Li ion protected. Lithium-ion batteries: how to protect them? Overcharge protection
http://radiokot.ru/forum/viewtopic.php?f=11&t=116399
Greetings, dear radio cats! Due to modernity, lithium-ion batteries are widely gaining momentum. As you know, they have excellent characteristics in terms of output power, service life, and all this with a relatively small size. But they have one small drawback: you definitely need to control the charge and discharge. Otherwise, they will simply fail irreversibly.
I hope that the discussion of my situation will help others with a similar problem: the button in the screwdriver failed, namely the microcircuit hidden in the compound. We don’t have such a button anywhere, so we had to redo it, eliminating the electronic filling completely, leaving only the contact for closing the electric motor circuit. After some time, it turned out that the batteries were discharged more than the permissible norm and further charging did not help. I concluded that the microcircuit in the button was responsible not only for the number of revolutions per minute, but also for discharge control. Having disassembled the battery, I found out that out of 5 cans, 3 are still working. There is a second similar "semi-working" battery. That is, you can combine two into one. But the problem will be finally solved if you assemble the discharge controller yourself (and at the same time figure out how it works) and build it into a screwdriver. The charge controller is already included in the charger.
On the Internet, alas, little is said about this and I did not find what I need there. I feel the spring smell of microcontrollers
http://www.kosmopoisk72.ru/index.php?op ... &Itemid=70 Here the controller acts only on 2 banks. Please help me calculate it so that it works for five cans.
http://www.radioscanner.ru/forum/topic38439.html here it only works for one bank.
http://radiokot.ru/konkursCatDay2014/06/ Here it is too complicated, since a programmer and a corresponding microcircuit are needed. In addition, in this scheme, a charge controller is also included in addition to everything. I am a beginner radio amateur. Maybe there is something more accessible and simple? If not, then I'm happy to learn microcontrollers.
1. Tell me how to calculate the discharge controller for 5 cans?
2. If the best option is on a microcontroller, which one to buy?
3. What kind of homemade (simplest) programmer can it be programmed with?
4. How to write a program (code) for the microcontroller yourself?
5. Can you better control the discharge of 5 cans, taking one as a basis? And build it into the battery itself, and not into a screwdriver? Just if in a screwdriver, then one circuit is enough for both the first battery and the second. (I can’t turn on two of them at once)
The load current of a screwdriver, as you know, is large: 10-12 A. The rated voltage of one can is standard: 3.7 V, therefore five cans: 18.5 V. It would be great if there was still short-circuit protection (that is, if current over 12 A)
There is only one solution .. use ready-made protection boards. Or collective farm with the power of keys for built-in cellular and other low-power scarves, or take ready-made ones such as http://zapas-m.ru/shop/UID_282.html (there are more powerful ones at the link, I threw out the IC keys and put the usual field workers .
Li-ion battery controller circuit
The device and principle of operation of the protective controller Li-ion / polymer battery
If you open any cell phone battery, you will find that a small printed circuit board is soldered to the terminals of the battery cell. This is the so-called protection scheme, or Protection IC. Due to its characteristics lithium batteries require constant monitoring. Let's take a closer look at how the protection scheme is arranged, and what elements it consists of.
An ordinary lithium battery charge controller circuit is a small board on which an electronic circuit of SMD components is mounted. The controller circuit of 1 cell ("bank") at 3.7V, as a rule, consists of two microcircuits. One microcircuit is a control one, and the other is an executive one - an assembly of two MOSFET transistors.
The photo shows a 3.7V battery charge controller board.
A microcircuit marked DW01-P in a small package is essentially the "brain" of the controller. Here is a typical wiring diagram for this chip. In the diagram, G1 is a cell of a lithium-ion or polymer battery. FET1, FET2 are MOSFET transistors.
Pinout, appearance and pin assignment of the DW01-P chip.
MOSFET transistors are not included in the DW01-P chip and are made as a separate assembly chip of 2 N-type MOSFET transistors. The assembly marked 8205 is usually used, and the package can be either 6-pin (SOT-23-6) or 8-pin (TSSOP-8). The assembly can be labeled as TXY8205A, SSF8205, S8205A, etc. You can also find assemblies marked 8814 and similar.
