So this is interesting, I felt something was not right with how fast the voltage drops on the test batteries I bought so decided to push them more. 4x 7.2ah batteries should give me 345wh, or 172wh usable (never want to actually fully discharge lead acid batteries). But as soon as I pull the plug, with just a light bulb running at 48v it drops below 48v within a minute.
Decided to let it go to see how fast it drops further. Well turns out, it stabilizes at around 47.37v.
Mind you this is a 120v 150w bulb running at 48v, so it's only like a 40w load. According to my calculations it should run for 3 hours but I highly doubt that. But it's still reassuring that it's not just dropping fast like I thought it would. Amp hour rating of batteries is based on a 20hr rate so when talking with small batteries like this you're only really getting that rating on a very small load.
I might actually look at getting an inverter soon since I'll technically have a fully working dual conversion UPS at this point. I'll plug the workstations into the inverter and if I get 5-10 minute run time out of this I'll be happy for now, until I get the proper batteries. Will be a good test before this goes live for real.