Why won't my Back-UPS CS run longer than 45mins with a low load connected?
BK350, BK500, BK500BLK BK350EI and BK500EI
Safety Runtime Limiter
The 120v and 230V International Back-UPS CS models BK350EI and BK500EI, that were made before January 1st 2004, have a max runtime cap of 45 minutes. Anything made after that date will not have a runtime cap. Instead with out the shutdown software they will run until then have exhausted their battery.