[Fot] UPS power backup

[Randall]

> I always wondered if it was possible to connect several car 
> batteries to a gel-cell UPS of any capacity (mine are 450-650 
> VA) to extend the time.

There are definitely UPS units available that are designed for use with
external batteries.  We had one at a former job that would keep the PC-based
phone system up for 8 hours, totally unattended; and as I recall it could
have more batteries for up to 24 hours runtime.  Even had a feature to call
for help (assuming the external phone lines still worked) when the battery
voltage started to drop.

But it looks to me like you could open up any cheap UPS and wire it to wet
lead-acid cells instead of gel cells.  Might have to adjust the charger a
bit to keep them charged, but fundamentally it should work.

-- Randall