Here is the pinout and composition of the S8205A chip in the TSSOP-8 package.
Two FETs are used to separately control the discharge and charge of the battery cell. For convenience, they are made in one case.
The transistor (FET1) that is connected to the OD pin ( Overdischarge) DW01-P chips, controls the battery discharge - connects / disconnects the load. And the one (FET2) that is connected to the OC pin ( over charge) – connects/disconnects the power supply (charger). Thus, by opening or closing the corresponding transistor, it is possible, for example, to turn off the load (consumer) or stop charging the battery cell.
Let's look at the logic of the control chip and the entire protection circuit as a whole.
Overcharge protection.
As you know, overcharging a lithium battery over 4.2 - 4.3V is fraught with overheating and even an explosion.
If the cell voltage reaches 4.2 - 4.3V ( Overcharge Protection Voltage - VOCP), then the control chip closes the FET2 transistor, thereby preventing further battery charging. The battery will be disconnected from the power source until the voltage on the cell drops below 4 - 4.1V ( Overcharge Release Voltage – VOCR) due to self-discharge. This is only if there is no load connected to the battery, for example, it is removed from a cell phone.
If the battery is connected to the load, then the FET2 transistor reopenswhen the cell voltage drops below 4.2V. Overdischarge Protection.
If the battery voltage drops below 2.3 - 2.5V ( Overcharge Protection Voltage- VODP), then the controller turns off the FET1 MOSFET transistor - it is connected to the DO pin.
There are very interesting condition. Until the voltage on the battery cell exceeds 2.9 - 3.1V ( Overdischarge Release Voltage - VODR), the load will be completely disconnected. The controller terminals will be 0V. Those who are not familiar with the logic of the protective circuit may take this state of affairs for the "death" of the battery. Here is just a small example.
Miniature Li-polymer battery 3.7V from an MP3 player. Composition: control controller - G2NK (series S-8261), assembly of field-effect transistors - KC3J1.
The battery is discharged below 2.5V. The control circuit disconnected it from the load. At the output of the controller 0V.
At the same time, if you measure the voltage on the battery cell, then after the load was turned off, it slightly grew and reached the level of 2.7V.
In order for the controller to reconnect the battery to the "outside world", that is, to the load, the voltage on the battery cell must be 2.9 - 3.1V ( VODR).
This raises a very reasonable question.
The diagram shows that the drain terminals (Drain) of transistors FET1, FET2 are connected together and are not connected anywhere. How does current flow through such a circuitwhen overdischarge protection is triggered? How can we recharge the “bank” of the battery again so that the controller turns on the discharge transistor again - FET1?
If you rummage through datasheets for Li-ion / polymer protection chips (including DW01-P,G2NK), then you can find out that after the deep discharge protection is triggered, the charge detection circuit is in effect - Charger Detection. That is, when the charger is connected, the circuit will determine that the charger is connected and allow the charge process.
Charging to a level of 3.1V after a deep discharge of a lithium cell can take a very long time - several hours.
To restore a lithium-ion / polymer battery, you can use special tools, for example, Turnigy Accucell 6 Universal Charger. I already talked about how to do this. here.
It was with this method that I managed to restore a Li-polymer 3.7V battery from an MP3 player. Charging from 2.7V to 4.2V took 554 minutes and 52 seconds, which is more than 9 hours! That's how long a "recovery" charge can last.
Among other things, the functionality of lithium battery protection circuits includes overcurrent protection ( Overcurrent Protection) and short circuit. Overcurrent protection is triggered in the event of a sharp drop in voltage by a certain amount. After that, the microcircuit limits the load current. In the event of a short circuit (short circuit) in the load, the controller completely turns it off until the short circuit is eliminated.
Controller charge-discharge (PCM) for Li-Ion battery 14.8V 4A 4S-EBD01-4http://zapas-m.ru/shop/UID_282.htmlArticle: 0293Rated voltage: 14.8V Rated operating current: 4A Overcharge/overdischarge/overload protection Built-in thermistor 335 rub.
