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

1-2 hours

Time

medium

Difficulty

high

Severity

3 min read

531 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

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the main battery before working on electrical systems.
•Allow the vehicle to cool down before inspecting electrical components.

Symptoms

•Battery drains significantly overnight or after prolonged periods of inactivity
•"Battery is low" warning message displayed on the dashboard
•Inability to power on the vehicle after a period of being off
•Increased frequency of charging required
•Possible malfunction of certain electronic features when the vehicle is off

Diagnostic Steps

1
Scan the vehicle's systems for any error codes using an OBD-II scanner to identify potential underlying issues.
2
Check the auxiliary battery voltage to ensure it is properly charged and functioning.
3
Inspect for any third-party devices or aftermarket accessories that may be drawing power.
4
Monitor the vehicle's energy usage through the Tesla app to identify any abnormal power consumption.
5
Perform a visual inspection of the wiring and connections for any signs of wear or damage.

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
•Torque wrench

Parts Required

•Auxiliary battery (if replacement is necessary)

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Symptoms

•Battery drains significantly overnight or after prolonged periods of inactivity

•"Battery is low" warning message displayed on the dashboard

•Inability to power on the vehicle after a period of being off

•Increased frequency of charging required

•Possible malfunction of certain electronic features when the vehicle is off

Diagnostic Steps

1
Scan the vehicle's systems for any error codes using an OBD-II scanner to identify potential underlying issues.
2
Check the auxiliary battery voltage to ensure it is properly charged and functioning.
3
Inspect for any third-party devices or aftermarket accessories that may be drawing power.
4
Monitor the vehicle's energy usage through the Tesla app to identify any abnormal power consumption.
5
Perform a visual inspection of the wiring and connections for any signs of wear or damage.

Solution

1. Preparation

Gather necessary tools and parts.
Ensure the vehicle is parked in a safe location and turned off.
Disconnect the vehicle from any charging sources.

2. Check Auxiliary Battery

Tools Required: Multimeter
Use a multimeter to measure the auxiliary battery voltage. It should read above 12.5 volts.
If the voltage is low, proceed to replace the auxiliary battery.

3. Inspect and Replace Auxiliary Battery

Tools Required: Socket set, Torque wrench
Remove the rear trunk cover to access the auxiliary battery.
Disconnect the negative terminal first, followed by the positive terminal.
Remove the old auxiliary battery and install the new one, securing it with the proper torque specifications.
Reconnect the positive terminal first, followed by the negative terminal.

4. Electrical System Check

Inspect the wiring harness connecting to the battery for any signs of shorts or corrosion.
Check for any parasitic draw using a multimeter set to measure current (amps) by connecting it in series with the battery.
If a significant draw is detected, isolate circuits to determine which component is causing the drain.

5. Monitoring and Final Steps

Reassemble any components removed during the inspection.
Monitor the vehicle's energy consumption for a few days to ensure the problem has been resolved.