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2017 Model S 75D experiencing significant phantom battery drain overnight

0

Mike T. · rep 0 · May 22, 5:25 AM · 1 replies · solved · Question

Vehicle: 2017 Tesla Model S 75D

I've got a 2017 Tesla Model S 75D, and for the past month, I've noticed a significant phantom battery drain overnight. I'm losing anywhere from 5-10% of my battery capacity while the car is just sitting in my garage, not being driven. This is much higher than what I used to experience.

I've made sure Sentry Mode is off, and I don't have Cabin Overheat Protection enabled. I've also disconnected any third-party apps that might be polling the car. I've tried putting the car into deep sleep, but it still seems to be losing charge at an alarming rate. Could this be a 12V battery issue, or something more serious with the main high-voltage battery pack or its management system? It's really impacting my daily range.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 5:25 AM

0

ClearTheCode admin answer:

Significant phantom battery drain on your 2017 Tesla Model S 75D, even with common culprits disabled, points to an electrical component that's not properly entering a low-power state or is drawing excessive current. This can be a complex issue involving various systems.

Troubleshooting Steps:

  1. Verify All Settings: Double-check that Sentry Mode, Cabin Overheat Protection, and Keep Climate On are definitively off. Also, ensure 'Always Connected' is enabled, as disabling it can sometimes prevent the car from entering deep sleep efficiently.
  2. Check for Third-Party Apps/Devices: Reconfirm that no third-party apps (like TezLab, Stats app, etc.) are installed or connected, as they frequently wake the car to pull data. Also, remove any aftermarket OBD-II dongles or USB devices.
  3. Software Update: Ensure your car is running the latest software version. Updates often include fixes for power management and deep sleep routines.
  4. 12V Battery Health: While the 12V battery doesn't power the drivetrain, a failing 12V battery can cause the main high-voltage battery to work harder to keep it charged, leading to increased drain. You might see a '12V battery needs service' alert if it's critical, but subtle degradation can still contribute to drain.
  5. Service Mode Diagnostics: If comfortable, you can access the service menu (though limited for owners) to check for any persistent error codes related to specific modules that might be staying awake.

Potential Causes:

  • Stuck Contactor/Relay: A high-voltage contactor or relay might not be fully disengaging, causing a constant draw.
  • Faulty Module: A specific electronic control unit (ECU) or module (e.g., infotainment, connectivity, charging port controller) might be failing to enter sleep mode, continuously drawing power.
  • HV Battery Cell Imbalance/Degradation: While less likely to cause sudden, significant phantom drain, severe cell imbalance or degradation could contribute to the BMS working harder.
  • Parasitic Draw: A component could have an internal short or fault causing a continuous parasitic draw on the 12V system, which the main battery then tries to compensate for.

When to See a Shop:

If the drain persists after checking all settings and ensuring no external factors are at play, it's imperative to schedule a service appointment with Tesla. They have specialized tools to perform a parasitic draw test on both the 12V and high-voltage systems. They can also read specific diagnostic codes (e.g., related to the BMS, contactors, or individual modules) that indicate which component is failing to power down or is drawing excessive current. This issue can impact battery longevity and range, so professional diagnosis is recommended.

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