Can You Jump Start a Petrol Car With an EV?

The short answer is: not via the high-voltage traction battery, which must never be connected to jump leads. However, many electric vehicles also carry a conventional 12V auxiliary battery, which powers the car's electronics and, in some models, can be used to jump-start another vehicle's 12V system in the traditional way, with the same caveats and cautions that apply to any jump-start. If you are unsure whether your EV supports this, check your owner's manual before attempting anything. For other EV accessories and useful kit to carry on the road, take a look at our range of EV charging accessories.

Why can't you connect jump leads to an EV's traction battery?

The high-voltage traction battery in an electric car operates at hundreds of volts, which is a completely different electrical system from the 12V battery found in a petrol or diesel car. Connecting standard jump leads to the traction battery's terminals is dangerous: the voltage and current levels are far beyond what jump leads are rated for, and doing so risks electric shock, arc flash, fire, and serious damage to both vehicles. No reputable manufacturer permits this, and attempting it is likely to void your warranty immediately. The traction battery is sealed, managed by sophisticated software, and should only ever be serviced by trained EV technicians.

What is the 12V auxiliary battery in an EV?

Nearly all electric vehicles carry a small 12V auxiliary battery alongside the main traction battery. This auxiliary battery powers the car's low-voltage systems: the lights, the infotainment, the door locks, the alarm, and the contactors that connect the traction battery when you switch the car on. It is similar in function to the 12V battery in any petrol car, though often smaller because it does not need to crank a starter motor. Like any lead-acid or lithium 12V battery, it can go flat, particularly if the car sits unused for a long time or if a parasitic drain develops. When the 12V auxiliary goes flat, the car will typically not power up at all, even though the main traction battery may be perfectly charged.

Can an EV's 12V battery jump-start a petrol car?

In principle, a healthy 12V auxiliary battery in an EV can supply jump-start current to another 12V vehicle, in the same way any 12V battery would. In practice, several cautions apply. First, check your EV owner's manual: some manufacturers explicitly state the 12V battery should not be used to jump-start other vehicles, as the auxiliary battery in many EVs is smaller and lighter-duty than a traditional starter battery. Second, access to the 12V terminals varies by model; on some cars they are under the bonnet, on others they are in the boot or behind a panel. Third, follow the standard jump-lead safety sequence (connect positive to positive, negative to a good earth point away from the battery) and avoid letting the vehicles touch. If in any doubt, call roadside assistance rather than risk damaging either vehicle.

What should you do instead if someone needs a jump-start?

The safest and most reliable option for occasional jump-starting, whether for your own car or to help a stranded motorist, is a portable lithium jump starter pack. These are compact devices that fit in a glove box or boot bag, hold their charge for months, and can deliver enough current to start a petrol or diesel engine without needing a second vehicle at all. They are inexpensive relative to the cost of a damaged battery or a breakdown call-out, and they work independently of your EV. Roadside assistance from your breakdown provider is the other straightforward option, particularly for unfamiliar situations or if the vehicle belongs to someone else. Trying improvised solutions in a hurry is how mistakes happen.

What about V2L: can an EV actually power things from its main battery?

Some electric vehicles support Vehicle-to-Load technology, commonly called V2L. This is a feature where the traction battery exports usable AC power through a dedicated socket, either in the charging port or via an adapter, at a safe, managed voltage suitable for appliances and devices. V2L is not the same as jump-starting: it does not produce the short high-current burst that starting a combustion engine requires, but it can run power tools, camping equipment, or even charge another EV slowly. If your EV supports V2L, the right adapter is a V2L discharge cable, which connects safely to the car's designated outlet. Never attempt to improvise a connection to the traction battery yourself.

How do you handle a flat 12V battery in your own EV?

If your own EV's 12V auxiliary battery goes flat, the safest approach is a portable jump pack or calling your breakdown provider. Do not rely on another vehicle connecting leads directly to your EV's traction system. Once the 12V battery is revived, the car should power up normally and allow the traction battery to take over. If the 12V battery keeps going flat, it may need replacement: most EV dealers and independent EV specialists can source and fit them. Some EV owners also use a trickle charger on the 12V battery during extended periods of storage to prevent this situation arising in the first place.

Frequently asked questions

Is it dangerous to connect jump leads to an electric car?

Connecting leads to the high-voltage traction battery is extremely dangerous and must never be attempted. The 12V auxiliary battery terminals, if your manual permits access, are safe to use with ordinary jump leads in the same way as any 12V battery. Always read your owner's manual before touching any terminals under the bonnet of an EV.

Where are the jump-start terminals on an electric car?

Location varies by manufacturer and model. On some EVs the 12V auxiliary battery or dedicated jump-start terminals are under the bonnet; on others they are in the boot or behind a panel. Your owner's manual will show the exact location and any model-specific instructions. Never guess or assume the layout matches a petrol car.

Can an EV with V2L power a petrol car's starter motor?

No. V2L outputs AC power suitable for appliances, not the short high-current DC burst needed to crank a combustion engine. It cannot be used as a jump-start source for another vehicle's 12V system. V2L is useful for running devices and equipment, not for emergency starting of other cars.

Will jump-starting another car drain my EV's range?

If you use the 12V auxiliary battery (where permitted), the drain is very small and the auxiliary is recharged by the traction system as you drive. The main traction battery range is unaffected. A brief jump-start via the 12V system takes negligible energy compared to the size of a typical traction battery pack.

Can I use a petrol car to jump-start a flat EV traction battery?

No. The EV traction battery is not 12V and cannot be charged via jump leads from any vehicle. If the traction battery is flat, the car needs to be plugged into a charger. If the 12V auxiliary battery is flat (preventing the car from powering up), that can be jump-started separately as described above, but the traction battery itself always charges via its charge port.

What is the best thing to carry in an EV for roadside emergencies?

A compact lithium jump starter pack covers most 12V battery emergencies for yourself or other road users. A quality charging cable means you can top up at any compatible public charger. Breakdown cover from a provider familiar with EVs is also worth having, as not all recovery services are equally equipped for electric vehicles.

Jump-starting situations are much less common with an EV than with a petrol car, since there is no cold-start cranking to drain a battery overnight. That said, carrying a portable jump pack and the right charging cable gives you peace of mind on any journey. Browse our V2L discharge cables if your vehicle supports power export, and our full range of EV charging accessories for everything else you might need on the road.