We countdown the top 5 maintenance steps that can be taken to extend the life of your EV battery.
5. Don’t leave your battery sit at a 100% state of charge
Most EVs have an option for a “Standard” charge or a “Range” or “Max” charge. By all means, do the maximum charge when you need it, but do it right before you start using the battery for the trip. Most EVs have charge timers to help you plan for this. If your EV doesn’t have that, do an overnight standard charge and then charge the last 10-20% in the AM before departure. Leaving a battery pack at max charge for even relatively short periods of time can possibly affect its life. As a rule of thumb, try to never let your battery sit at maximum state of charge for longer than 8 hours.
While you may be able to time your max charge and departure times well, daily charging to 100% is stressful to your battery. This is why most vendors offer “standard” or “normal” charge levels which wont help you achieve the maximum EPA range rated for your vehicle. If you don’t need the max charge, then don’t use it. Generally lithium-ion batteries do best when they operate in the 30% to 90% range for state of charge. Although a bit extreme, prolonging the time spent above or below that range theoretically may lead to a shorter pack life
Tesla Model S TIP: For overnight charging that requires a 100% MAX charge (ie prior to a Tesla road trip), set your “start charge time” to a time that will result in a full charge roughly 60 minutes before your departure.
4. Avoid deep discharging of the battery pack
Conversely, leaving your battery in a discharged state for an extended period may also impact its life. Most vendors protect batteries from becoming completely discharged as that can effectively “brick” the battery and leave it completely useless. The general rule of thumb is to plug in and charge whenever you can. That doesn’t mean going out of your way for a few kW of charge, but it does mean plugging your car in nightly and maintaining a reasonable charge level. What is a low state of charge? Under 30% charge is generally considered low and thus you should not let your EV sit at that low state of charge for an extended period.
MUST SEE: Decoding Your Tesla Battery Pack Version
Also beware that EVs consume power even when not being driven. With the Model S, it loses about 1% of its charge per day.
3. Be mindful of extreme temperature conditions
This is less applicable to the Tesla Model S which has its own built in thermal management system that pre-conditions the battery (ie. warms the pack when too cold and vice versa), but the general rule of thumb for batteries of Lithium-ion composition is to keep the battery pack between 20F – 85F.
Heat is the enemy of Lithium-ion and may increase battery degradation when consistently exposed to high temperatures. This phenomenon was enough to motivate Nissan to produce a “hot climate battery” for their LEAF after owners within hotter climates complained of battery loss.
Conversely, extreme cold weather can impact performance for a battery of lithium-ion chemistry while lowering the discharge capacity.
2. Plan ahead for extended storage
If you’re going away on vacation or for a business trip the best thing for your car is to set the charge level to 50% and leave it plugged in. If you’re leaving your EV at the airport or somewhere where you can’t leave it plugged in beware that you’re going to lose some charge per day. Charge to a level where you can get to the airport, let it sit for the trip and then still have enough charge with buffer to get home. Don’t let it sit unplugged at an airport for days on end at a 90% charge state if possible. Still, leaving it at 90% is better for the battery (and you) than leaving it at 10% and coming back to find the battery completely discharged.
1. Periodically fully charge and “balance” your battery
Lithium-ion batteries are designed to minimize the “memory” issues often found in older battery technologies, however the battery packs in EVs are more complex and often comprised of multiple individual batteries packed together into removable modules. There’s as many as 7,000 individual cells in the Model S.
Battery balancing is about maximizing your battery’s capacity and evening out the charge distribution. Modern EV battery packs include an automatic battery balancing component, but there’s steps that you can take to help the process along.
While you may never need the maximum range that your battery can provide and you may never take long trips, a periodic range or max charge is helpful to your battery’s management system. I’d suggest doing this about once every 3 months or so and keep in mind that after you fully charge you should not let it sit, that would be a violation of battery management rule #5.
Disclaimer: We’re dealing with expensive components. Read the manual for your EV, search your EV forums, develop your own rules, be consistent, but adjust as needed. The rules above are general rules for any EV that may help extend the life and health of your battery. Your own mileage (range!) may vary.