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fly boy318/06/2018 23:26:30
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3320 forum posts
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Hi all,tried out my new charger today. IMAX B6, Battery was a 2300mah, NiMh Rx and was brand new. Programmed charger to operate at 1amp. At end of charge the battery was quite warm to touch. Only ever having used the so called "overnight" charger and never experienced heat in this mode, have I made a mistake ? Cheers

john stones 118/06/2018 23:28:48
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Nimhs get warm when I charge them.

fly boy318/06/2018 23:33:51
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3320 forum posts
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Thanks John, I'm new to this type of charger. Would 1C be 2.3 amps in this case and got even warmer ? Thanks

john stones 118/06/2018 23:42:18
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Yep and fast charge makes them warmer for mine, all normal.

fly boy318/06/2018 23:52:56
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Thanks John, feeling better now lol, got a lot to learn. Cheers

Jon - Laser Engines19/06/2018 08:28:21
4087 forum posts
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I tend to charge everything at 500mA as it creates less heat and, i hope, makes the cells live longer. Stuffing an amp into an AA cell is quite a lot and to be fair i would only charge that fast if i was in a hurry and really needed it done quickly. In general, stick with half an amp if you can.

I also dont recommend doing a delta peak charge on a new battery. I charge them at about 100mA for as long as needed for a full charge (about 20 hours for your 2300) and then apply a small load with the charger and discharge them to about 50%. I then top them up slowly again, run them flat this time, and then slowly recharge them. After that i go back to my half amp and peak them without consequence. 

Edited By Jon - Laser Engines on 19/06/2018 08:30:59

Biggles' Elder Brother - Moderator19/06/2018 09:20:14
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I agree with Jon, I think its best to be a be gentle with NiMH batteries. Lipo's I will routinely charge at 1C, or even 2C. But I put a self imposed limit of 500mA on any NiMH.

TBH, these days, except for my Tx battery which I charge using the wall wart, I don't possess any NiMH's now. As you probably know I use electric power and on those larger models where I want separate power to Rx, servos etc., I usually use a 2 cell LiFe which is much lighter than a NiMH pack and charges about 4 times faster as it can be charged at 1C.

BEB

ken anderson.19/06/2018 09:42:57
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don't worry FB3.....the heat is normal...….I was told when I first started with the NIMH's that a slow charge (overnight) to allow them to form themselve's...after that a fast charge is the order of the day...…. job's a goodin… mind you I did in haste set my charger away on lipo setting for my NIMH's and ended up melting the TX back case....(Futaba) kulou

ken anderson...… ne...1..... job's a goodin dept.

AVC19/06/2018 13:36:02
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539 forum posts
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Agreed with Jon and BEB. My rule of thumb for NiMH has always been to charge them at 0.1C, unless you really need a quick charge, and in this case never more than 0.5C

I still have some old NiMH in working order, so this must work I guess...smiley

fly boy319/06/2018 16:31:40
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3320 forum posts
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Thanks all. Lesson learned, lower amps it is. Another query regarding this specific charger, manual says to alter amps and volts ? Do I have to change volts if using different cell counts or will charger automatically sort this out. Still learning. Cheers

Jon - Laser Engines19/06/2018 16:46:43
4087 forum posts
154 photos

in the case of nikel batteries the charger should sort it out on its own. In the case of lead acid or litium based batteries you need to tell it what to do.

I rebuilt one of our 120's a little while ago for a customer who got this wrong. The engine was quite fire damaged, as was the rest of the bottom floor of his house.

fly boy319/06/2018 18:11:15
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3320 forum posts
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Thanks Jon, you are right of course. The manual needs a lot of reading initially, but I will get there . Thanks again.

Allan Bennett19/06/2018 20:23:36
1399 forum posts
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Like some of the others, my normal charge rate for NiMh Rx batteries -- irrespective of their MAh capacity -- is 0.1C.

But NiMh packs that are designed for motors, usually Sub-C size and upwards, can generally be charged at 1C with a peak-detect charge mode. But even they benefit from a long slow charge from time to time to get their cells in balance.

fly boy319/06/2018 21:11:22
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3320 forum posts
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Ah ha, nice one Allan, manual does not mention nimh for motors, this is probably where I had the 1C from. As I said I have lots to learn and thanks to this forum for all the help. Cheers

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