Lithium protection ion batteries(Li-ion). I think that many of you know that, for example, inside the battery from mobile phone there is also a protection circuit (protection controller), which ensures that the battery (cell, bank, etc ...) is not recharged above a voltage of 4.2 V, or discharged less than 2 ... 3 V. Also, the protection circuit saves from short circuits, turning off the jar 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 - after 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.
Modern electronic devices(such as cell phones, laptops or tablets) are powered by lithium-ion batteries, which have replaced alkaline counterparts. Nickel-cadmium and nickel-metal hydride batteries have given way to Li─Ion batteries due to the best technical and consumer qualities of the latter. The available charge in such batteries from the moment of production is from four to six percent, after which it begins to decrease with use. During the first 12 months, the battery capacity decreases by 10 to 20%.
Original chargers
Chargers for ion batteries are very similar to those for lead-acid, however, they have higher voltages on batteries, named “banks” for their external similarity, so there are more stringent tolerance requirements (for example, the allowable voltage difference is only 0, 05 c). The most common format for a can of ion batteries is 18650, which means that it has a diameter of 1.8 cm and a height of 6.5 cm.
On a note. A standard lithium-ion battery takes up to three hours to charge, but more precisely, the time is determined by its initial capacity.
Manufacturers of Li-ion batteries recommend using only original chargers for charging, which are guaranteed to give the right voltage for the battery and will not destroy part of its capacity by recharging the cell and violating the chemical system, it is also undesirable to fully charge the battery.
Note! For long-term storage, lithium batteries should optimally have a small (no more than 50%) charge, and it is also necessary to remove them from the units.
If lithium batteries have a protection board, then overcharging does not threaten them.
The built-in protection board cuts off excessive voltage (more than 3.7 volts per cell) during charging and turns off the battery if the charge level drops to the minimum, usually 2.4 volts. The charge controller determines the moment when the voltage on the bank reaches 3.7 volts, and disconnects the charger from the battery. Also, this essential device monitors the temperature of the battery to prevent overheating and overcurrent. The protection is assembled on the basis of the DV01-P chip. After the circuit is interrupted by the controller, its restoration is carried out automatically when the parameters are normalized.
On the chip, a red indicator means charge, and green or blue indicates that the battery is charged.
How to properly charge lithium batteries
Well-known manufacturers of li-ion batteries (for example, such as Sony) use a two or three-stage charging principle in their chargers, which can significantly extend battery life.
At the output, the charger has a voltage of five volts, and the current value ranges from 0.5 to 1.0 of the nominal capacity of the battery (for example, for an element with a capacity of 2200 milliamp-hours, the charger current should be from 1.1 amperes.)
At the initial stage, after connecting the charging for lithium batteries, the current value is from 0.2 to 1.0 of the nominal capacity, while the voltage is 4.1 volts (per can). Under such conditions, the batteries are charged in 40 to 50 minutes.
To achieve a constant current, the charger circuit must be able to raise the voltage at the battery terminals, at which time the charger for most lithium-ion batteries works as a normal voltage regulator for electric current.
Important! If it is necessary to charge lithium-ion batteries that have a built-in protection board, then the open circuit voltage should not be more than six to seven volts, otherwise it will deteriorate.
By the time the voltage reaches 4.2 volts, the battery capacity will be 70 to 80 percent capacity, which will signal the end of the initial charging phase.
The next step is carried out if constant voltage.
Additional Information. In some units for more fast charging using the impulse method. If a lithium-ion battery has a graphite system, then they must comply with a voltage limit of 4.1 volts per can. If this parameter is exceeded, the energy density of the battery will increase and start oxidative reactions that shorten the life of the battery. AT modern models batteries use special additives that allow you to increase the voltage when you connect a charger for li ion batteries up to 4.2 volts plus / minus 0.05 volts.
In simple lithium batteries, chargers hold a voltage level of 3.9 volts, which is a reliable guarantee for a long service life for them.
When issuing a current of 1 value of the battery capacity, the time to obtain an optimally charged battery will be from 2 to 3 hours. As soon as the charge becomes full, the voltage reaches the cutoff rate, the current drops rapidly and remains at the level of a couple of percent of the initial value.
If the charging current is artificially increased, the time of using the charger to power lithium-ion batteries will not decrease almost. In this case, initially, the voltage grows faster, but at the same time, the duration of the second stage increases.
Some chargers can fully charge the battery in 60-70 minutes, in the process of such charging the second stage is excluded, and the battery can be used after the initial stage (the charge level will also be at 70 percent capacity).
At the third final stage of charging, a compensating charge is carried out. It is not carried out every time, but only once every 3 weeks, during storage (and not use) of batteries. In battery storage conditions, it is impossible to use jet charging, because in this case lithium metallization occurs. However, short recharging times with constant voltage help to avoid charge losses. The termination of charging ends as soon as the voltage reaches 4.2 volts.
