KOHLER 20RES / 20RCA Standby Generator Battery Charger Fail

RDC2 Controller Assembly

The battery charger is an integrated switch-mode power supply on the RDC2 logic board. If the board's internal DC regulation circuit fails or the charging MOSFETs suffer a dielectric breakdown, the controller will trigger a 'Charger Failure' fault. This assembly is the primary service part for charging logic issues.

Automatic Transfer Switch T1 Fuse

The generator's internal charger requires a constant 120VAC source from the transfer switch to operate during standby. This power is delivered via the T1 terminal and is protected by a 5-amp or 15-amp fuse (depending on the ATS model). If this fuse is blown due to a line surge, the charger loses its primary power source, resulting in a failure message.

12V Group 51R Lead Acid Battery

Internal plate sulfation or a shorted cell in the battery can cause the charging circuit to exceed its current limit or fail to reach the programmed float voltage within the expected timeframe. The RDC2 controller monitors the charge rate and will throw a charger failure code if the battery's internal resistance prevents proper voltage regulation.