another hot battery thread....sorry

[olvegrn]

Hi all! I finally, after 3 years, made the step up from a 1:18 to a 1:10 crawler. Because my older rig came with a battery and Charger, I had to buy both for the new rig.
So, here's my situation.... I am running a venom nimh 7.2v 5000mah battery. Runtime is a little over an hour, which is fine since my trigger finger is aggressive.
Here's my concern. I am charging it with a radiant ascend charger. The charger is set at 5a, but charges at 4.5 for safety. It starts charging at 8.4v and climbs from there to 9v by the time its done charging an hour later. The battery feels fine till the last 10 minutes of charge.....it gets super hot! Help!

[Trubble]

Perfectly normal.

You're charging at a rate of 4500 miliamps per hour, hopefully not using 100% of your rated capacity, so an hour for charge time sounds right where you should be.

The heat issue stems from the fact that NiMhs/NiCads start to radiate excess energy as heat once they've reached full capacity and you continue charging. Your charger's Delta Peak value is apparently set just a wee bit high for that battery pack. I doubt it's adjustable on that charger, don't know, though. If you're worried about it, check the battery after 55 minutes or so, and pull it off once it starts to heat up.




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[olvegrn]

Originally Posted by Trubble

Perfectly normal.

Your charger's Delta Peak value is apparently set just a wee bit high for that battery pack. I doubt it's adjustable on that charger, don't know, though.

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Thanks for the reply, it really helped put my mind at ease. This is all so new to me...I feel like a greenhorn.
My charger is set at a delta peak of 7. I can adjust it, and will do so. I still don't know the deal with it charging at 9v for a 7.2v battery though.....

[Ryan87zuk]

7.2 volts is nominal. Volt increase is normal. Just like a 2 cell lipo- 7.4 volts but fully charged is 8.4

[Charlie-III]

Originally Posted by Ryan87zuk

7.2 volts is nominal. Volt increase is normal. Just like a 2 cell lipo- 7.4 volts but fully charged is 8.4

+1, NiCD & NiMH cells are rated at "1.2VPC" (VPC = Volts Per Cell). Fully charged they are over that though.

As mentioned, what you see & feel is normal. Hot is relative, at a fast charge rate and full charge, it should be rather warm, but able to be picked up & held without burning your bare hand.