[NSRCA-discussion] charging NiMH with NiCD charger

[Bob Richards]

It is typical to charge a NiMh or Nicad pack at C/10, so this would be 250ma for the 2500mah pack.
   
  That being said, I would not charge at that rate with a standard wall wart or a fixed charge rate charger of any kind - with the battery in the radio. I would remove the battery if I were charging at that rate. The reason is that once all the cells have come up to full capacity, the current does nothing but develop heat, in this case close to 3 watts. It will be very warm to the touch!
   
  Most Futaba radios (if not all) come with diode protection. Taking the battery out of the radio allows you to bypass that diode. Some peak chargers will work through a diode, some won't. I have an Accucyle Elite that I like for this purpose. I will charge at a C/10 or C/5 rate then have it drop back to a lower rate (maybe 50ma) once the peak charge is done. This tells me how much it puts back into the pack, but the continued lower charge helps to equalize the cells without causing much heat.
   
  I may occasionally peak charge my batteries at a higher rate, but nothing beats a long charge at a low rate for equalizing all the cells. Constant peak charging (with a charger that does not continue afterwards at a lower rate) can lead to unequal charge state of the individual cells.
   
  I have some Futaba wall warts that charge the transmitter at 70ma, and some older ones that charge at 50ma. I would not hesitate to use those to charge the 9C, but keep in mind it will take many more hours to fully charge the batteries. Some would say that the battery would never reach full charge, but as long as the charge rate is higher than the self discharge rate of the battery, it will eventually reach full charge.
   
  JMHO.
   
   
  Bob R.
  

Ron Van Putte <vanputte at cox.net> wrote:
  My personal opinion is that it's probably better than many other ways 
to charge it. The 10C Futaba "wall wart" charger charges both nicad 
and NiMH 4.8 volt packs at the same low rate of 100ma. I am a little 
concerned that packing more mah into the same size cells is 
accomplished at least partly by thinner insulation within the cell. 
Charging at the high rates possible with some field chargers in this 
situation is just asking for compromise of the insulation. Maybe 
someone with more knowledge of these high mah cells can confirm or 
refute what I wrote.

Ron Van Putte

On Oct 16, 2008, at 9:22 PM, JShulman wrote:

> I just realized that the battery in my 9C is a 2500 NiMH, but have 
> been charging it with my standard Futaba NiCD wall charger. Any
> reason to worry?
>
> Regards,
> Jason
> www.jasonshulman.com
> www.shulmanaviation.com
> www.composite-arf.com
>
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