<P> Lithium - ion batteries have a higher specific energy than nickel metal hydride batteries, but they are significantly more expensive . They also produce a higher voltage (3.2 - 3.7 V nominal), and are thus not a drop - in replacement for alkaline batteries without circuitry to reduce voltage . </P> <P> As of 2005, nickel metal hydride batteries constituted three percent of the battery market . </P> <P> NiMH batteries have replaced NiCd for many roles, notably small rechargeable batteries . NiMH batteries are commonly available in AA (penlight - size) batteries . These have nominal charge capacities (C) of 1.1--2.8 Ah at 1.2 V, measured at the rate that discharges the cell in 5 hours . Useful discharge capacity is a decreasing function of the discharge rate, but up to a rate of around 1 × C (full discharge in 1 hour), it does not differ significantly from the nominal capacity . NiMH batteries nominally operate at 1.2 V per cell, somewhat lower than conventional 1.5 V cells, but can operate many devices designed for that voltage . </P> <P> Applications of NiMH electric - vehicle batteries include all - electric plug - in vehicles such as the General Motors EV1, first - generation Toyota RAV4 EV, Honda EV Plus, Ford Ranger EV and Vectrix scooter . Hybrid vehicles such as the Toyota Prius, Honda Insight, Ford Escape Hybrid, Chevrolet Malibu Hybrid and Honda Civic Hybrid also use them . </P>

Rechargeable nickel metal hydride (ni-mh) batteries