What should your car battery voltage be?

Consumer Editor

3 minute read|14th Jan 2026

Car battery health is an often overlooked part of car maintenance. Yet, without a fully functioning battery, your car wouldn't start or be able to run any of the key electrical systems.

That's why it's important to understand battery health and car battery voltage.

Whether you are trying to charge your battery, or troubleshoot issues with a dead one, keeping it working effectively is essential for overall car health.

In this guide, we explain what your car battery voltage should be, along with helpful tips to keep your battery in perfect working order.

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What is car battery voltage?

Car battery voltage is the electrical potential provided by the vehicle’s battery and alternator and is measured in volts.

Most cars use a 12-volt battery (also known as 12V) which powers the key components in your vehicle.

These include:

Starter motor
Ignition
Dashboard
Lights
Infotainment system
On-board computer

As a general rule, you should have your car battery checked during a full or interim service.

What is car battery voltage?

Car battery voltage is the measure of electrical potential between two points in a circuit, it is essential to push electricity through the car's wires and components.

Weak voltage means that there isn’t enough power going to the end of the wires, and too much voltage can overpower it and break the system.

What voltage should a car battery be?

There is no single answer to what your car battery voltage should be - it very much depends on the type of vehicle and its usage.

Below we list the voltage your car battery should be when it is off, idling and running.

Off

When the engine is switched off, the car battery should have a voltage of around 12.6 volts.

Idling

When the engine is running – but the car isn’t moving – then the car battery should have a voltage between 13.7 and 14.7 volts.

Running

After the driver has pulled away and the engine running, the battery should have a voltage between 13.7 and 14.7 volts.

Dangers of letting your battery voltage drop too low

The car battery is essential for the health of your car. If you allow the voltage to drop too low, the vehicle will stop and/or refuse to start.

Allowing the battery voltage to drop too low on a regular basis may also cause damage to the battery, which means it'll need to be replaced.

How to prevent your car battery voltage from depleting

There are some simple steps you can take to prevent your car battery voltage from depleting.

Regular car use: if you do not drive your car regularly then the battery voltage can drop. This is particularly true in cold temperatures, which affect the chemicals within the battery and reduce the ability to store energy. Using your car regularly will allow the alternator to keep the battery healthy and fully charged
Fit a trickle charger or battery conditioner: if you must leave your car standing for long periods, fit a battery conditioner or trickle charger to prevent it from losing charge and going flat or becoming damaged
Ensure the car is switched off: leaving your lights on, a phone plugged into a USB socket or a dash cam active will all deplete battery voltage. Ensure your car is switched off and no electrical items are plugged in to drain battery power
Replace the battery: a car battery will last between 3 and 5 years. The type of vehicle and how often you use it will decide how long your car battery will actually last, but it's important to note that all batteries will wear out and lose the ability to hold a voltage. RAC Mobile Mechanics can replace your car battery at your home or place of work