Looking for a UPS Design That Doesn't Overheat Batteries

Will · 2006-06-01T04:45:02+00:00

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. After working with an electrician, I have a theory about why this is happening, and if correct, the theory suggests a different design for UPS systems that would avoid the problem. I am hoping some manufacturer has already implemented this idea and someone can refer me to their products. On all of the UPS systems we use generic "brick" batteries are joined together in a series, then the leads from the ends of these battery chains are connected to the UPS. The problem is that batteries rarely fail all together. If a 12V battery should be considered discharged and not useful at around 10V, and you have two 12V batteries joined in series, what happens when one of the batteries maintains a full charge at 12V but the other battery in the series starts to lose its ability to hold charge and slips below some critical level? From the point of view of the UPS, it doesn't see anything about the state of individual batteries. The UPS only sees that the total voltage of the two 12V batteries in series has fallen from 24V to 22V. Maybe an electrical engineer can step in here and explain what is happening, but my pure guess is that to maintain the same power output, an increased amount of current probably has to flow through the batteries. That creates problems with heating for the "good" battery, which is still measuring 12V. Now that 12V is receiving too much current, overcharges,...

Jun 01, 2006 22 Replies

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You 20 years ago

Obviously this guy never heard of a Diesel injected engine..........

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no one that you know 20 years ago

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Roy L. Fuchs 20 years ago

On Thu, 08 Jun 2006 19:41:51 GMT, You Gave us:

I know more about internal combustion engines than a retarded twit like you ever will, including diesels. Diesels do not require an atomized fuel charge at all. Only pressure.

Sorry, liar boy... your "ten cylinder" car is NOT a diesel.

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