Need help with NiMH batteries....

[T Bone 347]

I have 3 batteries that I run in my Honcho and Slash, a 4600, 3000 & 1800. When I put them on the charger (onyx 220) they charge for around 10-15 minutes and then says it done. I've run them completely dry in my slash and then to the charger and same results. Went back through the charger to reconfirm the settings.

Any ideas, suggestions? Beside what everyone will say 'GO LIPO!'

Thanks

[ped453]

It could be your charger getting a false reading.

[benoj]

what plugs are on the batteries? ive had a bad deans make my charger read a higher voltage than what the pack was due to a poor connection and it was off anywhere from .5v to 1.5v

[T Bone 347]

Traxxas plugs, my soldering skills are lacking and I haven't changed them. Everything was working fine up until...about a month ago. I'm sure it's the charger and not that ALL 3 batteries pooped the bed at the same time. Besides, I've read where guys have pulled their NiMHs out 'retirement' after years and they were fine.

[Charlie-III]

What charge rate are you using? I suggest a "1C" rate, thus a 2000mah pack charges at 2amps. Too high a charge rate can lead to false peaks.

Are these new or old packs? You may want to meter each cell right after a charge to see if one is a lot different than the others.

You may also want to cycle the packs, if your charger allows, by charging at 1C, then discharge at 5C then recharge.

Also, when the pack is "charged", check it's temp. If it's room temp, start the charge again. They should be a little warmer than "room temp" when fully charged.

I still run REALLY old NiCD & newer NiMH in my carpet pan cars.

[Olle P]

What Charlie said, but even better:
Do a complete refresh of the batteries!
1. Discharge at 0.2C until the voltage drops to 1.0V/cell (6V for a 7.2V battery).
2. Let the battery rest for an hour.
3. Charge at 0.1C for 16 hours.
4. Rest one hour.
5. Discharge at 0.2C until the voltage drops to 1.0V/cell (6V for a 7.2V battery).
6. Let the battery rest for an hour.
7. Charge at 0.1C for 16 hours.
Done!

The low currents used will have the different chemicals involved spread evenly on the inner surfaces, maximising the battery performance.

Even at normal use with a delta peak charger the rule of thumb is to stay within 0.3-1.0C charge rate. The reason is that overcharging is very bad for the battery. At higher rate the charger might overshoot the target, adding too much charge between samples. At lower rate it might not even find the voltage dip that's supposed to halt the charging process.
Personally I stick to the 0.3-0.4C rate unless I'm in a hurry.

[bob1961]

wen i discharge mine i use the .9 volts a cell, 10 cell pack i have that's 9 volts discharge setting from the 10 cell packs 12 volts....mine are 1500 elites and i never charge over half the mah rating so that would be .75a or lower........bob

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