Charger for Li-Ion battery from junk. What are lithium batteries?
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 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.
Progress is moving forward, and the traditionally used NiCd (nickel-cadmium) and NiMh (nickel-metal hydride) are increasingly being replaced lithium batteries.
With a comparable weight of one element, lithium has a higher capacity, in addition, the element voltage is three times higher - 3.6 V per element, instead of 1.2 V.
The cost of lithium batteries has begun to approach that of conventional alkaline batteries, their weight and size are much smaller, and besides, they can and should be charged. The manufacturer says they can withstand 300-600 cycles.
There are different sizes and choosing the right one is not difficult.
The self-discharge is so low that they sit for years and remain charged, i.e. The device remains operational when needed.
"C" stands for Capacity
A designation like “xC” is often found. This is simply a convenient designation of the charge or discharge current of the battery with shares of its capacity. Derived from the English word “Capacity” (capacity, capacity).When they talk about charging with a current of 2C, or 0.1C, they usually mean that the current should be (2 × battery capacity)/h or (0.1 × battery capacity)/h, respectively.
For example, a battery with a capacity of 720 mAh, for which the charge current is 0.5 C, must be charged with a current of 0.5 × 720 mAh / h = 360 mA, this also applies to discharge.
You can do something simple or not so simple yourself Charger, depending on your experience and capabilities.
Circuit diagram of a simple LM317 charger
Rice. 5.
The application circuit provides fairly accurate voltage stabilization, which is set by potentiometer R2.
Current stabilization is not as critical as voltage stabilization, so it is enough to stabilize the current using a shunt resistor Rx and an NPN transistor (VT1).
The required charging current for a particular lithium-ion (Li-Ion) and lithium-polymer (Li-Pol) battery is selected by changing the Rx resistance.
The resistance Rx approximately corresponds to the following ratio: 0.95/Imax.
The value of resistor Rx indicated in the diagram corresponds to a current of 200 mA, this is an approximate value, it also depends on the transistor.
It is necessary to provide a radiator depending on the charging current and input voltage.
The input voltage must be at least 3 Volts higher than the battery voltage for normal operation of the stabilizer, which for one can is 7-9 V.
Circuit diagram of a simple charger on LTC4054
Rice. 6.
You can remove the LTC4054 charge controller from an old cell phone, for example, Samsung (C100, C110, X100, E700, E800, E820, P100, P510).
Rice. 7. This small 5-legged chip is labeled "LTH7" or "LTADY"
I won’t go into the smallest details of working with the microcircuit; everything is in the datasheet. I will describe only the most necessary features.
Charge current up to 800 mA.
The optimal supply voltage is from 4.3 to 6 Volts.
Charge indication.
Output short circuit protection.
Overheating protection (reduction of charge current at temperatures above 120°).
Does not charge the battery when its voltage is below 2.9 V.
The charge current is set by a resistor between the fifth terminal of the microcircuit and ground according to the formula
I=1000/R,
where I is the charge current in Amperes, R is the resistor resistance in Ohms.
Lithium battery low indicator
Here simple circuit, which lights up the LED when the battery is low and its residual voltage is close to critical.
Rice. 8.
Any low-power transistors. The LED ignition voltage is selected by a divider from resistors R2 and R3. It is better to connect the circuit after the protection unit so that the LED does not drain the battery completely.
The nuance of durability
The manufacturer usually claims 300 cycles, but if you charge lithium just 0.1 Volt less, to 4.10 V, then the number of cycles increases to 600 or even more.Operation and Precautions
It's safe to say that lithium polymer batteries the most “delicate” batteries in existence, that is, they require mandatory compliance with several simple but mandatory rules, failure to comply with which can lead to troubles.1. Charge to a voltage exceeding 4.20 Volts per jar is not allowed.
2. Do not short circuit the battery.
3. Discharge with currents that exceed the load capacity or heat the battery above 60°C is not allowed. 4. A discharge below a voltage of 3.00 Volts per jar is harmful.
5. Heating the battery above 60°C is harmful. 6. Depressurization of the battery is harmful.
7. Storage in a discharged state is harmful.
Failure to comply with the first three points leads to a fire, the rest - to complete or partial loss of capacity.
From the practice of many years of use, I can say that the battery capacity changes little, but increases internal resistance and the battery begins to work less time at high current consumption - it seems that the capacity has dropped.
For this reason, I usually install a larger container, as the dimensions of the device allow, and even old cans that are ten years old work quite well.
For not very high currents, old cell phone batteries are suitable.
You can get a lot of perfectly working 18650 batteries out of an old laptop battery.
Where do I use lithium batteries?
