Its a low tech way to do it, but for testing big SLAs like that I use a rig with an inverter that runs on 12v, several lamps, and a clock with hands from a thrift store. Once its hooked to a battery with the lamps running, it will go by itself in a fairly safe manner, and when the inverter reaches a low enough voltage, it turns itself off, like it would to save your car battery. Then the clock shows how long it ran (digital clock wont work), so you don't need to watch it every second.
Then you can get a set that all run for the same length of time, so the pack isn't constantly trying to unbalance itself.