I have found the perfect UPS!
It is a Best Power Systems MicroFerrups.
Mine is the 850VA model.
What makes this so great is the batteries are 12V!!!!
This ups is made up of 2 units, the inverter and battery cabinet.
The inverter is your basic high current inverter/charger.
The battery cabinet consists of 3 12V 100A GelCel batteries wired in parallel with AWG 1 welding cable. Each battery is fused on the positive side with a 200A fuse at each terminal. The connection to the UPS is made with an Anderson Power connector 300 Amps!!!
At 12.83V per battery most rigs will run great! If you go purely on capacity the current means that a std 20A draw for a modern HF radio at 100W could key down for 15 hours straight!!! At 2A recieve it goes to an unbelivable week or more!
Best is no longer in existence but you can find these being replaced by Telecom and datacenters, most, like mine with brand new batteries.
If you just want the batteries they are $220 each through most computer warehouses.