So, my Top 5 chargers for 18650 batteries. Which charger to choose, how to charge an 18650 battery for a flashlight or vape? There are tons of different models on Aliexpress and other stores. But when people come to me to buy a Li-Ion battery and/or charger for it, it turns out that a sadly small number understand what exactly they want.
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As expected, some “most popular and cheapest charger for 18650 on aliexpress” is the first choice for many, if only because of the price. To keep you from buying such rubbish, I’ll briefly tell you (fortunately there’s no point in going on and on here) that you can buy a good charger for lithium on Aliexpress for any budget, even the most modest one, and at the same time not fall into outright slag.
In all other cases, the chance of running into a fake is extremely high, unless we are talking about all sorts of batteries from flashlight manufacturers. The latter are hellishly expensive and are the same repackaging of other accounts. so there is no point in taking them. And I take normal accounts from nkon.nl.ru. So, the battery I’m talking about is a repackaging of the original Panasonic NCR18650B. The cells were rejected, but it seems that its logic boils down to discarding everything below 3350mah and selling these off-grade cans for further sale on the same Ali. Actually, almost all the cans I ordered were somewhere around 3250-3350mah, which I was more than happy with for the price. I ordered a LOT of these accounts, zero complaints. For household purposes, these low-current cans are enough for you. Here is the link. I repeat, for most flashlights this will be the best lithium-ion battery from aliexpress. The current output is small, but 3-4A is quite enough for most flashlights, and the protection board will save you from overdischarge.
The graphs in my reviews of flashlights showed that the most popular flashlight on Ali - convoy, in its again most popular models (s2+, c8, c8+) works on this battery in fact the same way as with some more expensive original medium or high current one. Therefore, I don’t see any point in using any other battery in an inexpensive Chinese flashlight. And if you need an 18650 battery for a cheap headlamp with Ali, then this is the only option - the risk of deep discharge and death of the battery is too great. There is no protection in such headbands; you have to rely on the corresponding one already in the 18650 battery itself.
Let me start with why you shouldn’t buy products like these from the world famous company noname. Considering the meager difference between this craft and a normal charger, I don’t see any point in taking something like this.
- work only with lithium. no nickel.
- God knows what charging algorithm.
- it’s good if it slightly undercharges, but it can drive up to 4.3V, which is very bad for chemistry
- The build quality matches the price - it's not a fact that it won't break or bang.
Well, an important point - charging for a 18650 battery = charging for a 26650 battery, all models below have a movable rod for charging almost all models of li-ion batteries
Xtar (after a recent rebrand they are sold under the allmaybe brand)
For me personally, the clear favorite in the segment of inexpensive single-slot chargers is the Xtar MC1. This is an extremely compact (about the size of an index finger) charger. Unlike the litocal, it cannot boast the same 1A charging current, but it does have a proprietary technology for lifting deeply discharged batteries. However, Xtar MC1plus 1A already has charging current.
From time to time, in the process of writing a review of flashlights, I came across the situation of battery discharge below 2v. And other charges, the same lithocals of different stripes simply do not determine such accounts. Of course, a completely damaged battery with degraded chemistry cannot be revived here. It comes with a case so you can take it with you anywhere.
0.5A current results in about 6 hours of charging, +\- depending on the capacity and depth of discharge of the battery. If you put it on overnight (and for the most part this is what happens), then this will be enough for the eyes. For charging in the car along the way, this will not be enough and you need to look at the same litocal.
Of course, charging also supports nickels, i.e. You can charge regular AA/AAA.
The price tag for both versions below on Ali is quite reasonable, about 4-7 bucks in regular and plus versions. I don’t give them in detail here because they wander back and forth.
Of the other versions, I will only mention VC2, which, with the same correct charging algorithm, has the advantage of a good and clear indicator. The other models, although interesting, are inferior to the litocal in terms of price/functionality, therefore they are less preferable and I will not talk about them here.
the price tag is around 14 bucks. and here, as in other models, you need to rely on the presence of points and coupons.
