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HelicopterRadio - Servo - Gyro - Gov - Batt › completely drained my tx 2700 mah nimh battery by​accident.....
08-09-2007 04:35 PM  10 years agoPost 1
patriot21

rrKey Veteran

Byron,MN

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My question is... is when i charge it the voltage on the charge was topping out at like 13.00 volts plus and the batteries were really warm....i am using the accucycle batteries...any recommendations or ideas...as to why the battery pack is getting so hot and why the high voltage

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08-09-2007 04:51 PM  10 years agoPost 2
tadawson

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Lewisville, TX

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You don't say how many cells the pack is, but assuming it's an 8 cell pack (most TX packs are), then the normal fully charged voltage is around 1.4 per cell, for a pack voltage of 11.2 . . . and to charge, you need to get over that, so 13 is not that unrealistic.

But, since you state that it is getting hot, the question becomes, what current are you trying to charge it at? Hot typically means too high a current, and the high charge voltage is also consistent with a charger trying to push too high a current . . . .

Set the charger for 1/10 C (270MA) unless it is a pack that has fast-charge capabilities, and go up accordingly. Myself, after dumping one totally like you did, I would charge at 1/10 C the first time no matter what the pack is rated for . . . (I recently goofed and charged my TX pack, an 1800 NiMH at 1 amp, and it got quite hot too! A lot of these NiMH cells just don't like fast charging . . . )

- Tim

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08-09-2007 06:24 PM  10 years agoPost 3
MJWS

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Airdrie, AB - Canada

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Yep. Good advise.

It isn't typically a problem to have drained a nimh all the way. I don't know what you have for a charger. I'd slow charge it and see what kind of capacity it takes. If normal, just move on. If it seems a little down, just cycle it a few times at a nice low rate. You can start increasing current after that depending on the cells.

No point in being hard on Tx cells. My 2700's will take a fast charge but still don't get hit over 1C.

Mike

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08-10-2007 01:24 PM  10 years agoPost 4
jsenicka

rrProfessor

Eagle River, WI

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The 2700's from Hangtimes recommend about 160mah for 20 hours.
The AA size packs generate a lot of heat, so they are recommending less than 1/10 for normal charge. Or you can go near 1C with thermal management.
I cooked one of my 2700 TX packs using an older charger with no temp probe and sometimes dodgy peak detection. Now I only charge faster than 200 or so MAH with my Accu Cycle Elite and temp probe

Jim Senicka
Team Manager, GrandRC Flight Team

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