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Well I just ordered a couple chargers for our iMacs. My Magic Mouse gets through a couple of Duracell AA batteries per week.
 
NiMH is many times simpler (no voltage control), more stable technology and last much longer (10 years is the industry standard) than Li-ion but does have disadvantages like excessive "leakage" and less power per mass/size.

Not much leakage anymore with LSD (Low Self Discharge) batteries. Based on the description on Apple website (retain 80% capacity after 1 year), they are rated exactly like Sanyo Eneloop batteries (rebadged?).
 
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