Why Does My Subaru Battery Keep Dying (How To Fix)

Why Does My Subaru Battery Keep Dying – In the whirlwind of changes that have swept our lives in recent months, the way we use our vehicles has undergone a significant transformation.

For many, the once-frequent journeys to the office have shifted to a work-from-home setup, while others find themselves relying on doorstep deliveries for everything from groceries to gadgets.

Perhaps you’ve re-entered the workforce and find yourself on longer commutes.

Or maybe, like many, you’ve felt the urge to break free from the confines of home, opting for aimless drives just to explore the open road.

Yet, amidst these shifts, one consistent frustration might have cropped up – your Subaru refusing to start or needing repeated attempts before the engine revs to life. While various issues can plague a vehicle’s ignition, the recurring culprit often lies within the heart of the car: the battery.

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The question on many Subaru owners’ minds is: “Why does my Subaru battery keep dying?”

We discuss the factors behind Subaru battery issues and explore effective solutions to ensure your Subie is always ready to hit the road when you are. Let’s start.

The Reason Why Does My Subaru Battery Keep Dying

Own a Subaru and find yourself grappling with recurrent battery issues. A dying battery can be a recurring headache, leaving you stranded at inconvenient times.

Understanding the underlying causes behind this problem is crucial to effectively resolving it.

Here, we delve into the various reasons why your Subaru’s battery might keep dying and explore effective fixes.

Common Causes of Subaru Battery Drain

why does my subaru battery keep dying

1. Battery Replacement

A typical car battery has a lifespan of around 5 years, although this can vary due to climate and usage. Extreme weather conditions, such as excessively hot or cold environments, can significantly shorten a battery’s life.

If your Subaru’s battery is over 5 years old, it might be time for a replacement to ensure optimal performance.

2. Short/Intermittent Drives

The alternator recharges the car battery as you drive. If your Subaru frequently undergoes short trips or stays parked for extended periods, the battery may not receive sufficient charging time from the alternator.

Consider taking longer drives occasionally to allow the alternator to adequately charge the battery.

3. Battery Corrosion

Hydrogen gas released from the battery’s sulfuric acid reacts with the atmosphere, leading to corrosion on the battery terminals.

This buildup of corrosion can disrupt the connection between the battery and the vehicle, hindering proper starting.

4. Faulty Alternator

An ineffective alternator can fail to recharge the battery while driving. Signs of a faulty alternator include engine stalling, electrical malfunctions, abnormal noises, and dimming lights.

A malfunctioning alternator can deplete the battery’s power until it dies.

5. Parasitic Drain

Parasitic drain occurs when electrical components draw power from the battery even when the vehicle is turned off. This drain can result from wiring shorts, malfunctioning electronic parts, or incorrectly installed aftermarket accessories.

6. Weather Conditions

Extreme temperatures, especially cold weather, can significantly impact a car battery’s performance.

In freezing conditions, a battery can lose a substantial portion of its strength, making it more challenging to start the engine.

The Fix for Subaru Battery Drain Issues

If you’ve experienced repetitive dead battery issues and conventional solutions haven’t worked, there’s a viable fix that might address your Subaru’s persistent battery drain problems.

why does my subaru battery keep dying

This fix, costing around $300, consists of three primary steps:

1. Remove the DCM Fuse

A faulty DCM (Data Communication Module) is a common source of parasitic drains in Subarus. Removing the DCM fuse can alleviate the drain issue, primarily affecting the Starlink system.

Replacing the faulty DCM might cost $800, but removing the fuse is a cost-effective workaround.

2. Software Update for Alternator

Subaru’s alternator is programmed to conserve fuel by not fully charging the battery. A software update from Subaru for the alternator can rectify this issue after confirming the DCM as the root cause.

This step typically involves a diagnostic test ($100) and a software update.

3. Replace the Battery

Getting a new battery, preferably one with increased capacity, helps start fresh without lingering issues from a battery weakened by repetitive complete drains.

Prices for a new battery can range from $150 to $250.

How long does a Subaru battery usually last?

The lifespan of a Subaru battery typically ranges from 3 to 5 years, although this duration can be influenced by various factors like weather conditions, battery type, size, and driving habits.

It’s important to note that even if the battery isn’t completely dead, it might not be functioning optimally.

Does Subaru have a battery problem?

Regarding battery problems in Subarus, there have been reported issues related to battery drain dating back to 2015. Subaru has acknowledged these problems and issued several technical service bulletins (TSBs) specifically addressing dead batteries occurring after repeated periods of short-trip driving.

What happens when the Subaru battery dies?

When a Subaru battery dies, the engine may not start or may turn over very slowly. In such cases, jump-starting the car might be necessary.

Additionally, even if the engine turns over quickly, it may not start due to the starter requiring more power than what a dead battery can provide.


Recurrent Subaru battery drain issues can be frustrating, but understanding the underlying causes and implementing targeted fixes can resolve the problem effectively.

By addressing issues like a faulty DCM, updating alternator software, and replacing the battery, you can potentially mitigate the persistent battery drain plaguing your Subaru.

If you’re experiencing issues with your Subaru battery repeatedly dying, it’s essential to consider the battery’s age, environmental factors, and driving patterns. Regular maintenance checks and addressing any underlying issues promptly can help prevent recurrent battery problems.

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