Battery Technology

History

The EV1 was the first production quality battery electric vehicle produced by General Motors in the United States. The first generation EV1s used lead-acid batteries in 1996 (as model year 1997), and a second generation batch with nickel metal hydride batteries in 1999. The "Gen I" cars got 55 to 95 miles (90 to 150 km) per charge with the lead acid batteries, while "Gen II" cars got an improved 75 to 150 miles (120 to 240 km) per charge with nickel metal hydride batteries.

General Motors, Ford, Honda and Toyota have all discontinued their electric vehicle (EV) programs - despite growing concern for the environment and over ever-increasing fuel costs, the market for EVs never really flourished. However, EV advocates and engineers are now looking at gas-electric hybrids, which, unlike current hybrid offerings, could be plugged in Plug-In Hybrid to provide a greater capacity for running purely on electric power.

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Battery Types

Lead Acid

Lead acid batteries were found to have too many limitations, making their continued use impractical. Because they are so heavy, it is unreasonable to add more or larger units in order to cope with the higher electrical demands of hybrid vehicles. They are also relatively slow charging, and do not lend themselves to deep cycling - a full discharge causes extra strain, and each cycle robs the battery of a small amount of capacity. They also pose more environmental concerns regarding proper disposal/recycling.

Lead-free alternatives, such as nickel metal hydride and lithium ion batteries, are already on the market in electric and electric-hybrid vehicles, and offer several advantages over conventional lead acid starter batteries. Performance and environmental benefits include:

• Higher energy (power) density
• Reduced weight/volume
• Longer battery life
• Improved fuel economy due to lighter weight and higher energy capacity
• Less material used, lower toxicity, and potentially recyclable

Nickel Metal Hydride

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. Most - not all - current hybrids have a rechargeable NiMH battery as an integral part of their hybrid system, to assist in fuel savings and lower emissions. Applications of NiMH type batteries include hybrid vehicles such as the Honda Insight and Toyota Prius.

Lithium Ion

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.

External Links

http://www.hybridcars.com/battery-comparison.html

http://www.evworld.com/view.cfm?section=article&storyid=1042