BALANCING LI-ION LI-POLYMER BATTERIES BATTERY BALANCING CIRCUIT Schematic Circuit Diagram
In addition to the ” Li-ion Battery Charge Integrators MCP73831 TP4056 “, ” Battery Protection Circuits “, “About Li-ion Li-Po LifePO4 Piller ” shared with Li-ion and Li-po batteries for charging, protection , balancing, balancing I will give you some information about …
In general, many projects are carried out with a single battery. Serial battery connection is required for higher voltages. In this case, if there is no balancing, balancing feature in the charger, deterioration occurs according to the capacity of the batteries, the batteries that are loaded early are overloaded and deteriorated, and this problematic battery, the charging circuit for charging the batteries prematurely finishes charging before the other batteries are charged.
For example; We need 12V in our project 3 Li-ion batteries in series with full charge 1 battery voltage 4.2V in this case 12.6V charger for 3 batteries needed We have started to charge our batteries and each battery has a different capacity and occupancy rate Some batteries have an early filling the middle battery in the schematic reaches the limit value of 4.2V and the others are not fully charged in this case the total voltage will not stop charging until the 12.2V charge cycle is 12.6V.
After charging, the battery will exceed the middle battery limit voltage. 4.4V will be charged. The other batteries are not fully charged. They are left at 4.1V but the total voltage is 12.6V.
We use our batteries when we charge them with a charger that does not have a new balancing circuit. Depending on the condition of the battery, the battery will be charged much faster and will be charging in the same way.
Battery balancing, the ripping circuit detects prematurely charging the battery to prevent this condition, and usually uses resistance as the load. In this case, the battery voltage does not exceed the limit value. The charging circuit continues charging until the other battery is charged.
There are many sophisticated systems for battery balancing , especially the Texas Instruments BQXXXX series battery protection, balancing integrators are often used in Laptop batteries, the other company that produces a more affordable variety is SII Semiconductor ( I think the company has changed hands by ABLIC Inc. )
SIMPLE BATTERY BALANCING CIRCUIT
Some of the most frequently used circuits are transistors with simple structure. Some use direct transistor load. Some of them use diode, load resistor, diode. In the following circuit, BD140 PNP is used as transistor load. TL431 REF can be precise voltage adjustment with trimpot connected to the foot.
There is no need to use this circuit for a single battery. One of the balance circuits is used for each battery in the serial connection Three serial Li-ion battery connection schemes for 12.6V;
For the circuit testing, we can think of the dimensions as perforated platelet lead test purposes, which can be done in much smaller sizes with regular PCB drawing and SMD materials.
Adjusting the battery balance circuit: First, set the voltage of your regulated power supply to 4.25V. Turn the 1K trimpod until it starts to give light ( or see 2.5V at the TL431 REF lamp ) . Meanwhile, look at the current drawn from the power supply. A value between 400 and 400 is sufficient. I use 300mA for the 18650 Li-ion battery
Basically TL431 REF should be resistance setting as 2.5V in the foot, if you use full value resistor you do not need trimpot but easiest is to use multi-turn timpot.
In this circuit, the direct BD140 transistor is used as the load. In some applications, 1W … 2W 5 … .10-OHM resistor or series 3 … 4 1N4007 diodes are connected to the collector of the PNP transistor. I did not use it in the tests, but if you use the BD140 transistors with a 1K trimmer you need to connect a small cooler, you can make more precise adjustments, and the voltage divider 15K, 22K resistors are better than 1% tolerances.
Above, the simplified version of the circuit seems to be used as a resistor directly connected to the series-connected diodes instead of this resistor, or as a direct transistor load without anything connected as in the first schematic. Using the additional transistor for the led indicator is more stable, but it can be connected at the transistor collector or never used.
This simple system is used in the charging adapter of many devices, especially in the chargers of products such as models, model cars, boats, helicopters on the market ..
There are even more sophisticated integrated control stabilizer circuits available in the more complex ones as well as microcontroller controlled ones. For example, the S8209B integration can be used with the SII Semiconductor products, which are not too complicated.
The battery stabilization cycle does not repair the problematic battery or make it perform better, but it prevents the battery from getting worse and causing more damage to the better battery. It is necessary to use in series connected …
UNLESS YOU USE THE BALANCE CIRCUIT?
There is a low chance that you sometimes have a lot of difference between the batteries and the battery pack does not have a problem for a long time.
By measuring, you will be able to identify the batteries that will cause the least problems and connect them in series, but I think that the seller will allow this and I need to sort out something like this in the article ” Matching the Transistors “.
For example, there are 10 unused Li-ion batteries in your hand. Overwrite the voltage of each battery that measures the voltage of all, then connect the load, repeat the measurement and write the voltage on the load onto the batteries. Be careful that you can connect and use series of batteries that have no load and load voltage or that are close to each other.
PIL -A loaded 3.0V without load 3.90V PIL
-B loaded 3.60V without load 3.85V
These batteries have very little unloaded voltages, but their voltage on the load is very different. This battery can not see our work for serial connection. You can use 15-OHM 2W resistor as load.
On used pillars; Fully charge all of them and do the same measurement a few days later ..
Finally, you can recharge the batteries separately if the serial connection is frozen and recharged but it is possible.