Liitokala
For a long time, the miller, whose poor design was compensated for by good giblets and a competent charging process, was extremely popular among knowledgeable people. This continued until the release of the 101st litocal. Even if it is the simplest, but the indication of the charging process and battery voltage, the variety of chemistry and standard sizes, the ability to work in power bank mode and a 0.5\1A current to choose from - this model instantly became a bestseller as the cheapest and at the same time a good charger for lithium batteries.
after that, models gradually began to come out for a larger number of accounts, 202 for two, 402 for 4, and recently a model for 3 accounts came out. They differ from 101 only in the number of connectors.
Of course, you need to understand that if your power supply produces 2A, then you can charge 4 batteries with no more than 0.5A for each.
If the release of 101 was removed from the market by Miller, then 202\402 completely dropped sales of Nightcore chargers. I remember how in 15/16 I traded them well. It all ended with the fact that I simply handed over the leftovers to a vape shop for purchase; no one got this nightcore for my money. In addition to the price, there is also a functional disadvantage - for example, boiling nickel with 1A current.
I’ll tell you separately about the popular 4-slot charger. Liitokala Lii-500 It's virtually an all-in-one harvester.
Charging, capacity test (if you force it to run over and over again, you can actually run the same refresh as in Opus), full indication (including resistance). Charging current from 0.3 to 1A per channel, a bunch of different chemistries and standard sizes.
For its low price, this charger is an excellent choice for those who want something more than just charging batteries or if you have a lot of them and need to assess their condition and charge quickly.
Opus
The final touch (I won’t talk about model chargers like Imax, since if you’re in this business, you already know about them) will be Opus BT - C3100 V2.2
This extremely A popular charger among those who constantly have to deal with batteries. I myself used this for about a year, but still switched to 500k. With an almost twofold difference in price, I did not see a clear advantage in functionality. 2A charging current is not important to me, and the refresh function can work in the 500th litocal, taking about 3-4 manual runs of the norm test, i.e. charging-discharging-charging.
Well, yes, another clear functional advantage is the presence of a fan, which is extremely reasonable when 4 batteries are being charged or discharged with high current at once
in principle, we can stop there. There are several other specific models, but I am sure that for the vast majority of readers one of the above will be enough. I used them all, sold dozens of them, and in all that time, only once did the charging stop work for one piece of 202 litocal, it drove the acc all the way. But this is one of several dozen.
Chargers for 21700 batteries.
Separately, it is worth mentioning the once popular Nitecore chargers.
The only thing that attracts me now is that even the simplest models fit 21700 batteries perfectly. And since it’s not at all difficult to buy a 21700 flashlight on aliexpress now, the fact that Litokalov’s chargers fit in with a creak is really sad. And some fancy brand 21700 batteries won’t fit at all.
So in such a situation it is justified to buy Nightcore chargers, only for 21,700 batteries. I recommend the one I use myself - nitecore UI2 (see my Nitecore chargers). Even cheaper - . 
If finances allow, then you can take something radically better, fortunately Nightcore has fixed almost all the jambs of previous models (such as frying AAA nickel batteries with a current of 1A)
So, Nitecore UM4(). By the way, now, adding this charger to the selection, I noticed that the price tag has dropped to the level of the Liitokala Lii-500, which is very good!
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 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. Otherwise, the protection board may be damaged.
At the moment when the voltage on the battery rises to 4.2 volts, the battery will gain approximately 70-80% of its capacity (the specific capacity value will depend on the charging current: with accelerated charging it will be a little less, with a nominal charge - a little more). This moment marks the end of the first stage of charging and serves as a signal for the transition to the second (and final) stage.
2. Second charge stage- this is charging the battery with a constant voltage, but a gradually decreasing (falling) current.
At this stage, the charger maintains a voltage of 4.15-4.25 volts on the battery and controls the current value.
As the capacity increases, the charging current will decrease. As soon as its value decreases to 0.05-0.01C, the charging process is considered complete.
An important nuance of the correct charger operation is its complete disconnection from the battery after charging is complete. This is due to the fact that for lithium batteries it is extremely undesirable for them to remain under high voltage for a long time, which is usually provided by the charger (i.e. 4.18-4.24 volts). This leads to accelerated degradation of the chemical composition of the battery and, as a consequence, a decrease in its capacity. Long-term stay means tens of hours or more.
During the second stage of charging, the battery manages to gain approximately 0.1-0.15 more of its capacity. The total battery charge thus reaches 90-95%, which is an excellent indicator.
