Building Better Batteries for Electric Vehicles

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From the July/August 2023 difficulty of Automobile and Driver.

In 2011, a Nissan Leaf carried a roughly 21.0-kWh battery that gave it an EPA vary of 73 miles. The 2023 Leaf battery provides practically thrice the capability and vary in a pack with simply barely larger dimensions.

Designing an EV with better vary does not at all times imply a much bigger, heavier battery, regardless of efforts just like the 170.0-kWh pack within the 8660-pound GMC Hummer EV SUV (pictured above).

Listed here are the elements battery engineers think about and the trade-offs car groups should grapple with.

Cell Chemistry

Essentially the most basic resolution in designing an EV battery is what particular chemistry to make use of. Battery engineers should stability vitality capability, energy supply, value, and volatility. In lots of circumstances, a cell provider and an automaker collectively develop vehicle-specific purposes, equivalent to Tesla and Panasonic or GM and LG Power Answer.

Within the U.S., many EVs use lithium-ion cells containing some mixture of nickel, manganese, cobalt, and aluminum with their lithium. These are often called NMCA cells.

In China, the prevailing chemistry is lithium-iron-phosphate, or LFP. It prices much less, makes use of fewer hard-to-source minerals, and is usually safer below excessive circumstances, however the expertise holds much less vitality in a given quantity. Tesla has begun utilizing LFP for some U.S. fashions, and Ford introduced it’s going to construct an LFP cell plant for its electrical automobiles.

Cell Format

Battery engineers should resolve what form (often called “format”) every cell needs to be—although, in apply, not each provider provides each cell chemistry in each format. Tesla pioneered the usage of hundreds of small-format cylindrical cells (just like AA batteries) in a battery pack; many different makers have opted for lots of of bigger cells in pouch or prismatic codecs, that are two variations of rectangular shapes. A number of cells are grouped into modules which might be positioned into a big rectangular container to make up the pack. Some batteries have eight modules, whereas others have dozens. Cells inside modules are wired in collection, and modules are wired in parallel.

gm ultium battery pack

Battery pack from GM’s Ultium household, which use cells with a nickel-manganese-cobalt-aluminum (NMCA) mix.

Automobile and Driver

The brand new GMC Hummer pickups and SUVs have two 400-volt module teams in parallel that swap to an 800-volt collection to permit DC fast-charging of as much as 300 kilowatts.

Cell and Pack Dimensions

Whereas there are normal sizes for cylindrical cells, a number of the different cell codecs are made in sizes particular to a given automaker. The problem engineers face is packing the utmost vitality right into a battery pack with the smallest potential dimensions whereas making certain there’s enough room for liquid-cooling channels, all of the wiring that connects cells inside modules and modules to one another, and correct separation of modules for security.

At this time, nearly any EV with a variety of 200 miles or extra has a battery below the cabin flooring that stretches from door to door, axle to axle. Typically there’s additionally a raised hump below the rear seat for extra capability, and generally what the Germans name “foot garages” are recessed into the pack to permit enough rear-seat legroom in decrease automobiles. These heavy underfloor packs do get pleasure from decreasing the middle of gravity, thus enhancing car stability and dealing with.

Capability (i.e., Vary)

Lastly, battery engineers, car product managers, and their accountants will debate what battery capacities to supply. The purpose is an EV they will promote on the proper worth with enough vary to reassure clients that it is a sensible possibility for his or her lives and travels. We have discovered that within the U.S., round 250 miles appears to be the minimal vary to get folks to think about buying and selling inside combustion for electrical motors for every day use. GM has mentioned it thinks 300 miles is the benchmark at which consumers cease worrying about vary. There are few EVs that may truly ship on the EPA vary posted on their window-sticker label, nonetheless.

Even so, throughout the previous decade of EV growth, that is the realm the place probably the most progress has been made. In 2013, the state-of-the-art was a Nissan Leaf with 75 miles of EPA vary at a worth round $30,000 or a Tesla Mannequin S with 265 miles at over $90K. The choices have an excellent wider unfold at this time. You should buy the dead-man-walking Chevrolet Bolt EV, with 258 miles of vary, for $27,495; one model of the Lucid Air luxurious sedan is rated at greater than 500 miles and comes with a six-figure price ticket.

However merely upping the battery capability has a diminishing return. A much bigger, heavier pack is inherently much less environment friendly, so automakers should parley good battery tech with different efficiencies to stay aggressive.

Headshot of John Voelcker

Contributing Editor

John Voelcker edited Inexperienced Automobile Experiences for 9 years, publishing greater than 12,000 articles on hybrids, electrical vehicles, and different low- and zero-emission automobiles and the vitality ecosystem round them. He now covers superior auto applied sciences and vitality coverage as a reporter and analyst. His work has appeared in print, on-line, and radio retailers that embrace Wired, Fashionable Science, Tech Overview, IEEE Spectrum, and NPR’s “All Issues Thought of.” He splits his time between the Catskill Mountains and New York Metropolis and nonetheless has hopes of sooner or later turning into a world man of thriller.

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