I converted my screwdriver and electric screwdriver to lithium a long time ago. I don't use these tools regularly. Now, even after a year of non-use, they work without recharging!I put small batteries in children's toys, watches, etc., where 2-3 “button” cells were installed from the factory. Where exactly 3V is needed, I add one diode in series and it works just right.
I put them in LED flashlights.
Instead of the expensive and low-capacity Krona 9V, I installed 2 cans in the tester and forgot all the problems and extra costs.
In general, I put it wherever I can, instead of batteries.
Where do I buy lithium and related utilities
For sale. At the same link you will find charging modules and other useful items for DIYers.The Chinese usually lie about the capacity and it is less than what is written.
Honest Sanyo 18650
Assessing the characteristics of a particular charger is difficult without understanding how an exemplary charge of a li-ion battery should actually proceed. Therefore, before moving directly to the diagrams, let's remember a little theory.
What are lithium batteries?
Depending on what material the positive electrode of a lithium battery is made of, there are several varieties:
- with lithium cobaltate cathode;
- with a cathode based on lithiated iron phosphate;
- based on nickel-cobalt-aluminium;
- based on nickel-cobalt-manganese.
All of these batteries have their own characteristics, but since these nuances are not of fundamental importance for the general consumer, they will not be considered in this article.
Also, all li-ion batteries are produced in various sizes and form factors. They can be either cased (for example, the popular 18650 today) or laminated or prismatic (gel-polymer batteries). The latter are hermetically sealed bags made of a special film, which contain electrodes and electrode mass.
The most common sizes of li-ion batteries are shown in the table below (all of them have a nominal voltage of 3.7 volts):
| Designation | Standard size | Similar size |
|---|---|---|
| XXYY0, Where XX- indication of diameter in mm, YY- length value in mm, 0 - reflects the design in the form of a cylinder |
10180 | 2/5 AAA |
| 10220 | 1/2 AAA (Ø corresponds to AAA, but half the length) | |
| 10280 | ||
| 10430 | AAA | |
| 10440 | AAA | |
| 14250 | 1/2 AA | |
| 14270 | Ø AA, length CR2 | |
| 14430 | Ø 14 mm (same as AA), but shorter length | |
| 14500 | AA | |
| 14670 | ||
| 15266, 15270 | CR2 | |
| 16340 | CR123 | |
| 17500 | 150S/300S | |
| 17670 | 2xCR123 (or 168S/600S) | |
| 18350 | ||
| 18490 | ||
| 18500 | 2xCR123 (or 150A/300P) | |
| 18650 | 2xCR123 (or 168A/600P) | |
| 18700 | ||
| 22650 | ||
| 25500 | ||
| 26500 | WITH | |
| 26650 | ||
| 32650 | ||
| 33600 | D | |
| 42120 |
Internal electrochemical processes proceed in the same way and do not depend on the form factor and design of the battery, so everything said below applies equally to all lithium batteries.
How to properly charge lithium-ion batteries
The most correct way to charge lithium batteries is to charge in two stages. This is the method Sony uses in all of its chargers. Despite the more complex charge controller, it provides more full charge 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. More about charging pulse current can be read.
So, let's look at both stages of charging in more detail.
1. At the first stage A constant charging current must be ensured. The current value is 0.2-0.5C. For accelerated charging, it is allowed to increase the current to 0.5-1.0C (where C is the battery capacity).
For example, for a battery with a capacity of 3000 mAh, the nominal charge current at the first stage is 600-1500 mA, and the accelerated charge current can be in the range of 1.5-3A.
To ensure a constant charging current of a given value, the charger circuit must be able to increase the voltage at the battery terminals. In fact, at the first stage the charger works as a classic current stabilizer.
Important: If you plan to charge batteries with a built-in protection board (PCB), then when designing the charger circuit you need to make sure that the open circuit voltage of the circuit can never exceed 6-7 volts. Otherwise, the protection board may be damaged.
At the moment when the voltage on the battery rises to 4.2 volts, the battery will gain approximately 70-80% of its capacity (the specific capacity value will depend on the charging current: with accelerated charging it will be a little less, with a nominal charge - a little more). This moment marks the end of the first stage of charging and serves as a signal for the transition to the second (and final) stage.
2. Second charge stage- this is the battery charge constant voltage, but with a gradually decreasing (falling) current.
At this stage, the charger maintains a voltage of 4.15-4.25 volts on the battery and controls the current value.
As the capacity increases, the charging current will decrease. As soon as its value decreases to 0.05-0.01C, the charging process is considered complete.
An important nuance of the correct charger operation is its complete disconnection from the battery after charging is complete. This is due to the fact that for lithium batteries it is extremely undesirable for them to remain under high voltage for a long time, which is usually provided by the charger (i.e. 4.18-4.24 volts). This leads to accelerated degradation of the chemical composition of the battery and, as a consequence, a decrease in its capacity. Long-term stay means tens of hours or more.
