Symmetra PX100 bad runtime w/ new batteries, calibration

[ElectricAvenue8]

Hello,

We started using a Symmetra PX100 (1 battery cabinet) in December 2024. It was relocated here and I was new to the unit, so we had an APC engineer examine the unit thoroughly and perform the startup; everything checked out fine, and the unit worked great for 6 months.

In June, it performed a scheduled battery test, and the runtime tanked.  We ran a runtime calibration test, and the runtime under similar load went from 68 minutes to 25.

Then there was a lot of back & forth about the finding that the batteries, dated 2024-06, sat in company storage for 6 months (due to unforeseen project delays).  The seller asserted that this caused damaging degradation to the packs, causing the issue.  Nothing else helped, so we relented and shelled out for 20 new battery packs, which I calculated should get us up to an acceptable runtime.

I installed those 20 new packs, removing all old ones. Charged them to 100.0%. Runtime was still bad. I performed yet another runtime calibration — and it's at 22 minutes for a 11.5kW load.

Compared to 75 minutes we should have per the specs (55% of a cabinet, 11.5kW load), this is severely off.

Our load fluctuates between 11.0 and 14.5 kW, and the low runtimes stay proportionally consistent over days.

We have 5 power modules, for a 40kW N+1 capacity, so 28~31% load.

Besides runtime / battery capacity warnings, the unit has not flagged any warnings/errors, and always reported all batteries were "OK".

I know that pairs are connected serially and it's recommend to fill out entire battery rows (=4 packs), but that is already what we're doing.

I'm at a loss here…