Tesla battery dies while plugged in and owner gets locked out — here’s why

tesla model s
(Image credit: Tesla)

Did you know electric cars actually have two batteries? There’s the big one that drives the car, and a regular 12v car battery that handles the smaller stuff like lights and the door.

The 12v battery can also die on you if you don’t drive very often, even if you keep your car plugged in all the time. It’s all thanks to a quirk of the electronics you might not have known about.

This was a problem faced by television car man James May recently, after discovering that he couldn’t unlock his Tesla Model S. Yes, even Tesla cars have this problem, much to May’s disappointment.

The thing about 12v car batteries is they tend to lose their charge if they’re not recharged often enough. Gas cars do this by driving around, while electric cars utilize power from the larger plug-in battery.

But as May discovered with his Tesla, which is kept plugged in all the time, the big battery stops providing power when it reaches 100%. So while the 12v battery was powering smaller parts of the Model S, like the computer, the larger battery wasn’t topping it up again. 

So it ran out of power, and because the 12v battery also controls the locks he couldn’t get inside to pop open the hood. Cue what can best be described as dismantling a Tesla-shaped jigsaw so May could jump start the battery.

It’s easy to assume that the big battery means electric cars have no need for a traditional 12v car battery. I know I did, until I actually did some reading ahead of purchasing one.

So if you are an EV owner make sure you don’t let that 12v battery die on you. And be prepared in case it does. Make sure you know how to get to it, and you have the appropriate tools to get it back to life. Whether that’s a simple pair of jump cables, a trickle charger or an emergency battery pack.

Nissan Leaf

Nissan Leaf (Interior) (Image credit: Tom's Guide)

Thankfully, not all cars are as tricky to handle as a Tesla. I went out to check my own Nissan Leaf, and the biggest problem I had was actually finding the hood latch. Access to the battery isn’t blocked by plastic sheets, and like many modern cars there’s still a backup lock and key mechanism that doesn’t need power.

TOPICS
Tom Pritchard
UK Phones Editor

Tom is the Tom's Guide's UK Phones Editor, tackling the latest smartphone news and vocally expressing his opinions about upcoming features or changes. It's long way from his days as editor of Gizmodo UK, when pretty much everything was on the table. He’s usually found trying to squeeze another giant Lego set onto the shelf, draining very large cups of coffee, or complaining about how terrible his Smart TV is.

Read more
Composite image of Lucid Air Pure, Rivian R1T and Kia EV9
I've driven over 30 electric cars in the last year — and these are the coolest features that really stand out for me
A Tesla Powerwall next to a utility meter on the exterior wall of a green house
I deal with major snowstorms every winter and these Powerwall batteries are a game changer in my home
2025 Honda Civic Sport Touring Hybrid test drive review.
I drove the Honda Civic Hybrid for a week — and it’s better than the cheapest EV
2024 Hyundai Kona Electric test drive.
I tested more than 25 EVs this year — here's the top 5 most efficient models
2024 Kia Sportage PHEV X-Line Prestige.
I drove the Kia Sportage PHEV for a week — and it’s the hybrid car most families should buy
2025 Chevrolet Silverado EV test drive.
I drove the Chevrolet Silverado EV for a week — here’s my pros and cons
Latest in EVs
2025 Mini Cooper Countryman SE All4 review.
I drove the Mini Cooper Countryman EV for a week — here’s my pros and cons
2025 Nissan Ariya Platinum+ AWD review.
I drove the Nissan Ariya EV for a week — and it's nearly the perfect crossover
Composite image of Lucid Air Pure, Rivian R1T and Kia EV9
I've driven over 30 electric cars in the last year — and these are the coolest features that really stand out for me
2025 Chevrolet Silverado EV test drive.
I drove the Chevrolet Silverado EV for a week — here’s my pros and cons
2025 Hyundai Santa Cruz Limited review.
I drove the Hyundai Santa Cruz for a week — here’s my pros and cons
2025 Hyundai Tucson Hybrid Limited review.
I drove the Hyundai Tucson Hybrid for a week — here's my pros and cons
Latest in News
Disney Plus logo
Disney Plus upgrade just fixed one of my biggest problems with the home page
Tom Hiddleston as Robert Laing in "High Rise" now streaming on Netflix
5 best Netflix movies in March you haven't watched yet
iPhone 16 with Apple Intelligence logo for iOS 18.1
iOS 18.4: All the newest Apple Intelligence features coming to your iPhone
Maria Debska in "Just One Look" now streaming on Netflix
3 best Netflix shows in March you haven't watched yet
Split image featuring the Galaxy S25 Edge (left) and Galaxy S25 Ultra (right)
Samsung Galaxy S25 Edge just tipped for two Galaxy S25 Ultra-level features
Wolfenstein: The Old Blood
Amazon is giving away a ton of free games for its Big Spring Sale — here’s how to claim yours