why does my Tesla Model S Original (2012-2020) battery die when the car is off

Tesla Model S Plaid/Refresh (2021-present)

Error Codes

1-3 hours

Time

medium

Difficulty

high

Severity

3 min read

558 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix battery drain issues in Tesla Model S (2012-2020). Step-by-step guide with diagnostic procedures and repair instructions.

Affected Component

Electrical

Estimated Time

1-3 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems to prevent shock or short circuits.
•Allow the vehicle to sit for a few minutes after turning off before performing diagnostics to ensure systems are fully powered down.

Symptoms

•Battery drains excessively when the vehicle is not in use
•"Battery is low" warning message displayed
•Inability to start the vehicle after a period of inactivity
•Decreased range on a full charge
•Unexpected shutdown of electronic systems

Diagnostic Steps

1
Use an OBD-II scanner to check for error codes related to the battery management system.
2
Inspect the vehicle's energy consumption settings in the Tesla app to identify any unusual energy draw.
3
Perform a parasitic draw test by measuring the current flow from the battery with the vehicle off.
4
Verify that all settings, including "Sentry Mode" and "Always Connected," are configured correctly.
5
Check for software updates that may address battery management issues.
6
Inspect the 12V battery health using the Tesla diagnostics to ensure it is functioning correctly.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Multimeter
•Socket set
•Insulated wrenches

Parts Required

•New 12V battery (ensure compatibility with Model S)

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Diagnostic Steps

1
Use an OBD-II scanner to check for error codes related to the battery management system.
2
Inspect the vehicle's energy consumption settings in the Tesla app to identify any unusual energy draw.
3
Perform a parasitic draw test by measuring the current flow from the battery with the vehicle off.
4
Verify that all settings, including "Sentry Mode" and "Always Connected," are configured correctly.
5
Check for software updates that may address battery management issues.
6
Inspect the 12V battery health using the Tesla diagnostics to ensure it is functioning correctly.

Solution

1. Preparation

Gather necessary tools and parts.
Ensure the vehicle is parked in a safe location with adequate ventilation.
Disconnect the vehicle from any charging source.

2. Inspect and Replace 12V Battery

Remove Access Cover:
- Use a socket set to remove the screws holding the access cover to the 12V battery.
Disconnect the Battery:
- Disconnect the negative terminal first, followed by the positive terminal.
- Use insulated wrenches to avoid short-circuiting.
Remove the Old Battery:
- Unscrew the battery hold-down bracket and carefully lift the battery out of its compartment.
Install New Battery:
- Place the new 12V battery into the compartment, ensuring it is seated securely.
- Reattach the hold-down bracket and tighten to manufacturer specifications (typically 5-7 Nm).
Reconnect Battery Terminals:
- Connect the positive terminal first, followed by the negative terminal.

3. Check for Parasitic Draw

Reconnect the Battery:
- Ensure all connections are tight and secure.
Measure Battery Draw:
- Use a multimeter to measure current draw while the vehicle is off. A draw over 50 mA may indicate an issue.
Identify Faulty Components:
- If excessive draw is found, systematically disconnect fuses to isolate the cause, checking each circuit and component.