We looked at two main stages of charging. However, coverage of the issue of charging lithium batteries would be incomplete if another charging stage were not mentioned - the so-called. precharge.
Preliminary charge stage (precharge)- this stage is used only for deeply discharged batteries (below 2.5 V) to bring them to normal operating mode.
At this stage, the charge is provided with a reduced constant current until the battery voltage reaches 2.8 V.
The preliminary stage is necessary to prevent swelling and depressurization (or even explosion with fire) of damaged batteries that have, for example, an internal short circuit between the electrodes. If a large charge current is immediately passed through such a battery, this will inevitably lead to its heating, and then it depends.
Another benefit of precharging is pre-heating the battery, which is important when charging at low ambient temperatures (in an unheated room during the cold season).
Intelligent charging should be able to monitor the voltage on the battery during the preliminary charging stage and, if the voltage does not rise for a long time, draw a conclusion that the battery is faulty.
All stages of charging a lithium-ion battery (including the pre-charge stage) are schematically depicted in this graph: 
Exceeding the rated charging voltage by 0.15V can reduce the battery life by half. Lowering the charge voltage by 0.1 volt reduces the capacity of a charged battery by about 10%, but significantly extends its service life. The voltage of a fully charged battery after removing it from the charger is 4.1-4.15 volts.
Let me summarize the above and outline the main points:
1. What current should I use to charge a li-ion battery (for example, 18650 or any other)?
The current will depend on how quickly you would like to charge it and can range from 0.2C to 1C.
For example, for a battery size 18650 with a capacity of 3400 mAh, the minimum charge current is 680 mA, and the maximum is 3400 mA.
2. How long does it take to charge, for example, the same 18650 batteries?
The charging time directly depends on the charging current and is calculated using the formula:
T = C / I charge.
For example, the charging time of our 3400 mAh battery with a current of 1A will be about 3.5 hours.
3. How to properly charge a lithium polymer battery?
All lithium batteries charge the same way. It doesn't matter whether it 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, it is prohibited to use lithium batteries in household appliances unless they have a built-in protection board. That's why all cell phone batteries always have a PCB board. The battery output terminals are located directly on the board: 
These boards use a six-legged charge controller on a specialized device (JW01, JW11, K091, G2J, G3J, S8210, S8261, NE57600 and other analogues). The task of this controller is to disconnect the battery from the load when the battery is completely discharged and disconnect the battery from charging when it reaches 4.25V.
Here, for example, is a diagram of the BP-6M battery protection board that was supplied with old Nokia phones: 
If we talk about 18650, they can be produced either with or without a protection board. The protection module is located near the negative terminal of the battery. 
The board increases the length of the battery by 2-3 mm. 
Batteries without a PCB module are usually included in batteries that come with their own protection circuits.
Any battery with protection can easily turn into a battery without protection; you just need to gut it. 
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 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 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, 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 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). 
Any pnp transistor is suitable, the main thing is that it is designed for a given charging current.
There is no charge indicator on the indicated diagram, but on the LTC1734 it is said that pin “4” (Prog) has two functions - setting the current and monitoring the end of the battery charge. For example, a circuit with control of the end of charge using the LT1716 comparator is shown. 
The LT1716 comparator in this case can be replaced with a cheap LM358.
TL431 + transistor
It is probably difficult to come up with a circuit using more affordable components. The most difficult thing here is to find the TL431 reference voltage source. But they are so common that they are found almost everywhere (rarely does a power source do without this microcircuit). 
Well, the TIP41 transistor can be replaced with any other one with a suitable collector current. Even the old Soviet KT819, KT805 (or less powerful KT815, KT817) will do.
Setting up the circuit comes down to setting the output voltage (without a battery!!!) using a trim resistor at 4.2 volts. Resistor R1 sets the maximum value of the charging current.
This circuit fully implements the two-stage process of charging lithium batteries - first charging with direct current, then moving to the voltage stabilization phase and smoothly reducing the current to almost zero. The only drawback is the poor repeatability of the circuit (it is capricious in setup and demanding on the components used).
MCP73812
There is another undeservedly neglected microcircuit from Microchip - MCP73812 (see). 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 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.
