2015 Ram 3500 Battery Size & Group

Quick answer

• BCI Group Size: Group 65 (gasoline) or Group 31 (diesel)
• CCA Rating: 800 CCA Minimum (gasoline), 950-1000 CCA Minimum (diesel)
• Reserve Capacity: 150-180 minutes (gasoline), 180+ minutes (diesel)
• AGM vs. Flooded: Both can be used, but AGM is often preferred for its durability and resistance to vibration, especially in heavy-duty applications. Some diesel models may have come with AGMs from the factory.
• Terminal Layout: Top post (SAE terminals)
• Physical Dimensions: Dimensions vary slightly by manufacturer, but generally: Group 65 (approx. 12" L x 7.5" W x 7.5" H), Group 31 (approx. 13" L x 6.8" W x 9.4" H)
• Dual-Battery Setup: The 2015 Ram 3500 with the 6.7L Cummins diesel engine uses a dual-battery setup, wired in parallel for increased cranking power and reserve capacity.

Replacement battery options

Here are some popular replacement battery options for your 2015 Ram 3500. Always double-check the BCI group size and CCA rating to ensure compatibility with your specific engine (gasoline or diesel).

• Interstate (Gasoline - Group 65): MTP-65
• Interstate (Diesel - Group 31): 31-MHD
• Optima (Gasoline - Group 65): YellowTop D34/78 (requires adapter for proper fit in Group 65 tray, though not a direct Group 65 match)
• Optima (Diesel - Group 31): YellowTop D31T (direct fit for Group 31 applications)
• DieHard (Gasoline - Group 65): Platinum AGM Group 65
• DieHard (Diesel - Group 31): Platinum AGM Group 31
• Odyssey (Gasoline - Group 65): ODP-AGM65 Extreme Series
• Odyssey (Diesel - Group 31): 31-PC2150S Extreme Series
• ACDelco (Gasoline - Group 65): ACDelco Professional AGM 65
• ACDelco (Diesel - Group 31): ACDelco Professional AGM 31

AGM vs. flooded — which does this vehicle need?

The 2015 Ram 3500 can utilize both AGM (Absorbent Glass Mat) and traditional flooded lead-acid batteries. While flooded batteries are generally less expensive, AGM batteries offer several advantages that make them particularly well-suited for heavy-duty trucks like the Ram 3500, especially those with diesel engines. AGMs are more resistant to vibration, have a slower self-discharge rate, are leak-proof, and generally offer a longer lifespan. For diesel models, which experience more vibration and require higher cranking power, an AGM battery is often the preferred choice and may have been original equipment. If your Ram 3500 is equipped with a lot of aftermarket accessories or sees frequent short trips, an AGM can also provide better performance due to its enhanced cycling capabilities.

Post-installation relearn / reset procedure

After replacing the battery in your 2015 Ram 3500, it's important to understand that some electronic systems may require a relearn or reset. While not as extensive as in some other vehicles, a few things to keep in mind:

1. Radio Presets: You will likely lose your radio station presets. Simply reprogram them.
2. Clock: The clock will need to be reset to the correct time.
3. Power Windows: In some cases, the "one-touch up/down" feature for power windows may need to be reset. To do this, fully lower the window, hold the down button for a few seconds, then fully raise the window and hold the up button for a few seconds.
4. Idle Relearn: The engine computer (PCM) may need to relearn its idle parameters. After connecting the new battery, start the vehicle and let it idle for 10-15 minutes without touching the accelerator. This allows the PCM to re-adjust its fuel trims and idle speed.
5. Steering Angle Sensor (if applicable): While less common after a simple battery disconnect, some vehicles with electronic stability control (ESC) or traction control may require a steering angle sensor calibration if a warning light appears. This usually involves driving straight for a short distance at a specific speed. If a warning light persists, consult your owner's manual or a professional technician.

Signs of a failing battery

Recognizing the signs of a failing battery can save you from being stranded. Look out for these common indicators:

• Slow Engine Crank: The most obvious sign. If your engine cranks slowly or struggles to turn over, especially in cold weather, your battery is likely weakening.
• Dim Headlights or Interior Lights: When you try to start the vehicle, if your lights dim considerably, it indicates the battery isn't holding a sufficient charge.
• Check Engine Light / Battery Light: A "Check Engine" light or a specific battery warning light on your dashboard can indicate a charging system issue, which includes the battery.
• Corrosion on Terminals: White, powdery, or bluish-green corrosion around the battery terminals can impede current flow and indicate a failing battery or a leaking one.
• Swollen Battery Case: If the battery case appears swollen or bulging, especially on the sides, it's a sign of internal damage and potentially overcharging.
• Age: Automotive batteries typically last 3-5 years. If your battery is older than this, it's a good idea to have it tested preventatively.

Common battery issues for this generation

The 2015 Ram 3500, like many heavy-duty trucks, can experience some specific battery-related issues:

• High Accessory Drain: Many Ram 3500 owners use their trucks for work or recreation, often adding aftermarket accessories like winches, auxiliary lighting, or sound systems. These accessories can put a significant drain on the battery, especially when the vehicle is off, leading to premature battery failure if not properly managed or if the charging system isn't upgraded.
• Vibration Damage: Heavy-duty trucks operate in demanding environments, which can lead to increased vibration. Traditional flooded batteries are more susceptible to internal damage from vibration, leading to shorter lifespans. This is where AGM batteries excel.
• Parasitic Draws: While not unique to the Ram 3500, parasitic draws (components drawing power when the vehicle is off) can slowly kill a battery. Common culprits include aftermarket accessories, faulty modules, or issues with the TIPM (Totally Integrated Power Module).
• Starter/Alternator Issues (misdiagnosed as battery): Sometimes, what appears to be a battery issue is actually a failing starter or alternator. A weak starter will draw too much current, making the battery seem dead, while a failing alternator won't adequately recharge the battery.
• Cold Weather Performance (Diesel): Diesel engines require substantially more cranking amperage to start, especially in cold weather. A battery that is adequate in warm weather might struggle or fail completely when temperatures drop, particularly if it's not rated for the cold or is older.

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