Understanding UPS Operation7-16 EATON Powerware® 9390 UPS (100–160 kVA) Installation and Operation Manual S 164201554 Rev E powerware.comAn ABM charging cycle starts with the charger driving the battery voltage, at maximumcurrent limit, to a battery charge level of 2.34 volts/cell. The time it takes for the voltage toreach to the battery charge level is saved as the battery charge time. If the battery chargetime exceeds 100 hours, an alarm sounds.As soon as a battery charge level of 2.34 volts/cell is reached, the battery is charged at afloat level of 2.31 volts/cell for 48 hours (battery float time) plus 150% of battery chargetime. Twenty-four hours into the float period, a series of battery tests are performed tocheck the battery health. The float level charge continues after a successful test.At initial startup, the battery run time on the front panel display indicates two minutes.After the 24-hour float charging period and battery testing, the actual battery run time isdetermined and the actual battery run time is displayed.After the float period is completed, the charger is disconnected and the batteries areallowed to rest for 672 hours (28 days) maximum rest time. If the battery voltage fallsbelow the opportunity charge level of 2.1 volts/cell during the first 240 hours of the restperiod, an alarm sounds.An ABM charge cycle is initiated whenever one of these four conditions occurs since thelast charge cycle: The batteries have rested over the maximum rest time of 672 hours. Accumulated discharge time is over a maximum battery discharge time of 20 seconds. Battery voltage is under the opportunity charge level of 2.1 volts/cell and the unit hasbeen in rest mode for longer than 240 hours. An XCP command Initiate Battery Test is received.7.4.4 BypassThe bypass has a continuous-duty fully-rated SCR switch in the bypass circuit and acontactor in the inverter leg. In Normal mode, the contactor connects the inverter to theoutput. A backfeed contactor is also provided.7.4.5 BatteriesThe UPS operates from battery strings from 192 cells (384V nominal) to 240 cells(480V nominal).