A 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.
In the previous article, I considered the issue of replacing nickel-cadmium (nickel-manganese) NiCd (NiMn) screwdriver batteries with lithium ones. It is necessary to consider several rules for charging batteries.
Li-ion batteries of the 18650 size can generally be charged to a voltage of 4.20V per cell with a tolerance of no more than 50mV because increasing the voltage can damage the battery structure. The battery charge current can be 0.1xC to 1xC (here C-capacity). It is better to select these values from the datasheet. I used brand batteries in remaking the screwdriver. We look at the datasheet - charging current -1.5A.
The most correct way would be to charge lithium batteries in two steps using the CCCV method (constant current, constant voltage).
The first stage must provide a constant charging current. The current value is 0.2-0.5C. I used a battery with a capacity of 3000 mAh, which means the nominal charge current will be 600-1500 mA. After the can is charged at a constant voltage, the current constantly decreases.
The battery voltage is maintained within 4.15-4.25V. The battery is charged if the current decreases to 0.05-0.01C. Taking into account the above, we use electronic boards from Aliexpress. Step-down CC/CV board with current limiting on the XL4015E1 chip or on the LM2596. A board like this is preferable as it is more convenient to configure.
XL4015E1 Specifications.
Maximum output current up to 5 A.
Output voltage: 0.8V-30V.
Input voltage 5V-32V.
has similar parameters, only current up to 3 A.
List of tools and materials.
Adapter 220\12 V, 3 A - 1 piece;
-standard screwdriver charger (or power supply);
-CC/CV charge board on or -1pc;
- connecting wires - soldering iron;
-tester;
- plastic box for charge board - 1 piece;
- minivoltmeter - 1 piece;
-variable resistor (potentiometer) for 10-20 kOhm - 1 piece;
- power connector for the battery compartment of the screwdriver - 1 pc.
Step one. Assembling a screwdriver battery charger on an adapter.
We have already chosen the cccv board above. As a power source, you can use any one with the following parameters - output voltage not lower than 18 V (for a 4S circuit), current 3 A. In the first example of making a charger for lithium-ion batteries of a screwdriver, I used a 12 V, 3 A adapter.
First, I checked what current it can produce at the rated load. I connected a car lamp to the output and waited half an hour. It produces 1.9 A freely without overload. I also measured the temperature on the transistor radiator - 40°C. Quite normal mode.
But in this case there is not enough tension. This can be easily fixed using just one cheap radio component - a variable resistor (potentiometer) of 10-20 kOhm. Let's look at a typical adapter circuit.
There is a controlled zener diode TL431 in the diagram; it is located in the feedback circuit. Its task is to maintain a stable output voltage in accordance with the load. Through a divider of two resistors, it is connected to the positive output of the adapter. We need to solder to the resistor (or unsolder it completely and solder it in its place, then the voltage will be regulated downwards) which is connected to pin 1 of the TL431 zener diode and to the negative bus a variable resistor. Rotate the potentiometer axis and set the desired voltage. In my case, I set it to 18 V (small margin from 16.8 V for drop on the CC/CV board). If the voltage indicated on the housings of the electrolytic capacitors located at the output of the circuit is greater than the new voltage, they may explode. Then you need to replace them with a 30% voltage reserve.
Next, we connect the charge control board to the adapter. We set the voltage on the board with a trimmer resistor to 16.8 V. With another trimmer resistor we set the current to 1.5 A, and first connect the tester in ammeter mode to the output of the board. Now you can connect the lithium-ion screwdriver assembly. Charging went well, the current dropped to a minimum at the end of the charge, and the battery was charged. The temperature on the adapter was between 40-43°C, which is quite normal. In the future, you can drill holes in the adapter body to improve ventilation (especially in the summer).
The end of the battery charge can be seen by the LED on the board on the XL4015E1 turning on. In this example, I used another LM2596 board in the same way that I accidentally burned the XL4015E1 during experiments. I advise you to do better charging on the XL4015E1 board.
Step two. Assembling a screwdriver battery charger circuit using a standard charger.
I had a standard charger from another screwdriver. It is designed to charge nickel-manganese batteries. The task was to charge both nickel-manganese and lithium-ion batteries.
