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Old 04-18-2014, 06:15 PM   #15 (permalink)
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I did manage to over heat 1 cell in a pack. I did some research and the highest temp I could find that was acceptable is 60C or 140F. In Texas the inside of the car can get to 120 so I'm not sure if that is a good number.

The problem I ran into was that I was charging my worst cells at 5A with a 7500mah limit with no fan. I looked when they were at about 7000mah and I checked the cells with an IR thermometer. 5 of the cells were 120F and 1 was 140F. In about 5 minutes it went to 160F and I aborted.

At that point I changed to 3A charge, 6500mah limit and added the fan.

So the problem with a single point temp sensor is you may not be on the cell that needs it.

Here is a really good site that talks about NiMh charging in general.

Technical Tips for NiCd and NiMH Battery Pack Users — CamLight Systems
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