APC SRT2200XLI – Overcharging batteries (80V output, swollen batteries, burned connector)

[ApertureSC]

Hello everyone,

I have a question about my APC Smart-UPS SRT2200XLI.

I recently opened it after noticing problems with the battery pack.

Here’s the situation:

The UPS had been working normally for a long time.

All six internal 12 V 5 Ah batteries (LONG WP5-12) are now swollen, and one of the negative connectors is burned.

The inside of the UPS looks clean — no visible burn marks or damaged components.

Out of curiosity, I measured the voltage on the battery connector coming from the UPS, with no batteries connected, and I get around 80 V DC.

So my question is simple:

Is it normal for the SRT2200XLI to show around 80 V DC on the battery connector when no batteries are attached,

or does that indicate a problem with the charging circuit or voltage regulator?

Any help or confirmation from someone who has tested this model before would be really appreciated.

Thanks a lot!

– Esteban

[Teken]

The SRT2200 is a 72 VDC battery system as such the float voltage would hover around (approximately) 78 VDC using 13 VDC as a reference.

Real world the individual cells would be 13.6 VDC for a floating pack voltage of 81.60 VDC.

Maximum (charging) voltage using the battery makers specification data sheet is 14.4 ~ 15.X VDC. Using the lower (maximum charging) voltage that would be 86.4 VDC.

I can tell by the battery name (Long) this specific RBC has been in place well past five years!

The average service life is 2-5 years based on usage, temperature, and environmental conditions.

The cells inside are rated to provide 260 full depletion cycles before signs of degradation.

If we ignore over charging as the root cause for now - still possible.

The fact the RBC internal cells are swollen indicates this unit has been cooking off for a very long time! 🤦‍♂️

Show me a photo of the serial number of the system and the production date sticker for the RBC that’s swollen. Along with the following logs in their entirety: Event, Data, UPS, Diagnostic.

Long branded cells haven’t been used in any APC UPS for years!

NOTE: DC Voltage measurements must be taken at the Anderson connector with and without the RBC connected.

As the DC voltage measured isn’t under load.

Questions Ask . . . 👍