limit the maximum charge current, so at least the most primitive memory will still be required.
The simplest charger for any lithium battery is a resistor connected in series with the battery: 
The resistance and power dissipation of the resistor depend on the voltage of the power source that will be used for charging.
As an example, let's calculate a resistor for a 5 Volt power supply. We will charge an 18650 battery with a capacity of 2400 mAh.
So, at the very beginning of charging, the voltage drop across the resistor will be:
U r = 5 - 2.8 = 2.2 Volts
Let's say our 5V power supply is rated for a maximum current of 1A. The circuit will consume the highest current at the very beginning of the charge, when the voltage on the battery is minimal and amounts to 2.7-2.8 Volts.
Attention: these calculations do not take into account the possibility that the battery may be very deeply discharged and the voltage on it may be much lower, even to zero.
Thus, the resistor resistance required to limit the current at the very beginning of the charge at 1 Ampere should be:
R = U / I = 2.2 / 1 = 2.2 Ohm
Resistor power dissipation:
P r = I 2 R = 1*1*2.2 = 2.2 W
At the very end of the battery charge, when the voltage on it approaches 4.2 V, the charge current will be:
I charge = (U ip - 4.2) / R = (5 - 4.2) / 2.2 = 0.3 A
That is, as we see, all values do not go beyond the permissible limits for a given battery: the initial current does not exceed the maximum permissible charging current for a given battery (2.4 A), and the final current exceeds the current at which the battery no longer gains capacity ( 0.24 A).
The main disadvantage of such charging is the need to constantly monitor the voltage on the battery. And manually turn off the charge as soon as the voltage reaches 4.2 Volts. The fact is that lithium batteries tolerate even short-term overvoltage very poorly - the electrode masses begin to quickly degrade, which inevitably leads to loss of capacity. At the same time, all the prerequisites for overheating and depressurization are created.
If your battery has a built-in protection board, which was discussed just above, then everything becomes simpler. When a certain voltage is reached on the battery, the board itself will disconnect it from the charger. However, this charging method has significant disadvantages, which we discussed in.
The protection built into the battery will not allow it to be overcharged under any circumstances. All you have to do is control the charge current so that it does not exceed the permissible values for a given battery (protection boards cannot limit the charge current, unfortunately).
Charging using a laboratory power supply
If you have a power supply with current protection (limitation), then you are saved! Such a power source is already a full-fledged charger that implements the correct charge profile, which we wrote about above (CC/CV).
All you need to do to charge li-ion is set the power supply to 4.2 volts and set the desired current limit. And you can connect the battery.
Initially, when the battery is still discharged, the laboratory power supply will operate in current protection mode (i.e., it will stabilize the output current at a given level). Then, when the voltage on the bank rises to the set 4.2V, the power supply will switch to voltage stabilization mode, and the current will begin to drop.
When the current drops to 0.05-0.1C, the battery can be considered fully charged.
As you can see, the laboratory power supply is an almost ideal charger! The only thing it can’t do automatically is make a decision to fully charge the battery and turn off. But this is a small thing that you shouldn’t even pay attention to.
How to charge lithium batteries?
And if we are talking about a disposable battery that is not intended for recharging, then the correct (and only correct) answer to this question is NO.
The fact is that any lithium battery (for example, the common CR2032 in the form of a flat tablet) is characterized by the presence of an internal passivating layer that covers the lithium anode. This layer prevents a chemical reaction between the anode and the electrolyte. And the supply of external current destroys the above protective layer, leading to damage to the battery.
By the way, if we talk about the non-rechargeable CR2032 battery, then the LIR2032, which is very similar to it, is already a full-fledged battery. It can and should be charged. Only its voltage is not 3, but 3.6V.
How to charge lithium batteries (be it a phone battery, 18650 or any other li-ion battery) was discussed at the beginning of the article.
Modern electronic devices(such as cell phones, laptop computers or tablets) are powered by lithium- ion batteries, which replaced alkaline analogues. Nickel-cadmium and nickel-metal hydride batteries have given way to Li─Ion batteries due to the better technical and consumer qualities of the latter. The available charge in such batteries from the moment of production ranges from four to six percent, after which it begins to decrease with use. During the first 12 months, battery capacity decreases by 10 to 20%.
