737 MAX Flight Crew Operations Manual
Electrical -
System Description
MN-FLT-OH-201
6.20.9
Battery Charger Transformer/Rectifier
Dual Battery
The purpose of the battery chargers is to restore and maintain the batteries at full
electrical power. The main battery charger is powered through AC ground service
bus 2. The auxiliary battery charger is powered through AC ground service bus 1.
The battery chargers provide a voltage output tailored to maximize the battery
charge. Following completion of the primary charge cycle, the main battery
charger reverts to a constant voltage TR mode. In the TR mode, it powers loads
connected to the hot battery bus and the switched hot battery bus. The main battery
charger TR also powers the battery bus if TR3 fails. With loss of AC transfer bus
1 or the source of power to DC bus 1, the AC and DC standby buses are powered
by the main and auxiliary battery/battery chargers.
The auxiliary battery charger and battery are isolated from the power distribution
system under normal operation. When the main battery is powering the standby
system, the auxiliary battery is connected to operate in parallel with the main
battery.
March 1, 2021