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[luke1993]

hi
I purchased 4 x 6v 3700 nimh batteries from a well known supplier cant give there name as there being very good and I don't think its right.
anyway used the batteries and charged two of them on a 600mah nimh charger all fine .
charged the other two on the same chargers all was fine.
the last two I took off charge and put on the shelf about a foot apart.
all was l ok until I went up stairs 6 hours later to face a room full of smoke and hissing the the last two batteries were melting all wires melted and packaging melted .
I contacted supplier and sent photos they say they never heard or seen this before as they never shorted out or the first two cells would of been affected it was the middle two cells on both packs.
they are saying cells were damaged internally or during post.
had chargers checked all ok charged more batteries all ok .
the batteries had no bare wires and was new has anyone else experienced this ?
could of been worse than it was .
please let me know if you have any ideas cheers .

[Stavros]

Are these NEW batts thatyou have just bought....if so what the trader is telling more than likely is correct.I charge my Batt packs at well above 600mah ....more like 1.9amps YES they will get hot during charging BUT I allways check them to see they have cooled down after around 5mins....Only ever had 1 go up in flames BUT this was due to a faulty charger and to be honest with you the batt was old and had been knocked about
 
 
Dave

[luke1993]

yes brand new batts I used them and ran them down a bit but yes it was there first charge .
just bought 2 new chargers now so I can charge at 1amp or 2 amp hopefully all will be ok
cheers

[StuartL]

Only time I've seen this occur is with overcharging.  NiMH deal with overcharging by dispersing the energy as heat.  Does your charger cut off automatically or is it a constant supply (constant current/constant voltage)?

Generally I check NiMH packs frequently during charging and if they're noticeably warm I immediately stop charging.

If the pack had overheated during charging it's possible that a battery shorted internally and then the rest, as they say, is history.

These days I charge all my batteries (Lipo or NiMH) in an old metal oven tray.  It serves to protect the surroundings if anything should go wrong.  I've had a single Lipo and a single NiMH battery go.  The Lipo I think was internally damaged, unclear whether that was my fault or manufacturing defect.  The NiMH went while I was charging it with some new software I'd written and the software didn't cut off the charge current correctly.  I'll take full blame for that one :)