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My 2017 Model S is Acting Weird - Could it be the 12V Battery?

0

Mike T. · rep 0 · May 25, 4:03 AM · 1 replies · solved · Question

Vehicle: 2017 Tesla Model S 75D

Hi everyone,

I've got a 2017 Tesla Model S 75D and lately, it's been acting a bit strange. I'm experiencing phantom drains more often, sometimes the touchscreen flickers, and a couple of times, it's been slow to 'wake up' when I approach it. I even got a '12V Battery Low' alert on the screen once, but it went away.

I know Teslas have a big main battery, but they also have a traditional 12V battery. Could these symptoms be related to a dying 12V battery? I'm wondering if this is a DIY job or if I need to take it to Tesla service.

What's the typical lifespan of these 12V batteries, and what are the signs of failure? Any advice on replacement, or should I just book a service appointment? Thanks!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:03 AM

0

ClearTheCode admin answer:

Your symptoms are classic indicators of a failing 12V auxiliary battery in your 2017 Tesla Model S. While the main high-voltage battery powers the drivetrain, the 12V battery is crucial for operating all the low-voltage electronics, including the infotainment screen, door locks, lights, and even the contactors that connect the main battery.

Common Symptoms of a Failing 12V Battery:

  • Slow 'wake up' or unresponsive vehicle: The car may take longer to respond to key fob or app commands.
  • Screen flickering or intermittent issues: The main touchscreen may act erratically.
  • Phantom drains: The vehicle may lose charge more quickly than usual when parked.
  • Error messages: Alerts like '12V Battery Low' or 'Replace 12V Battery' will appear.
  • Inability to open doors/frunk: In severe cases, the car may become a 'brick' if the 12V dies completely.

Lifespan & Replacement: The 12V battery in Teslas typically lasts 3-5 years, similar to traditional car batteries. Given your 2017 Model S, it's highly probable your original 12V battery is at the end of its life.

DIY Replacement Steps (for Model S/X, Model 3/Y is different):

  1. Safety First: Put the car in 'Service Mode' via the touchscreen (Controls > Safety & Security > Power Off > Service Mode). This safely disconnects the main battery.
  2. Access: Open the frunk. You'll need to remove the plastic trim pieces covering the battery, usually involving a few clips and possibly a 10mm bolt.
  3. Disconnect: Disconnect the negative (black) terminal first, then the positive (red) terminal. Use a 10mm wrench.
  4. Remove & Replace: Remove the hold-down clamp. Carefully lift out the old battery (it's heavy!). Place the new battery in the tray.
  5. Reconnect: Connect the positive (red) terminal first, then the negative (black) terminal. Reinstall the hold-down clamp and all trim pieces.
  6. Exit Service Mode: Turn the vehicle back on from the touchscreen. The car will go through a reboot cycle.

Tools Needed:

  • 10mm wrench or socket
  • Plastic trim removal tool

When to See a Shop: If you're uncomfortable working with car batteries or if the '12V Battery Low' alert persists after replacement, it's best to contact Tesla service. They can perform diagnostic checks to ensure no other underlying electrical issues are present. While there isn't a standard OBD-II code for this, Tesla's internal diagnostics will log the low voltage events.

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