Original chargers
Charging units for ion batteries are very similar to similar devices for lead-acid batteries, however, their batteries, called “banks” for their external similarity, have a higher voltage, so there are more stringent tolerance requirements (for example, the permissible voltage difference is only 0. 05 c). The most common format of a 18650 ion battery bank is that it has a diameter of 1.8 cm and a height of 6.5 cm.
On a note. A standard lithium-ion battery requires up to three hours to charge, and the more precise time is determined by its original capacity.
Manufacturers 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 overcharging the element and breaking chemical system, it is also undesirable to fully charge the battery.
Note! During long-term storage, lithium batteries should optimally have a small (no more than 50%) charge, and it is also necessary to remove them from the units.
If lithium batteries have a protection board, then they are not in danger of being overcharged.
The built-in protection board cuts off excessive voltage (more than 3.7 volts per cell) during charging and turns off the battery if the charge level drops to a minimum, usually 2.4 volts. The charge controller detects the moment when the voltage on the bank reaches 3.7 volts and disconnects the charger from the battery. This essential device also monitors the temperature of the battery to prevent overheating and overcurrent. The protection is based on the DV01-P microcircuit. After the circuit is interrupted by the controller, its restoration is carried out automatically when the parameters are normalized.
On the chip, a red indicator means charge, and green or blue indicates that the battery is charged.
How to properly charge lithium batteries
Well-known manufacturers of li-ion batteries (for example, Sony) use a two- or three-stage charging principle in their chargers, which can significantly extend 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 capacity of the battery (for example, for an element with a capacity of 2200 milliamp-hours, the charger current should be from 1.1 amperes.)
At the initial stage, after connecting the charger for lithium batteries, the current value is from 0.2 to 1.0 of the nominal capacity, with a voltage of 4.1 volts (per cell). Under these conditions, the batteries charge in 40 to 50 minutes.
To achieve 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 acts as a conventional voltage regulator.
Important! If it is necessary to charge lithium-ion batteries that have a built-in protection board, then the open circuit voltage should not be more than six to seven volts, otherwise it will deteriorate.
When the voltage reaches 4.2 volts, the battery capacity will be between 70 and 80 percent capacity, which will signal the end of the initial charging phase.
The next stage is carried out if there is DC voltage.
Additional Information. In some units for more fast charging The pulse method is used. If the lithium-ion battery has a graphite system, then they must comply with the voltage limit of 4.1 volts per cell. If this parameter is exceeded, the energy density of the battery will increase and trigger oxidation reactions, shortening the life of the battery. In modern battery models, special additives are used that allow the voltage to be increased when connecting a charger for li ion batteries to 4.2 volts plus/minus 0.05 volts.
In simple lithium batteries, chargers maintain a voltage level of 3.9 volts, which for them is a reliable guarantee of long service life.
When delivering a current of 1 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 cutoff norm, the current value rapidly drops and remains at the level of a couple of percent of the initial value.
If the charging current is artificially increased, the time of use of the charger to power lithium-ion batteries will hardly decrease. In this case, the voltage initially increases 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 eliminated, and the battery can be used after the initial stage (the charging level will also be at 70 percent capacity).
At the third and final charging stage, a compensating charge is carried out. It is not carried out every time, but only once every 3 weeks, when storing (not using) batteries. In battery storage conditions, it is impossible to use jet charging, because in this case lithium metallization occurs. However, short-term recharging with constant voltage current helps to avoid charge losses. Charging stops when the voltage reaches 4.2 volts.
Lithium metallization is dangerous due to the release of oxygen and a sudden increase in pressure, which can lead to ignition and even explosion.
DIY battery charger
Charger for lithium-ion batteries is inexpensive, but if you have a little knowledge of electronics, you can make it yourself. If there is no accurate information about the origin of the battery elements, and there are doubts about the accuracy of the work measuring instruments, you should set the charge threshold 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 many 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 discharged to “zero”.
