What is the difference between 12 and 24 volts?

12 and 24 volts are two different voltage levels used in vehicle electrical systems.

Most passenger cars and light commercial vehicles have a 12-volt system, while many lorries, buses and other heavy vehicles use 24 volts.

Why do some vehicles use 24 volts?

A 24-volt system can transmit the same electrical power at a lower current than a 12-volt system.

This is particularly beneficial in larger vehicles where electrical components may require a lot of power.

For example:

• Equipment consuming 120 watts draws approximately 10 amperes at 12 volts.

• The same power corresponds to approximately 5 amperes at 24 volts.

A lower current can reduce heat generation and voltage drop in the cables, among other benefits.

Can I use the same equipment in both 12- and 24-volt systems?

It depends on the product’s specifications.

Some products are designed to work with both 12 and 24 volts. They may be labelled 12–24 V DC or with a wider voltage range, for example.

Other products are intended only for a particular voltage.

A product designed for 12 volts may be damaged if connected directly to 24 volts.

How do I know my vehicle’s voltage?

The information is normally in the vehicle’s owner’s manual.

You can also check the labels on batteries and electrical components.

A multimeter can be used to measure the voltage in the vehicle’s electrical system.

Bear in mind that the actual voltage may be higher than the nominal voltage while the batteries are charging. A 12-volt system may be at around 14 volts, for example, and a 24-volt system around 28 volts.

Important: Always check the product’s permitted input voltage range before connecting electrical equipment.