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davidh
01-05-2009, 11:15 AM
what is the difference between NMH batterys and ni-cad for power tools, except price ?

i was told NMH were considered "green" and that the ni-cads actually held a charge longer and lasted longer. don't know if it was b/s or not.

davidh

Scishopguy
01-05-2009, 12:28 PM
Davidh...They use a different chemistry with different requirements for charge and discharge. NiCads are much more picky about charge and discharge cycles. They develop a memory if not fully drained each cycle.
NiMh allow charging at any point in the cycle and don't have charge memory issues. The electrolyte is less toxic, or at least less damaging to the environment since there is no cadmium involved. This is what I have been told, for what it is worth.

DICKEYBIRD
01-05-2009, 01:11 PM
NiMH has a higher energy density as well, ie: mo' power than NiCd in the same size package.

Your Old Dog
01-05-2009, 03:08 PM
One more advantage to Nimh, they don't mind sitting on the shelf in a charged state just waiting for you to need them. They also don't seem to mind colder weather either. I just bought a new 1/2 battery operated drill and I wanted the nimh cells. I used 3 in rotation as a tv newsphotographer on my camera/light and they were still going strong long after an accident forced me into retirement.

I have 4 sets of AA (4 in each set) used for my flash system that I got at Radio Shack and they are over 7 years old and they still work fine.

winchman
01-05-2009, 03:33 PM
There's been lots of discussion about NiCd and NiMH batteries in the various RC forums. The best info available (and my experience) indicates:

the self-discharge rate for NiMH is higher than for NiCd.

NiMH has signifacantly higher capacity on a weight and on a size comparison.

"memory" is no longer an issue for NiCd batteries.

I use NiMH cells in the flight pack of my sailplane, and I use NiCd cells in the transmitter. The transmitter has a battery level indicator, and I know the flight pack will still be going strong when the transmitter is getting low on charge.

Roger