Originally Posted by Tyrod
When the battery charger operates and charges the battery, does it also continue to feed the hot batt and switched hot batt busses? Or does it just charge the battery and the battery powers those busses?
Looking at the wiring schematics, there is no way of diverting the power from the charger to one user only. The charger (if outputting volts) will always feed both bus and battery. i.e. there are no tie breakers between these items (other than one CB which feeds both Bat and bus).
However, the "nature" of the power from the charger changes. There is 'full on' charge mode (Constant current) and there is trickle charge mode (Constant voltage/ 27.5v/TRU mode).
When the battery is fully charged (and more), the charger switches to constant voltage mode. In this situation, the battery charger supplies the Hot Bat Bus with this voltage and trickle charges the battery (I assume, since there is no way of outputting different power (individually) to Battery and Bus, "trickle charge" simply occurs because of the constant voltage output from the charger).
The battery charger goes into charge mode (constant current) when the battery voltage is less than 23 volts. The charger will overcharge the battery for a certain period. Then the charger switches to TRU mode and provides 27.5volts.
Because the charger trickle charges the battery, "charge mode" is not often required. It happens only if the Battery Charger input power is off for more than 1 second or if the battery voltage is less than 23 volts. Charge mode is also electronically inhibited if the fuelling station door is open, the APU is being started, the Standby Power switch is in BAT (or in AUTO and conditions require BAT mode) or if there is a main battery overheat.
Hope this makes sense.
Rgds
NSEU