It used to be that when you talked about car batteries, you were talking about those black, cinder block-sized things under the hood. You know, the things you connect your jumper cables to because the lights were left on. (OK, I know it wasn’t you…it was one of the kids, right?) Well, for many years that type of battery was the only one used in cars and trucks. It’s called a lead-acid battery and they have been made for over one hundred years. Lead-acid batteries are nice mature technology, however today’s Electric Vehicles (EVs) or Hybrids can’t use them. The continuous power requirements of electric vehicles requires new types of batteries.
The Old Standard
As mentioned before, lead acid batteries have been around for a long time. There are a couple reasons for this. First, lead acid batteries are well known technology and are inexpensive to make. All that is required is some common materials like plastic, lead and sulfuric acid. Second, they perform perfectly well for standard internal combustion-powered cars. Why change what isn’t broken?
Your standard lead-acid battery is a heavy plastic box with a series of heavy lead plates inside. These plates are suspended in a mix of water and sulfuric acid. The way it all works is that when needed, current flows from the lead-oxide plates (called cathodes) to the pure lead plates (called anodes). During this process both plates are slowly converted to lead sulfate. Charging the battery reverses the process.
Each individual set of anodes and cathodes can only generate 2.1 volts so a set of six is necessary to generate the voltage that cars and trucks need (12.6 volts.) The biggest problem with lead-acid batteries is that they aren’t terribly good for “deep discharge” applications They are perfect for starting internal combustion engines, but they aren’t good for continuous use. Helping us with this article was Boardwalk Dodge of Redwood City, a local Chrysler, Dodge, Jeep, Ram dealer in Redwood City, CA. They explained that lead-acid batteries could be used for deep discharge under some circumstances. For example, golf cart batteries are special deep discharge designs.
Another type of battery technology is called Nickel-Metal Hydride (Ni-MH). Do you remember the Ni-Cd batteries of years ago? They were the state-of -the-art in rechargeable batteries back then. The main problem with Ni-Cd batteries was that they “wore out” after repeated charges. Because of this problem, engineers developed nickel-metal hydride batteries (Ni-MH). Ni-MH batteries have twice the energy density of Ni-Cd batteries, they can be charged quickly, and they don’t wear out. As a result, Ni-MH batteries has become the mainstay in rechargeable batteries today. Toyota and Honda employ NiMH battery technology in their hybrids.
In the continuous search for higher power density, Li-ion technology was developed. Li-ion cells offer 11 times the power of Ni-MH. One small disadvantage is that in electric car use, a full bank of batteries requires its own cooling and heating system to maintain optimal operating temperatures. A major advantage to Li-ion cells is that they can be recycled. For their EVs and hybrid cars, Mercedes-Benz, Mini, Smart, and Tesla rescue small consumer lithium-ion (Li-ion) cells from used laptops and reprocess them into the larger cells that power their cars.