HP Parallel Uninterruptible Power System - Manual (Page 63)

ERM installation 63
Switching on the ERM circuit breaker
Switching on the UPS battery circuit breaker
When the UPS is plugged in and the battery circuit breaker is on, the UPS automatically enters Standby mode
and begins charging the batteries.
Charging the ERM batteries
Connect the UPS to a grounded utility power outlet. When the UPS is plugged in, it automatically enters
Standby mode and begins charging the ERM batteries. With the UPS in Standby mode, allow the ERM
batteries to charge for at least 24 hours before putting the UPS into service.