Jetavia,
My thoughts were along the lines of Alexban with the thought that the battery may short, die on you, whatever. Boeing says it's impossible. But nothing is impossible.
Alexban,
My initial thoughts were similar to yours. Looking at the circuit diagram I'd have thought the battery charger would power the Hot Battery bus, after all once it's done charging it reverts to a TR mode.
However a TRE in my company has come up with this one and I'm not sure he's right. My Boeing Vol 2 diagram suggests that the battery charger would power the hot battery bus whilst in TR mode. But then say the battery had shorted would the battery drag the charger down with it therebye rendering the hot battery bus unpowered? Just trying to figure out where he's coming from!
Multiple multiple failures! But interesting nonetheless!