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Specifications Model: 4S-EBD01-4 Number of series-connected Li-Ion batteries: 4pcs Operating voltages: 11.2V ... 16.8V Cell overcharge voltage (VCU): 4.275±0.025V Overdischarge voltage (VDD): 2.3±0.1V Rated operating current: 3A - 4A Threshold current (IEC): 4A - 6A Overcharge protection Overdischarge protection Short circuit protection Dimensions, mm: 15 x 46.1 x 2.62 Weight, gr: 2 Controller: S-8254A datasheeton S-8254A Voltage control on each of the cells: When the voltage on any of the cells exceeds the threshold values, the entire battery is automatically turned off. Current control: When the load current exceeds the threshold values, the entire battery is automatically switched off. Pin Description:
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Protection of lithium-ion batteries (Li-ion). I think that many of you know that, for example, inside a mobile phone battery there is also a protection circuit (protection controller) that ensures that the battery (cell, bank, etc ...) is not overcharged above 4.2 V , or discharged less than 2 ... 3 V. Also, the protection circuit saves from short circuits, disconnecting the bank itself from the consumer at the time of the short circuit. When the battery reaches its end of life, you can remove the protection controller board from the battery and discard the battery. The protection board can be useful to repair another battery, to protect a can (which does not have protection circuits), or you can simply connect the board to the power supply and experiment with it.
I had a lot of protection boards from worn-out batteries. But an Internet search on the markings of microcircuits did not give anything, as if the microcircuits were classified. In the internet there was documentation only for assemblies of field-effect transistors, which are included in the protection boards. Let's take a look at the design of a typical lithium-ion battery protection circuit. Below is a protection controller board assembled on a controller chip with the designation VC87 and an 8814 transistor assembly ():
In the photo we see: 1 - protection controller (the heart of the whole circuit), 2 - an assembly of two field-effect transistors (I will write about them below), 3 - a resistor that sets the protection trip current (for example, during a short circuit), 4 - a power supply capacitor, 5 - resistor (to power the controller chip), 6 - thermistor (it is on some boards to control the battery temperature).
Here is another version of the controller (there is no thermistor on this board), it is assembled on a microcircuit with the designation G2JH, and on an 8205A transistor assembly ():
Two field-effect transistors are needed in order to be able to separately control the charging protection (Charge) and the discharge protection (Discharge) of the battery. Datasheets for transistors were almost always found, but for controller microcircuits - not in any !! And the other day, I suddenly came across one interesting datasheet for some kind of lithium-ion battery protection controller ().
And then, out of nowhere, a miracle happened - comparing the circuit from the datasheet with my protection boards, I realized: The circuits are the same, it's the same thing, clone microcircuits! After reading the datasheet, you can use such controllers in your homemade products, and by changing the resistor value, you can increase the allowable current that the controller can give before the protection trips.
It's no secret that Li-ion batteries don't like deep discharge. From this, they wither and wither, as well as increase internal resistance and lose capacity. Some specimens (those with protection) can even plunge into deep hibernation, from where it is rather problematic to pull them out. Therefore, when using lithium batteries, it is necessary to somehow limit their maximum discharge.
For this, special circuits are used that disconnect the battery from the load at the right time. Sometimes such circuits are called discharge controllers.
Because the discharge controller does not control the magnitude of the discharge current; strictly speaking, it is not a controller. In fact, this is a well-established, but incorrect name for deep discharge protection circuits.
Contrary to popular belief, built-in batteries (PCB-boards or PCM-modules) are not intended either to limit the charge / discharge current, or to timely turn off the load when fully discharged, or to correctly determine the end of the charge.
Firstly, protection boards, in principle, are not capable of limiting the charge or discharge current. This should be done by the memory. The maximum that they are capable of is to cut down the battery in case of a short circuit in the load or when it overheats.
Secondly, most protection modules disable the li-ion battery at 2.5 volts or even less. And for the vast majority of batteries, this is a very strong discharge, this should not be allowed at all.
