2015 GMC Sierra 2500HD Battery Size & Group

Quick answer

• BCI Group Size: Group 48 (H6) for the gas engine, dual Group 31 for the 6.6L Duramax diesel.
• Cold Cranking Amps (CCA): 730 CCA for the gas engine, 720 CCA per battery for the diesel.
• Reserve Capacity (RC): Approximately 120 minutes for the gas engine, 150 minutes per battery for the diesel.
• AGM vs. Flooded: AGM is recommended, especially for the diesel and for vehicles with many accessories.
• Terminal Layout: Top post. Left-positive for the primary battery in dual-setup.
• Physical Dimensions (approximate):
  • Group 48 (H6): 12.1" L x 6.9" W x 7.6" H
  • Group 31: 13" L x 6.8" W x 9.4" H
• Dual-Battery Setup: Yes, the Duramax diesel model comes with a dual-battery setup.

Replacement battery options

• Interstate: MTX-48/H6 (AGM), 31-MHD (diesel)
• Optima: YellowTop DH6 (AGM), YellowTop D31A (diesel)
• DieHard: Platinum AGM H6, Platinum AGM 31
• Odyssey: Odyssey Performance 48-720, Odyssey Performance 31-740
• ACDelco: 48AGM (AGM), 31-900CT (diesel)

AGM vs flooded — which does this vehicle need?

The 2015 GMC Sierra 2500HD, especially models equipped with the 6.6L Duramax diesel engine, benefit significantly from Absorbed Glass Mat (AGM) batteries. AGM batteries are more resistant to vibration, offer better deep-cycling capability, and provide more reliable starting power in extreme temperatures. Given the high electrical demands of modern trucks, with their numerous electronic modules, infotainment systems, and optional accessories, AGM is the preferred choice. While a standard flooded lead-acid battery will work in a pinch, it may not offer the same longevity or performance, particularly in cold climates or if you frequently use accessories when the engine is off.

Post-installation relearn / reset procedure

After replacing the battery on a 2015 GMC Sierra 2500HD, a relearn procedure is recommended to ensure all vehicle systems function correctly. The most important is the battery sensor relearn, which allows the truck's computer to optimize charging for the new battery. While some systems will relearn on their own after a few drive cycles, you may notice erratic behavior with the radio, windows, or other accessories. To perform a full relearn, you may need a professional scan tool. However, a simple DIY procedure can often resolve most issues:

1. Connect the new battery and ensure the terminals are tight.
2. Turn the ignition to the "ON" position without starting the engine.
3. Leave the ignition on for 3-5 minutes to allow the various modules to reset and relearn.
4. Turn the ignition off, then start the truck.

If you experience persistent issues, consult a professional technician.

Signs of a failing battery

• Slow engine crank: The engine turns over sluggishly, especially on cold mornings.
• Dimming lights: Headlights and interior lights dim when starting the engine or when using accessories.
• Warning lights: A battery or charging system warning light appears on the dashboard.
• Swollen battery case: The battery case appears bloated or warped, indicating overheating.
• Corrosion: A white, powdery substance builds up on the battery terminals.

Common battery issues for this generation

The 2011-2019 generation of GMC Sierra HD trucks are known for their robust electrical systems, but they are not without their quirks. One of the most common issues is premature battery failure, often due to the high electrical demands of the vehicle. This is especially true for the diesel models with their dual-battery setup. Another common complaint is parasitic draw, where an electrical component continues to draw power even when the truck is off. This can be difficult to diagnose and may require the help of a professional technician.

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