Battery Technology

All hybrid vehicles still have lead acid batteries, but most - not all - hybrids have nickel-metal hydride batteries to assist in fuel savings and lower emissions. Currently, the nickel-metal hydride battery (NiMH) is an integral part of a hybrid system.

A nickel-metal hydride battery (abbreviated NiMH) is a type of rechargeable battery similar to a nickel-cadmium (NiCd) battery, but has a hydride absorbing alloy for the anode instead of cadmium, which is an environmental hazard; therefore, it is less detrimental to the environment. Applications of NiMH type batteries include hybrid vehicles such as the Honda Insight and Toyota Prius.

Lithium ion batteries (sometimes abbreviated Li-Ion) are a type of rechargeable battery commonly used in consumer electronics. They are currently one of the most popular types of battery, with one of the best energy-to-weight ratios, no memory effect and a slow loss of charge when not in use. Lithium ion battery applications have the potential of eclipsing the NiMH battery in hybrid vehicles [1]; compared to a lithium ion battery, the NiMH battery's volumetric energy density (amount of potential energy stored in the battery) is lower and self-discharge is higher. Lithium ion batteries are smaller, lighter, and have fewer volatile gases than NiMH batteries. However, they are not currently scaled for use in hybrid vehicle applications - while they have potential cost-saving attributes, they can be dangerous if mistreated, and, because they are less durable, may have a shorter lifespan compared to other battery types.

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