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Sunday, September 10, 2023

Tesla Model 3 New Battery

Like thousands of other excited, soon to be Tesla owners, I stood in line to reserve a Model 3 on March 31, 2016. This was a game-changing car. Tesla was moving from the high-end luxury market, towards more affordable EVs.    

Two year later, our pick-up date finally arrived. The initial deliveries were rear-wheel-drive vehicles. We ordered the all-wheel-drive, so we were far from the front of the delivery queue. On August 21st of 2018, we were handed the key cards and drove off in our new Tesla Model 3. 

Model 3 Delivery Day 2018

Five years and 24 thousand miles later, we still love this car. The white seats have held up well even through car seats, kids, and dogs. Other than a couple of filter changes after the wildfire summers, we haven't done much maintenance until this month.

The app recently popped up a message that we needed to schedule service. Going to the car, I found this waiting for me on the touchscreen. 

The Learn More provided the following: 

VCFRONT_a402 Error Tesla

VCFront_a402 error message: Our 12V battery was dying. A couple clicks in the app and service was scheduled. It would be mobile service and it was about a week out. Luckily, I work from home and this is not our only car, so we didn't need a loaner. 

Mobile service is great! Instead of taking time out of my day, driving to service, waiting around... I get to remain in the comfort of my home, the service technician comes to me.

The estimate was $110 ($85 parts, $25 labor); I approved this in the app. Our service day arrived. A message in the app let me know they had arrived. Earlier that day, we moved the car from the garage to the driveway for easy access. I saw the driver's door and the frunk pop open in the app. 20 or 30 minutes later, another message informed me that they were done.

I went out said thanks and good-bye. I checked that the error message had been cleared and moved the car back into the garage.

Why Does An EV Have A "Starter" Battery? 

The 12V system runs the accessories and safety systems. EVs generally have a DC-to-DC converter that allows the high voltage of the traction pack to be stepped down to allow the traction pack power to be used to run the 12V system and charge the 12V batter when needed. However, during a severe crash, Tesla vehicles (and most other EVs) uses a pyrotechnical safety switch system to disconnect the high voltage pack. This system uses miniature explosive charges to blow apart the connection between the traction pack and the rest of the vehicle. This reduces the risk of electric shock or fire during a crash.

Safety first, we certainly want to avoid fires, but after a crash, you may still want to do something like open your electronically locked door or roll down your electrically powered windows to get out of the car. To do this, if the traction pack is isolated, you'll need that accessories battery.

If the 12V battery is damaged or disconnected during the crash too, you're not stranded in the vehicle. There are mechanical overrides to open the doors. These are conveniently located located on the Model 3; a little to convenient in some cases where people new to the car pull this handle instead of pushing the open button.

Whenever you get into a car with electronically locked doors (most new vehicles nowadays), make sure you know where the mechanical overrides are located. This is not something you want to be frantically looking for after a crash. 

Why Not Upgrade To A Lithium Starter?

Lithium starter batteries are smaller and lighter than the current lead-acid standard. I'm sure these will become the standard soon (maybe as the industry transitions to 48V). 

In an EV, the "starter" battery does not have to turn the crank to start car, there's just a lot less stress on the battery. 

Today's cars were not designed for a lithium starter battery. This means that the battery storage area is not temperature managed. Lithium batteries are more temperature sensitive than lead-acid batteries. If you want it to work in summer heat and winter cold, I (for now) am going to stick with a lead-acid starter battery. 

Not all lithium-ion batteries are the same. Iron-based lithium batteries (LFP, LiFePO4 and the like) are more temp tolerant than the nickel-based chemistries are a much better choice for a starter battery that would not receive all of the comforts of a liquid cooling system.

Lithium starter batteries are coming, but I plan on waiting until the auto-OEMs have qualified them with hot weather, cold weather, and crash testing. But if you want to try it out, don't let me stop you from voiding your warranty. Just make sure it's the right voltage, amperage, physicals fits, and is well-secured.

Hays Energy Lithium Battery


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I am long Tesla 

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