No one wants to come home to a dead car battery.
Where to Keep Your Car
The easiest and best place to leave your EV for a long period of time is your own garage (if you have one). An enclosed space protects your vehicle from the elements and helps maintain a moderate temperature. If a garage isn’t an option, consider other storage options, like renting a space in a covered self-storage garage. You’ll want to avoid storing your EV in extreme temperatures, as heat and cold can have negative effects on the health of your battery. If a garage or self-storage isn’t an option for you, try to park your vehicle in a low traffic area, preferably some place with shade and out of the way from other elements that might put your car at risk (say construction or an overhead pigeon roost).
There are times when you may need to park in a specific place, for example, if you’re leaving your car at the airport. There may be spaces reserved for all electric vehicles, but think carefully before leaving your car in a charging space. Many public spaces charge idling fees and it may be unnecessary, expensive, and even damaging to charge your vehicle fully if you won’t be driving it for a while.
There are a few best practices for long-term storage that apply to all types of vehicles. Cars are meant to be driven and leaving them sitting in one place for too long can lead to problems. You might want to throw a few dryer sheets in the interior to discourage rodents from taking up residence and chewing on your wires. If you’re storing a car for prolonged periods of time but have access to it, like a hobby car or a vehicle you save for special occasions, you may want to drive it a short distance every two weeks to keep your tires from forming flat patches. You can also reduce the likelihood of patches by inflating your tires to the recommended PSI. EVs weigh more than cars with internal combustion engines, so their tires need to be replaced, rotated, and refilled more frequently. You don’t want to speed up that process or damage your EV tires unnecessarily. If you won’t be able to drive at all while it’s stored, consider elevating the vehicle on jacks to avoid putting pressure on the tires. Especially if you don’t have a garage or enclosed storage option, you’ll want to get a car cover for your vehicle to protect it from dirt, dust, and the elements.
It’s a good idea to check your fluid levels (brake fluid, steering fluid, etc.) and top them off if necessary. Be sure to maintain your car insurance, too!
12 Volt Battery Issues
Then there’s the biggest concern: the 12-volt battery. Like cars with combustion engines, EVs have a 12-volt battery to power accessories, like lights or electronic door locks. If the battery is dead, you may have trouble starting the car. While you can jump start an EV, it’s probably a step you’d rather avoid when you come back after a long break.
An EV’s 12-volt battery draws power from the main battery of the vehicle. If your EV’s main battery runs out of charge, or if there are wiring issues, the 12-volt battery will slowly lose charge as well. Even if your main battery doesn’t hit zero, the 12-volt could pull more power than you’d like, leaving you with a lower battery percentage than you feel comfortable with when you return to your car. This is where trickle charging can help. Trickle charging is using a level 1 charger or slow charging setting to add just enough power to keep the battery from draining while the car sits idle. Many EV have trickle charging settings as part of their battery management systems. You can use trickle charging when the car is not in use for extended periods to prevent the 12-volt battery from dying. Generally, if your EV is plugged in you won’t have an issue with the 12-volt battery depleting your charge.
To Plug In or Not to Plug In?
If your parking location has access to a power outlet, you may be wondering whether or not it’s best to leave your car plugged in while you’re not using it. The truth is it depends! Different manufacturers recommend different strategies to keep the battery at optimum health. Be sure to check your vehicle manual for specific recommendations. Here’s the scoop on some popular makes and models:
Tesla: Plug In
Tesla recommends leaving your car plugged in for storage. This should prevent normal range loss and help keep the battery at the ideal temperature. Tesla says it’s safe to leave their vehicles plugged in for any length of time. If you’ll be gone for weeks or more, you can set it up so the vehicle will stop charging when it reaches 50%, where the battery is most stable. Tesla also recommends not checking your car’s status too frequently via the mobile app, as checking will automatically wake the vehicle from its low power “sleep mode” and resume normal battery consumption. Some Tesla owners suggest turning off Sentry Mode and other features like Summon while you’re not using the vehicle, and checking to make sure Energy Saving Mode is turned on in order to reduce vampire drain.
Nissan LEAF: Unplugged
Nissan recommends keeping their vehicle unplugged for extended storage. Try to charge the vehicle to between 50% and 80% before you leave to help stabilize the battery and ensure you’ll have some charge available when you want to drive the car again. The 12-volt battery should recharge automatically in short bursts when the EV is not in use for a while. Avoid storing your car in extreme temperatures and try to make sure it won’t be left on 100% or 0% charge for too long. Nissan LEAF owners reported they had minimal range loss even after storing their vehicles for months.
