@ captain87
With RAT out, the AC buses remains on battery power until reaching a minimum level of 22.5 v ... to allow an APU start on ground ...
NO, SIR!
Tha'ts not making any sense at all.
In your first an last posting you stated twice that AC BUS 1 an d 2 remain powered in EMER ELEC (i.e. during RAT-Operation). That's not correct, I'm afraid.
With RAT out AND EMER GEN running, the AC ESS BUS and the DC ESS BUS are powered and off course the HOT BAT Busses. That's it.
An APU Start on GND after Landing with EMER ELEC would be the least of my concerns
Kind Regards, MAX