2025 Tesla Model S Battery Replacement and Specs

Quick answer

• BCI Group Size: The 12V auxiliary battery in the Tesla Model S typically uses a Group 51R battery.
• CCA Rating: 400-500 CCA (approximate, often not a primary spec for auxiliary batteries in EVs).
• Reserve Capacity: 60-90 minutes (approximate).
• AGM vs. Flooded: AGM is recommended and often required due to location and vehicle demands. Tesla originally used flooded lead-acid but transitioned to AGM.
• Terminal Layout: Top post, typically positive on the right (R).
• Physical Dimensions: (Varies slightly by manufacturer, but generally): 9.375" L x 5.0625" W x 8.75" H.
• Dual-Battery Setup: Not applicable; Tesla Model S uses a single 12V auxiliary battery.

Replacement battery options

Identifying specific part numbers for the 2025 Tesla Model S auxiliary battery can be challenging as Tesla often sources batteries directly and specifications can evolve. However, reputable battery manufacturers offer compatible Group 51R AGM options. Always verify compatibility with your vehicle's VIN.

• Optima: Optima YellowTop DH5 (Note: Some sources suggest this may be an alternative fit, verify dimensions and terminal orientation).
• DieHard: Look for DieHard Platinum AGM Group 51R.
• Interstate: Interstate MTX-51R (AGM).
• Odyssey: Odyssey PC925L (verify terminal posts and dimensions for a Group 51R direct fit).

AGM vs. flooded — which does this vehicle need?

The Tesla Model S operates with a 12V auxiliary battery that powers various vehicle systems, including the infotainment, lights, power windows, and acts as a failsafe for the high-voltage battery contactors. Initially, earlier Model S vehicles used flooded lead-acid batteries. However, Tesla has largely transitioned to Absorbent Glass Mat (AGM) batteries for their auxiliary 12V system. AGM batteries are sealed, maintenance-free, more vibration resistant, and offer a longer lifespan, making them ideal for the demands of an electric vehicle.

For the 2025 Tesla Model S, an AGM battery is strongly recommended and often required. Using a flooded battery might lead to premature failure due to the charging profile and demands of modern EVs. Always consult your owner's manual or a Tesla service center for the most accurate and up-to-date recommendation.

Post-installation relearn / reset procedure

Replacing the 12V auxiliary battery in a Tesla Model S often requires a specific procedure to ensure the vehicle correctly recognizes the new battery and avoids error messages. While the process can vary slightly by software version, here's a general guideline:

1. Safety First: Ensure the vehicle is off and in "Jack Mode" (if possible) before disconnecting the old battery. Disconnect the negative terminal first, then the positive.
2. Install New Battery: Connect the positive terminal first, then the negative terminal of the new battery.
3. Wake Up Vehicle: Close all doors, and allow the vehicle to "sleep" for a few minutes (at least 5-10 minutes). Do not interact with the vehicle during this time.
4. Initiate Power Cycle: Open the driver's door, then close it. The vehicle should wake up. Observe the dashboard for any error messages related to the 12V battery.
5. Software Reset (if necessary): If error messages persist, a soft reset of the vehicle's infotainment system might be required. This is usually done by holding down both scroll wheels on the steering wheel until the Tesla logo appears on the main screen.
6. Drive Cycle: Driving the vehicle for a short period (15-30 minutes) can help the battery management system (BMS) recalibrate and learn the new battery's characteristics.

Crucially, it is highly recommended to consult a Tesla service manual or a certified Tesla technician for the most accurate and up-to-date post-installation procedure for your specific model year and software version. Incorrect procedures can lead to persistent error codes or issues with vehicle functionality.

Signs of a failing battery

While the main propulsion battery gets most of the attention, the 12V auxiliary battery in a Tesla Model S is critical. Here are common signs it might be failing:

• "12V Battery Needs Service" or similar warning on the touchscreen: This is the most direct indicator.
• Inconsistent or sluggish infotainment system: Slow boot-up, freezing, or unresponsiveness.
• Failure to "wake up": The car doesn't respond to the app or touching door handles.
• Warning lights: Other seemingly unrelated warning lights on the dash.
• HVAC issues: Inconsistent climate control operation.
• Loss of key fob functionality: The key fob may not unlock or lock the car reliably.
• Vehicle doesn't shift into Drive: While rare, a severely depleted 12V battery can prevent the car from engaging Drive.

Common battery issues for this generation

The 12V auxiliary battery in the Tesla Model S, like all batteries, has a finite lifespan, typically 3-5 years. Common issues for this generation often revolve around:

• Premature failure of early flooded batteries: Tesla