This was solved simply - I soldered the wires to the CC/CV board to the output wires (red plus, black minus).
The no-load voltage at the output of the standard charger was 27 V, this is quite suitable for our charging board. Further everything is the same as in the version with the adapter.
The charger for lithium batteries is very similar in structure and principle of operation to the charger for lead-acid batteries. Each lithium battery bank has a higher voltage value. In addition, they are more sensitive to overvoltage and overcharging.
The jar is one life-giving element. It got its name from its resemblance to tin cans for drinks. For lithium cells, the most common option is 18650. This number is easy to decipher. The thickness is indicated in millimeters - 18 and height - 65.
If other types of batteries allow you to have a greater variation in the supplied voltage when charging, then for lithium batteries this indicator should be much more accurate. When the battery voltage reaches 4.2 volts, charging should stop; overvoltage is dangerous for them. A deviation from the norm of 0.05 volts is allowed.
The average charge time for lithium batteries is 3 hours. This is an average figure, yet each individual battery has its own value. Their service life depends on the charging quality of lithium batteries.
Long-term storage conditions
Advice. Lithium-ion batteries must be stored correctly. If the device will not be used for a long time, it is better to remove the battery from it.
If a fully charged battery cell is left in storage, it may permanently lose some of its capacity. If a discharged battery is left in storage, it may not recover. This means that even if you try to revive her, you can fail. Therefore, the optimal recommended charge for storing lithium cans is 30-50%.
Using original chargers
Some manufacturers indicate that using non-original chargers for li ion batteries may void the warranty on the device. The thing is that a bad charger can destroy the battery cell. Lithium batteries can deteriorate due to incorrect voltage or incorrect attenuation at the end of charging. Therefore, using an original charger is always the best choice.
Danger of overcharging and complete discharge
Based on the design of lithium batteries, it is not recommended to allow them to be completely discharged or recharged.
For example, nickel-cadmium batteries have a memory effect. This means that incorrect charging mode leads to loss of capacity. The mode is considered incorrect when a battery is recharged that is not completely discharged. If you start charging it when it is not completely discharged, it may lose its capacity. Chargers for such batteries are manufactured with special operating modes that first discharge the battery to the required level, then begin to recharge it.
Lithium batteries do not require such troublesome maintenance. They do not have a memory effect, but they are afraid of complete discharge. Therefore, it is better to recharge them when the opportunity arises, without waiting for a complete discharge. But overcharging is also unacceptable for them. Therefore, it would be optimal not to allow the discharge to fall below 15% and the charge to exceed 90%. This can increase battery life.
This only applies to batteries without protection. If the batteries have protection implemented on a separate board, then it cuts off the charge beyond measure; if the discharge reaches a minimum level, it turns off the device. Usually these are indicators of more than 4.2 Volts and 2.7 Volts, respectively.
Attitude to temperature changes
The operating temperature range for lithium batteries is small - from +5 to +25 degrees Celsius. Strong temperature changes are undesirable for their operation.
When overcharging, the temperature of the battery may rise, which has a negative effect on its performance. Low temperature also has a negative effect. It has been noted that in cold weather the batteries lose their charge faster and run out, although in warm conditions the device shows a full charge.
Features of lithium batteries
Li-ion batteries are very unpretentious to use. If handled with care, they will last about 3-4 years. However, it is worth focusing on the fact that even if batteries are not used, they slowly die. Therefore, stocking up on batteries for the device for future use is not entirely reasonable. 2 years is the normal time from the date of production. If more has passed, then these may be already failed batteries.
Interesting. The most common 18650 can size has an average capacity of 3500 mAh. The normal price for such a battery is 3-4 dollars. Therefore, manufacturers who promise a 10,000 mAh Power bank for $3 are, to put it mildly, deceiving. It would be good if there was at least 3000 mAh.
How to properly charge a polymer battery
A polymer battery differs from an ion battery only in the internal consistency of the filler. Charging and operating rules apply to both types of these lithium batteries.
