NiMH and NICAD Charger

NiMH and NICAD Charger

Post by Cliff Griffi » Mon, 04 Oct 1999 04:00:00



The peak is less pronounced.

Quote:

> I cant remember now but the NiMH peaks slightly lower/sharper than the
> nicad dosnt it!

> So I should be able to use the nicad fast charger with the NiMH pack!

> Just that they had phone batteries on sale for $10 and I got one just to
> try it out for things such as on board glow or other projects that
> require power other than the RX pack!

> Thanks
> Gavin

--
Cliff Griffin
Remove the obvious for no spam.
 
 
 

NiMH and NICAD Charger

Post by Gavi » Tue, 05 Oct 1999 04:00:00


I cant remember now but the NiMH peaks slightly lower/sharper than the
nicad dosnt it!

So I should be able to use the nicad fast charger with the NiMH pack!

Just that they had phone batteries on sale for $10 and I got one just to
try it out for things such as on board glow or other projects that
require power other than the RX pack!

Thanks
Gavin

 
 
 

NiMH and NICAD Charger

Post by Red Scholefiel » Tue, 05 Oct 1999 04:00:00


Big difference in peak of  Ni-Cd vbs. Ni-NH. The charge process in Ni-Cd
is endothermic (absorbs heat), while the Ni-MH is exoothermic (gives off
heat). Only when the Ni-Cd goes into overcharge and oxygen starts
recombining on the negative does the Ni-Cd become exothermic with the
resulting sharp voltage rise. Ni-Mh heats from the start of charge so the
voltage peak while essentially the same magnitude is much less defined.

Red S.

  Red's R/C Battery Clinic
http://yoda.fdt.net/~redscho

Quote:

> I cant remember now but the NiMH peaks slightly lower/sharper than the
> nicad dosnt it!

> So I should be able to use the nicad fast charger with the NiMH pack!

> Just that they had phone batteries on sale for $10 and I got one just to
> try it out for things such as on board glow or other projects that
> require power other than the RX pack!

> Thanks
> Gavin

 
 
 

NiMH and NICAD Charger

Post by Stuart Robins » Wed, 06 Oct 1999 04:00:00


One of the hazards in using a fast NiCd charger for NiMh batteries, a
dangerous practice, is that the NiMh cells appear to get hot very quickly
after the point of full charge, i.e. the production of heat is
exponential.

Is there a specific reason for this, the effect is far less pronounced
with NiCd ?

Stuart

Mail me on srnet at cix full stop co full stop uk

 
 
 

NiMH and NICAD Charger

Post by Red Scholefiel » Wed, 06 Oct 1999 04:00:00


Yes, Ni-Cd charge process is endothermic, while Ni-MH is exothermic. So
the Ni-Mh are already at a higher temperature when they go into
overcharge, thus the appearance of the cumulative effect of the exothermic
reaction and the heat of recombination in overcharge.

Red S.

  Red's R/C Battery Clinic
http://yoda.fdt.net/~redscho

Quote:

> One of the hazards in using a fast NiCd charger for NiMh batteries, a
> dangerous practice, is that the NiMh cells appear to get hot very quickly
> after the point of full charge, i.e. the production of heat is
> exponential.

> Is there a specific reason for this, the effect is far less pronounced
> with NiCd ?

> Stuart

> Mail me on srnet at cix full stop co full stop uk

 
 
 

NiMH and NICAD Charger

Post by Stuart Robins » Thu, 07 Oct 1999 04:00:00


Ta, I have under controlled conditions fast charged NiMh on a NiCd
charger, Sometimes the charger cuts out long before full charge, sometimes
it does not cut out until very late in the NiMh charge cycle, by which
time the NiMh cell has reached a case temp of 50C+, not good, dangerous
even.

Stuart

Mail me on srnet at cix full stop co full stop uk