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  1. #1
    RC Enthusiast
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    Temperature of nimh cells

    I have several 7C batteries and I'm curious if anyone else has ever tested the temperature of each cell after charging.

    Since I've started, I've noticed that the temperatures continue to rise after being removed from the charger and the temps usually rise another 10-15 degrees after being removed. I hear that 125 is the ideal temperature, but the cells hit 140 if I stop the charging at 125...can anyone explain this? Am I destroying my cells?

  2. #2
    RC Turnbuckle Jr.
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    The temperature rise you described after the charge cycle has ended is completely normal. A 125F charge-ending temperature is a little high. If your charger has an adjustable cutoff feature, try lowering that setting until the cells finish charging about 5 to 10 lower.

  3. #3
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    I completely agree with you on the temp setting.

    I was following http://promatchracing.com/4600.php and the MAX rating is 140, after which damaged could occur. Since I'm hitting 141 after stopping at 125, I was confused on which one to follow.

    Thanks for your help. Stopping at 115 or 120 would only be a different of like 50mAh, so there is no real need to create that much heat.

  4. #4
    RC Qualifier
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    Yea mine got that hot, and after i went to 13 cell , the 6 pack got even hotter enough to melt electrical tape off of them. 185F LOL(after a run not charging) . I don't recommend it. play with the delta voltage of the charger it might be missing the high point. The thing i didnt like was , after about 6 or 8 charges i noticed the cell imbalance , because some cells would be at 120, while others at only 85F.

    My advise keep the nimh for under water sports, and get some lipos, they will give you very nice power , very reliable, and last longer , if treated well. and if you don't treat them well, they will bite you anyway.you'll need more then battery's if they get mad . Lipo's are the future. I have been running them in my aircraft since 2006 . some are still going. but i have never had good luck with nimh.

    yes along with lipos, need charger, balancer, LVC, and all that. but its well worth it.

  5. #5
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    I agree and much prefer lipos to nimh. Easier to charge, VERY easy to balance, faster to charge, etc.

    I only got these nimh packs for underwater work and driving in a frozen pond :-) Oddly enough though, these promatchracing cells perform better than my 4S 5000mAh 30C lipo configuration. The power is just crazy! Then again, I could always increase the pinion size to account for the lower voltage, but them I'd be risking a lot when I drive in the lake or pond.

    Thanks for the tips on heat issues. While the batteries are awesome at PMR, the website could use some upgrading.

  6. #6
    RC Turnbuckle Jr.
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    Quote Originally Posted by fidelity007 View Post
    I ... Oddly enough though, these promatchracing cells perform better than my 4S 5000mAh 30C lipo configuration. The power is just crazy!
    Neither odd nor surprising at all.

  7. #7
    RC Racer
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    Jan 2010
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    Quote Originally Posted by fidelity007 View Post
    I agree and much prefer lipos to nimh. Easier to charge, VERY easy to balance, faster to charge, etc.

    I only got these nimh packs for underwater work and driving in a frozen pond :-) Oddly enough though, these promatchracing cells perform better than my 4S 5000mAh 30C lipo configuration. The power is just crazy! Then again, I could always increase the pinion size to account for the lower voltage, but them I'd be risking a lot when I drive in the lake or pond.

    Thanks for the tips on heat issues. While the batteries are awesome at PMR, the website could use some upgrading.
    Yeah, mine last about 50-55 minutes and the Summit screams now. Non-PM NiMh batteries ho-hum now. I dropped to a 12T Pinion. I'm sure Lipo's might give a lot of punch, time, etc, too. Right now I just don't need anymore power or runtime, so I'm sitting tight.

    Can you charge at a lower rate? What rate are you at now? I think mine are at about 110 when the charge peaks.

  8. #8
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    Charging at 4A gives me 115 when peaked. 5A is about 120. Both hit 135-140
    after removing from charger.

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