EV Battery Technology Trade-offs

Most EV batteries use the same basic li-ion technology as portable electronics, and the most common type found in vehicles sold in the U.S. contain a blend of nickel, manganese, and cobalt (NMC), though a different type of li-ion battery known as lithium iron phosphate (LFP) has grown in popularity. Like all batteries, NMC and LFP technologies have their strengths and weaknesses. NMC batteries have a higher energy density and charge better in low temperatures, but they cost more because they use more expensive materials (i.e., cobalt, nickel, and manganese) and they don’t last as long. LFP batteries have a lower energy density but last longer, tolerate high temperatures better, and cost less since they contain iron, which is more readily available than other elements.

Mercedes Benz EQS semi solid state battery test 3

Several other EV battery technologies are on the horizon. One that’s been hovering like a mirage for years is solid-state batteries, which replace highly flammable liquid electrolytes with solid materials, offer higher energy density in a smaller and lighter form, charge much faster (potentially less than 10 minutes to get a battery to at least 80 percent charge), and provide longer range.

Last year, Mercedes-Benz began testing a prototype EQS electric sedan with a semi-solid-state battery pack co-developed with its Formula 1 powertrain subsidiary, while Volkswagen Group recently placed a solid-state battery on a Ducati V21L MotoE motorcycle as a “tech demonstrator.” Other future potential battery chemistries being tested include lithium-sulfur and sodium-ion, while researchers are also tweaking electrode materials to improve existing battery performance.

EV Battery Charging Options

But enough with the chemistry lesson. Most vehicle shoppers simply want to know in the short term how fast an EV battery will charge and how long will it last during the lifetime of the car. It turns out the two are related, but again, with EVs batteries it’s complicated.

You have two general options to charge most portable electronics: fast charging using an AC 120-volt power cord and outlet or slower charging using USB power cords and outlets. EVs have three charging options. Level 1 is the slowest from a regular 120-volt AC outlet and supplies only a few miles of charge each hour. Level 2 charging is faster and usually occurs while parked at home, work, or a hotel, using either a 240-volt outlet, like the ones used for large household appliances such as electric dryers, or more typically a wall-mounted home charger. Level 2 charging is also available at public chargers that operate at 208 volts. Level 3 DC fast charging is only available at public charging stations, and the charging speed depends on factors such as the power output of the charger, measured in kilowatts (kW), and even the number of EVs charging at the same time.

While DC fast chargers provide the fastest recharging times for EV batteries, they are also affected by variables that aren’t usually an issue with Level 1 and Level 2 AC charging. While all levels are impacted by battery temperature and the battery’s state of charge (SOC), Level 3 are more heavily affected by the battery’s maximum acceptance rate, the station’s total power output (because many public charging stations use load management to split available power between vehicles), and other factors. In short, Level 3 real-world charging times can and will fluctuate, sometimes substantially, depending on the situation. And while larger battery packs generally accept higher power (measured in kW) for longer periods than smaller ones, due to their size they can also take longer to charge. But a larger battery in a vehicle with an 800-volt architecture may charge faster than a smaller battery in a vehicle with a 400-volt architecture, all things being relatively equal.