12V vs. High-Voltage Batteries: What’s the Difference?

Every electric vehicle (EV) runs on not just one battery, but two. While the high-voltage battery pack gets most of the attention for powering the car, the smaller 12V battery is equally important for safety and everyday functions.

So what’s the difference between the two, and why does your EV need both? Let’s take a closer look.

The High-Voltage Battery: Driving the Car Forward

The high-voltage battery is the large lithium-ion pack that:

Powers the electric motor and drives the car.
Provides the energy for acceleration and range.
Typically stores anywhere from 200V to 800V depending on the model.

This is the main power source that makes an electric vehicle move — but it doesn’t do everything.

The 12V Battery: Running the Electronics and Safety Systems

Alongside the main pack, every EV contains a smaller 12V battery, similar to those found in petrol or diesel cars. Its job is to:

Power electronics like lights, radio, navigation, and climate control
Keep driver assistance systems and alarms running.
Operate safety-critical systems such as brakes, wipers, and power steering.
Supply stable power for vehicle start-up before the high-voltage pack is engaged.

Without a healthy 12V battery, the car’s safety systems won’t work — and in many cases, the car won’t even start.

How the Two Work Together

The high-voltage battery and the 12V battery are linked by a DC/DC converter. This unit reduces the high-voltage pack’s energy down to 12V to keep the smaller battery charged.

This means that:

The high-voltage battery drives the car
The 12V battery keeps the car safe, connected, and comfortable.
Both are essential, one can’t replace the other.

Why EVs Still Need a 12V Battery.

You might wonder: why not just power everything from the high-voltage pack?

The answer comes down to safety and reliability. The 12V system is a standard across all vehicles, making it compatible with a huge range of accessories, electronics, and safety systems. More importantly, it ensures that even if the high-voltage system is shut down, critical functions like brakes and steering still operate.

Replacement Considerations

The high-voltage battery is designed to last the life of the car, but replacement can cost thousands.
The 12V battery wears much faster (3–5 years) and needs routine checks and replacements.
EVs often use AGM or lithium 12V batteries, hich must be fitted correctly to work with the control electronics.

Keep Both Batteries in Top Shape with Battery Town

At Battery Town, we specialise in 12V EV batteries, the part of your electric vehicle most likely to need replacement. Our expert team can:

Test your battery health.
Recommend the right replacement.
Fit it professionally for long-lasting performance.

Book your free EV battery check at Battery Town today and drive with confidence.