Yeah, this APU/battery running out problem is ridiculous.  I had that happen yeserday after spending 20 minutes getting everything set up while on external power, fire up the generator, push back, get ready to start the engines and wham everything goes dead.  I had to reload the aircraft and then setup everything all over again.   Just stupid and totally unrealistic.  They need an "infinite battery" option like some other products have to avoid this problem.

I also had just the radios untuneable problem also.  Had to do another restart.  Starting with the default Cessna is no fix.  Maybe I should try the default glider :-/