Thirdly, The Chinese are riveting these modules by the millions... Do you really believe that they use quality precision components? Or that someone there tests and adjusts them before installing them in batteries? Of course, this is not so. In the production of Chinese boards, only one principle is strictly observed: the cheaper, the better. Therefore, if the protection will disconnect the battery from the charger exactly at 4.2 ± 0.05 V, then this is more likely a happy accident than a pattern.
It's good if you got a PCB module that will fire a little earlier (for example, at 4.1V). Then the battery simply will not reach a dozen percent of the capacity and that's it. It is much worse if the battery is constantly recharged, for example, up to 4.3V. Then the service life is reduced and the capacity drops and, in general, can swell.
It is IMPOSSIBLE to use the protection boards built into the lithium-ion batteries as discharge limiters! And as charge limiters - too. These boards are intended only for emergency shutdown of the battery in case of abnormal situations.
Therefore, separate charge limiting and/or over-discharge protection circuits are needed.
We considered simple chargers on discrete components and specialized integrated circuits in. And today we’ll talk about the solutions that exist today that allow you to protect a lithium battery from too much discharge.
To begin with, I propose a simple and reliable Li-ion protection circuit from overdischarge, consisting of only 6 elements. 
The ratings indicated in the diagram will lead to the disconnection of the batteries from the load when the voltage drops to ~ 10 Volts (I made protection for 3x 18650 batteries connected in series, which are in my metal detector). You can set your own trip threshold by selecting R3.
By the way, the voltage of a full discharge of a Li-ion battery is 3.0 V and no less.
A field worker (such as in a circuit or similar) can be dug out of an old motherboard from a computer, usually there are several of them there at once. TL-ku, by the way, can also be taken from there.
Capacitor C1 is needed to initially start the circuit when the switch is turned on (it briefly pulls the gate T1 to minus, which opens the transistor and energizes the voltage divider R3, R2). Further, after charging C1, the voltage necessary to unlock the transistor is maintained by the TL431 microcircuit.
Attention! The IRF4905 transistor indicated in the diagram will perfectly protect three lithium-ion batteries connected in series, but it is absolutely not suitable for protecting one 3.7 Volt bank. About how to determine whether a field effect transistor is suitable or not, it is said.
The disadvantage of this circuit: in the event of a short circuit in the load (or too much current consumption), the field-effect transistor will not close immediately. The reaction time will depend on the capacitance of the capacitor C1. And it is quite possible that during this time something will have time to burn out properly. A circuit that instantly responds to a short stack in the load is presented below: 
Switch SA1 is needed to "restart" the circuit after the protection has tripped. If the design of your device provides for the removal of the battery to charge it (in a separate charger), then this switch is not needed.
The resistance of the resistor R1 should be such that the TL431 stabilizer enters the operating mode at the minimum battery voltage - it is selected so that the anode-cathode current is not less than 0.4 mA. This gives rise to another drawback of this circuit - after the protection is triggered, the circuit continues to consume energy from the battery. The current, although small, is quite enough to completely drain a small battery in a couple of months.
The scheme below for self-made control of the discharge of lithium batteries is devoid of this drawback. When the protection is triggered, the current consumed by the device is so small that my tester does not even detect it. 
Below is a more modern version of the lithium battery discharge limiter using the TL431 stabilizer. This, firstly, allows you to easily and simply set the desired response threshold, and secondly, the circuit has high temperature stability and clear shutdown. Clap and all! 
Getting TL-ku today is not a problem at all, they are sold for 5 kopecks per bunch. Resistor R1 does not need to be installed (in some cases it is even harmful). The trimmer R6, which sets the response voltage, can be replaced by a chain of fixed resistors, with selected resistances.
To exit the blocking mode, you need to charge the battery above the protection threshold, and then press the S1 "Reset" button.
The inconvenience of all the above schemes lies in the fact that in order to resume the operation of the schemes after going into protection, operator intervention is required (turn SA1 on or off or press a button). This is the tradeoff for simplicity and low power consumption in blocking mode.
The simplest circuit for protecting li-ion from overdischarge, devoid of all the shortcomings (well, almost all) is shown below: 
The principle of operation of this circuit is very similar to the first two (at the very beginning of the article), but there is no TL431 microcircuit, and therefore the own consumption current can be reduced to very small values - about ten microamperes. A switch or reset button is also not needed, the circuit will automatically connect the battery to the load as soon as the voltage on it exceeds the specified threshold value.
