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Unfortunately, I haven't a clue what their capacity is; everything I know is printed on the label.

I didn't really expect too much out of them; just that if they could run our data center with dozens of 400-1000 watt servers for 25 minutes then it should be able to run the house for a couple hours...

I do need to figure out the pack capacity though - based on the info displayed on the sticker, is there a formula to figure out how to convert from "284W/cell 15min" to Amp-hours/kilowatt-hours?
Well, the label says 284 W/cell for 15 minutes, which with 6 cells/battery would be 142 amps @ 12V for a quarter of an hour, or 35.5 amp-hours per battery at a 4C discharge rate. That's 284 W/cell * 6 cells *0.25 hours = 0.426 kWh each. The set of 72 of them should then deliver 123 kW for 15 minutes (and half that for half an hour).

Yes, at an 8-hour discharge rate (C/8) they're 70 Ah each... as expected, much higher than the 4C rate. The 20-hour (C/20) capacity would presumably be even better.

At this slow rate, energy capacity is nominally 70 Ah * 12 V = 0.840 kWh each, and the average discharge power over 8 hours would be about 100 W each. That's 7,200 W for the whole bank to power the house, which is a lot for a house... good, because my guess is that you don't really want to discharge to 1.75 V/cell if you can avoid it.
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