Tesla Won't Turn On: High-Voltage Battery vs Low-Voltage Battery

Two batteries doing two jobs

The high-voltage traction battery moves the vehicle. A separate low-voltage battery runs the computers, locks, screens and the contactors that connect the high-voltage system in the first place.

That last part is the key. Without low-voltage power, the car cannot close the contactors, so it cannot use the energy in the big pack even if the pack is full.

Signs it is the traction battery

• The screen works and shows 0% or a very low charge
• The car unlocks and you can sit in it normally
• Warnings mentioned low range before it stopped

Signs it is the low-voltage battery

• Nothing responds — no lights, no screen, no door handle movement
• The mobile app reports the vehicle offline and will not wake it
• The car recently displayed a 12V or low-voltage service warning
• The vehicle sat unused for an extended period

Why this matters at the roadside

These two problems need different equipment and different procedures, and the procedure is vehicle-specific. Telling the dispatcher which symptoms you actually have determines whether the right approach shows up the first time.

Not sure which one you are looking at? Describe the symptoms on the phone at 478-202-3221 and we will work it out with you.