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Keeping up the voltage: this much current flows through an electric car

Electric cars have powerful batteries to drive them and have a separate 12-volt battery on board. One vehicle, two batteries, and two voltages – why is this?

Find out more about the voltage in electric cars here:

  • Electric cars have a high-voltage system and a low-voltage system.
  • The high-voltage system supplies energy to the vehicle’s powertrain,
  • while the low-voltage system supports many other systems and equipment. What does 'voltage' mean?
Image of a battery
High-voltage and 12 V system

To explain exactly what the word ‘voltage’ refers to, let’s look at electrical current. Current means that an electric charge is flowing through a material – a wire, for example, that connects the positive and negative terminals of a battery via a consumer.

Here’s an analogy to illustrate the basic principle: Imagine two buckets, one of which is higher than the other. The higher bucket is full of water, the lower one is empty, and the buckets are connected by a tube. The buckets can be thought of as the battery terminals, the tube is the conductor, and the water is the flowing electricity. The gradient between the buckets represents the voltage that is always produced when separate positive and negative charges are present – as in the terminals of a battery. It is indicated in volts (V).

Electric cars have two batteries: a high-voltage (rechargeable) battery carrying several hundred volts, and a 12 V starter battery, which is installed in all cars for starting.

In electric cars, such as the ID. models from Volkswagen, two types of battery are used: the high-voltage rechargeable battery, or drive battery, which can be recharged using a charging cable or through regenerative braking, and a traditional car battery. The high-voltage battery consists of several battery modules, which in turn are made up of several battery cells. The high-voltage battery system carries up to 408 volts. To compare, in most European countries, a domestic socket carries 230 volts. The familiar car battery, on the other hand, gets by with 12 volts. However, this battery may be somewhat smaller in an electric car, because it doesn't need to supply power to a starter for the combustion engine.

Illustration showing car and battery
Electric cars and plug-in hybrids need a powerful battery to drive the electric motor. (Image: Adobe Stock)
 The higher the voltage, the greater the potential for current – and therefore the power.

Why do electric cars use different batteries?

As explained above, the voltage is what gets the electricity flowing. And it, therefore, plays a key part in determining how much power an electric car has to offer. The higher the voltage, the greater the potential for current – and therefore the power.

While the high-voltage battery provides the electric car with energy for driving, the 12 V battery supplies various consumers and equipment in the vehicle. These include the electronic control unit (ECU), lights, power steering, wipers, radio, windows, etc. And even in electric cars, the 12 B battery is also needed for starting.

Hybrid vehicles also have a dedicated battery for the drive. Plug-in hybrids, which can also drive long distances on electricity alone, have high-voltage batteries. In mild hybrids, in which the electric motor supports the combustion engine, this battery has a voltage of 48 V.

Experience electric mobility

Electric mobility is an exciting and forward-looking topic, and not just because of the different voltage systems. Experience it for yourself and book a test driveOpens an external link at a Volkswagen dealership near you.

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