EV batteries rely on thermal management, but parked features can still drain charge

Most EVs pump coolant through tubes or metal plates pressed against the battery, collecting heat and carrying it to a radiator or the air-conditioning system. Many also use navigation-linked pre-conditioning: Tesla's manual tells owners to set a fast charger as a destination 30 to 45 minutes before arrival, and Porsche warns that without such preparation charging power may be lower, according to Engadget.

Engadget cited a Geotab study of more than 22,700 EVs that found batteries lost an average of 2.3 percent of their health each year. Cars in hot climates lost about 0.4 percentage points more annually than those in mild climates, and cars that frequently used fast chargers above 100 kW lost 3 percent a year, against 1.5 percent for those that rarely did. A 2021 review in the journal Energies found that a temperature difference of more than 5 degrees Celsius across a cell can accelerate aging by 25 percent. Cold poses separate risks: internal resistance rises, and fast charging can cause lithium plating. Recurrent, which studied more than 30,000 US EVs, found batteries averaged 78 percent of ideal range at freezing temperatures and about 70 percent at minus 7 degrees Celsius; cabin heating accounted for about two-thirds of the extra energy used in cold weather.

The first Nissan Leaf in 2010 used passive air cooling for a 24 kWh pack, while Tesla, GM and Ford used liquid systems. Leaf owners in Phoenix tested 12 cars from the 2011 and 2012 model years and found range losses; Nissan said the issue affected fewer than 0.3 percent of US models, Engadget reported. The third-generation Leaf unveiled in 2025 switched to a liquid-cooled 75 kWh battery. Liquid cooling needs two to three times less energy than air to hold a pack at the same temperature, according to Energies. BMW's i3 ran refrigerant from the air-conditioning system directly to the battery, and McLaren's Speedtail submerged its cells in electrically insulated oil, a design that simulations cited by Energies suggested could move heat up to three times better than cooling plates.

Battery coolant loops usually connect to a radiator for light loads and, through a heat exchanger, to the air-conditioning system for heavier loads such as fast charging. Nissan's system switches between the two modes and routes heat from the charger into the battery during home charging, a feature the newer Leaf uses to warm the pack. Tesla's Model Y uses a valve nicknamed the Octovalve to move coolant among the motors, battery and electronics. Tesla is also exploring a patent for running the drive motor inefficiently on purpose so its waste heat can warm the battery. General Motors says its Ultium heat pump collects waste heat from the battery, power electronics and passengers to warm the cabin, adding about 10 percent more range. China has introduced rules requiring new EVs to show that their batteries do not catch fire or explode when a cell enters thermal runaway, a requirement that depends on cooling and insulation stopping heat from spreading.

A locked EV does not shut down every electrical system. The battery-management system periodically checks conditions, and the high-voltage battery can recharge the smaller low-voltage battery used for locks, computers and electronics. Tesla says its Model 3 performs such checks and battery maintenance while parked; Rivian says its R1T uses the high-voltage battery to maintain its 12V battery. Connected services, app requests, climate functions and infotainment also consume power, and third-party apps that repeatedly wake a sleeping vehicle can add to the drain. Cabin cooling in hot weather is not free, Engadget reported. Slate's barebones electric pickup may have an advantage with fewer connected features, though its actual parked drain remains untested.

Tesla's Sentry Mode and Rivian's Gear Guard Motion Cam can capture activity around a parked vehicle but require power. Tesla's Model 3 manual says the battery can lose approximately 1 percent per day depending on settings and conditions. Recurrent reports that sleeping Teslas can lose just 0.1 to 0.3 percent a day, while those running energy-intensive features can lose several percent daily; Engadget noted that the figures reflect different conditions. Battery size affects how noticeable a loss is: 0.5 kWh is about 1.2 percent of a 42 kWh battery and 0.6 percent of an 80 kWh battery. For long storage, Tesla recommends keeping a Model 3 plugged in when not in use, especially for several weeks, and maintaining around 50 percent charge. Drivers can also turn off unneeded surveillance and climate controls and limit apps that wake the vehicle.