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Old May 20, 2003, 9:05 PM   #1
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Default Adding a fan to my battery charger?

I plan on buying a Maha C204F charger for my piles of NiMh batteries. I know like all fast chargers it causes the batteries to get a bit warm, and they don't like that. I was thinking...would it do me any good if I was to somehow attach a small cooling fan above the batteries?
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Old May 20, 2003, 10:26 PM   #2
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I doubt it would hurt, but they do design the charger with the heat in mind (some chargers say to leave the lid open, I don't know if that one does.) So I'm not actually sure it would help.
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Old May 21, 2003, 4:25 PM   #3
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the Maha 401 certainly does tell you to leave the lid open

Stefan
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Old May 21, 2003, 4:57 PM   #4
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Buy the Maha 401FS charger, it has a slower COOL charging feature, and it even charges fuller in this mode.
I have one and it is a great charger.
Even in the fast mode it is not hot, sometimes warm and sometimes much warmer, but not what I would call hot (I have had the Rayovac 1 hour charger and that is HOT).

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Old May 21, 2003, 8:12 PM   #5
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The instructions for the Maha 204F say to leave the lid open while charging . . .so I do. I have charged depleted AAs (4-up) whith battery capacities ranging from 1600mAh to 1850 mAh as well as 750 mAh AAAs and have stuck my (calibrated) little pinkie on the battery case(s) periodically during charging right through to the end and, while the battery cases get hot, they were never too hot to touch/hold (which according to my pinkie calibration chart says the bats are 120 deg.F or less).

IMHO, a fan isn't needed, although it certainly wouldn't hurt either.


By the way, the Maha 204F is an excellent charger...recommended.
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Old May 21, 2003, 8:32 PM   #6
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I know it isn't needed and won't hurt...but is it worth my time?
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Old May 21, 2003, 9:45 PM   #7
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Quote:
I know it isn't needed and won't hurt...but is it worth my time?
I don't think so. It might increase the batteries some.... but I doubt it would be much. Add in the noise of the fan, the danger of keeping things away from it (ok, I have a cat...) and the hassle of building it and maintaining it. I wouldn't do it.
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Old May 23, 2003, 4:09 PM   #8
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Most decent chargers use some form of temperature monitoring for shutting down after the delta voltage charge measurement has calculated its figures. I know some chargers use air temeperature in the batt compartment (which I think is pretty useless), some using the same charge reg,. chip have nothing, and the better ones have a contact thermistor, and the best in proprietary packs, have the temperature sensor bonded within the pack.

So fan cooling might just push more charge into the batt. than what's good for it and negate any overcharge monitoring by the chip. Anyway, I doubt whether you could air cool sufficiently to affect the central core temperature much, which is what matters. You'd need fins on your batts!
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Old May 24, 2003, 5:30 AM   #9
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Why does Maha put a cover on their chargers and then expect people to read the manual (most probably don't) and leave the cover open? It has to cost extra to manufacture the charger with a cover that is not supposed to be used while charging. Sounds like they are inviting some enterprising attorney to sue them since they are liable by installing a cover in the first place knowing that it could cause problems if closed.

From what I've read on the issue, if the batteries are hot but able to be handled you are well within the safety zone. I don't know the exact figures but I recall either Rayovac or eveready stating that temperatures around 200 degrees celcius would damage the batteries. You would not be able to touch or hold one at that temperature for quite a while after charging. My Rayovac One Hour charger is the fastest available and the batteries get very warm, but not to the point of being unable to handle. I've had my charger and batteries for almost 2 years and have had no loss of capacity.
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