Can You Jumpstart an Electric Car

Introduction

When drivers think about flat batteries, the natural instinct is to reach for a set of jump leads and find a helpful neighbour with a running engine. For decades, jumpstarting has been a routine solution for petrol and diesel car owners across the UK. However, with the rapid shift toward electric vehicles, many drivers are wondering whether the same approach applies. Can you jumpstart an electric car in the same way you would a traditional vehicle? The short answer is both yes and no. Electric cars do have 12-volt batteries that can be jumpstarted under certain circumstances, but the main high-voltage battery that powers the motor should never be jumpstarted. Attempting to do so could cause serious damage or even present safety risks. This article explores how jumpstarting works in electric vehicles, what to do if your EV won’t start, and how to keep your system healthy and ready to drive.

Understanding the Batteries Inside an Electric Car

To understand whether an electric car can be jumpstarted, it is essential to know that it has two distinct batteries. The first is the large, high-voltage traction battery that drives the electric motor. This battery stores the energy used for propulsion and typically operates at several hundred volts. The second is a smaller 12-volt auxiliary battery, which powers standard electrical components such as lights, infotainment systems and door locks.

The 12-volt battery is similar in purpose to the one found in a petrol or diesel car. It acts as the control power source that starts the car’s computer systems. When you press the start button, this small battery activates relays and systems that connect the main high-voltage battery to the rest of the car. If the 12-volt battery becomes flat, the car’s main systems will not start, even if the main traction battery is fully charged.

This is where jumpstarting can be relevant. While you must never attempt to jumpstart the high-voltage battery, it is safe to jumpstart the 12-volt system following the manufacturer’s guidelines. Doing so can restore enough power to allow the vehicle’s systems to boot up and reconnect the main traction battery.

Why You Should Never Jumpstart the Main Battery

The high-voltage battery in an electric vehicle is a completely different system from the 12-volt circuit. It operates at voltages far beyond what jump leads or conventional starter batteries can handle. Attempting to connect a petrol or diesel car’s 12-volt system to the traction battery would be dangerous and could result in serious injury or electrical damage.

High-voltage batteries are carefully isolated from the rest of the vehicle. They include sophisticated management systems that regulate charging and discharging, as well as safety circuits that disconnect the power if faults are detected. These systems are designed to be charged only through an EV charger, not through external jump connections.

Manufacturers build multiple safety layers into electric vehicles to prevent accidental high-voltage contact. The orange cables you may see under the bonnet or beneath the car are high-voltage lines and should never be handled or connected to external devices unless by a trained technician. Attempting to jumpstart this system is not only unnecessary but could also void the warranty and compromise the car’s electrical safety.

When You Can Jumpstart an Electric Car

If your electric car fails to start or power up, it is likely the 12-volt battery that is flat. This smaller battery can indeed be jumpstarted in a similar way to that of a petrol or diesel car. The process involves connecting jump leads or a jump pack to the designated terminals of the 12-volt system. However, it is crucial to follow the vehicle manufacturer’s instructions, as the connection points and procedures vary between models.

In many electric cars, the 12-volt battery is located under the bonnet, but in some models, it may be hidden in the boot or beneath a panel. The vehicle manual will show the correct access point for jumpstarting. Once connected, a jumpstart can provide enough power for the car’s systems to initialise. Once the electronics come to life, the high-voltage battery can take over and begin charging the 12-volt system automatically.

Drivers can also use a portable lithium-ion jump pack instead of another vehicle. These devices are small, easy to store and safer than traditional lead-acid jump setups. Using a jump pack eliminates the risk of electrical spikes from another car’s alternator, which can sometimes damage sensitive EV electronics.

Step-by-Step Overview of the Safe Jumpstart Process

To safely jumpstart the 12-volt battery in an electric car, always ensure that the vehicle you are using as a power source is also an EV or a car with the engine turned off before connecting the leads. Follow the manufacturer’s step-by-step instructions, which typically involve connecting the positive (red) lead to the positive terminal of the flat battery and the negative (black) lead to a suitable grounding point, such as an unpainted metal surface.

Once connected, the supporting battery should supply enough voltage to activate the car’s control systems. After a few moments, turn on the electric car and allow its systems to power up. Once the main traction battery connects, it will start to recharge the 12-volt battery automatically. Remove the leads in reverse order and allow the car to remain powered on for several minutes to replenish the small battery.

Never attempt to start the car repeatedly or leave the jump leads attached for long periods. If the battery fails to hold charge or the car will not start after several attempts, it may indicate a deeper issue with the 12-volt system or the high-voltage control circuits. In such cases, professional diagnosis is required.

Why Electric Car Batteries Go Flat

A flat 12-volt battery in an electric car can occur for several reasons, most of which are familiar to owners of traditional vehicles. The most common cause is leaving the car unused for long periods. Even when parked, the 12-volt system powers background electronics such as the security alarm, telematics and battery management systems. Over time, these small power draws can deplete the battery.

Cold weather can also reduce battery efficiency, particularly in winter. Low temperatures slow chemical reactions inside the 12-volt battery, reducing its ability to hold charge. For this reason, EV owners are encouraged to keep their vehicles plugged in during cold months, allowing the main battery to maintain auxiliary systems automatically.

Frequent short journeys can also prevent the 12-volt system from fully recharging. Although the main battery does recharge it when driving, this process can take time. A series of short trips might drain the system faster than it can replenish.

