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The Telltale Signs of a Failing Hybrid Battery

Failing Hybrid Battery

Greetings, fellow hybrid enthusiasts! Like any other component of your aging hybrid vehicle, the battery isn’t immune to wear and tear. Recognizing the signs of an failing hybrid battery can save you some time and money (i.e., don’t take your car on a road trip with a struggling battery).

Signs of Failure

A failing hybrid battery can exhibit several symptoms. Here are some of the most common ones:

1. Decreased Fuel Efficiency: A noticeable drop in fuel efficiency can be an early sign of a failing hybrid battery. This occurs because a deteriorating battery can’t store and provide energy as efficiently, causing the vehicle to rely more on the gasoline engine. A worn hybrid battery isn’t the only reason for a drop in MPG’s, but it’s a good idea to keep an eye on the fuel economy over time.

2. Fluctuating State of Charge: A healthy hybrid battery should maintain a relatively consistent state of charge. Many hybrids have a battery icon on the display that shows a representation of the battery charging and discharging. If it’s fluctuating erratically, it’s a red flag. The icon should show the battery slowly charging up and slowly draining. On a failing battery, the icon may show the battery jumping from full to empty and visa versa within seconds. This could indicate that the battery cells aren’t charging and discharging evenly, which can lead to premature battery failure. *Also- if your battery meter is full when your park the car in the evening and empty in the morning, this is a good indication that the battery isn’t able to hold a charge and may fail soon.

3. Warning Lights: Your vehicle’s dashboard is your first line of defense against potential issues. If the “check hybrid system” light or the check engine light illuminates, don’t ignore it! These lights are designed to alert you when something is amiss with your vehicle’s systems, including the hybrid battery. If the car is drivable and you feel safe doing so, take it to an auto parts store and ask them to check the diagnostic codes. This is typically a free service. The codes will help you discover what is causing the lights to come on.

4. Unexpected Power Loss: Sudden power loss while driving could be due to a failing hybrid battery. This can be particularly hazardous if it happens while you’re on the road, so it’s crucial to get your battery checked if you experience this issue. Typically, when the hybrid battery fails the car will still drive, but it may be sluggish and hesitate upon accelerating.

5. Cooling Fan Running Constantly: If you hear a loud persistent fan sound coming from the rear of the car, your batteries cooling fan is working overtime. When the battery fails, the car’s computer will turn the fan on full speed to reduce heat damage to the rest of the battery pack, as a failing module will rapidly overcharge and discharge, generating significant heat. It’s normal to hear this fan intermittently in our hot Texas summers, but you shouldn’t hear it all the time. Note: It’s always a good idea to check and clean this fan yearly to prevent it from becoming clogged.

Staying aware of the signs of a failing hybrid battery is crucial for every hybrid vehicle owner. Regular maintenance, taking action at the first sign of trouble, and ensuring proper ventilation can save you from costly repairs and keep your hybrid running smoothly. As always, if you suspect a problem with your hybrid battery, don’t hesitate to reach out to us at


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