During the second stage of charging, the battery manages to gain approximately 0.1-0.15 more of its capacity. The total battery charge thus reaches 90-95%, which is an excellent indicator.
We looked at two main stages of charging. However, coverage of the issue of charging lithium batteries would be incomplete if another charging stage were not mentioned - the so-called. precharge.
Preliminary charge stage (precharge)- this stage is used only for deeply discharged batteries (below 2.5 V) to bring them to normal operating mode.
At this stage the charge is 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 should be able to monitor the voltage on the battery during the preliminary charging stage and, if the voltage does not rise for a long time, draw a conclusion that the battery is faulty.
All stages of charging a lithium-ion battery (including the pre-charge stage) are schematically depicted in this graph: 
Exceeding the rated charging voltage by 0.15V can reduce the battery life by half. Lowering the charge voltage by 0.1 volt reduces the capacity of a charged battery by about 10%, but significantly extends its service life. The voltage of a fully charged battery after removing it from the charger is 4.1-4.15 volts.
Let me summarize the above and outline the main points:
1. What current should I use to charge a li-ion battery (for example, 18650 or any other)?
The current will depend on how quickly you would like to charge it and can range from 0.2C to 1C.
For example, for a battery size 18650 with a capacity of 3400 mAh, the minimum charge current is 680 mA, and the maximum is 3400 mA.
2. How long does it take to charge, for example, the same rechargeable batteries 18650?
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 typical diagram inclusions: 
If there is a guarantee that the voltage at the output of your adapter cannot under any circumstances exceed 7 volts, then you can do without the 7805 stabilizer.
The USB charging option can be assembled, for example, on this one. 
The microcircuit does not require either external diodes or external transistors. In general, of course, gorgeous little things! Only they are too small and inconvenient to solder. And they are also expensive ().
LP2951
The LP2951 stabilizer is manufactured by National Semiconductors (). It provides the implementation of a built-in current limiting function and allows you to generate a stable charge voltage level for a lithium-ion battery at the output of the circuit.
The charge voltage is 4.08 - 4.26 volts and is set by resistor R3 when the battery is disconnected. The voltage is kept very precisely.
The charge current is 150 - 300mA, this value is limited by the internal circuits of the LP2951 chip (depending on the manufacturer).
Use the diode with a small reverse current. For example, it can be any of the 1N400X series that you can purchase. The diode is used as a blocking diode to prevent reverse current from the battery into the LP2951 chip when the input voltage is turned off. 
This charger produces a fairly low charging current, so any 18650 battery can charge overnight.
The microcircuit can be purchased both in a DIP package and in a SOIC package (costs about 10 rubles per piece).
MCP73831
The chip allows you to create the right chargers, and it’s also cheaper than the much-hyped MAX1555. 
A typical connection diagram is taken from: 
An important advantage of the circuit is the absence of low-resistance powerful resistors that limit the charge current. Here the current is set by a resistor connected to the 5th pin of the microcircuit. Its resistance should be in the range of 2-10 kOhm.
The assembled charger looks like this: 
The microcircuit heats up quite well during operation, but this does not seem to bother it. It fulfills its function.
Here is another version of a printed circuit board with an SMD LED and a micro-USB connector: 
LTC4054 (STC4054)
Very simple scheme great option! Allows charging with current up to 800 mA (see). True, it tends to get very hot, but in this case the built-in overheating protection reduces the current. 
The circuit can be significantly simplified by throwing out one or even both LEDs with a transistor. Then it will look like this (you must admit, it couldn’t be simpler: a 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, VS6102 , 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 the 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 ready-made modules add protection against overcurrent and overdischarge (for example, you can choose which board you need - with or without protection, and with which connector). 
You can also find ready-made boards with a contact for a temperature sensor. Or even a charging module with several parallel TP4056 microcircuits to increase the charging current and with reverse polarity protection (example).
LTC1734
Also a very simple scheme. The charging current is set by resistor R prog (for example, if you install a 3 kOhm resistor, the current will be 500 mA).
Microcircuits are usually marked on the case: LTRG (they can often be found in old Samsung phones). 
A transistor will do just fine any p-n-p, the main thing is that it is designed for a given charging current.
There is no charge indicator on the indicated diagram, but on the LTC1734 it is said that pin “4” (Prog) has two functions - setting the current and monitoring the end of the battery charge. For example, a circuit with control of the end of charge using the LT1716 comparator is shown. 
The LT1716 comparator in this case can be replaced with a cheap LM358.
TL431 + transistor
It is probably difficult to come up with a circuit using more affordable components. The 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). Based on it, a very budget charging option is obtained (and inexpensive!). The whole body kit is just one resistor!
