UPS Lithium Battery Selection
UPS batteries are cycled on every outage, so lithium's cycle life pays back fast. Here is how to specify one.
Match the string voltage
UPS banks are series strings of 12 V blocks — 240 V (20 blocks), 480 V (40 blocks) or 48 V for small units. A lithium drop-in replaces the VRLA blocks at the same string voltage; the BMS sits inside each module.
Runtime and capacity
Decide the required minutes at the UPS load (W), then size Ah. Lithium's ~90% usable DoD means a smaller nameplate than the VRLA it replaces for the same runtime. Work it against the runtime method (same Wh math).
Charger compatibility
- Confirm the UPS charger supports a LiFePO4 charge profile (CC-CV, temperature-compensated).
- Some legacy UPS need a firmware/setup change to avoid alarming on the different charge curve.
Communication
Bring per-block voltage, temperature and SoH to the UPS/management via RS485 or SNMP so the UPS can report battery health — see the BMS communication guide. XGW's UPS Lithium Battery ships with this built in.