You may not know that electric cars actually come with two batteries inside. There’s the large battery, which powers the motor and makes the car go, alongside a second smaller battery. The second battery powers the low-energy features such as lights, wipers and locks, and is essential to actually switching the car on.
In some high-end cars, the second battery is a smaller lithium-ion unit, but in a lot of cases you’ll open the hood to find a regular old 12-volt car battery — the same kind you’d find in a gasoline-powered car, complete with all the same limitations on how long it can hold a charge.
Right now, you might be wondering about the relationship between electric vehicles and jump-starting. We’ve all had to jump-start our car at one point, or known someone who has, because those 12-volt car batteries are pretty finicky things.
Do EVs ever need jump-starting? Can you jump-start another car with an EV? The answer, unfortunately, is a little bit complicated.
Can you jump-start an EV?
Fortunately, in this instance, things are pretty simple. You can indeed jump-start an EV the same way you can with a gas-powered car. However, the chances of you ever having to do this are rare, thanks to the way the power system in an EV works.
Batteries in gas-powered cars are recharged by the car itself, with the alternator (or dynamo, if your car is old enough) generating electricity from the engine's rotations. These batteries are known for losing their charge fairly quickly, and if you don’t intend to drive your car for a few weeks, it pays to switch on the engine for about 15 minutes every week to ensure the battery stays charged up.
If an EV uses a 12V battery, which the majority do, the battery will be identical to those found in other cars. However the smaller battery draws its power from the car’s main power-train battery if its charge level dips too low.
It’s important to remember that this borrowing of charge usually does not happen when the car is plugged in. If you leave an EV on zero-percent main battery for long enough, the 12V battery will eventually die too.
What’s more, in some cases having a dead 12V battery may prevent the main battery from being recharged. That is not a situation you want to find yourself in.
It’s pretty rare for an EV’s 12V battery to completely die, but it can happen. In those cases you can get a jump from another car, just as you would if your car still used gas. Or you can get a trickle charger to supply power more directly provided you’re not in a hurry.
Should you ever need a jump-start, the process is exactly the same as if you were driving a gas car. Just make sure to unplug the car from a charger, because otherwise you risk causing damage to the car's electrical system.
Can a jump-start give you more range?
No. A jump-start only applies to the smaller 12V battery, which can’t transfer power to the larger lithium-ion battery that powers an electric car’s wheels. The 12V battery is a lot less powerful than its bigger sibling and doesn’t have anything close to what it takes to generate the motors that turn an electric car’s wheels.
Trying to recoup lost range from a jump-start is entirely fruitless and a pretty dumb thing to attempt. One of the benefits of driving an electric car is the fact that it doesn’t produce any pollution while you drive. Trying to use a gasoline engine to recharge the battery defeats the purpose and means you might as well be driving a hybrid.
If you need more range, you'll just have to find an EV charging station near you.
Can you use an EV to jump-start another car?
You can, technically, but that doesn’t mean you should try to jump-start a gas-powered car from an electric or hybrid vehicle.
It is physically possible for an EV or hybrid to jump-start another car, although the process is a little different from the regular method. It can usually be accomplished by connecting both car batteries with a standard set of jumper cables and waiting for power to change hands. (In a regular jump-starting procedure between two gasoline engines, you would connect the negative clamp on the cables to a grounding point on the receiving car's frame, not to the receiving battery's negative pole.)
But you shouldn’t actually do this, because it risks causing some significant damage to your car.
Why? It seems to be because of how EVs operate, and what the EV's 12V battery actually does. On a gas-powered car, the battery gives the electric starter the juice it needs to get the internal combustion engine physically moving quickly enough to achieve ignition.
EVs don't have an ignition circuit, because there’s no physical fuel that needs igniting, and their 12V batteries lack that same kick. That means they don’t have what it takes to jump-start the engine in another car.
Attempting a jump from an EV can put stress on its 12V battery, which isn’t good for the battery itself. It can also confuse the battery-monitoring software, leading to unnecessary headaches down the road and potentially damaging the car’s DC-to-DC converter.
The DC-to-DC converter is an essential part of an electric car, since that’s how the 12V battery is able to draw power from the main battery, and is also how the smaller battery powers the low-voltage systems like lights, doors, climate control and so on. If that converter dies on you, then your electric car is pretty much useless.
That’s exactly why a lot of manufacturers specifically advise against using an EV to jump-start a gas-powered vehicle.
The Nissan Leaf’s owner’s manual (opens in new tab) features a warning that says “LEAF cannot be used as a booster vehicle because it cannot supply enough power to start a gasoline engine. However, a gasoline engine vehicle can be used to jump start LEAF's 12-volt battery.”
Meanwhile, the Tesla Model S handbook (opens in new tab) states that the car can not be used to jump-start another vehicle, and that doing so can result in damage to the Tesla. The manual also points out that using the car as a stationary power source, which a jump-start qualifies as, will void your warranty.
You won't be able to do that for much longer anyway. Tesla's 2021 Model S and Model X cars feature a proprietary 12V lithium-ion battery instead of the more common lead/acid battery. This change is also rumored to be happening to the 2022 Model 3 and Model Ys.
Both Nissan and Tesla, and plenty more, confirm that it’s perfectly safe for their electric cars to receive a jump from a gas-powered engine as long as the EVs are using regular 12V batteries. So don’t let the fact your EV can’t be used as a power source put you off.
As different as EVs are from their gas counterparts, a lot of things are still the same. The 12V battery is probably the best example of that and remains a key component of every car on the road — excluding the few Teslas that have already fully switched to lithium-ion batteries.
If you have an EV, be sure to keep a pair of jumper cables in the trunk, just as you would have done before. Just remember that with electric vehicles, the jump-start system is a one way street — you can receive power, but you can't give it back.
It’s unfortunate, but EV owners should be aware that these gestures of generosity will put your own vehicle at risk. Trying to jump-start someone else's car may be good for your karmic balance, but when the dust clears, your bank balance won’t feel the same way.