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

Tesla Model S Plaid/Refresh (2021-present)

Error Codes

1-2 hours

Time

medium

Difficulty

high

Severity

3 min read

537 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

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems to prevent short circuits.

Symptoms

•12V battery frequently discharges, requiring jump-starts
•Battery Management System warning displayed on the dashboard
•Car unable to power on without external charging
•Decreased range indicated upon startup
•Increased frequency of charging cycles

Diagnostic Steps

1
Use an OBD-II scanner to check for error codes related to battery management.
2
Inspect the 12V battery for corrosion or damage.
3
Measure the voltage of the 12V battery to assess its health.
4
Check for any parasitic draw by disconnecting the negative terminal and measuring current draw with a multimeter.
5
Inspect the vehicle's software for updates that may address battery management issues.
6
Test the main battery pack's voltage and capacity 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
•Basic hand tools

Parts Required

•New 12V battery (if replacement is needed)

Related Faults

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Diagnostic Steps

1
Use an OBD-II scanner to check for error codes related to battery management.
2
Inspect the 12V battery for corrosion or damage.
3
Measure the voltage of the 12V battery to assess its health.
4
Check for any parasitic draw by disconnecting the negative terminal and measuring current draw with a multimeter.
5
Inspect the vehicle's software for updates that may address battery management issues.
6
Test the main battery pack's voltage and capacity to ensure it is functioning correctly.

Solution

1. Preparation

Gather tools: OBD-II scanner, multimeter, socket set, and basic hand tools.
Ensure the vehicle is parked in a safe location with the ignition off.

2. Inspect and Test 12V Battery

Sub-steps:
- Remove the cover of the 12V battery compartment.
- Disconnect the negative terminal first, followed by the positive terminal.
- Use a multimeter to measure the voltage; a healthy battery should read around 12.6V or higher.
- If the voltage is low, consider replacing the 12V battery.
Tools Required: Multimeter.

3. Check for Parasitic Draw

Sub-steps:
- With the vehicle off, disconnect the negative battery terminal.
- Connect the multimeter in series between the negative terminal and the battery cable.
- Measure the current draw; a normal draw should be below 50mA.
- If the draw is excessive, begin removing fuses one by one to identify the circuit causing the drain.
Tools Required: Multimeter.

4. Update Software

Sub-steps:
- Connect the vehicle to Wi-Fi.
- Navigate to settings and check for any available software updates.
- Follow on-screen prompts to install updates.
Tools Required: None.

5. Replace 12V Battery (if necessary)

Sub-steps:
- If determined that the 12V battery is faulty, install a new battery by reversing the disconnection steps.
- Ensure terminals are securely tightened and reconnect the battery cover.
- Dispose of the old battery properly.
Tools Required: Socket set.