rechargeable batteries > Nickel Metal Hydride

Nickel Metal Hydride (Ni-MH, NiMH) rechargeable batteries are the next level up from NiCad. The biggest advantage is their ability to accept a charge at any time without suffering the 'memory effect'. Thus are the ideal choice for digital cameras, torches, and as general replacement for standard NiCad or Alkaline batteries.

 

Nickel-metal hydride cells contain a high capacity anode made of a hydrogen storage metal alloy. The cathode is nickel oxide, and the electrolyte is an aqueous potassium hydroxide solution. The spirally wound electrodes are separated by a synthetic, non-woven material and are sealed into a cylindrical nickel-plated steel can. Providing up to 1000 cycles, with metal hydride cells are stable and have built-in protection against overcharging and abuse.

 

Advantages

Disadvantages

Long cycle life leads to lower overall energy cost.	Storage life is poor; may lose 20+% of charge per month
Minimizes the Ni-Cd memory effect.	High initial cost.
Excellent high-power performance.
Excellent low temperature performance.
Excellent leakage protection.
Quick recharge capability
Up to 100% longer-lasting than Ni-Cd

 

The memory effect is the loss of capacity (to a cutoff voltage) that occurs when a cell is repeatedly partially discharged.

 

 

Affected Chemistries - NiCd and to a lesser extent NiMH batteries

	“Forgets” it has the original designed capacity
	Can be avoided by full charge/discharge - at least once every 2 - 3 weeks