shops sell AAA NiMH Brian - get your coat on
The NiMH battery uses a hydrogen-absorbing alloy for the negative electrode instead of cadmium. As in NiCd cells, the positive electrode is nickel oxyhydroxide (NiOOH). A NiMH cell can have two to three times the capacity of an equivalent size NiCd. However, compared to the lithium-ion cell, the volumetric energy density is lower and self-discharge is higher. NiMH cells are commonly packaged and sold individually in common sizes. They are also fashioned into batteries for applications where a higher voltage is needed, such as in hybrid cars, radio control vehicles, cordless phones, and spacecraft.