[PLUG] Recommended battery UPS?

[Tom]

In my experience, I've had the best luck buying broken rack mounted UPS
units from data-centers and utility companies, ignoring all the high
voltage/death/no-user-serviceable-parts-inside warnings, safely
discharging the capacitors and fixing the units usually by soldering
replacements for the broken parts in.

After that you can build your own battery packs by just buying sealed
lead-acid batteries and wiring them in such a way that they produce the
current voltage and current as the factory packs, though if the cooling
is good enough on the inverter you can put better batteries in
extending the life of the unit past factory abilities.

Most of the time the part that goes bad on them are the transfer
relays. APC likes to use cheap Chinese ones that die from arcing well
before the rest of the unit goes bad.

One of the things I have been looking into but have not tried yet is
using MOSFETs to do the switching instead of sourcing compatible
replacement relays. It would be much more reliable and power efficient
as well and last much longer being completely solid state in design,
however the biggest problem is less isolation of the control circuitry
and the gate signal voltage when adapting into an existing design.

If someone has experience with MOSFETs in power designs I'd love to
connect with you.
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