The charger is assembled in the following order:
- a suitable housing is located;
- a five-volt power supply and other circuit parts are mounted (strictly follow the sequence!);
- a pair of brass strips is 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 require recharging from time to time, however, overcharging as well as completely discharging should be avoided. Maintaining the functionality 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
I liked the small microcircuits for simple chargers. I bought them from our local offline store, but as luck would have it, they ran out there, they took a long time to be transported from somewhere else. Looking at this situation, I decided to order them in small bulk, since the microcircuits are quite good, and I liked the way they work.
Description and comparison under the cut.
It was not in vain that I wrote about comparison in the title, since during the journey the dog could have grown up. Microphones appeared in the store, I bought several pieces and decided to compare them.
The review will not have a lot of text, but quite a lot of photographs.
But I’ll start, as always, with how it came to me.
It came complete with other various parts, the mikruhi themselves were packed in a bag with a latch and a sticker with the name. 
This microcircuit is a charger microcircuit for lithium batteries with a charge end voltage of 4.2 Volts.
It can charge batteries with a current of up to 800mA.
The current value is set by changing the value of the external resistor.
It also supports the charge function with a small current if the battery is very discharged (voltage lower than 2.9 Volts).
When charging to a voltage of 4.2 Volts and the charging current drops below 1/10 of the set value, the microcircuit turns off the charge. If the voltage drops to 4.05 Volts, it will again go into charging mode.
There is also an output for connecting an indication LED.
More information can be found in, this microcircuit has a much cheaper one.
Moreover, it is cheaper here, on Ali it’s the other way around.
Actually, for comparison, I bought an analogue. 
But imagine my surprise when the LTC and STC microcircuits turned out to be completely identical in appearance, both were labeled LTC4054. 
Well, maybe it’s even more interesting.
As everyone understands, it’s not that easy to check a microcircuit; it also needs a harness from other radio components, preferably a board, etc.
And just then a friend asked me to repair (although in this context it would be more likely to remake) a charger for 18650 batteries.
The original one burned out, and the charging current was too low.
In general, for testing we must first assemble what we will test on.
I drew the board from the datasheet, even without a diagram, but I’ll give the diagram here for convenience. 
Well actually printed circuit board. There are no diodes VD1 and VD2 on the board; they were added after everything. 
All this was printed out and transferred to a piece of textolite.
To save money, I made another board using scraps; a review with its participation will follow later. 
Well, the printed circuit board was actually made and the necessary parts were selected. 
And I will remake such a charger, it is probably very well known to readers. 
Inside it is a very complex circuit consisting of a connector, an LED, a resistor and specially trained wires that allow you to equalize the charge on the batteries.
Just kidding, the charger is located in a block that is plugged into an outlet, but here there are simply 2 batteries connected in parallel and an LED constantly connected to the batteries.
We'll return to our original charger later. 
I soldered the scarf, picked out the original board with contacts, soldered the contacts themselves with the springs, they will still be useful. 
I drilled a couple of new holes, in the middle there will be an LED indicating the device is turned on, in the sides - the charging process. 
Soldered into new board contacts with springs, as well as LEDs.
It is convenient to first insert the LEDs into the board, then carefully install the board in its original place, and only after that solder it, then they will stand evenly and equally. 
The board is installed in place, the power cable is soldered.
The printed circuit board itself was developed for three power supply options.
2 options with a MiniUSB connector, but in installation options on different sides of the board and under the cable.
In this case, at first I didn’t know how long the cable would be needed, so I soldered a short one.
I also soldered the wires going to the positive contacts of the batteries.
Now they go through separate wires, one for each battery. 
Here's how it turned out from above. 
Well, now let's move on to testing
On the left side of the board I installed the mikruha bought on Ali, on the right I bought it offline.
Accordingly, they will be located mirrored on top.
First, mikruha with Ali.
Charge current. 
Now purchased offline. 
Short circuit current.
Likewise, first with Ali. 
Now from offline. 
