Dewalt 5s 18650 BMS recommendations?

Hi folks, I’m considering building some custom hardware that will be powered by the Dewalt “20V Max” li-ion packs and I’m hoping to source a BMS to monitor cell voltages and handle over-discharge protection.

The cursory searching I’ve done didn’t turn up anything that looked super promising so I am hoping somebody here might have a good recommendation.

Ideally, I’m looking for something akin to the Overkill Solar BMS, but a little smaller.


  • 5s
  • 3.0v (or configurable) cell LVD
  • 10A or higher amperage rating
  • Low-ish <50mA quiescent draw when in use


  • RS232/RS485 interface for configuration/monitoring (decent protocol docs would be nice, but existing library/software isn’t a requirement)
  • Ideally <0.1mA after LVD

Thanks in advance! :slight_smile:

Check out the LibreSolar BMS series. They’re well specified. But good luck getting the necessary parts right now.

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Thanks, that looks awesome! Not sure about getting the parts for a build like that either, but I’ll definitely see how feasible it would be…

If you’re hacking something together consider just getting the “trigger side” electronics from a Dewalt (or Deadwalt) tool (or charger) with it already.

Not all tools have it - and some batteries have smarts, some don’t. But if you dig around you Amy find something surprising cheap and with a battery mount already in place.

Yeah, that would be a good approach. Now to find some good DeWalt tool teardowns…

For now I’ve scaled back my ambitions for the project and I think I’m going to see whether the LVD feature on this product will be sufficient to get the project off the ground.

Tangentially related, I’ve written up my findings on a number of adapters for DIY projects connecting with DeWalt batteries: DIY Adapters for DeWalt Batteries | Symbioquine

Your experience with those matches mine with some Milwaukee adapters. Any low-voltage protection is in the tools themselves, as the basic adapters will let you drain them very VERY dead. So dead the charger doesn’t want to charge them (you can get them to charge by plugging and unplugging the battery a number of times).