NiMH batteries, specifics

[Keith Black]

NiMH batteries are terrific for our use. They are lighter per mah than the NiCads, memory isn't an issue so they don't have to be completely discharged like NiCads (though I do a full cycle periodically just to check capacity), and they don't loose their charge as quickly as NiCads while sitting unused. 

The only real advantage that I know of for NiCads is in high current discharge such as powering large electric motors.  NiCads still seem have the edge in some cases here. But for our use NiMH clearly is a better choice IMO. You'll also hear that NiCad batteries can be rapid charged more quickly than NiMH. This is probably true to some degree, however, this doesn't mean you can't rapid charge NiMH's, they just require different peak detection (supported by practically all modern chargers) and the charge should probably be more conservative. Even with this you can still charge them quite rapidly.

FYI, there were some problems experienced with the early NiMH cells and this turned off many people. My guess is that those who still prefer NiCad over NiMH were aware of these early problems and are not aware how good the improved NiMH batteries are. 

Keith Black
  ----- Original Message ----- 
  From: Mike Hester 
  To: discussion at nsrca.org 
  Sent: Saturday, May 08, 2004 2:55 PM
  Subject: NiMH batteries, specifics


  Ok, I'm sure we're all intimately familiar with nicads, and lately, we've become all too familiar with lithium-ions and lithium polymers. (If I never hear about another lithium battery, it'll be too soon).

  What I'd like is some detailed specifics regarding the red headed stepchild of the battery world, the Nickel Metal Hydride.

  What's the deal with it's performace at low temps? What temps are we talking here?

  What's the scoop on fast charging, rates, overheating, etc?

  I'd like some experienced opinions on this.

  Thanks,
  -Mike


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