The best way to test the batteries of your UPS, and I assume you are talking about a big UPS, is to mesure them with a multimeter (digital) on the different working states. That is on discharge cycle, on charging cycle, and depending on the UPS on flote cycle. To do that you should be VERY carefull, you better call a technician, it could be DANGEROUS!!!!!
If you need more info just emailme the UPS characteristics, and I will tell you how to do it.
Regards,
Jose.-
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Pablo Mir
pm@pablomir.com