Do I need OD/OC/OV Protection for Small LiPo Batteries with a Protection PCB already?

Electrical Engineering Asked on October 29, 2021

I’m building a small design that is designed to only take smaller LiPo packs, those that often terminate in a JST PH 2.0 connector with example below:

It seems like most of these similar batteries I find online already include some form of protection circuitry in the PCB behind the Kapton tape. Currently, my design includes a FS312F-G battery protection IC in series, for overdischarge, overcurrent, and overvoltage protection.

Will this IC interfere with the protection already on the batteries in any meaningful way? If not, can I just get rid of this IC entirely instead, if the onboard protection PCB already does the same thing?

It’s important to note that in the physical design, there is almost no physical way for a user to actually connect an unprotected 18650 [or other common cell], unless they go about soldering a JST connector on and dremel out a large hole for one. If that battery blows up, that’s on them-problem and don’t want to increase BOM cost for unintended use cases.

One Answer

It is a good safety practice that you should always have at least an extra layer of protection when dealing with Li-ion batteries.

A proper design shall have:

  1. A well designed, robust charging and discharging circuit
  2. A battery protection circuit
  3. A battery with protection circuit built-in

#3 would be the last resort in case both 1 & 2 failed.

You can easily find many designs in China skipped #2, and some I have came across even without #3 and a poorly designed #1, and with a crappy power supply. Not too difficult to imagine how these would ended up after being used for a while.

Answered by Edwios on October 29, 2021

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