When you own any APC Smart UPS, and especially SUA1000XL or greater, you should always follow APC Specific rules about run-time calibration, or you will be in trouble.
SUA1000XL this operates with 24V pack = two 12V cells in series, and up to ten external battery packs.
I am using a pair of car batteries 45AH its one, the one go bad and I did replace it with another one.
My SUA1000XL calibration this were messed up, as the old and damaged battery was not able to hold more than 9 minutes (PC on idle), the second culprit was the APC monitoring software, it was filing up Windows event viewer long with alerts every time that my PC was not idle … with insufficient runtime Alerts.
At my first attempt to calibrate the UPS with a good pair of batteries, the UPS failed to do so, even if it did hold for two hours and a bit more.
Reason: My PC was on idle approximately 150W of AC load.
I was had to search over the internet and find the golden advice of APC. The long story in short, I did use
375Watt (2x 150W + 75W) of Incandescent light bulbs, a pure resistive load.
b) Removed the USB cable
c) Turned off AC power
d) Leave the UPS to run until to shutoff by itself (batteries depleted)
And thanks God, the miracle it did happen, and my UPS calibration this is now restored.
2023 New record: 180 Minutes on idle, 157 minutes (2.5 Hours) at light loads (watching video or other).
The replacement battery this is a used one, pulled from a car that was not having frequent activity, and this battery developed the symptom to require higher charging time period.
My SUA1000XL this has an exceptional charger which ends up to constant Float charge when batteries are full, in the form of pulsing.
This magic pulsing technique, succeed several times to recover batteries which was having slow top-up issue, it might take one month or two, but any not permanent damaged battery this will eventually wake up.
I feel lucky that I did find a good used battery again, but its winter time at average indoor temperature of 15C,
and due temperature compensation issue at SMF and AGM cells, the top-up voltage is not enough as they require a bit higher, in contrast when indoor temperature this rise at 25C~30C, the charging voltage (from the UPS) this will be sufficient to charge them, and run-time this will further increase by 15% because both cells will have a better energy absorption behavior.
I did write down this fresh adventure of my, so to never forget again this lesson.