How to make a charger for a lithium battery with your own hands
Let's look at one of the simplest charger circuits for lithium-ion batteries. A homemade charging circuit is implemented on a microcircuit that acts as a zener diode and charge controller, and a transistor. The base of the transistor is connected to the control electrode of the microcircuit. Lithium batteries do not like overvoltage, so the output voltage must be set to the recommended voltage of 4.2 V. This can be achieved by adjusting the microcircuit with resistances R3 R4, which have values of 3 kOhm and 2.2 kOhm, respectively. They are connected to the first leg of the microcircuit. The adjustment is set once, and the voltage remains constant.
To be able to adjust the output voltage in place of the resistor R, install a potentiometer. The adjustment must be made without a load, that is, without the battery itself. With its help, you can precisely adjust the output voltage to 4.2 V. Then, instead of the potentiometer, you can install a resistor of the obtained value.
Resistor R4 is used to turn on the base of the transistor. The nominal value of this resistance is 0.22 kOhm. As the battery charges, its voltage will increase. This will cause the control electrode on the transistor to increase the emitter-collector resistance. This, in turn, will reduce the current going to the battery.
You also need to adjust the charging current. To do this, use resistance R1. Without this resistor, the LED will not light up; it is responsible for indicating the charging process. Depending on the required current, a resistor with a nominal value of 3 to 8 ohms is selected.
How to choose a battery
Special attention should be paid to battery manufacturers. There are reputable brands and some unknown analogues. Sometimes unscrupulous manufacturers can sell goods that are 3 times or more lower than the declared characteristics.
Note! Brands that have gained popularity include Panasonic, Sony, Sanyo, Samsung.
Purchasing lithium batteries should not be a big problem. You can buy them at local electronics stores, online stores, or order them directly from China. Don't go after cheap prices. A good battery cannot be very cheap. Some manufacturers supply high-quality banks, but poor boards responsible for power supply. This will inevitably lead to the death of the battery.
Video
Lithium-ion batteries are not as finicky as their nickel-metal hydride counterparts, but they still require some care. Sticking to five simple rules, you can not only extend the life cycle of lithium-ion batteries, but also increase the operating time of mobile devices without recharging.
Do not allow complete discharge. Lithium-ion batteries do not have the so-called memory effect, so they can and, moreover, need to be charged without waiting for them to discharge to zero. Many manufacturers calculate the life of a lithium-ion battery by the number of full discharge cycles (up to 0%). For quality batteries this 400-600 cycles. To extend the life of your lithium-ion battery, charge your phone more often. Optimally, as soon as the battery charge drops below 10-20 percent, you can put the phone on charge. This will increase the number of discharge cycles to 1000-1100
.
Experts describe this process with such an indicator as Depth Of Discharge. If your phone is discharged to 20%, then the Depth of Discharge is 80%. The table below shows the dependence of the number of discharge cycles of a lithium-ion battery on the Depth of Discharge:
Discharge once every 3 months. Fully charging for a long time is just as harmful to lithium-ion batteries as constantly discharging to zero.
Due to the extremely unstable charging process (we often charge the phone as needed, and wherever possible, from USB, from a socket, from an external battery, etc.), experts recommend completely discharging the battery once every 3 months and then charging it to 100% and holding it on charge 8-12 hours. This helps reset the so-called high and low battery flags. You can read more about this.
Store partially charged. The optimal condition for long-term storage of a lithium-ion battery is between 30 and 50 percent charge at 15°C. If you leave the battery fully charged, its capacity will decrease significantly over time. But the battery, which has been collecting dust on a shelf for a long time, discharged to zero, is most likely no longer alive - it’s time to send it for recycling.
The table below shows how much capacity remains in a lithium-ion battery depending on storage temperature and charge level when stored for 1 year. 
Use the original charger. Few people know that in most cases the charger is built directly inside mobile devices, and the external network adapter only lowers the voltage and rectifies the current of the household electrical network, that is, it does not directly affect the battery. Some gadgets, such as digital cameras, do not have a built-in charger, and therefore their lithium-ion batteries are inserted into an external “charger”. This is where using an external charger of questionable quality instead of the original one can negatively affect the performance of the battery.
Avoid overheating. Well, the worst enemy of lithium-ion batteries is high temperature - they absolutely cannot tolerate overheating. Therefore, do not expose your mobile devices to direct sunlight or place them near heat sources such as electric heaters. Maximum permissible temperatures at which lithium-ion batteries can be used: from –40°C to +50°C
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