2025 Tesla Model 3 Battery Size, Replacement & Reset Guide

As an ASE-certified master technician, I’ve seen electric vehicle architecture evolve rapidly. If you are looking for battery specs for a 2025 Tesla Model 3, you need to know right away that this vehicle does not use a traditional 12V lead-acid battery. Starting in late 2021 and continuing into the 2025 model year, Tesla transitioned the Model 3 to a proprietary 16V Lithium-ion (Li-ion) low-voltage battery.

Here is everything you need to know about servicing the low-voltage electrical system on a 2025 Tesla Model 3.

Quick answer: 2025 Tesla Model 3 low-voltage battery specs

• BCI group size: N/A (Proprietary Tesla form factor; does not use standard BCI sizes like H6, Group 65, or Group 31).
• Cold Cranking Amps (CCA): N/A (EVs do not have a starter motor to crank).
• Reserve capacity: Approximately 6.9 Ah (roughly 100 Wh).
• AGM vs flooded requirement: Neither. Requires a Tesla-specific 16V Lithium-ion battery.
• Terminal layout: Proprietary quick-disconnect plug with integrated data/BMS communication (no standard lead posts).
• Physical dimensions: Custom compact housing, significantly smaller and lighter than standard automotive batteries.
• Dual-battery setup: N/A (The vehicle utilizes a High-Voltage traction pack and a single Low-Voltage 16V pack).

Replacement battery options

Because the 2025 Tesla Model 3 uses a deeply integrated 16-volt lithium-ion battery, traditional aftermarket brands like Interstate, Optima, DieHard, Odyssey, and ACDelco do not make a compatible drop-in replacement.

You cannot install a 12V AGM or flooded battery in this vehicle. The vehicle’s DC-DC converter outputs around 15.5V to 16V to charge the low-voltage system. Installing a 12V battery will result in catastrophic component failure or a complete vehicle shutdown.

Your only option for replacement is an OEM Tesla 16V Lithium-Ion Battery.

• Tesla OEM: You must purchase this directly from a Tesla Service Center or via the Tesla app. Keep in mind that part numbers change frequently with hardware revisions, so provide your VIN to Tesla’s parts counter to ensure you get the exact matching 16V lithium pack for your 2025 model.

AGM vs flooded — which does this vehicle need?

The 2025 Model 3 requires neither. While early generation Model 3s (2017–2021) used a 12V lead-acid battery (typically an 85B20LS AGM), the 2025 model requires the proprietary 16V lithium-ion pack.

Tesla made this switch because lithium-ion batteries hold their voltage better, last significantly longer (matching the lifespan of the car much better than lead-acid), and are drastically lighter. The integrated Battery Management System (BMS) communicates directly with the vehicle's computer to monitor cell health.

Post-installation relearn / reset procedure

Replacing the 16V lithium battery in a 2025 Model 3 requires specific high-voltage safety procedures and software resets. Warning: High voltage systems are dangerous. Only trained professionals should perform this.

1. Power down: Roll down the windows and open the frunk. Navigate to Safety & Security on the main MCU screen and tap "Power Off."
2. Disconnect the High Voltage (HV) loop: Under the rear seat (or under the hood, depending on specific routing for your build), disconnect the first responder cut loop or the HV battery disconnect. This isolates the high-voltage pack.
3. Swap the battery: Disconnect the proprietary low-voltage plug from the 16V battery and remove the battery. Install the new 16V OEM lithium battery.
4. Reconnect and wake: Reconnect the 16V plug, then reconnect the HV loop. The vehicle's contactors will close (you will hear a "clunk").
5. Software relearn: In many cases, the vehicle will automatically recognize the new module on the CAN bus. However, accessing Tesla's "Service Mode" via the MCU may be required to clear historical low-voltage fault codes (such as VCFRONT alerts).

Signs of a failing battery

The 16V lithium battery is designed to outlast traditional 12V batteries, but when it begins to fail, the vehicle's computer usually catches it before you are stranded. Symptoms include:

• A persistent warning on the screen: "Electrical system power reduced - Vehicle may shut down unexpectedly."
• Warning message: "Schedule service to replace low voltage battery."
• Software updates failing to install.
• In extreme cases where the battery dies completely, you will be locked out of the vehicle and the screen will not turn on, requiring you to manually pop the frunk using an external 9-15V power source on the tow eye wires.

Common battery issues for this generation

Because the 16V lithium architecture is relatively new, long-term degradation issues are rare. The most common issue isn't the battery degrading, but rather software glitches falsely flagging the BMS, or issues with the vehicle's DC-DC converter failing to keep the 16V battery adequately charged. Always ensure the vehicle is running the latest firmware, as Tesla frequently pushes over-the-air (OTA) updates to optimize the low-voltage power management.

If your Model 3 is throwing low-voltage codes or you need professional assistance safely working around the high-voltage systems, do not risk a DIY disaster. Find a trusted shop on Repairius.