New hydride alloys discovered in the 1980s offered better stability and the development of NiMH advanced in earnest. Today, NiMH provides 40 percent higher specific energy than a standard NiCd, but the decisive advantage is the absence of toxic metals.
NiMH has two major advantages over Li-ion here. These are price and safety. Makers of hybrid vehicles claim that NiMH costs one-third of an equivalent Li-ion system, and the relaxation on safety provisions contribute in part to this price reduction.
NiMH has become one of the most readily available and low-cost rechargeable batteries for portable devices. NiMH is non-toxic and offers a higher specific energy than NiCd. Energy Technology have recognized the need for a durable and low-cost rechargeable battery for consumers and offer NiMH in AA and AAA sizes.
What is of ongoing concern to the consumer using rechargeable batteries is the high self-discharge, and NiMH behaves like a leaky basketball or bicycle tire. A flashlight or portable entertainment device with a NiMH battery gets “flat” when put away for only a few weeks. Having to recharge the device before each use does not sit well. The Eneloop NiMH by Sanyo has reduced the self-discharge by a factor of six. This means that you can store the charged battery six times longer than a regular NiMH before a recharge becomes necessary.