[AFMUG] another battery question

[George Skorup]

I've got a Tripp Lite 2U UPS that recently needed new batteries. They 
have two internal 48v strings. 4x 12v 5Ah per string. Ordered completely 
OEM replacement string, threw them in, everything is fine.

The old ones however would cause the UPS to shut down instantly when AC 
was lost. I figured I'd find one bad 12v battery pulling the whole thing 
down. No, instead each string had one bad battery. What's odd is that 
the two bad ones were both at the "end" of the strings. The other six 
tested fine.

I've seen this multiple times now on different stuff. If all of them 
aren't bad, it's always the battery at the end. I've noticed this on 24 
and 48v systems. My question is why? Is that battery taking the brunt of 
the surge current upon transfers?

The other thought I had with this Tripp Lite thing is that both of those 
batteries were probably the closest to the heat generating components, 
inverter, etc.