NiMH cells emit smell of gas
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Posted by Jon D on May 21, 2006, 7:29 pm
Please log in for more thread options eof AA or AAA cells there is a smell of gas in the chamber under the lid. Seems to me that the cells are getting overcharge and are venting. This is a charger with a sensor for "negative delta-V" to edermine the end of the charging. The cells are about 10 to 15C above room temperatre. Is the charger cooking my cells? Or is the smell noticeable because of the enclosed battery compartment? | |||||||||||||||||||
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Posted by kony on May 21, 2006, 10:50 pm
Please log in for more thread options Yes >
>This is a charger with a sensor for "negative delta-V" to edermine the >end of the charging. The cells are about 10 to 15C above room >temperatre. Possibly the cells had vented previously and the seal is now open. I would throw them away, then wonder why they'd gotten hot enough to vent previously. Some Delta-V chargers only have a Delta-V detection but not temp monitoring, so if a cell were fully charged and an event like AC power flicker occured at long enough duration to reset the charger, it might then start charging at the fast-charge rate again, but there will be no Delta-V to detect since the cells were past that stage already... so if they get too hot, they vent which was better than an explosion. At the very least if you continue to use that charger, you might not want to fold down the cover to increase passive cooling. There are other things you could do like pointing a fan at the cells but it seems a hassle instead of just seeking a different charger, IF it seems the charger doesn't have the temp cutoff feature. >
>Is the charger cooking my cells? Or is the smell noticeable because of >the enclosed battery compartment? No with undamaged cells and proper charging (not overcharging) there is no gas escaping to be building up in the compartment. | |||||||||||||||||||
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Posted by UCLAN on May 22, 2006, 1:43 am
Please log in for more thread options Jon D wrote:
> I have a rapid charger with a fold down cover. When I charge a couple
> eof AA or AAA cells there is a smell of gas in the chamber under the > lid. > > Seems to me that the cells are getting overcharge and are venting. You need a better charger, like a Maha MH-C401FS. http://www.thomas-distributing.com/mhc401fs.htm | |||||||||||||||||||
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Posted by Evgenij Barsukov on May 22, 2006, 1:39 pm
Please log in for more thread options Jon D wrote:
> I have a rapid charger with a fold down cover. When I charge a couple
Not all cells can be rapid-charged, some have just too high impedance
> eof AA or AAA cells there is a smell of gas in the chamber under the > lid. > > Seems to me that the cells are getting overcharge and are venting. > > This is a charger with a sensor for "negative delta-V" to edermine the > end of the charging. The cells are about 10 to 15C above room > temperatre. > > Is the charger cooking my cells? Or is the smell noticeable because of > the enclosed battery compartment? > for that, as result they would heat up and went. Good rapid chargers come with the cells designed for rapid charging, or must at least have a list of recommended cells. Regards, Evgenij | |||||||||||||||||||
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Posted by on May 22, 2006, 3:24 pm
Please log in for more thread options
Jon D wrote: > I have a rapid charger with a fold down cover. When I charge a couple
> eof AA or AAA cells there is a smell of gas in the chamber under the > lid. > > Seems to me that the cells are getting overcharge and are venting. > > This is a charger with a sensor for "negative delta-V" to edermine the > end of the charging. The cells are about 10 to 15C above room > temperatre. > > Is the charger cooking my cells? Or is the smell noticeable because of > the enclosed battery compartment? deltaV doesn't work very well with NiMH cells because NiMH voltage either doesn't drop or drops only a very small amount when full charge approaches. Some chargers are much worse than others. The best use not only deltaV but also temperature, temperature difference, rate of temperature rise, and, as a last resort, time. | |||||||||||||||||||
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>eof AA or AAA cells there is a smell of gas in the chamber under the
>lid.
>
>Seems to me that the cells are getting overcharge and are venting.