Trouble With Tesla’s New 12 Volt Li-Ion Battery

Drive Tesla Canada is reporting on a string of customer issues with the new 12 volt lithium ion battery. It seems Model 3 owners in Europe are experiencing trouble with battery failures under certain conditions.

It’s also reported that this problem only impacts newly delivered Model 3s with the lithium iron phosphate or LFP battery pack. 

So, in the past, Tesla’s had the same 12 volt battery as any other car, big and heavy with lead acid chemistry. That seems weird because they already have a gigantic battery pack under the floor, but most automotive components are designed to run off of 12 volt power. With the Model S Plaid in 2021 Tesla introduced a much smaller and lighter 12 volt battery that ran off of lithium ion chemistry. In 2022 that new 12 volt was added to the Model 3 and Model Y as well. In theory, the 12 volt lithium ion battery should resolve a long-standing issue of the traditional lead acid batteries dying much faster in EVs than they typically do in ICE vehicles.

But it appears as though the problem hasn’t been completely resolved as numerous owners in Europe are reporting the new battery can also fail very quickly under certain conditions.

The problem only impacts newly delivered vehicles with an LFP main battery pack, where the 12 volt can die within 20 minutes of the vehicle’s main battery reaching a state of charge less than 10 percent. 

So, a very low charge in the main battery leads to failure of the secondary battery, and that leads to the vehicle being stranded and undrivable even though the car shows there is still range left in the main pack. This problem is made even worse because you can’t boost the lithium ion 12 volt from a regular car with a lead acid battery.

Tesla says that it is aware of the issue, and believes this is happening because the LFP battery hasn’t been calibrated properly since leaving the factory. Apparently with an uncalibrated battery, the vehicle computer is estimating it still has some range left, but in reality it is actually at 0 percent. And when there is no power in the main battery, the 12 volt isn’t being charged anymore and dies within minutes.

Tesla has already issued an internal memo recommending new owners charge their LFP battery straight to 100 percent as soon as possible after taking delivery. This will calibrate the battery and the computer will know more precisely how much range the battery has left in it.

Tesla is also recommending to avoid running the main battery to below 10 percent until you have performed the calibration.

So, not a big deal, but just a little FYI. When you get your new Model 3 home, charge it to max and then try your best not to run it down too low.