One should buy the original battery for this UPS perhaps. These batteries have a very poor performance, which hold more than a minute without electricity by! Tested multiple, normally should for a few minutes but can bridge at least 15 minutes, but even with the low power requirements of my TS-809 QNAP captures the UPS with a bit more power consumption directly to flash. I have the batteries also explicitly calibrated with the use of APC several times, no improvement! Dear original batteries next time.
