ELECTRICAL POWER (EPS)
The Electrical Power Subsystem consists of the following major components: foursilver-zinc Descent batteries, two Descent electrical control assemblies, two silver-zinc Ascent batteries, two Ascent electrical control assemblies, a relay junetion box, a deadface relay, two circuit breaker panels, two inverters, and one lighting control assembly.
The four Descent batteries will supply power to the LM during all but the translunar phase on a normal mission from T-minus 30 minutes up to powered ascent. In the event of a battery failure, an abbreviated mission can be flown with the three remaining Descent batteries.
The Ascent batteries are used during a normal mission from powered ascent to docking, and during an abort requiring separation of the Ascent Stage from the Descent Stage. Prior to separation and during lunar stay, the Ascent batteries will be checked periodically. During powered descent they will be paralleled with the Descent batteries. Failure of an Ascent battery would require an abort.