Capacitor C1 suppresses false triggering when operating on a pulsed load. Any low-power diodes are suitable, it is their characteristics and quantity that determine the voltage of the circuit operation (you will have to select it locally).
The field effect transistor can be used any suitable n-channel. The main thing is that it can withstand the load current without straining and be able to open at a low gate-source voltage. For example, P60N03LDG, IRLML6401 or similar (see).
The above circuit is good for everyone, but there is one unpleasant moment - the smooth closing of the field effect transistor. This is due to the flatness of the initial section of the current-voltage characteristic of the diodes.
This shortcoming can be eliminated with the help of a modern element base, namely, with the help of micropower voltage detectors (power monitors with extremely low power consumption). Another scheme for protecting lithium from deep discharge is presented below: 
The MCP100 is available in both DIP and planar packages. For our needs, a 3-volt option is suitable - MCP100T-300i / TT. Typical current consumption in blocking mode is 45 μA. The cost of small wholesale is about 16 rubles / piece.
It is even better to use the BD4730 monitor instead of the MCP100, because. it has a direct output and, therefore, it will be necessary to exclude transistor Q1 from the circuit (connect the output of the microcircuit directly to the gate Q2 and resistor R2, while increasing R2 to 47 kOhm).
The circuit uses a microohm p-channel MOSFET IRF7210, which switches currents of 10-12 A without problems. The field switch fully opens already at a gate voltage of about 1.5 V, in the open state it has negligible resistance (less than 0.01 Ohm)! In short, a very cool transistor. And, most importantly, not too expensive.
In my opinion, the last scheme is the closest to the ideal. If I had unlimited access to radio components, I would choose her.
A slight change in the circuit allows the use of an N-channel transistor (then it is included in the negative load circuit): 
BD47xx power monitors (supervisors, detectors) are a whole line of microcircuits with a response voltage from 1.9 to 4.6 V in 100 mV steps, so you can always choose for your purposes.
small digression
Any of the above circuits can be connected to a battery of several batteries (after some tweaking, of course). However, if the banks are of different capacities, then the weakest of the batteries will constantly go into deep discharge long before the circuit will work. Therefore, in such cases, it is always recommended to use batteries not only of the same capacity, but preferably from the same batch.
And although in my metal detector such protection has been working flawlessly for two years now, it would still be much more correct to monitor the voltage on each battery individually.
Always use your personal Li-ion battery discharge controller for each can. Then any of your batteries will serve happily ever after.
How to choose the right FET
All of the above circuits for protecting lithium-ion batteries from deep discharge use MOSFETs operating in a key mode. The same transistors are commonly used in overcharge protection, short circuit protection, and other applications where load control is required.
Of course, in order for the circuit to work properly, the FET must meet certain requirements. First, we will decide on these requirements, and then we will take a couple of transistors and, based on their datasheets (according to technical characteristics), we will determine whether they are suitable for us or not.
Attention! We will not consider the dynamic characteristics of FETs, such as switching speed, gate capacitance, and maximum drain current. These parameters become critical when the transistor operates at high frequencies (inverters, generators, PWM modulators, etc.), but discussion of this topic is beyond the scope of this article.
So, we must immediately decide on the circuit that we want to assemble. Hence the first requirement for a field effect transistor - it must be of the right type(either N- or P-channel). This is the first.
Let's assume that the maximum current (load current or charge current - it doesn't matter) will not exceed 3A. This is where the second requirement comes in. field worker must withstand such a current for a long time.
Third. Let's say our circuit will protect the 18650 battery from deep discharge (one can). Therefore, we can immediately determine the operating voltages: from 3.0 to 4.3 Volts. Means, maximum allowable drain-source voltage U ds must be greater than 4.3 volts.
However, the last statement is true only if only one lithium battery can (or several connected in parallel) is used. If a battery of several series-connected batteries is used to power your load, then the maximum drain-source voltage of the transistor must exceed the total voltage of the entire battery.
