[Motorola] MTR-2000 Battery Revert Questions

[Coote, Jay]

The manuals are  vague about 14 or 28V battery revert in the MTR-2000
low or high-power repeaters.
Motorola insists on using "their" revert unit.
I saw a few Batlab posts about someone using another unit, or making
their own....
 
Couldn't you just disconnect the AC power, and run the repeater from a
DC supply with it's own
revert and trickle system-  such as an Astron BB- series? 
 
Thanks