There is complete identity of the microcircuits, which is good news :)
It was noticed that at 4.8 Volts the charge current is 600 mA, at 5 Volts it drops to 500, but this was checked after warming up, maybe this is how the overheating protection works, I haven’t figured it out yet, but the microcircuits behave approximately the same.
Well, now a little about the charging process and finalizing the rework (yes, even this happens).
From the very beginning I was thinking of just setting the LED to indicate the on state.
Everything seems simple and obvious.
But as always, I wanted more.
I decided that it would be better if it was extinguished during the charging process.
I soldered a couple of diodes (vd1 and vd2 on the diagram), but got a small bummer, the LED indicating the charging mode shines even when there is no battery.
Or rather, it doesn’t shine, but flickers quickly, I added a 47 µF capacitor in parallel to the battery terminals, after which it began to flash very briefly, almost imperceptibly.
This is exactly the hysteresis of switching on recharging if the voltage drops below 4.05 Volts.
In general, after this modification everything was fine.
The battery is charging, the red light is on, the green light is not on, and the LED does not light up where there is no battery. 
The battery is fully charged. 
When turned off, the microcircuit does not pass voltage to the power connector, and is not afraid of shorting this connector; therefore, it does not discharge the battery to its LED. 
Not without measuring the temperature.
I got just over 62 degrees after 15 minutes of charging. 
Well, this is what a fully finished device looks like.
External changes are minimal, unlike internal ones. A friend had a 5/Volt 2 Ampere power supply, and it was quite good.
The device provides a charge current of 600 mA per channel, the channels are independent. 
Well, this is what the original charger looked like. A friend wanted to ask me to increase the charging current in it. It couldn’t stand even its own, where else to raise it, slag. 
Summary.
In my opinion, for a chip that costs 7 cents it's very good.
The microcircuits are fully functional and are no different from those purchased offline.
I am very pleased, now I have a supply of mikrukhs and don’t have to wait for them to be in the store (they recently went out of sale again).
Of the minuses - This is not a ready-made device, so you will have to etch, solder, etc., but there is a plus: you can make a board for a specific application, rather than using what you have.
Well, in the end, getting a working product made by yourself is cheaper than ready-made boards, and even under your specific conditions.
I almost forgot, datasheet, diagram and trace -
And again a device for homemade ones.
The module allows you to charge Li-Ion batteries (both protected and unprotected) from USB port via miniUSB cable.
The printed circuit board is double-sided fiberglass with metallization, the installation is neat. 
Charging is assembled on the basis of a specialized charge controller TP4056.
Real scheme. 
On the battery side, the device does not consume anything and can be left constantly connected to the battery. Short circuit protection at the output - yes (with current limitation 110mA). There is no protection against battery reverse polarity.
The miniUSB power supply is duplicated by nickels on the board. 
The device works like this:
When connecting power without a battery, the red LED lights up and the blue LED blinks periodically.
When you connect a discharged battery, the red LED goes out and the blue LED lights up - the charging process begins. As long as the battery voltage is less than 2.9V, the charging current is limited to 90-100mA. With an increase in voltage above 2.9V, the charge current sharply increases to 800mA with a further smooth increase to a nominal 1000mA.
When the voltage reaches 4.1V, the charging current begins to gradually decrease, then the voltage stabilizes at 4.2V and after the charging current decreases to 105mA, the LEDs begin to switch periodically, indicating the end of the charge, while the charge still continues by switching to the blue LED . Switching occurs in accordance with the hysteresis of the battery voltage control.
The nominal charge current is set by a 1.2 kOhm resistor. If necessary, the current can be reduced by increasing the resistor value according to the controller specification.
R (kOhm) - I (mA)
10 - 130
5 - 250
4 - 300
3 - 400
2 - 580
1.66 - 690
1.5 - 780
1.33 - 900
1.2 - 1000
The final charge voltage is hard-set at 4.2V - i.e. Not every battery will be 100% charged.
Controller specification.
Conclusion: The device is simple and useful for a specific task.
Planning to buy +166 Add to favorites I liked the review +96 +202