Lithium plating is dangerous due to the release of oxygen and a sharp build-up of pressure, which can lead to ignition and even an explosion.
DIY battery charger
Charger for lithium-ion batteries is inexpensive, but with a little knowledge in electronics, you can make it yourself. If there is no exact information about the origin of the battery elements, and there are doubts about the accuracy of the measuring instruments, the charge threshold should be set in the region from 4.1 to 4.15 volts. This is especially true if the battery does not have a protective board.
To assemble a charger for lithium batteries with your own hands, one simplified circuit is enough, of which there are a lot of freely available on the Internet.
For the indicator, you can use a charging-type LED that lights up when the battery charge is significantly reduced, and goes out when it is discharged to zero.
The charger is assembled in the following order:
- a suitable housing is located;
- a five-volt power supply and other details of the circuit are mounted (strictly follow the sequence!);
- a pair of brass strips is cut out and attached to the socket holes;
- using a nut, the distance between the contacts and the connected battery is determined;
- a switch is installed to change the polarity (optional).
If the task is to assemble a charger for 18650 batteries with your own hands, then a more complex circuit and more technical skills will be required.
All lithium-ion batteries require recharging from time to time, however, overcharging as well as overdischarging should be avoided. Maintaining the performance of batteries and maintaining their working capacity for a long time is possible with the help of special chargers. It is advisable to use the original chargers, but you can assemble them yourself.
Video
We assemble a simple charger for Lithium-ion batteries, almost from trash.
I have accumulated a large number of batteries from laptop batteries, 18650 format. Thinking about how to charge them, I decided not to bother with Chinese modules, and I had run out of them by that time. I decided to put together two schemes. Current sensor and BMS board from mobile phone battery. Proven in practice. Although the circuit is primitive, it works and successfully, not a single battery was damaged.
Charger circuit
Materials and tools
- USB cord;
- crocodiles;
- BMS protection board;
- plastic egg from Kinder;
- two LEDs of different colors;
- transistor kt361;
- 470 and 22 ohm resistors;
- two-watt resistor 2.2 ohm;
- one diode IN4148;
- instruments.
Charger manufacturing
We disassemble the USB cable and remove the connector. I have it from some kind of iPad.
We solder the wires to the crocodiles.
We weight the deep part of the plastic kinder, I filled the M6 nut with hot glue.
We solder our simple circuit. Everything is done by surface mounting and soldered on the BMS board. I used a dual LED, but two single-color ones are possible. The transistor fell out of the old Soviet radio equipment.
We thread the wires into the hole in the second, small, half of the plastic kinder. We solder the scheme.
We stuff everything compactly into a plastic egg. We make a hole for the LED.
We connect to USB port PC or Chinese charging, they still have little current.
Lights up orange while charging. Those. both LEDs are lit.
When the charge is over, green is on, the one that is connected through the diode IN4148.
You can check the circuit by disconnecting from the battery, the green LED will light up, indicating the end of the charge.
Progress is moving forward, and lithium batteries are increasingly replacing the traditionally used NiCd (nickel cadmium) and NiMh (nickel metal hydride) batteries.
With a comparable weight of one cell, lithium has a large capacity, in addition, the cell voltage is three times higher - 3.6 V per cell, instead of 1.2 V.
The cost of lithium batteries has begun to approach conventional alkaline batteries, the weight and size are much smaller, and besides, they can and should be charged. The manufacturer says 300-600 cycles can withstand.
There are different sizes and choosing the right one is not difficult.
The self-discharge is so low that they lie for years and remain charged, i.e. the device remains operational when it is needed.
"C" stands for Capacity
Often there is a designation of the form "xC". This is just a convenient notation for the charge or discharge current of a battery in fractions of its capacity. It is formed from the English word "Capacity" (capacity, capacity).When talking 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 0.5C, must be charged with a current of 0.5 × 720mAh / h = 360 mA, this also applies to the discharge.
And you can make yourself a simple or not very simple charger, depending on your experience and capabilities.
Diagram of a simple charger on the LM317
Rice. 5.
The circuit with the application provides a fairly accurate voltage stabilization, which is set by the potentiometer R2.
Current stabilization is not as critical as voltage regulation, 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 resistance Rx.
The resistance Rx approximately corresponds to the following ratio: 0.95/Imax.
The value of the 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 charge 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 bank is? 7-9 V.
Diagram of a simple charger on the LTC4054
Rice. 6.
You can desolder the LTC4054 charge controller from the old cell phone, for example, Samsung (C100, C110, X100, E700, E800, E820, P100, P510).
Rice. 7. This small 5-leg chip is labeled "LTH7" or "LTADY"
I will not 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 the voltage on it is below 2.9 V.
The charge current is set by a resistor between the fifth output of the microcircuit and ground according to the formula
I=1000/R,
where I is the charge current in amperes, R is the resistance of the resistor in ohms.
Lithium battery low indicator
Here simple circuit, which lights the LED when the battery is low and its residual voltage is close to critical.