Here is a picture explaining this point: 
As can be seen from the diagram, for a battery of 3 18650 batteries connected in series, in the protection circuits of each bank, it is necessary to use field devices with a drain-source voltage U ds > 12.6V (in practice, you need to take it with some margin, for example, 10%).
At the same time, this means that the field-effect transistor must be able to open completely (or at least strongly enough) already at a gate-source voltage U gs less than 3 volts. In fact, it is better to focus on a lower voltage, for example, 2.5 Volts, so that with a margin.
For a rough (initial) estimate, you can look in the datasheet for the "Cutoff voltage" indicator ( Gate Threshold Voltage) is the voltage at which the transistor is at the threshold of opening. This voltage is typically measured when the drain current reaches 250µA.
It is clear that it is impossible to operate the transistor in this mode, because. its output impedance is still too high, and it will simply burn out due to excess power. That's why the cutoff voltage of the transistor must be less than the operating voltage of the protection circuit. And the smaller it is, the better.
In practice, to protect one can of a lithium-ion battery, a field-effect transistor with a cut-off voltage of no more than 1.5 - 2 Volts should be selected.
Thus, the main requirements for field effect transistors are as follows:
- transistor type (p- or n-channel);
- maximum allowable drain current;
- the maximum allowable drain-source voltage U ds (remember how our batteries will be connected - in series or in parallel);
- low output impedance at a certain gate-source voltage U gs (to protect one Li-ion can, you should focus on 2.5 Volts);
- maximum allowable power dissipation.
Now let's take concrete examples. For example, we have transistors IRF4905, IRL2505 and IRLMS2002 at our disposal. Let's take a closer look at them.
Example 1 - IRF4905
We open the datasheet and see that this is a transistor with a p-type channel (p-channel). If it suits us, we look further.
The maximum drain current is 74A. Overkill, of course, but it fits.
Drain-source voltage - 55V. According to the condition of the problem, we have only one can of lithium, so the voltage is even greater than required.
Next, we are interested in the question of what the drain-source resistance will be, with an opening voltage at the gate of 2.5V. We look in the datasheet and so we do not immediately see this information. But we see that the cutoff voltage U gs(th) is in the range of 2...4 Volts. We are absolutely not satisfied with this.
The last requirement is not met, so we reject the transistor.
Example 2 - IRL2505
Here is his datasheet. We look and immediately see that this is a very powerful N-channel field worker. Drain current - 104A, drain-source voltage - 55V. As long as everything suits.
We check the voltage V gs (th) - a maximum of 2.0 V. Great!
But let's see what resistance the transistor will have at gate-source voltage = 2.5 volts. Let's look at the chart: 
It turns out that with a gate voltage of 2.5V and a current through the transistor of 3A, a voltage of 3V will drop across it. In accordance with Ohm's law, its resistance at this moment will be 3V / 3A \u003d 1 Ohm.
Thus, when the voltage on the battery bank is about 3 volts, it simply cannot deliver 3A to the load, since for this the total load resistance, together with the drain-source resistance of the transistor, must be 1 ohm. And we have only one transistor already has a resistance of 1 ohm.
In addition, with such an internal resistance and a given current, power (3 A) 2 * 3 Ohm = 9 W will be released on the transistor. Therefore, it will be necessary to install a radiator (the TO-220 case without a radiator will be able to dissipate somewhere around 0.5 ... 1 W).
An additional wake-up call should be the fact that the minimum gate voltage for which the manufacturer indicated the output resistance of the transistor is 4V.
This, as it were, hints at the fact that the operation of the field worker at a voltage U gs less than 4V was not envisaged.
Considering all of the above, we reject the transistor.
Example 3 - IRLMS2002
So, we get our third candidate out of the box. And immediately we look at his performance characteristics.
N-type channel, let's say that's all right.
The maximum drain current is 6.5 A. Suitable.
The maximum allowable drain-source voltage is V dss = 20V. Excellent.
Cut-off voltage - max. 1.2 Volts. Still alright.
To find out the output resistance of this transistor, we don’t even have to look at the graphs (as we did in the previous case) - the required resistance is immediately shown in the table just for our gate voltage.
