A Tesla owner says he was locked out after 12-volt battery died in the Texas heat

• Dennis Hegstad said his Model 3 was stuck in his driveway after its 12-volt battery died.
• The Tesla owner attributes the issue to the impact of the Texas summer heat on the battery.
• He had to get his EV towed and called the issue “annoying as hell.”

A Tesla owner said he was locked out of his Model 3 in his driveway after the 12-volt battery, which powers the car’s smaller functions including windows and doors, died last week amid the Texas summer heat.

The low-voltage battery is not only crucial for powering smaller electronics in the car, but also for charging the EV’s main battery pack — and the Tesla can’t charge without it, requiring a jump much like a traditional gas-powered car.

“What do you do when it’s so hot your @tesla won’t respond to the mobile app or physical key?” Dennis Hegstad, the founder of a startup, wrote on Twitter. “I can’t open the car or move the car to reach a charging point.” 

In a video that showed him unsuccessfully trying to get into the EV with his Tesla key card, Hegstad said his 2018 Model 3 had about 130 miles of range left when he woke up that morning. He also posted a photo from the Tesla app showing that it “could not find vehicle” to unlock it.

“Confusing situation when you need to leave to be somewhere @elonmusk,” Hegstad tweeted.

—dennis hegstad (@dennishegstad)
June 21, 2023

Tesla’s don’t have traditional keys so the key card uses short range radio signals to communicate with the car and unlock the door.

Hegstad told Insider he later found out that the Tesla’s 12-volt battery had died. It works alongside the much larger lithium-ion battery pack and powers smaller functions inside the vehicle, including the interior lights, door locks, and windshield wipers. As of last year, Tesla has begun sending push notifications to owners when it’s time for the battery to be replaced — Hegstad said he doesn’t remember receiving the notification. Newer Model 3 cars also have a 16-volt lithium-ion battery instead of a 12-volt.

While Hegstad said Tesla didn’t confirm how the battery died, Hegstad thinks it could be due to the high Texas heat, which ranged from 80 to 96 degrees Fahrenheit in Austin on June 21. Hot weather conditions are known to decrease a batteries life span, reduce the range of an EV, and increase the amount of time it takes the vehicle to recharge.

Ultimately, Hegstad said on Twitter that the issue was “annoying as hell” and added that he felt he’d overpaid for the car by about $15,000 amid recent Tesla price cuts.

“Some buyer remorse,” he said on Twitter.

The Tesla owner said he had to spend about $200 to have the electric car towed to Tesla and was essentially stuck until the tow truck arrive because the dead Model 3 was blocking in his gas-powered car. But, before he called a tow truck, Hegstad said on Twitter that he tried all manner of things to get the car back up and running — from hosing it down to cool it off to attempting to jump the 12-volt battery and wasn’t even able to get the access point to the charging port open. He also noted that he had kept the vehicle in the shade and had used Tesla’s cabin overheat protection system, a function that prevents a Tesla’s interior temperature from exceeding 105 degrees. 

Hegstad told Insider he got his Model 3 back under 24 hours after reporting the issue and spent about $117 to replace the 12-volt battery. Luckily, the Tesla’s much more expensive main battery pack was still intact. Insider viewed Hegstad’s invoice from Tesla, confirming the battery issue and its resolution.

A spokesperson for Tesla did not respond to a request for comment from Insider ahead of publication.

Hegstad is not the first Tesla owner to report issues with getting into his EV. Last year, a Tesla owner went viral on TikTok after he said he was locked out of his Model S after the lithium-ion battery died. “BlackBerry” and “It’s Always Sunny in Philadelphia” actor Glenn Howerton was also locked out of his Tesla last year after his key fob was unable to connect to WiFi on the lowest level of a Los Angeles parking garage.