With most UPS's there is electronic circuitry to reduce the home voltage to 12 or 24v to store in the battery, and then another circuit to raise the voltage back to the home voltage. I know there is always a loss when attributes of electricity are changed. This seems very wasteful to me. I want to build a UPS for my notebook computer, that I use as a home server. The power adapter for the notebook creates 19 volts but the notebook itself uses 12 - the other 7 is perhaps used to charge the battery while the computer is on. I would like to put together a UPS made of 12 volt Ni or LiFe packs - would most likely be 13 volts but I don't think that would be a problem to avoid the double switching of the power. Can anyone point me in the right direction?