I was given a 1440W Triplight UPS. Battery was dead so I ordered a new one and installed. Everything was working fine, then we had some T-Storms coming in so I put my computer on it and was good for about 6 hours then it just shut off (Main power never went off). I put the computer back on the power strip, and moved the UPS to the bench. I ran it with no-load and it shut off after about 16 hours. I then plugged a shop light in and the UPS shut off again after about 16 hours. I performed the self tests described in the manual and it performed as described.
I am not against tearing into this as I only have $19.99 tied up with the new battery. Inverter works, Switching from mains to battery and back again works. I am guessing an issue with the power on circuit. Could not find a diagram, so this could prove to be difficult with my skill level.
Suggestions?