From the July/August 2023 issue of Car and Driver.
In 2011, the Nissan Leaf carried an approximately 21.0-kWh battery that gave it an EPA range of 73 miles. The 2023 Leaf’s battery offers nearly three times the capacity and range in a pack with slightly larger dimensions.
Designing EVs with greater range doesn’t necessarily mean bigger and heavier batteries, although there are efforts like the 170.0-kWh pack in the 8660-pound GMC Hummer EV SUV (pictured above).
Here are the factors that battery engineers consider and have to contend with compensation vehicle teams.
The most fundamental decision in designing an EV battery is the specific chemistry to use. Battery engineers must balance energy capacity, power delivery, cost and volatility. In most cases, cell suppliers and automakers jointly develop vehicle-specific applications, such as Tesla and Panasonic or GM and LG Energy Solution.
In the US, many EVs use lithium-ion cells that contain some mixture of nickel, manganese, cobalt and aluminum with their lithium. These are known as NMCA cells.
In China, the chemistry used is lithium-iron-phosphate, or LFP. It costs less, uses fewer hard-to-find minerals and is often safer in extreme conditions, but the technology holds less energy in a given volume. Tesla has started using LFP for some US models, and Ford announced it will build an LFP cell plant for its electric vehicles.
Battery engineers must specify the form (known as the “format”) of each cell—although, in practice, not every supplier offers every cell chemistry in every format. Tesla pioneered the use of thousands of small format cylindrical cells (similar to AA batteries) in battery packs; many other makers have opted for larger hundreds of cells in pouch or prismatic formats, which are two versions of the rectangular shape. Multiple cells are grouped into modules that are placed into a large rectangular container to form a pack. Some batteries have eight modules, while others have dozens. Cells in modules are wired in series, and modules are wired in parallel.
The new GMC Hummer pickup and SUV have two groups of 400-volt modules in parallel that switch to 800-volt series to enable DC fast charging of up to 300 kilowatts.
Cell and Pack Dimensions
While there are standard sizes for cylinder cells, some other cell formats are made in specific sizes for specific car makers. The challenge facing the engineers is to put maximum energy into a battery pack with the smallest possible dimensions while ensuring there is enough space for the liquid cooling channels, all the wiring that connects the cells in the module and the modules to each other, and the proper separation of the modules for safety.
Today, almost any EV with a range of 200 miles or more has a battery under the cabin floor that stretches from door to door, axle to axle. There is often also a raised hump under the rear seat for greater capacity, and sometimes what the Germans call a “foot garage” is included in the pack to allow for adequate rear seat legroom in lower vehicles. This heavy underfloor pack does have the benefit of lowering the center of gravity, thus improving vehicle stability and handling.
Capacity (ie, Range)
Finally, battery engineers, vehicle product managers and their accountants will debate the battery capacity on offer. The goal is an EV they can sell at the right price with enough range to convince customers it’s a practical choice for their lives and commutes. We found that in the US, about 250 miles seems to be the minimum range to get people to consider trading internal combustion for an electric motor for everyday use. GM has said it thinks 300 miles is the benchmark where buyers stop worrying about range. However, there are few EVs that can actually deliver the EPA range posted on their window sticker labels.
Even so, over the past decade of EV development, this is the area where the most progress has been made. In 2013, the state of the art was a Nissan Leaf with 75 EPA miles for around $30,000 or a Tesla Model S with 265 miles for over $90K. Options have a wider spread today. You can buy a walking dead Chevrolet Bolt EV, with a range of 258 miles, for $27,495; one Lucid Air luxury sedan model is rated at more than 500 miles and comes with a six-figure price tag.
But simply increasing battery capacity has diminishing returns. Bigger, heavier packs are inherently less efficient, so automakers must combine good battery technology with other efficiencies to stay competitive.
John Voelcker edited Green Car Report for nine years, published more than 12,000 articles on hybrids, electric cars, and other low- and zero-emission vehicles and the energy ecosystem around them. He currently covers advanced auto technology and energy policy as a reporter and analyst. His work has appeared in print, online and radio media including Wired, Popular Science, Technology Review, IEEE Spectrum, and NPR’s “All Things Considered.” He splits his time between the Catskill Mountains and New York City and still has hopes of one day becoming an international man of mystery.