I have two APC battery packs. Each one consists of 8 12V/7AH SLA's wired in series/parrallel for 54.4V output. The units have a built in auto charger that charges the batteries when 10% less than full charge and then switch off again.
I had been using them to power a pair of UcD 400 amps (two in series for -54/0/54 rails). They are *extremely* heavy and I don't have an appropriate box, so local pick up only. $200.
These could be used to power whole systems if well thought out, or TT's, source components, preamps, whatever.
edit; gordy is right, these are 7ah battery, which are standard.