Rice. eight.
Transistors are any low-power ones. The ignition voltage of the LED is selected by a divider of resistors R2 and R3. It is better to connect the circuit after the protection unit so that the LED does not drain the battery at all.
The nuance of durability
The manufacturer usually claims 300 cycles, but if you charge lithium just 0.1 volts less, up to 4.10 V, then the number of cycles increases to 600 or even more.Operation and Precautions
It is safe to say that lithium-polymer batteries are the most “gentle” batteries in existence, that is, they require mandatory compliance with a few simple but mandatory rules, due to non-observance of which troubles happen.1. Charge to a voltage exceeding 4.20 volts per can is not allowed.
2. Not allowed short circuit battery.
3. It is not allowed to discharge with currents exceeding the load capacity or heating the battery above 60 ° C. 4. A discharge below a voltage of 3.00 Volts per jar is harmful.
5. Battery heating above 60°C is harmful. 6. Battery depressurization is harmful.
7. Harmful storage in a discharged state.
Failure to comply with the first three points leads to a fire, the rest - to a 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 starts to work less in time at high consumption currents - it seems that the capacity has fallen.
Therefore, I usually put a larger capacity, which the dimensions of the device allow, and even old cans, which are ten years old, work pretty well.
For not very high currents, old cell batteries are suitable.
You can pull out a lot of perfectly working 18650 batteries from an old laptop battery.
Where do I use lithium batteries
I have long converted a screwdriver and an electric screwdriver to lithium. I use these tools on a regular basis. Now even after a year of non-use, they work without recharging!I put small batteries in children's toys, watches, etc., where there were 2-3 "tablet" elements from the factory. Where exactly 3V is needed, I add one diode in series and it turns out just right.
I put 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 it turns out, instead of batteries.
Where do I buy lithium and usefulness on the topic
Are on sale. At the same link you will find charging modules and other useful things for DIYers.At the expense of capacity, the Chinese usually lie and it is less than written.
Honest Sanyo 18650
You can get acquainted with the charger circuit, which is perfect for lithium Li-Ion batteries.
At first, its author wanted to present a simple option on the lm317 chip, but in this case, the charging must be powered from a voltage higher than 5 volts. The reason is that the difference between the input and output voltages of the lm317 chip must be at least 2 volts. The voltage of a charged lithium-ion battery is about 4.2 volts. Therefore, the voltage difference is less than 1 volt. And this means that you can come up with another solution.
On AliExpress, you can buy a specialized board for charging lithium batteries, which costs about a dollar. Yes, it is, but why buy something that can be done in a couple of minutes. Moreover, it takes a month until the order is with you. But if you decide to purchase it ready-made, in order to immediately use it, buy it in this Chinese store. In the search for the store, enter: TP4056 1A
The simplest scheme
Today we will consider options for a UDB charger for lithium batteries, which everyone can repeat. The scheme is the simplest one you can think of.
Decision
This is a hybrid circuit, where there is voltage stabilization and current limitation of the battery charge.
Description of charging
Voltage stabilization is built on the basis of a fairly popular tl431 adjustable zener diode microcircuit. Transistor as an amplifying element. The charge current is set by the resistor R1 and depends only on the parameters of the battery being charged. This resistor is advised with a power of 1 watt. And all other resistors are 0.25 or 0.125 watts.
As we know, the voltage of a single cell of a fully charged lithium-ion battery is about 4.2 volts. Therefore, at the output of the charger, we must set exactly this voltage, which is set by the selection of resistors R2 and R3. There is a lot online programs according to the calculation of the stabilization voltage of the tl431 microcircuit.
For the most accurate setting of the output voltage, it is recommended to replace the resistor R2 with a multi-turn resistance of about 10 kilo-ohms. By the way, such a solution is also possible. We have an LED as a charge indicator, almost any LED, color to your taste, will do.
The whole setting comes down to setting the output voltage to 4.2 volts.
A few words about the zener diode tl431. This is a very popular microcircuit, not to be confused with transistors in a similar package. This chip is found in almost any impulse block power supply, for example, a computer, where the microcircuit is most often strapped.
The power transistor is not critical, any reverse conduction transistor of medium or high power is suitable, for example, from the Soviet ones, KT819, KT805 are suitable. Of the less powerful KT815, KT817 and any other transistors with similar parameters.
Which batteries are suitable for the device?
The circuit is designed to charge only one can lithium battery. You can charge standard 18650 batteries and other batteries, you just need to set the appropriate voltage at the output of the charger.
If suddenly, for some reason, the circuit does not work, then check for voltage at the control output of the microcircuit. It must be at least 2.5 volts. This is the minimum operating voltage for external source reference voltage of the microcircuit. Although there are versions where the minimum operating voltage is 3 Volts.
It is also advisable to build a small test bench for the indicated microcircuit in order to check its performance before soldering. And after assembly, we carefully check the installation.
In another publication, material about the improvement.