You may be surprised to learn that, as well as its main 400V battery, your Tesla has a far smaller 12V battery too. But why do Teslas need a 12V battery? Can’t the main battery just power everything?
In this article, we help you to gain a better understanding of your Tesla’s batteries by explaining the difference between the main battery and the 12V battery. We also cover the two different types of 12V battery that you might find under the hood of your Tesla.
Why Do Teslas Need a 12V Battery?
Teslas need a 12V battery to power electrical systems such as the lights, door locks, heating, and touchscreen display. Using a separate low-voltage battery for these systems is safer than using the traction battery and means they still work even if the main battery is depleted.
Another advantage of using a 12V battery is that it allows Tesla to use standardized components, such as windscreen wipers, designed to run on the 12V batteries found in internal combustion engine cars.
How Long do Tesla 12V Batteries Last?
Some Teslas use a lead-acid 12V battery that needs replacing every three or four years. However, in 2021, Tesla upgraded the Model S and Model X to use Lithium-Ion batteries, which should last at least three times longer.
While the old lead-acid 12V battery had a short life and was usually one of the first components that needed replacing, the new 12V battery has a cycle life that matches the main battery pack.
If there is an issue with the 12V battery in your Tesla, or if it needs replacing, then a message will appear on your in-car display to alert you to the problem.
How Much Does a 12V Tesla Battery Cost?
Tesla will replace a 12V battery free of charge under the car’s basic warranty, which covers your vehicle for four years or 50,000 miles, whichever comes first.
The main battery is covered for longer, with an 8-year warranty (or between 100,000 and 150,000 miles, depending on which model Tesla you own).
If your Tesla is outside of its warranty, a replacement Li-Ion battery will cost over $400. In contrast, the older lead-acid battery can be replaced for less than $100.
Though they are more expensive, Li-Ion batteries need to be replaced much less frequently and offer other benefits, including being smaller and lighter.
How To Replace a 12V Tesla Battery
Though it is possible to replace a 12V Tesla battery yourself, we recommend contacting Tesla to have a qualified engineer do the work for you. This avoids risking damaging your car and is particularly important if you are within your warranty period, as Tesla will replace the 12V battery free of charge.
If you’re determined to replace your 12V Tesla battery yourself, you can do so. All you need is a new battery, a 10mm battery, and about an hour of free time.
14 Steps to Replace a 12V Tesla Battery
To replace your Tesla’s 12V battery, follow these easy steps:
- Open your Tesla’s doors and windows and power off.
- Open the back seats, remove the black cover and disconnect the black cord. This is important for your safety, as it disconnects the high-voltage power.
- Open the frunk and remove the cover by the windshield.
- Remove the passenger-side air vent.
- Remove the battery brackets.
- Remove the black (negative) battery terminal.
- Remove the 12V battery.
- Insert the new battery.
- Re-attach the middle bracket.
- Attach the red (positive) terminal to the new battery.
- Attach the black (negative) terminal to the new battery.
- Reattach the driver and passenger side brackets.
- Reattach the passenger-side air vent.
- Behind the back seats, re-connect the black high-voltage cable.
12V Tesla Batteries: In Summary
The 12V battery on your Tesla is an important feature that means you don’t have high-voltage power running around your vehicle. Instead, your Tesla can use standardized parts that can run independently of the main traction battery.
Though it may seem strange to have a small battery in your Tesla alongside a huge main battery pack, you will certainly appreciate your 12V battery if you run out of main battery power and need to use your touchscreen, lock or unlock your doors, or switch on your hazard lights.
You may find that your Tesla has a lead-acid or lithium-ion 12V battery. The latter is smaller, lighter, and has a longer life.
However, if you have an older battery, there is no need to worry. Your 12V battery may need replacing more frequently, but it is relatively inexpensive, and you will likely get your first replacement free under your vehicle’s four-year warranty.