Why does Tesla Car have a 12-volt Starter Battery?

Tesla Car have a 12-volt Starter Battery

Did you know that most electric cars have a 12-volt battery pack just like your conventional gas-powered cars have? But Why does Tesla Car have a 12-volt Starter Battery?

The simple answer is safety. There is a very high risk when we use a DC converter to run the basic 12-volt-based tech like rolling down windows, the main screen of the car, all the locks, and many more things as well, and the main battery sends out 400 volts this poses a risk because 400-volt is lethal if touched, and it has to run all the 12-volt functions by being converted down.

Also when the car crashes the main battery has to shut down, and then the hazard lights cannot be turned on, along with many other techs the car contains, even the airbags would not be able to come out as they also use the same systems. 

If you want a more detailed answer and to understand everything better then read the following headings.

What is a 12-volt Starter Pack?

A 12-volt ‘starter’ battery is, the battery that is usually found in most conventional gas-powered cars, it is used to start up and car by jolting the engine with high voltage currents. And it is usually made up of either two materials lead acid or lithium-ion.

After that, the battery does not have any role to play, because the alternator in the engine powers all the accessories that run on 12 volts

Even when the car is off the battery is not really used all that much, it only comes into use to unlock and lock the car. 

What is Powered by the 12-volt Battery in an Electric Car? (~200)

Now you must be wondering what powers does the 12-volt battery power? I have mentioned a couple of things before. Here is a table that shows everything in detail on what the 12-volt battery runs and what the main battery powers 

Feature Powered by which Battery 
Motor(s)Main Battery
A/C compressor and cabin heater Main Battery
Battery coolant and heater Main Battery 
DC to DC converter Main Battery 
Main Screen 12 volt battery
lights12-volt battery
Side window motors12-volt battery
Wiper motors12-volt battery
Power liftgate for the trunk12-volt battery
Washer fluid pumps for the windshield 12-volt battery
ABS electronics12-volt battery
Feature of 12-volt battery in an Electric Car

The 12-volt battery controls many other features are well like the locks, doors, etc. 

Why does Tesla Car have a 12-volt Starter Battery?

There are many reasons why Tesla needs to use a 12-volt battery to run its systems. Here are the leading 3

  1. Safety
  2. 12-volt systems
  3. DC converter issue. 

Watch this video and see the explanations explained in detail. 

  1. Safety

There are many safety hazards to considering using the main battery pack for 12-volt systems. Yes, the main battery can power the 12-volt system with a DC converter, but there is a high risk involved because the main battery puts out 400 volts, and the system runs on 12 volts.

Although the converter does do its job there is still a risk involved when doing this procedure, which can be lethal, although touching 12 volts would hurt it would definitely not kill you; furthermore, if the main battery pack dies the system would not be able to run at all, which would leave you stranded because the doors and locks would also not work. 

Another major concern related to safety is that when the car goes into an accident, the main battery pack shuts off, and in that case, you can turn your hazard lights and open doors or locks because all those systems would have been connected to that main battery pack.

Also if the systems were run by the main battery pack the car would also not be able to trigger the airbags to release, which would a major safety hazard.

  1. 12 Volt systems compatibility
Tesla Model 3 Battery Consumption
Tesla Model X 12V Battery

Another reason that Tesla does not use the main battery pack to power the electronics in the car, is that most systems already run on 12 volts like the screen and all the other things that are run by the 12-volt battery. So adding in a 12-volt battery will get rid of the problem of converting high voltage into low voltage, and would be a lot more practical in a manufacturing sense.  

  1. DC converter issue

The car needs to have a DC converter to run all the 12-volt systems with the main battery, the problem is that the DC converter uses power to do so which is a downside; Furthermore, even if the car is not on the DC converter will still use power. 

This will cause the range to decrease because the battery will drain a lot quicker. This problem came up with the first-gen Tesla Roadster. 

Was there a 12-volt Battery Added to the Roadster Gen 1? 

The initial roadster generation 1 did not have a 12-volt battery and all accessories were run on the main battery with the help of a DC converter.

But the same safety problems kept occurring like during an emergency the hazard lights were not able to turn on, and airbags were not able to come off.  So the next generation included a 12-volt battery to simply fix these issues. 

Learn more with this video


All in all, there are many reasons why all-electric cars and Telsa’s put a conventional 12-volt battery into their cars here are the reasons why:- 

  1. Safety
  2. 12 Volt systems
  3. DC converter issue

So these are the reasons why electric cars have 12-volt batteries, we have also discussed what a 12-volt battery is and all of its functions in a gas-powered vehicle as well as in electric vehicles, read the FAQ section to answer more of your questions and learn more. 


How is the 12-volt battery charged in a Tesla? 

The 12-volt battery in the Tesla is charged with a DC converter, and it is by the main battery itself, if the DC converter stops working or something else happens the 12-volt battery will start to run out of battery and a notification will pop up telling you to change your battery. 

What type of 12-volt battery does Tesla use? 

Modern Teslas use lithium-ion batteries but there are still some models which use lead-acid batteries, the batteries are called AGM (absorbed glass matte) which means that they can be recharged many times and they have more charging cycles as well. These batteries are needed because the Telsa needs to run all the 12-volt auxiliaries even when the car is on, unlike a conventional gas-powered car because it has an alternator when the engine is running to power the accessories. 

How to change a Tesla 12-volt battery? 

Here are the main steps to follow. 
Open the frunk, all doors and windows 
Disconnect the high-voltage wires under the rear-right passenger seat. And unplug the wire
Power off the car with the main screen. 
Under the windshield open up the case in the frunk and take out the air inlet. 
Then take out the ‘bracket’ that holds the battery in place and take out the positive and then the negative terminal of the battery. 
CAREFULLY, take out the positive and negative terminals.
Take out the battery after that. 
And insert your new battery, and connect the negative and positive terminals. 

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Bharat Suthar

I am principal creator of electriccarexperience.com. I like riding Electric Car, UTV in mountains and Terrain, Also I try to share all the real life experience here in the site.I am really dedicated to write about my experience. I love doing all the outdoor activity including riding electric car, dirt biking and hiking.

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