NiMH rechargeable (nickel metal hydride)

Positive characteristics

• Can give very high current output.

• Not much capacity loss under heavy loads (little to no Peukert Effect).

• Very level output voltage.

• Can be recharged many times (500+) if good quality and treated well. • Little voltage depression (“memory” effect).

• No cadmium (more environmentally friendly than NiCd).

• Roughly 150% the gravimetric storage density (by weight) or up to 220% the volumetric storage density of NiCd.

• Can be stored in any state of charge.

Negative characteristics

• Must not be over discharged (and prefers shallow discharges).

• Moderately high self discharge (30% per month), although Sanyo Eneloop claims to hold a 90% charge over 6 months and 85% over 12 months.

• Need special chargers because overcharging can damage the battery - this means an ordinary NiCd charger may damage your NiMH battery.