Ford Mustang Mach-E: Unplugged
Ford recommends leaving the car unplugged and keeping the state of charge around 50% if storing the vehicle for more than 30 days. They also recommend disconnecting the negative terminal of the 12-volt battery to prevent depletion and damage. If you’re not comfortable disconnecting the 12-volt, you can leave the car plugged in or connect the 12-volt to a trickle charger instead. Mach-E owners report they’ve had no trouble with a serious drop in charge even leaving the vehicle unplugged and the 12-volt battery connected as usual. Consult the owner’s manual for more details on preparing your car for storage.
BMW: Plugged in
Like most EV manufacturers, BMW recommends keeping your vehicle between 20% and 80% charge for maximum battery life. You can leave the vehicle plugged in to take advantage of the battery’s thermal management system. BMW recommends increasing the vehicle’s tire pressure if you’ll be storing it for more than 3 months. Be sure to check your tire pressure and fluid levels when you return! As with other EVs, you may want to consider disconnecting the 12-volt battery to prevent vampire drain.
Some Rivian owners have noticed high battery drain when left unplugged. As with any vehicle, you should check the owner’s manual for specific advice, but leaving the vehicle plugged in or unplugged for a few weeks shouldn’t damage your battery. Rivian drivers recommend keeping the vehicle plugged in while storing, if possible, and disabling battery draining features like Gear Guard. Putting the car in Transport Mode and limiting maximum charge to 70% should also reduce vampire drain.
Chevy Bolt: Plugged In
The Chevy Bolt is another vehicle manufacturers recommend leaving plugged in during storage. The 12-volt battery is monitored daily. Keeping the vehicle plugged in helps maintain the ideal battery temperature and you can always set the target charge to prevent the battery from overcharging. Chevy recommends setting the state of charge to 30% and using a trickle charger for the 12-volt battery for long term storage. If you can’t leave the vehicle plugged in, charge it fully before storing. The Chevy Bolt also has a Transport Mode that can be turned on during prolonged periods of disuse.
Hyundai: Plugged In
Hyundai suggests charging the vehicle to 100% at least once every 3 months, but the main concern is not to let the battery reach 0%. The company suggests leaving the vehicle plugged in so the battery management system can run. Some Hyundai vehicles come with a “12V reset” that “jump starts” the 12-volt battery from the main traction battery, meaning there’s essentially no need for maintenance. For vehicles without the 12-volt reset, a trickle charger can be used. It’s a good idea to keep your car in a shaded area if it will be parked for a long time. Hyundai drivers have different suggestions, but generally agree there is minimal charge loss and that leaving the battery at 60% - 80% charge will keep the traction and 12-volt batteries running for a long time.
Range Loss - Planning for the Return Journey
If you’re going on a trip and leaving your car somewhere without access to a charger, like an airport or a parking lot, how much range can you expect to lose while you’re gone? How do you make sure there’s still enough juice in your battery to get you the rest of the way home?
Generally, you can expect to lose a few percentage points of charge every month. But it’s important to note some cars, especially those with a lot of over-the-air features, lose charge much faster. Ultimately, every car is different and you’ll need to check your vehicle manual to find out what the manufacturer recommends. Most EV owners seem to have no trouble provided they charged their cars to 50% - 80% before a trip. If you’re nervous about range loss, maybe do a test run before your trip, leaving your car unplugged for a few days, to see how much range you lose, or scope out nearby charging stations that you can use on your way home from the airport. Many airports have charging stations available in their parking lots or DC fast chargers nearby. You might consider getting a portable charger for emergencies. With a little bit of planning, you’re unlikely to have any trouble getting home, even if your EV has been sitting for a long time.
Behind the Scenes - How EV Batteries Work Best
You may be wondering why EV manufacturers generally don’t recommend charging your vehicle to 100%. More power is better, right? Actually, no. Keeping the lithium-ion battery in a state of charge between 20% and 80% helps keep the battery at optimum health. We tend not to think about it too much, but charging a battery is actually a physical process. Lithium ion batteries produce energy when lithium ions move from one electrode (the negative anode) to the other (the positive cathode) and are charged when the lithium ions move in the opposite direction. It’s the physical side to side movement of these ions that creates electricity. Much of the aging process of a battery is due to the physical wear and tear of ions pushing back and forth. Fast charging, which pushes the ions around more forcefully, can wear out your battery more quickly.
An EV battery is most stable at about 50% charge. It’s a balanced state, with no major electrochemical imbalance. Batteries are less likely to experience physical or chemical stress in this state. This is part of why depth of discharge is so important to battery health. Recharging a battery from 50% to 80% puts less stress on the battery than recharging from 20% to 80%. Recharging your EV battery more frequently, in smaller amounts, can help extend your battery life and prevent long term range loss. When thinking about storing an EV for a long time, leaving the state of charge close to 50% helps keep the battery stable.
Written by River James, a writer, editor, and researcher based in San Diego, California.