How To Tell If A Prius Battery Is Going Bad

In the recent past, the love for hybrid cars has continued to grow. Toyota Prius, for instance, can run on both an internal combustion engine and an electric motor, hence economical. Therefore, their batteries remain an essential component. Understanding how a Prius runs and how to maintain the battery can be overwhelming for the first-timers.

So, how can I tell if the battery of my Prius is about to die? Some of the warning signs to watch out for include:

● Reduced MPG
● Internal combustion engine running more than usual
● Large margins in the state of charge
● Engine noises

How Does the Engine of a Prius Operate?

Before we proceed to explain these common signs of a failing hybrid, it would be best if you understood how hybrid cars run. Hybrid cars can be used as a good example to define how the motor vehicle industry has evolved. These types of cars usually run on two engines as opposed to the standard cars.

After opening the hood, you will learn that these advanced cars have an internal combustion engine and an electric motor. The car can run on a single-engine or both and that’s based on the situation at hand.

So, How Does it Switch from One Engine to the Other?

Well, it uses power from the battery when you don’t need much acceleration. When your foot is pressed hard on the accelerator, the car uses gasoline. But, it can as well use both engines and that’s when you find yourself in the city traffic and it’s not moving fast.

1. Internal Combustion Engine (ICE) Running More than Expected

As said earlier, a hybrid vehicle is designed to switch in between the two types of engines and that’s based on the power requirements. Therefore, if you notice that the gasoline engine is being used more than the expected; the high chances are that the battery of your hybrid is failing.

Also, you may notice that the gasoline engine is being used in weird places. Say, for example, when you are driving off that basement parking, the car is supposed to use the electric motor.

But, with a poor battery, you may realize that the car is using a gasoline engine. If you notice this change, it’s recommended that you consult with your mechanic on the way forward.

If the battery is at stake, you should start planning for a replacement. By working on the replacement, you will help revive the many benefits that come with having a twin-engine.

2. The Consumption of Gasoline Goes High

How much gas do you spend on your hybrid vehicle? It’s one of the many questions you need to ask yourself when it comes to evaluating the state of your hybrid battery. When the battery is faulty, it means that the car will run more on the internal combustion engine.

With the ICE being used more often, it means that your car will consume much gas than expected. Therefore, if you notice your gasoline budget going high, it’s the high time you considered checking on the battery. If you fail to work on the battery, it means that you will be losing the primary objective of hybrid cars, which is saving on fuel.

3. Unusual Engine Noises

Hybrid vehicles are known for offering a smooth and quiet drive. The presence of an electric motor makes that possible. With a working battery, it means that you can cruise along the highway smoothly.

However, when the battery starts failing, it means that the car will have to switch to the internal combustion engine more often. This engine tends to be a bit noisy. Therefore, if you notice an increase in the engine noises, it means that the battery has an issue.

You shouldn’t wait for the noise to interfere with your smooth rides. Instead, you can seek for a battery replacement.

4. Large Fluctuations in the Battery’s State of Charge

How often do you check the hybrid’s battery? Most people tend to ignore their batteries until they develop a problem. One thing that you can watch out for when it comes to the battery is the state of charge. As you are aware, your car will use a charge drain charge from the battery, while on the move.

However, the lost charge is supposed to be compensated while driving. Therefore, if you notice those large fluctuations in the battery’s state of charge, it should tell you that something is not ok with the battery in question.

5. Mileage

When it comes to batteries, they also do have a lifespan. There is a specified period in which the batteries are expected to take you through. A while ago, when Toyota was selling the Prius model, they stated that the batteries in these models are expected to last the life of the vehicle.

Therefore, whenever you hit a specific mileage, there is nothing you can do rather than wait for the death of the battery.

What Happens When a Hybrid’s Battery Dies?

When Toyota Prius hit the market, many people were worried about the car’s battery. Well, with the price of the battery being high, it’s ok to know what will happen if the battery dies.

First, you should know that when the battery dies, it doesn’t that the car is dead too. You can continue running on the internal combustion engine. However, with this engine, fuel efficiency will have reduced. Also, with a dead battery, the car will reduce the performance because it’s through the two engines that your Prius can provide those smooth rides.

Thus, if you are faced with a dead battery, you shouldn’t hesitate to get a new battery. The good thing is that with a warranty, Toyota can help replace the battery for free.

Here is the related article: Can You Drive A Prius With A Dead Battery?


When Prius hit the market, it was met by a lot of criticism from people who were scared about the cost of its battery. Its battery can cost even more than the old Toyota Prius. With the price and functions, this battery, therefore, remains important.

Explained in this article are some of the common signs to tell you that the battery is about to die. Read through the article to understand each.