2025 GMC Sierra 2500HD Battery Size & Group

Quick answer:

• BCI Group Size: Varies by engine – most gasoline models use a Group 48/H6 or Group 65. Diesel models typically use dual Group 49/H8 (main) and Group 31 (auxiliary).
• CCA Rating: 720-800 CCA for gasoline, 750-850 CCA for diesel main, 900-1000 CCA for diesel auxiliary.
• Reserve Capacity: 120-150 minutes for gasoline, 130-160 minutes for diesel main, 180-220 minutes for diesel auxiliary.
• AGM vs. Flooded: All 2025 GMC Sierra 2500HD models from the factory come with AGM (Absorbed Glass Mat) batteries. Replacements should also be AGM for optimal performance and longevity.
• Terminal Layout: Top post. Specific arrangements (positive left/right) may vary slightly but are generally standard for the group sizes mentioned.
• Physical Dimensions: These vary by BCI group size. Always confirm the dimensions against your specific battery tray.
• Dual-Battery Setup: Diesel models come standard with a dual-battery setup for enhanced starting power and to support the higher electrical demands of the diesel engine and associated accessories.

Replacement battery options

When it's time to replace the battery in your 2025 GMC Sierra 2500HD, opting for high-quality AGM batteries is crucial. While specific part numbers can vary by retailer and a particular battery line, here are popular options by brand for the common group sizes:

• Interstate Batteries:
  • Group 48/H6 (Gas): MTP-48/H6 (flooded equivalent, but they also offer AGM versions like MTX-48/H6)
  • Group 65 (Gas): MTP-65 (flooded equivalent, AGM options like MTX-65)
  • Group 49/H8 (Diesel Main): MTZ-49/H8 (AGM)
  • Group 31 (Diesel Auxiliary): MTZ-31 (AGM)
• Optima Batteries: (Known for their Spiralcell Technology AGM batteries)
  • YellowTop: Often a good choice for trucks with accessories or demanding electrical needs.
    • Group 48/H6 (Gas): DS48 (often cross-references to Group 48)
    • Group 65 (Gas): DS34/78 (often cross-references to Group 65)
    • Group 49/H8 (Diesel Main/Auxiliary): DH6 (often cross-references to H6/H8, but always verify fitment)
• DieHard Batteries:
  • Platinum AGM: High-quality AGM options for various group sizes.
    • Group 48/H6 (Gas): DieHard Platinum AGM H6
    • Group 65 (Gas): DieHard Platinum AGM Group 65
    • Group 49/H8 (Diesel Main): DieHard Platinum AGM H8
    • Group 31 (Diesel Auxiliary): DieHard Platinum AGM Group 31
• Odyssey Batteries: (Premium AGM performance)
  • Group 48/H6 (Gas): ODP-AGM48/H6
  • Group 65 (Gas): ODP-AGM65
  • Group 49/H8 (Diesel Main): ODP-AGM49/H8
  • Group 31 (Diesel Auxiliary): ODP-AGM31
• ACDelco: (Original equipment supplier)
  • AGM Line: Often available through dealerships or parts stores.
    • Look for models matching the Group 48/H6, 65, 49/H8, or 31 designations for ACDelco AGM batteries.

*Always double-check the specific part number with your retailer to ensure compatibility with your 2025 GMC Sierra 2500HD's engine and trim.

AGM vs. flooded — which does this vehicle need?

For the 2025 GMC Sierra 2500HD, AGM (Absorbed Glass Mat) batteries are the factory standard and are highly recommended for replacement. Modern heavy-duty trucks like the Sierra 2500HD have significant electrical demands, powering numerous onboard computers, infotainment systems, advanced safety features, and, in diesel models, glow plugs and other high-current accessories. AGM batteries are superior to traditional flooded lead-acid batteries in several key aspects:

• Durability: AGM batteries are more resistant to vibration and shock, which is beneficial for a truck that may go off-road or be used for heavy hauling.
• Performance: They offer more consistent power delivery, especially during cold starts, and recharge more efficiently.
• Longevity: Generally, AGM batteries have a longer lifespan than flooded batteries under similar conditions.
• Safety: They are sealed and maintenance-free, significantly reducing the risk of acid leaks and corrosion.

Using a flooded battery where an AGM is specified can lead to premature failure of the battery and potentially affect the performance of the vehicle's electrical system.

Post-installation relearn / reset procedure

After disconnecting and replacing the battery in your 2025 GMC Sierra 2500HD, it's important to be aware of certain systems that may require a relearn or reset:

1. Engine Control Module (ECM) / Powertrain Control Module (PCM): The ECM/PCM will lose its learned fuel trims and idle parameters. The vehicle may run slightly rough or have a low idle for a short period after the new battery is connected. Driving the vehicle normally for 50-100 miles will allow the computer to re-learn these parameters. Some vehicles benefit from an