Three-string active balanced mini version

By driving the mos tube, the flying capacitor C5, the flying capacitor C7, the battery C4 and the battery C6 are connected in parallel. After fully charged, switch between flying capacitor C5, flying capacitor C7, battery C6 and battery C8.

By constantly switching, the voltages on each capacitor tend to be equal to achieve battery voltage balance.

The drawing of the flying line in the picture has been corrected.

In the actual measurement, the C45678 capacitor used is 47uf X5R 6.3V 0805 package.

Test principle:

By connecting an adjustable resistor in parallel to the position of the balanced version of the 2S battery, the balanced charging of the battery is simulated. Measure the voltage of each S point to the ground and calculate it.

measuring instrument:

Use DH1766A digitally controlled power supply with current limiting protection to test the low voltage protection threshold and simulate the working state of the battery when the battery voltage is full and the battery is running low.

Use VC980D to measure the current and 86E to measure the voltage at each endpoint.

The measurement results are organized as follows:

in conclusion:

The board stops working when the battery pack voltage drops below 8.6v, and the standby current is 36ua. When the battery voltage rises above 9.2v, the board starts to resume operation.

When each battery is balanced, the balancing error is 0~2mv .

When the battery voltage difference is 10mv, the balancing current is about 10ma.

For high-frequency boards, when the battery voltage difference is 140mv , the equilibrium current is about 100ma .

For low-frequency boards, when the battery voltage difference is 240mv , the equilibrium current is about 100ma .

For high-frequency boards, when the battery voltage difference is 530mv , the equilibrium current is about 300ma .

For low-frequency boards, when the battery voltage difference is 800mv , the equilibrium current is about 300ma .

A well-balanced battery pack can further reduce the operating frequency to further reduce power consumption.

If large current is needed, more capacitors can be connected in parallel.