Ran more and final test today using 5ah 7s rc lipo cells. 24V Conext (APC) 750VA ups, 100W load. Ran it down until the ups actually shut itself off. Monitoring the cells, the lowest one got to 3.49V just before shutdown. It recovered to 3.52V before I plugged it back in. Or approx. 3-4% soc. These are cells over 4 years old. When fully charged, software was reporting total voltage of 28.1V, which averages out to 4.01V per cell. A check of cells with a medic showed them at ~3.95V per cell. but either way, well within the max charge of 4.2V per cell. So my conclusion is 7s rc lipo on a 24V ups system not only works good, but will be far superior to sla batteries. As a disclaimer, it is not recommended by the manufacturer, and will possibly void the warranty, which will probably be up by the time the original batteries die anyway. Also the risk of lipo batteries catching fire will be greater, so do so at your own risk. I'm not worried about it.