This device has already been briefly described, I will try to write in more detail and put it into practice.
Sent well wrapped in bubble wrap 
The boards have not yet been separated, but are separated well 
Board size 27x17x4mm
Connection to charging via a standard microUSB connector or via redundant contacts + and -
The battery is connected to pins B+ and B-
The load is connected to the OUT+ and OUT- contacts. 
All chips are well known and tested 
Real device diagram 
There is no limiting resistor at the TP4056 input - apparently the connection cable performs this function.
The real charge current is 0.93A.
Charging turns off when the voltage on the battery is 4.19V
The current consumption from the battery is only 3 μA, which is much less than the self-discharge of any battery.
Description of some elements
TP4056 - 1A lithium charge controller chip
Described in detail here
DW01A - lithium protection chip
FS8205A - electronic key 25mOhm 4A
R3 (1.2 kOhm) - setting the battery charging current
By changing its value, you can reduce the charging current
R5 C2 - DW01A power supply filter. It also monitors the battery voltage.
R6 - needed to protect against charging reversal. Through it, the voltage drop on the keys is also measured for the normal operation of the protection.
Red LED - indication of the battery charging process
Blue LED - indication of the end of the battery charge
The board withstands battery polarity reversal only for a short time - the FS8205A key quickly overheats. By themselves, FS8205A and DW01A are not afraid of battery reversal due to the presence of current-limiting resistors, but due to the connection of TP4056, the polarity reversal current begins to flow through it.
With a battery voltage of 4.0V, the measured impedance of the switch is 0.052 Ohm
With a battery voltage of 3.0V, the measured impedance of the switch is 0.055 Ohm
Protection against current overload - two-stage and is triggered if:
- load current exceeds 27A for 3µs
- load current exceeds 3A for 10ms
The information is calculated according to the formulas from the specification, this cannot really be verified.
The long-term maximum recoil current turned out to be about 2.5A, while the key heats up noticeably, because. 0.32W is lost on it.
Battery overdischarge protection works at a voltage of 2.39V - it will not be enough, not every battery can be safely discharged to such a low voltage.
I tried to adapt this scarf into an old small simple children's radio-controlled car along with old 18500 batteries from a laptop in the 1S2P assembly
The machine was powered by 3 AA batteries, because. 18500 batteries are much thicker than them, I had to remove the battery cover, bite out the partitions, and glue the batteries. In thickness, they turned out flush with the bottom. 
I glued the scarf with sealant to the roof, made a cutout under the connector. 
Batteries can now be charged 
The red charging indicator shines through the red roof well. 
The blue indicator of the end of charging through the roof is almost invisible - it is visible only from the side of the connection connector. 
The machine below looks like with gas cylinders :) 
The machine rides on these cylinders for about 25 minutes. Not too much, but oh well, enough to play enough. The machine takes about an hour to charge.
Conclusion: a small and very useful device for creativity - you can take it. I will order more.
I plan to buy +227 Add to favorites Liked the review +103 +259Voltage control on each of the cells:
When the voltage on any of the cells exceeds the threshold values, the entire battery is automatically turned off.
Current control:
When the load current exceeds the threshold values, the entire battery is automatically switched off.
Pin Description:
"B-"- total battery minus
"B1"- +3.7V
"B2"- +7.4V
"B3"- +11.1V
"B+"- total battery plus
"P-"- minus load (charger)
"P+"- plus load (charger)
"T"- NTC 10K thermistor output
Controller: S-8254A
Datasheet on S-8254A.
Specifications
Model: 4S-EBD01-4.
Number of series-connected Li-Ion batteries: 4 pcs.
Operating voltages: 11.2V ... 16.8V.
Cell overcharge voltage (VCU): 4.275±0.025V.
Overdischarge voltage (VDD): 2.3±0.1V.
Rated operating current: 3A - 4A.
Threshold current (IEC): 4A - 6A.
Overcharge protection.
Overdischarge protection.
Short circuit protection.
Dimensions, mm: 15 x 46.1 x 2.62.
Weight: 2 gr.
