Let the uswork withinside the mains nation, set the multimeter withinside the voltage range, join the take a look at pen to the Anderson plug at the again of the UPS, and at once degree the DC voltage achieving the UPS. Ar yr adeg hon, one character observes the show of the multimeter, and the opposite unplugs the enter line of the UPS, and observes the show of the multimeter in the mean time of strength failure. If the voltage price drops lots instantly, it approach that there's a hassle with the battery. If the relationship hassle may be eliminated, and the battery It has been used for approximately years, so that you want to bear in mind changing the battery pack.