Our company has had a long-standing problem where UPS batteries will at
>various points in their lifetime suddenly overheat, sometimes
>catastrophically to the point where the battery casing starts to melt and
>you can actually smell the gases from the battery leaking. So far we have
>been lucky to catch such thermal events with temperature sensors but it has
>always been a goal of mine to better understand why this happens, and to
>find some UPS system where it can be avoided entirely. To date, we have
>seen these problems with APC Symmetra tower, Symmetra rackmount, and
>SmartUPS.
Thermal runaway has been an aspect of sealed batteries for some years, we saw this in the early 1980's when we were distributors for Gates Energy.
Temperature compensation on the charge circuit will help get around this, but cell failure in a block, batteries too close together with no airflow around them and unbalanced batteries in a string all contribute.
It is more prevalent in UPS's with enclosed cases and where they are trying to screw the maximum output from the minimum battery.... :-))
I have only replied to this newsgroup, not the long list of others it was posted to.
Peter
-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:
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