What to Do if Jumpstarting Doesn’t Work

If your electric car still refuses to start after a safe jumpstart attempt, do not keep trying repeatedly. Continuous attempts can overload the circuits and damage the electronics. The best course of action is to contact roadside assistance or the manufacturer’s emergency helpline.

Most breakdown services in the UK, including the AA, RAC and Green Flag, are now equipped with electric vehicle recovery and diagnostic tools. They can safely assess whether the problem lies with the 12-volt battery or the main traction system. Some vehicles may require a system reset or a software update if the power management system fails to engage properly.

In rare cases, the problem might be caused by a deeper electrical fault, such as a failed relay or an issue with the high-voltage battery’s contactors. These components are highly specialised and must be inspected only by technicians trained to work on electric vehicles. Attempting to access them yourself could be dangerous and void any warranties.

Can You Use an Electric Car to Jumpstart Another Vehicle?

This is one of the most common questions among EV owners, and the answer is almost always no. Electric vehicles are not designed to provide power to external 12-volt systems. The smaller auxiliary battery in an EV is not built to deliver the high current required to start a petrol or diesel engine. Attempting to do so could damage the EV’s electrical components or trigger safety shutdowns.

While it might be technically possible in some cases to use an EV’s 12-volt output to assist another battery, manufacturers generally warn against it. The safer approach is to carry a portable jump pack or call for roadside assistance. These jump packs are inexpensive and designed specifically for such emergencies.

Using an EV to jump another vehicle could also interfere with the onboard computer’s voltage management systems. Electric cars rely on precisely regulated circuits, and sending or receiving unexpected electrical surges can create faults that require professional reset procedures.

Maintaining the 12-Volt Battery in an Electric Vehicle

Preventing a flat 12-volt battery is much easier than dealing with one. Regular use of the vehicle keeps both the traction and auxiliary batteries healthy. Driving or charging at least once a week helps maintain the correct voltage levels. If you plan to leave the car unused for long periods, plug it into a charger or use a maintenance mode if available.

Many modern EVs include software that monitors the health of the 12-volt battery and displays warnings before it becomes completely discharged. Paying attention to these alerts allows owners to address issues early, avoiding unexpected breakdowns.

During annual servicing, technicians will check the 12-volt system’s voltage and replace the battery if its capacity has dropped significantly. Most last between three and five years, depending on use. Regular cleaning of terminals and ensuring tight, corrosion-free connections also help maintain reliability.

How Manufacturers Design Safety Around Flat Batteries

Electric cars are engineered to handle low-voltage situations safely. In many models, the high-voltage battery can automatically recharge the 12-volt system periodically, even when the vehicle is not being driven. This feature prevents the auxiliary battery from becoming completely flat. However, if the car’s software encounters a fault or if the 12-volt battery degrades over time, this automated recharging may fail.

Manufacturers design safety systems that disconnect the high-voltage battery when the 12-volt system goes flat, preventing accidental activation. This is why even a small 12-volt failure can leave a car completely unresponsive. It might appear as though the entire vehicle is dead, but in reality, the main traction battery is simply offline until the control systems receive power again.

This layered safety approach ensures that electrical faults do not cause fires or shocks, protecting both occupants and first responders. Once the 12-volt system is restored, the car’s main electronics can safely reconnect to the high-voltage system.

Cold Weather and Jumpstarting Challenges

UK winters can present challenges for electric vehicle owners, particularly in maintaining battery performance. Cold temperatures slow chemical activity inside batteries, making both the 12-volt and traction systems less efficient. When combined with higher energy demand for heating and demisting, this can increase the risk of a flat auxiliary battery.

Keeping the vehicle plugged in during cold weather helps prevent this problem. Many EVs allow preconditioning, which warms the cabin and batteries before driving while connected to the mains. This reduces strain on the systems and ensures the 12-volt battery receives regular top-ups.

If your EV becomes unresponsive during cold conditions, always check the 12-volt system first before assuming the main battery is depleted. A simple voltage test can confirm whether a jumpstart might be necessary. Using a portable jump pack designed for EVs is the safest and most efficient solution.

Frequently Asked Questions

Can you jumpstart an electric car?

Yes, but only the 12-volt battery. Never attempt to jumpstart the high-voltage traction battery.

What should I do if my electric car won’t start?

Try safely jumpstarting the 12-volt system according to the manual. If that fails, call for professional assistance.

Can I use an EV to jump another car?

No. The 12-volt battery in an EV is not designed to deliver enough power to start a combustion engine.

What causes a flat battery in an electric car?

Leaving the car unused, cold weather, or natural ageing of the 12-volt battery are common causes.

How long does a 12-volt battery last in an EV?

Typically between three and five years, depending on driving habits and environmental conditions.

Conclusion

The ability to jumpstart an electric car depends on understanding its two-battery system. While the main traction battery must never be jumpstarted, the smaller 12-volt auxiliary battery can be, provided it is done safely and correctly. Following manufacturer guidelines is essential to avoid damage and ensure personal safety.

As electric vehicles become more advanced, manufacturers are incorporating systems that automatically maintain the 12-volt battery to prevent flat situations altogether. However, knowing how to handle a dead auxiliary battery remains important for every EV owner. With the right knowledge, preparation and equipment, you can quickly and safely restore power to your vehicle without risk.

Electric cars continue to simplify vehicle ownership, reducing the need for frequent maintenance or complex repairs. Understanding the basics of their electrical systems helps drivers handle occasional issues confidently. For UK motorists making the transition to electric driving, the good news is that a flat battery need not spell disaster. With careful attention and the right approach, jumpstarting an electric car’s 12-volt system is straightforward, safe and effective.