Akom's Tech Ruminations

Various tech outbursts - code and solutions to practical problems

Hardware Hacks Adventures in Modifying a UPS for external DC power and LiFePO4 batteries

Posted by Admin • Saturday, June 26. 2021 • Category: Hardware Hacks

I have an ancient APC Smart-UPS 1400 RMNET. It's a very nice UPS, but I have frequent multi-hour power outages and battery life becomes a problem. I have these issues:

  1. Short battery runtime, especially as batteries age
  2. Lead-acid batteries require frequent replacement and quickly lose capacity (and there are 4 of them)
  3. UPS will not accept 110v from a cheap generator (mine is a 700w). This means that I can't do a live power transfer from mains to this generator, and I have to reboot everything to switch

So, I had a few ideas

  • What if I could feed externally-generated DC battery voltage directly to the batteries? For example, via a generator powering a AC-DC power supply
  • What if I could substitute Lithium batteries for Lead-Acid? LiFePO4 would be ideal in this application because weight doesn't matter but the long cycle life does. A 4S pack would have a similar voltage to a 12v lead-acid battery

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