A solution I found was to add the following line to the CFG file of the aircraft under the electrical section:

electric_always_available = 1

I had the same errors other had that after about 10 min of operating the avionics and starters no longer worked.  It appears that the battery either doesn't charge the electical coding doesn't swith over to the generators in some cases.  The only draw back this solution has is you don't have realistic battery life - its indefinit, but it a small price to pay to have you avionics or starters not stop.