How do batteries for electric cars work?

The energy storage system in electric cars comes in the form of a battery. Battery type can vary depending on if the vehicle is all-electric (AEV) or plug-in hybrid electric (PHEV). Current battery technology is designed for extended life (typically about eight years or 100,000 miles). Some batteries can last for 12 to 15 years in moderate climates or eight to 12 years in extreme climates. Four main kinds of batteries are used in electric cars: lithium-ion, nickel-metal hydride, lead-acid, and ultracapacitors.

Lithium-ion batteries

Lithium-ion batteries are the most common type of battery used in electric cars. This kind of battery may sound familiar – these batteries are also used in most portable electronics, including cell phones and computers. Lithium-ion batteries have a high power-to-weight ratio, high energy efficiency, and good high-temperature performance. In practice, this means that the batteries hold a lot of energy for their weight, which is vital for electric cars – less weight means the car can travel further on a single charge. Lithium-ion batteries also have a low "self-discharge" rate, which means they are better than other batteries at maintaining the ability to hold a full charge over time.

Additionally, most lithium-ion battery parts are recyclable, making these batteries a good choice for the environmentally conscious. This battery is used in both AEVs and PHEVs, though the exact chemistry of these batteries varies from those found in consumer electronics.

Nickel-metal hydride batteries

Nickel-metal hydride batteries are more widely used in hybrid-electric vehicles but are also used successfully in some all-electric vehicles. Hybrid-electric vehicles do not derive power from an external plug-in source but instead rely on fuel to recharge the battery, excluding them from the definition of an electric car.

Nickel-metal hydride batteries have a longer life cycle than lithium-ion or lead-acid batteries. They are also safe and tolerant of abuse. The most significant issues with nickel-metal hydride batteries are their high cost, high self-discharge rate, and the fact that they generate substantial heat at high temperatures. These issues make these batteries less effective for rechargeable electric vehicles, which is why they are primarily used in hybrid electric vehicles.

Lead-acid batteries

Lead-acid batteries are only currently used in electric vehicles to supplement other battery loads. These batteries are high-powered, inexpensive, safe, and reliable, but their short calendar life and poor cold-temperature performance make them difficult to use in electric vehicles. There are high-power lead-acid batteries in development, but the batteries are now only used in commercial vehicles as secondary storage.

Ultracapacitors

Ultracapacitors are not batteries in the traditional sense. Instead, they store polarized liquid between an electrode and an electrolyte. As the liquid's surface area increases, the capacity for energy storage also increases. Ultracapacitors, like lead-acid batteries, are primarily useful as secondary storage devices in electric vehicles because ultracapacitors help electrochemical batteries level their load. In addition, ultracapacitors can provide electric vehicles extra power during acceleration and regenerative braking.

All-electric vehicles have an electric traction motor in place of the internal combustion engine used in gasoline-powered cars. AEVs use a traction battery pack (usually a lithium-ion battery) to store the electricity the motor uses to drive the vehicle's wheels. The traction battery pack is the part of the car that is plugged in and recharged, and its efficiency helps determine the vehicle's overall range.

In plug-in hybrid electric vehicles, a traction battery pack powers the electric traction motor, much like an AEV. The primary difference is that the battery also has a combustion engine. PHEVs run on electric power until the battery is depleted and then switch to fuel which powers an internal combustion engine. The battery, usually lithium-ion, can be recharged by plugging in, through regenerative braking, or using the internal combustion engine. The combination of battery and fuel gives PHEVs a longer range than their all-electric counterparts.

Methods of Electric Vehicle Battery Recharging

Charging your vehicle with electricity allows you to cut your greenhouse gas emissions by fueling your vehicle with a renewable resource like solar power. On average, 80 percent of electric car charging is done at home, and solar panels can both offset the costs of charging a vehicle regularly and reduce the use of nonrenewable fuels in the recharging process. Additionally, many public chargers use solar panels to reduce the use of nonrenewable energy throughout the process. If you're interested in a solar panel installation plus installing an EV charging station at home, simply join the EnergySage Marketplace today and mention your interest in EV charging when filling out your profile questions.