Hybrid and Electric Car Battery Wars

Hybrid and electric cars use different types of batteries, with battery technology continuously evolving to better suit the needs of engineers and car buyers. Here's a rundown of the major battery types of the modern EV era, the strengths and weaknesses of each, environmental impacts and examples of vehicles using each type. What will the green car battery future hold?

Lead-Acid Batteries

Some of first modern electric cars, like the early Toyota RAV4 EV, used rechargeable lead-acid batteries similar to the standard Duracells powering small electronics. This technology was quickly phased out as it was replaced with more stable, higher-capacity and more environmentally friendly technologies.

Nickel-Metal Hydride (NiMH) Batteries

Nickel-metal hydride batteries have traditionally been most-commonly used for gasoline-electric hybrids. All standard Toyota Prius models from model-years 2001 to 2012 use nickel-metal hydride battery packs, which are actually a large conglomeration of individual cells. Most other hybrids made during the same period, and today, use this type. Advantages lie in durability, long life and low cost of manufacture. The chief disadvantage is low power density when compared with newer types.

NiMH packs can easily outlast the 8- to-10-year warranties they usually come with, though a few older hybrids are already returning to dealerships for replacement due to outright failure or gradual loss of capacity.

Lithium-Ion (Li-ion) Batteries

Some modern hybrids (2012 Honda Civic Hybrid), as well as the vast majority of full-electric and plug-in electric hybrid vehicles (Nissan Leaf, Chevrolet Volt, Toyota Prius Plug-in) use Lithium-ion battery packs, the same basic technology found in your cell phone and laptop. Their chief advantage lies in their higher power density, allowing batteries with more capacity and higher discharge rates to be made smaller and lighter. They are quicker to charge and can provide more power at any given time. Disadvantages lie in higher cost to manufacture, a high concentration of rare-earth elements and the need to constantly monitor heat to avoid damage or even explosion.

Li-ion packs come in several flavors, differentiated by the material used to make the cathode (positive electrode). Formulas include cobalt dioxide, nickel-cobalt-maganese, nickel-cobalt-aluminum, manganese oxide spinel and iron phosphate. Each chemical makeup has its own strengths and weaknesses with automakers continuously experimenting to find the right blend.

Future Hybrid/Electric Car Battery Types

Research continues to improve battery technology with a focus on capacity, discharge rate, durability, cost and environmental impact. Lithium-ion polymer (Li-Po) batteries house each individual cell in a flexible polymer laminate case, rather than a rigid metal unit. This seriously saves on weight. New lithium-air batteries promise big gains in capacity relative to weight. A proprietary technology, called the Zebra battery, uses sodium in its cathode and has shown promise.

The key issues to overcome are storage capacity and discharge rate. Future electric cars will have greater range, power and battery durability than today's EVs.