External Battery UPS for PC

[rsaeon]

If the charging voltage doesn’t exceed 14.6 (3.65V x 4), it’s safe for LiFePO4. For 2x12V, that would be 29.2 (3.65V x 8). You can overvolt a bit (some BMS go to 3.75V), but it’ll noticeably degrade the battery pack’s life.

The bigger concern is this (the entire thread is worth going through):

@rsaeon

However, some people on youtube have noticed some BMSs will block the UPS from powering on after the pack is drained completely. They got around this by installing a push button that’ll bypass the BMS wiring to allow the UPS to sense that there’s a battery so that it will power on. This is for UPS models that need a battery to turn on even if they’re connected to the mains ac. Most UPSs will let you turn on without a battery with a long press of the power button.