OT: Battery backup

[Jay Ashworth]

----- Original Message -----
> From: "Richard Kreiss" <rkreiss at gccconsulting.net>

> I have mentioned this before, I have a client who built his own battery
> backup system for his offices. It consists of 100 large backup batteries
> taking up a whole room. These batteries are fed by power filtered through
> power regulators. I am not sure if the batteries are connected in series or
> parallel.

The common method -- for reasons of equipment availability, would be to have
25 parallel strings of 4 12V batteries in series, for a total pack voltage
of 48VDC... just like the telcos do it.  Rectifiers (which is what they
seem to call chargers) are more easily available for that voltage, and
inverters work most efficiently on higher voltages -- 96V and 120V strings
are not uncommon either.

The problem is, it ain't cheap: I recently priced Group 8 deep cycle
batteries, which are the power/size ratio champs at 12V, I think, and
they're something like $700 *per battery*.  You can buy a pretty new
Corvette for that amount of money.

Cheers,
-- jra