By the way, the microcircuit is made in a solder-friendly package - SOT23-5. 
The only negative is that it gets very hot and there is no charge indication. It also somehow doesn’t work very reliably if you have a low-power power source (which causes a voltage drop). 
In general, if the charge indication is not important for you, and a current of 500 mA suits you, then the MCP73812 is a very good option.
NCP1835
A fully integrated solution is offered - NCP1835B, providing high stability of the charging voltage (4.2 ±0.05 V).
Perhaps the only drawback of this microcircuit is its too miniature size (DFN-10 case, size 3x3 mm). Not everyone can provide high-quality soldering of such miniature elements. 
Among the undeniable advantages I would like to note the following:
- Minimum number of body parts.
- Possibility of charging a completely discharged battery (precharge current 30 mA);
- Determining the end of charging.
- Programmable charging current - up to 1000 mA.
- Charge and error indication (capable of detecting non-chargeable batteries and signaling this).
- Protection against long-term charge (by changing the capacitance of the capacitor C t, you can set maximum time charge 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 point 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 passivation 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.
For my latest projects I have been using Li-Pol cell phone batteries. They are truly wonderful. High energy density, low self-discharge, no memory effect. But Li-Pol batteries, unlike others, require more complex chargers. You must avoid exceeding the charging voltage and overcharging - this can damage the battery.
I used the MAX1555 based Sparkfun LiPoly charger for some time and it worked really well. The only thing that didn’t work was controlling the charge current. After conducting several experiments, I decided to try another chip - MCP73833.
MC73833 Features
(copied from the specification):
- High accuracy of output voltage setting
- Output Voltage Control Options
- User programmable output current up to 1 A
- Two status outputs with open drain
- Precharge and completion options
- Overvoltage protection
- Output “charge complete”
I liked the chip’s ability to set the charging current and status outputs, which are extremely useful in serious devices.
Scheme
Resistor R4 sets the charging current. I installed this resistor in the contacts of the connector to make it more convenient to change the current for charging other types of batteries. With a resistor resistance of 10 kOhm, the battery charging current is 100 mA.
Result
All components used are 0805 SMD, except for the MCP73833 chip, which has an MSOP-10 package. This was my first attempt to make a device using SMD components. I used a soldering station. It turned out that a very precise dosage of solder paste is required. Excess solder must be removed with a special desoldering braid.
conclusions
The next version should have a socket for connecting network adapter. The two pins are inconvenient for connecting a power source.
Note: as you can see, the board has a mini-USB connector to be able to connect the charger to the laptop.
I highly recommend using some type of USB hub to test any USB device you build.
I didn't do this, and now I have the first mock-up of the charger that burned out and the only one that survived USB port in the laptop. And although the OS warned me “High current consumption, the port will be disabled,” it was too late. In short, you have been warned.
Imported microcircuits / MICROCHIP 1A Li-Ion/Li-Poly Charge mgmt controller, PG output MSOP10
| Provider | Manufacturer | Name | Price |
|---|---|---|---|
| Triema | MCP73833-CNI/MF | 1 rub. | |
| PPE standard | Microchip | MCP73833T-FCI/UN | 20 rub. |
| Dessie | Microchip | MCP73833T-FCI/UN | 72 rub. |
| LifeElectronics | Microchip | MCP73833T-FCI/MF | on request |
- VERY, VERY USEFUL ARTICLE AUTOMATIC BATTERY CHARGING IS CURRENT.
- I also liked it, it’s very relevant, and most importantly it has practical value.
- Additional information on batteries. http://www.compitech.ru/html.cgi/arh...9/stat_116.htm
- It is correctly noted - it is practical value. And the additive from lllll is very...
- Tell me where is part 2, Li Ion batteries for robots. technology?
- If you mean the article Lithium-ion batteries for robotics. Part 1. Introduction, firstly, this question should have been asked not in this topic, but in the comments of that article; secondly, look at the publication date of the article - yesterday, June 23. Next, look at the very bottom of the article - To be continued In my opinion, everything is logical. Or is everything not obvious? Well, give the translators and editors at least some time to prepare a continuation.
- The chip is good, but I didn’t like how the author of the article used it, no wonder he burned the port in the laptop. Take a closer look at part of the miniUSB connector diagram.
- Tell me how to change the circuit to secure the USB port when charging from it? But it was possible to power the charger from the mains adapter.
- install an appropriate resistor, 3-5kOhm, it will take about 350-200mA from the port, 1kOhm will draw 1A current. I assembled the circuit using the datasheet and now there are two questions that I don’t understand: why does the microcircuit charge only up to 4.10-4.13V? and how to connect a light bulb so that it turns off when the minimum voltage for the battery is reached?
