I am making a 1S2P Li-ion battery pack. One of the requirement is I need to protect over-charge and over-discharge by detecting the voltage of each cell. The protection circuit/IC should interrupt the battery when any one of the cells is over or under voltage.

I find most of the protection IC is to protect the cells connected in series, such as LV51131T. When connecting the cells in parallel, the way I can think of is to add multiple protection IC, such as DW01-P. Each protection IC connects to a single cell and adding diode on each branch. Therefore there will be two identical protection IC on the board.

However, by searching from the web, it seems nobody is using this method. I would like to ask what is the normal or correct practice for this purpose?

Thank you very much

  • \$\begingroup\$ I only can add the following to what Neil_UK said: "Now use a single BMS to avoid over/under voltage on the entire parallel assembly." Yes and you can do this, because all the batteries which are physically hard-connected in parallel always have the same voltage, due to their parallel connection. \$\endgroup\$
    – Burination
    Dec 25, 2020 at 22:28

1 Answer 1


To protect cells in parallel, you put a fuse in series with each cell. This protects the pack from the possibility of one cell failing short circuit, and the other cells then driving a fire-starting current through it.

Now use a single BMS to avoid over/under voltage on the entire parallel assembly.

With a series assembly, the cells can have different voltages, so a BMS channel per cell is required. In a parallel assembly, they all have the same voltage, so all have the same protection voltage requirements.

  • 2
    \$\begingroup\$ I agree. But do think through what happens if one fuse blows. Will that create a hazardous condition for the remaining cell in terms of charge rate or anything else? Or can you detect when one fuse blows and disable the pack completely? Just a few system design things to consider. \$\endgroup\$
    – user57037
    Dec 28, 2020 at 22:09

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