Electric vehicle battery information

An electric-vehicle battery (EVB) (also known as a traction battery) is a battery used to power the electric motors of a battery electric vehicle (BEV) or hybrid electric vehicle (HEV). These batteries are usually rechargeable (secondary) batteries, and are typically lithium-ion batteries. These batteries are specifically designed for a high ampere-hour (or kilowatt-hour) capacity.

Nissan leaf cutway showing part of the battery

Electric-vehicle batteries differ from starting, lighting, and ignition (SLI) batteries as they are designed to give power over sustained periods of time and are deep-cycle batteries. Batteries for electric vehicles are characterized by their relatively high power-to-weight ratio, specific energy and energy density; smaller, lighter batteries are desirable because they reduce the weight of the vehicle and therefore improve its performance. Compared to liquid fuels, most current battery technologies have much lower specific energy, and this often impacts the maximum all-electric range of the vehicles.

The most common battery type in modern electric vehicles are lithium-ion and lithium polymer, because of their high energy density compared to their weight. Other types of rechargeable batteries used in electric vehicles include lead–acid ("flooded", deep-cycle, and valve regulated lead acid), nickel-cadmium, nickel–metal hydride, and, less commonly, zinc–air, and sodium nickel chloride ("zebra") batteries.The amount of electricity (i.e. electric charge) stored in batteries is measured in ampere hours or in coulombs, with the total energy often measured in kilowatt-hours.

Since the late 1990s, advances in lithium-ion battery technology have been driven by demands from portable electronics, laptop computers, mobile phones, and power tools. The BEV and HEV marketplace has reaped the benefits of these advances both in performance and energy density. Unlike earlier battery chemistries, notably nickel-cadmium, lithium-ion batteries can be discharged and recharged daily and at any state of charge.

The battery pack makes up a significant cost of a BEV or a HEV. As of December 2019, the cost of electric-vehicle batteries has fallen 87% since 2010 on a per kilowatt-hour basis. As of 2018, vehicles with over 250 mi (400 km) of all-electric range, such as the Tesla Model S, have been commercialized and are now available in numerous vehicle segments.

In terms of operating costs, the price of electricity to run a BEV is a small fraction of the cost of fuel for equivalent internal combustion engines, reflecting higher energy efficiency.

Electric vehicle battery types

Old: Banks of conventional lead-acid car batteries are still used for propulsion of some BEVs.

Cylindrical cell 

Lithium ion battery monitoring electronics (over- and discharge protection)

Flooded lead-acid batteries are the cheapest and, in the past, most common vehicle batteries available. There are two main types of lead-acid batteries: automobile engine starter batteries, and deep cycle batteries. Automobile engine starter batteries are designed to use a small percentage of their capacity to provide high charge rates to start the engine, while deep cycle batteries are used to provide continuous electricity to run electric vehicles like forklifts or golf carts.Deep cycle batteries are also used as the auxiliary batteries in recreational vehicles, but they require different, multi-stage charging.No lead acid battery should be discharged below 50% of its capacity, as it shortens the battery's life.Flooded batteries require inspection of electrolyte levels and occasional replacement of water, which gases away during the normal charging cycle.

Previously, most electric vehicles used lead-acid batteries due to their mature technology, high availability, and low cost, with the notable exception of some early BEVs, such as the Detroit Electric which used a nickel–iron battery. Deep-cycle lead batteries are expensive and have a shorter life than the vehicle itself, typically needing replacement every 3 years.

Lead-acid batteries in EV applications end up being a significant (25–50%) portion of the final vehicle mass. Like all batteries, they have significantly lower specific energy than petroleum fuels—in this case, 30–50 Wh/kg.[6] While the difference isn't as extreme as it first appears due to the lighter drive-train in an EV, even the best batteries tend to lead to higher masses when applied to vehicles with a normal range. The efficiency (70–75%) and storage capacity of the current generation of common deep cycle lead acid batteries decreases with lower temperatures, and diverting power to run a heating coil reduces efficiency and range by up to 40%.

Charging and operation of batteries typically results in the emission of hydrogen, oxygen and sulfur, which are naturally occurring and normally harmless if properly vented. Early Citicar owners discovered that, if not vented properly, unpleasant sulfur smells would leak into the cabin immediately after charging.

Lead-acid batteries powered such early modern EVs as the original versions of the EV1.

Battery capacity

Non–plug-in hybrid cars have battery capacities between 0.65 kWh (2012 Honda Civic Hybrid) and 1.8 kWh (2001 Toyota Prius).
Plug-in hybrid cars have battery capacities between 4.4 kWh (2012 Toyota Prius Plug-in Hybrid) and 34 kWh (Polestar 1).
All-electric cars have battery capacities between 6.0 kWh (2012 Renault Twizy) and 100 kWh (2012 Tesla Model S and 2015 Tesla Model X).

Battery cost

In 2010, scientists at the Technical University of Denmark paid US$10,000 for a certified EV battery with 25 kWh capacity (i.e. US$400/kWh), with no rebates or surcharges.Two out of 15 battery producers could supply the necessary technical documents about quality and fire safety. In 2010 it was estimated that at most 10 years would pass before the battery price would come down to one-third.

According to a 2010 study, by the United States National Research Council, the cost of a lithium-ion battery pack was about US$1,700/kWh of usable energy, and considering that a PHEV-10 requires about 2.0 kWh and a PHEV-40 about 8 kWh, the manufacturer cost of the battery pack for a PHEV-10 is around US$3,000 and it goes up to US$14,000 for a PHEV-40. The MIT Technology Review estimated the cost of automotive battery packs to be between US$225 to US$500 per kilowatt hour by 2020. A 2013 study by the American Council for an Energy-Efficient Economy reported that battery costs came down from US$1,300/kWh in 2007 to US$500/kWh in 2012. The U.S. Department of Energy has set cost targets for its sponsored battery research of US$300/kWh in 2015 and US$125/kWh by 2022. Cost reductions through advances in battery technology and higher production volumes will allow plug-in electric vehicles to be more competitive with conventional internal combustion engine vehicles. In 2016, the world had a Li-ion production capacity of 41.57 GW⋅h.

The actual costs for cells are subject to much debate and speculation as most EV manufacturers refuse to discuss this topic in detail. However, in October 2015, car maker GM revealed at their annual Global Business Conference that they expected a price of US$145/kWh for Li-ion cells entering 2016, substantially lower than other analysts' cost estimates. GM also expects a cost of US$100/kWh by the end of 2021.[39]

According to a study published in February 2016 by Bloomberg New Energy Finance (BNEF), battery prices fell 65% since 2010, and 35% just in 2015, reaching US$350/kWh. The study concludes that battery costs are on a trajectory to make electric vehicles without government subsidies as affordable as internal combustion engine cars in most countries by 2022. BNEF projects that by 2040, long-range electric cars will cost less than US$22,000 expressed in 2016 dollars. BNEF expects electric car battery costs to be well below US$120/kWh by 2030, and to fall further thereafter as new chemistries become available