To assess the battery condition you need to check the battery voltage. If opening the UPS and measuring the voltage with a multimeter is not possible, you can use the in-software provided measurement tool. Please avoid misinterpreting the reading: When the UPS is charging, it will apply a charging voltage approx. of 13.7 VDC to the battery and it will try to boost the battery voltage to this value. If the charger is active, the software wont read the battery voltage, instead it will read the charger voltage. To avoid this, you need to switch into battery mode (simulate a mains failure). Without AC input, the charger will switch off and the battery voltage will shortly stabilize at its real voltage. At this point, you can get an accurate reading of the battery voltage. Unfortunately, if the battery is in very bad shape it may immediately switch off the UPS and you may experience immediate shutdown. If the software was monitoring the UPS, it might have recorded one entry with very low voltage before shutdown.