Jeeze, you have some nice batteries. I'm not sure what the UPS battery is, but they are usually not a lot of amp-hours. My guess is your 170 Ah battery will be far more than the one it came with. It doesn't HAVE to fit in there either. You can run the cables out. Also, if you wire them in parallel you will get the combined Ah of the batteries. Make sure they are not near dead by testing the voltage because this will kill the other battery if you don't (it will always ruin a battery array).Originally Posted by samtheman
Lastly, charge your batteries before running the test so you know how long it will last in a real situation. Just wire them up and plug them in for a day or two or three... it depends how fast it charges, etc.