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I am designing a power management board. The board should be able to distribute the power across a system and manage the power coming from a solar panel, while recharging batteries with excess power. I used TI's BQ25703A to perform this task, achieving MPPT with input voltage regulation and charging 4 Li-ion batteries put in series.

Unfortunately the chip does not handle battery balancing. Implementing this - either with Amazon boards or adding a balancing IC to the board - would result in a huge complexification of the board design, so I'd be quite happy if that could be avoided.

I'm worried about safety issues, not performance/longevity of the batteries as we are in an early prototyping phase. Each Li-ion battery already has a circuit for protection against overvoltage, overcharging and overdischarging.

Is just monitoring each battery voltage and performing manual balancing as needed a suitable approach?

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  • \$\begingroup\$ Not if you're worried about safety, no. You also need a proper charging circuit, not just protection. \$\endgroup\$
    – Finbarr
    Aug 20, 2022 at 11:39
  • \$\begingroup\$ The charging part itself is managed by the BQ25703A chip in 14.4V setting. But it can't balance the cells. \$\endgroup\$
    – Gianfranco Di Domenico
    Aug 20, 2022 at 12:45
  • \$\begingroup\$ If a human is part of a safety chain, this is sometimes considered good and sometimes bad. So this question will likely receive opinion based answers. \$\endgroup\$
    – Jens
    Aug 20, 2022 at 14:55

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In the final version of the power managenment board you have to solve this problem anyway. But if you start the evaluation of the board with initially balanced cells, they will not run apart that much during some cycles.

However in the final phase of charging, the cell voltages rise quickly and you should stop it early without balancing at all, or monitor in very short intervals.
Consider beeing distracted by a phone call and, oops, one cell is in danger.

We do much more dangerous things all day, like driving cars.

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