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Old 03-05-2008, 10:20 PM   #1
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Default NIMH Charging Safety

Hey all,
I've never had a nimh cell blow up on me while charging, however, reading some threads and seeing some cells that have blown up kinda has me a little concerned. Being still in college, thus living in an apartment, I usually cycle my batteries in my room. However, I would hate to have one of my IB 4200's blow up on me.
Are there any types of precautions one could take...like some sort of container to charge the batteries in for safety? I would hate to catch the apartment on fire.
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Old 03-05-2008, 10:35 PM   #2
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you can buy a charging sack for them
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Old 03-06-2008, 12:58 AM   #3
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always monitoring with temp sensor under 50degree
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Old 03-06-2008, 01:22 AM   #4
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Id have to say the use of some sort of container is essential and should be requirement at all clubs, events etc...
the saying goes "prevention is better than the cure"

The temp sensor is good for charging but with only 1 cell being monitored its not a perfect option.
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Old 03-06-2008, 05:40 AM   #5
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Make sure you discharge the cells properly before you charge them. Discharge the cells to 0.9V/cell and straight after discharging, charge them on a good linear charger at 6A and set the threshold not higher than 5mV/cell (if your charger values the threshold for the entire pack it will be 20mV for a 4cell pack, 25mV for a 5cell pack & 30mV for a 6cell pack). If your charger has a temp. probe, set this to a max of 50-55 deg. CELCIUS. When you are done racing for the day, make sure you discharge the pack and then charge it at least half full for storage. NiMH cells don't like to be put away empty.

When the next race comes up, discharge & charge as mentioned in the above. This way the cells can live a long time and will not explode.

p.s. I can not be held responsible if the cells do explode because it can always happen. Therefore, keep monitoring the cells during the charge!!!
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Old 03-06-2008, 07:10 AM   #6
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I would caution about using a sack or anything that prohibits ambient cooling of the battery pack. It is the build-up of pressure inside the cell that causes the ends to pop off. I have yet to pop a single cell, never mind a whole pack. I always equalize before charging. Most of the time I use a temp sensor set to 120 F and the peak detect set to 3mv/cell. This doesn't mean that my settings will never pop a cell, there is always that rogue cell that can possibly get by. I figure that by the time that I get the batteries, the matcher has already weeded out the potentials, and I have a relatively safe pack.

If you really want to charge in something that will capture glowing embers of a blown pack, if it were me, I'd pick-up a 5 gallon pail from you local home center and charge in that.
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Old 03-06-2008, 07:20 AM   #7
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I should clarify what i meant by container.
Anything that will prevent debris from traveling horizontaly would be in the event of a cell blowing.
A 4 sided box with no lid should do.
In most if not all cases seen its usually 1 cell that vents/explodes.
After my experience 2 weeks ago i can tell you i dont want this happening to any other person out there, its just scary when it does happen.
On all 4200 packs run 3mv delta peak and nothing above 50 deg/c although my chargers all came preset at 47deg/c so i havent changed them.
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Old 03-06-2008, 07:25 AM   #8
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Thanks for the replies. I'll look for some sort of container to sit the batteries down in while charging.
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Old 03-06-2008, 09:03 AM   #9
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Default Latest sugestions from the distributor`s of Nk-Ml battery`s

If someones Nk- Ml battery blows up next to you ..


Duck & cover !!!

Sorry, if one of our battery`s does explode next to you , its not our problem...
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Old 03-06-2008, 10:58 AM   #10
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Just a little note. 2 nights ago I was discharging/ charging one of my bros' duratrax 4200 packs on my ice.. After discharge, i trayed it up to get .9V p/cell After the pack had cooled. I charged it at 4.2 amps and let it cool and then repeaked it.. I set the pack on my kitchen counter when finished. That was at 730pm.. The NEXT night at 900pm, after not being touched for 26 hrs, I heard the venting sound and boom. two cells blew. So I guess the Venting, bursting cells can happen not only while charging but also up 2 two days after a charge, you never know.. stay away from these packs...
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Old 03-06-2008, 11:16 AM   #11
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I went to lunch with Jim Morrison last Saturday. He has these weird theories about the afterlife.
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Old 03-06-2008, 11:16 AM   #12
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It is also possible that cells explode because the venting doesn't work due to poor soldering. If there is too much solder on the cell it cannot vent as it should and then pressure starts to build up causing serious damage or even exploding cells.

Always make sure that you use no more solder than the battery bar is wide so the cell can vent when it has to. To prevent this from happening, use slimmer batterybars. And offcoarse a good high power soldering iron that can do the job quickly and secure.

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Old 03-06-2008, 11:18 AM   #13
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Quote:
Originally Posted by timmay70 View Post
I went to lunch with Jim Morrison last Saturday. He has these weird theories about the afterlife.
Where were you mister mojo rising? In Paris, France???
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Old 03-09-2008, 09:07 PM   #14
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We had one pop the other day at the track. It was an EnerG 4600 mah six cell pack. One of the end cells blew the positive cap right off. Sounded like a .22 rifle. He was using the Checkpoint charger. The pack had just finished charging and was taken off to cool down for a bit.
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Old 03-09-2008, 09:29 PM   #15
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Oh man, off subject a little, but this cracks me up. We can't switch to lipos because we're scared of a possible fire. So our solution is to use things that frickin' explode! With acid if I'm not mistaken.
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