Online UPS (SURT2000XLI) died suddenly with an internal vault: DC imbalance

[Neo_apc]

Therefore I'm looking for an answer, if this type of error is known and if it might be triggered by the battery pack age or if it's probably really a HW error of the SURT2000XL. We were satisfied for 28 month with this UPS model and expected, that it would work a bit longer after the warranty is passed for 4 month.

Before we invest in a new battery pack, I'll appreciate your support, because we replaced the UPS already with a SMX1500RMI2U and have run in an issue with the NMC2 communication after power failure.

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It does not make sense to buy a new battery pack, just for a test, which might be useless afterwards.

Attached you'll find a screenshot of the eventlog of the defunct SURT2000XL.

[Anonymous user · Accepted solution]

DC imbalance is usually a hardware problem I'm afraid. It relates to the DC voltages entering the UPS inverter (DC to AC) circuits...I don't have a block diagram of APC"s ups as they don't release these, but for other makes of ups from the battery pack voltage sometimes a DC-to-DC converter is used to derive separate positive and negative DC voltages with a center "common" or "zero" point...then it enters the inverter stages where its converted to the AC waveform...if there is any difference between the positive and negative DC voltages (the "imbalance") protective circuits kick in to shut down the show.