2015 Subaru Forester Battery Size & Group

Quick answer

• BCI Group Size: Group 35
• Cold Cranking Amps (CCA): 390 CCA (OEM)
• Reserve Capacity (RC): 80 minutes (OEM)
• Battery Type: Flooded Lead-Acid (standard); AGM is a recommended upgrade
• Terminal Layout: Left Positive (+)
• Dimensions (L x W x H): 9 1/16" x 6 7/8" x 8 7/8"
• Dual-battery setup: Not applicable

Replacement battery options

The original Panasonic battery in the 2015 Forester is known to have a relatively short lifespan. Upgrading to a battery with higher CCA and reserve capacity is a wise investment. Here are some popular, high-quality replacements:

• Interstate MTX-35: A well-regarded AGM option that offers improved cold-weather starting power and vibration resistance.
• Optima RedTop 35: A high-performance AGM battery known for its durability, long life, and excellent cranking power.
• DieHard Gold 35: A reliable flooded lead-acid battery that meets or exceeds OEM specifications, offering good value for the price.
• Odyssey Performance Series 35-PC1400T: A premium AGM battery with exceptional cranking power and a very long service life.
• ACDelco Gold 35AGM: A top-tier AGM battery that provides excellent performance and reliability.

AGM vs flooded — which does this vehicle need?

The 2015 Subaru Forester came from the factory with a standard flooded lead-acid battery. While a direct replacement with another flooded battery is acceptable, upgrading to an Absorbed Glass Mat (AGM) battery is highly recommended. AGM batteries offer several advantages:

• Better cold-weather performance: AGM batteries have lower internal resistance, allowing them to deliver more cranking power in cold temperatures.
• Longer lifespan: They are more resistant to vibration and can handle more charge/discharge cycles than traditional flooded batteries.
• Spill-proof design: The electrolyte is absorbed in fiberglass mats, making them safer and less likely to leak.

Given the known issues with the OEM battery's longevity, an AGM upgrade is a smart choice for improved reliability and peace of mind.

Post-installation relearn / reset procedure

After replacing the battery in a 2015 Forester, a simple reset procedure is required to ensure the engine and other systems operate correctly. The vehicle's computer needs to relearn the engine's idle characteristics.

1. Turn off all lights and accessories.
2. Start the engine and let it idle for 5-10 minutes. This allows the Engine Control Unit (ECU) to recalibrate.
3. Drive the vehicle for several miles to allow the ECU to fully relearn all parameters.

You may also need to reset your radio presets and clock.

Signs of a failing battery

• Slow engine crank: The engine turns over sluggishly when you try to start it.
• Dimming lights: Headlights and interior lights may dim, especially at idle.
• Warning lights: The battery or charging system light may illuminate on the dashboard.
• Corrosion: A white, powdery substance around the battery terminals is a sign of leaking acid.
• Age: Car batteries typically last 3-5 years. If your battery is approaching this age, it's a good idea to have it tested.

Common battery issues for this generation

The fourth-generation Forester (2014-2018) is known for having a weak original equipment (OEM) battery. Many owners report needing to replace the factory-installed Panasonic battery within the first 2-3 years of ownership. The relatively low 390 CCA rating of the OEM battery can be inadequate, especially in colder climates. Upgrading to a replacement battery with a higher CCA rating (500 CCA or more) is a common and effective solution to prevent future starting issues.

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