saptzae;
3. Bus voltage remains essentially the same at 32V
Where is the source of information that sez the battery is charged by the bus. Iīve heard of a diode.
The direct connection of a Li Ion stack of cells to a bus seems very dangerous. A much safer approach would be:
1) Batteries being monitored and kept charged.
2) Batteries going to the DC bus only when necessary. A diode in the main battery path can perform the switching.
3) For APU battery itīs a different story. Much simpler issue.
We are needing more details in order to analyze better. Like schematic diagram. Not just block diagrams.