EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: edpalmer42 on April 25, 2022, 09:39:17 pm
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I'm looking for a small (1 or 2 amps, maybe 5 - 10 AH capacity) BMS for an LiFePO4 battery backup system operating in float mode.
I have 5 or 6 devices that had internal battery backup. They were either Lead-Acid or Ni-Cd based. I'd like to upgrade them to LiFePO4, but I haven't been able to find a suitable BMS. They all have inputs for an external 24V battery system and that's also what their internal battery packs are designed for. Small 8S BMS boards are easy to find, but since the batteries are floating, the voltage has to be lowered to about 3.3 - 3.4V rather than the normal charge voltage of 3.65V per cell. A large, high power, programmable BMS can do this, but that would be total overkill for this project.
I've also thought of building an external 24V system that could power all the units, but I don't see that as an upgrade to my current arrangement of plugging them into a big UPS. The internal batteries would make them somewhat portable, even if it was just for equipment rearrangements. These devices are precision frequency sources that you really don't want to lose power, even for a few seconds.
So does anyone know of a source for a small BMS that either is set for 3.3 - 3.4 V per cell or is adjustable - probably via a pot? Is there another way to accomplish the same thing?
Thanks,
Ed