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

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

559 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 symptoms, diagnostic steps, and repair instructions.

Affected Component

Electrical

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the 12V battery before working on electrical components to ensure safety.

Symptoms

•Battery drains completely after a short period of inactivity
•Vehicle will not power on or respond to key fob
•Battery reserve low notifications when attempting to start
•Increased frequency of needing to jump-start the vehicle
•Cabin lights or other electronics remain active when the vehicle is off

Diagnostic Steps

1
Scan the vehicle's system for error codes using a Tesla service tool or OBD-II scanner.
2
Check the battery state of charge (SOC) via the vehicle's display or diagnostics menu.
3
Inspect the battery management system (BMS) for any faults or irregularities.
4
Verify if any accessories or modules are staying active after the vehicle is turned off.
5
Use a multimeter to check for parasitic draw from the battery while the car is off.
6
Review recent software updates or changes that may have affected battery management settings.

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

•Multimeter
•OBD-II scanner or Tesla service tool
•Basic socket set

Parts Required

•New 12V battery (if needed)
•Fuses (if blown during diagnosis)

Related Faults

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Symptoms

•Battery drains completely after a short period of inactivity

•Vehicle will not power on or respond to key fob

•Battery reserve low notifications when attempting to start

•Increased frequency of needing to jump-start the vehicle

•Cabin lights or other electronics remain active when the vehicle is off

Diagnostic Steps

1
Scan the vehicle's system for error codes using a Tesla service tool or OBD-II scanner.
2
Check the battery state of charge (SOC) via the vehicle's display or diagnostics menu.
3
Inspect the battery management system (BMS) for any faults or irregularities.
4
Verify if any accessories or modules are staying active after the vehicle is turned off.
5
Use a multimeter to check for parasitic draw from the battery while the car is off.
6
Review recent software updates or changes that may have affected battery management settings.

Solution

1. Preparation

Gather necessary tools and parts.
Ensure the vehicle is parked in a safe area and the environment is conducive for repair.
Disconnect the 12V battery to ensure safety while working on electrical components.

2. Inspect and Diagnose Parasitic Draw

Sub-step 1: Reconnect the 12V battery and use a multimeter set to measure amperage.
Sub-step 2: Connect the multimeter in series with the negative battery terminal and the battery cable.
Sub-step 3: Note the amperage reading. A reading over 50mA indicates excessive parasitic draw.
Sub-step 4: Pull fuses one at a time to identify which circuit is causing the draw.

3. Repair or Replace Faulty Components

Sub-step 1: Once the problematic circuit is identified, inspect all components in that circuit for faults (e.g., defective modules, shorted wiring).
Sub-step 2: Repair any wiring issues or replace defective modules as necessary.
Sub-step 3: If a software issue is suspected, perform a software update via the Tesla service center.

4. Battery Maintenance

Sub-step 1: If the 12V battery is old (over 4-5 years), consider replacing it with a new OEM battery.
Sub-step 2: Clean battery terminals and ensure tight, corrosion-free connections.
Sub-step 3: Charge the battery fully after repairs to reset the system.

5. Final Checks

Sub-step 1: Reconnect the battery and ensure all systems are operational.
Sub-step 2: Monitor the vehicle for a few days to confirm that the issue is resolved.