Why Do Hybrid Vehicles Have Two Batteries?

by | Mar 13, 2020 | Hybrid Battery Reconditioning, Technology


Why do hybrid vehicles have two batteries?

Most hybrid vehicles, like the Toyota Prius, have two batteries. A smaller 12 Volt auxiliary battery, and the much larger high voltage Hybrid System Battery.

The purpose of the 12V, is to power the computer and accessories when the hybrid system is not in Ready Mode, and to assist in starting the vehicle. The 12v battery in a hybrid doesn’t start the car like you’d expect – it provides power to the computer, relays, ECU, etc. The heavy lifting of starting the engine is actually done by the hybrid battery. The 12V battery is also there to reduce unnecessary drain on the hybrid battery by supplying power to:

  • Headlights
  • Audio systems
  • Computer controls
  • Accessory systems

The 12V battery provides a few safety features as well. When the vehicle is not in ready mode, the 12V allows the high voltage hybrid battery to be disconnected from the rest of the system. So in the case of an accident, the 12V helps lower the risk of high voltage going where it shouldn’t.

Depending on your make and model, these 12V auxiliary batteries can be located under the hood or in the trunk. They are usually made from either Lead-acid or Absorbed Glass Mat (AGM).


OK, what about the hybrid battery?

The larger, high voltage, hybrid battery is the heart of the Hybrid Power System. It is what starts the car, and what powers the electric motors in your vehicle to make it go. So it’s this battery that’s responsible for the better fuel economy that’s become central to hybrid technology. When running the electric motor, it puts less pressure on the gasoline engine and stretches out the amount of fuel the vehicle burns in between trips to the gas station.

The hybrid battery is typically located in the trunk or behind the back seat and are made from either Lithium-ion (Li-ion) or Nickel Metal Hydride (NiMH). NiMH is the most popular battery technology, and is found in the majority of hybrid vehicles on the road. NiMH is subject to memory wear or voltage depressions, and will eventually fail. However, the major benefit of a NiMH battery, is that it can be reconditioned! Curious about Hybrid Battery reconditioning? You can read more about Hybrid Battery Reconditioning in this guide. Keep in mind that hybrid batteries start to become a risk when they’re 10 to 15 years old and they’ve covered 120,000 to 150,000 miles.

So, if you find yourself with a failing hybrid battery, you can take a look at this article on What to do if your hybrid battery dies. Because Green Bean Battery’s premium reconditioned hybrid batteries are put through a multi-step reconditioning process, which results in a well balanced and perfectly matched hybrid battery that will last for many years. They are a great alternative to a brand new battery from the dealership because they’re nearly half the cost. Green Bean is an even better alternative because we come to your location, replace your failing hybrid battery with a reconditioned one and cover it all with our Green Bean Warranty!

Ready to get a Green Bean Reconditioned Hybrid Battery?