If really long backup times are required then why not scrap the whole
idea of large banks of batteries, that require constant charging,
replacement, and maintenance, and instead look toward the usage of
emergency AC backup generators. Any cheap UPS could be used to keep the
system up for the brief time interval that no AC power is available. The
power goes out, the UPS keeps the computer system up by switching from
line to backup battery. Then the generator starts, switches itself in to
the AC supply line, the UPS see's that once again it is receiving
120/240 Volts AC again (only now it's coming from the generator) and it
switches from backup battery back to line. Viola!! the system is up and
running as long as you can keep a supply of gasoline, alcohol, cow
manure (or whatever is used to fuel the generator). When the AC power is
restored the generator shuts down and everything goes back to full
normal...
Just an idea but, if possible, I think that a generator, even a small
compact AC generator, might be a more efficient way to go if it is
important to keep a system up and running during a power outage, for
periods much longer than the average high capacity UPS allows. No messy,
dangerous, hazardous, acid filled batteries need be kept on the
premises, no fancy charging schemes, etc...
/John
-- email: iojx.wgqapmi@inherent.org Local mailserver <landreau.ruffe.edu> , remote <ns.computer.net>He was not at all afraid for to be mashed into a pulp, or to have his eyes gouged out and his elbows broken.