Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.

12 volt battery warning: Experimenting for truth...


New Member
May 25, 2019
Hello everyone

My name is Sean, I come from a M3LR 2020 with huge amount of technical problems, so I have decided to finally get a Model S P85D 2015 (july 15) second hand.

I got the car the 22-Jan-2021. On the 03-feb-2021 I got the warning for warning "12v battery needs to be replaced soon...".

Now, I removed it, reconnected it, the error message disappeared for a couple of hours, then I it appeared again. I called Tesla Roadside Assistance and they told me to schedule a replacement as soon as I was getting back home, there was no rush and the car could be safely driven for a couple of weeks. Fair enough

All considered, in those weeks, I have learnt how to remove and modified my car's front mask, so that I break into my frunk easily in case of lockout and jump start my car. I stored in the frunk also the jump start cables and a spare 12v battery from an ICE car, just to make sure to be self sufficient.

Back home in Finland, it took me a lot, literarily, to get the car serviced due to bureaucracy issues. The battery was finally replaced and the CCS retrofit performed on the 18-03-2021, 6 weeks and 1 days after the first warning.


I have been discussing, on different Tesla Clubs (Finland, Italy and Bulgaria), how long actually the battery can survive, even in the rigid Finnish weather, before dying completely. At the service centre they thought that the usual estimated limit is 4 weeks, but they never actually tested it. I volunteered at that point, and after the CCS retrofit we have put back the old dying 12v battery (DCS-33IT) in place, so that we can actually monitor and see when the 12v will actually end up in a complete drain and get some data on the actually limit time after the warning pops up.

I will keep you up to date on my experiment and let you know when the battery will definitely die.

Yours Sean


  • 87d36a4a-c656-49b7-a962-a3b6a27c2996.jpg
    340.7 KB · Views: 30


Dec 22, 2011
I hope you have plenty of patience.
A couple of years ago I drove for half a year with the replace 12V message.
Still worked when it was replaced, no issues.


Active Member
Mar 24, 2017
St Augustine, Fl
My car died last year 400 miles on the way home. I was on the interstate. Towed to super charger. I tried to figure it out, no luyock. Roadside couldn't figure it out. ""Tow it 300 miles to nearest SC"". Finally a woman at Roadside said the 12v was dead. What? She said to get a truck with big batteries to jump car, charge 12v to 14.5 volts. 30 minutes on jump the car came alive. Never had error again. Last month car was acting funny. Roadside couldn't figure it out. No error message. All of a sudden, 12v error appeared. I changed the battery, it cleared all battery errors. Might be noted here. It was original battery from 2012. Florida is hard on batteries because of heat. The coolant system should keep your frunk warm, allow the hoses run thru it. Your water pumps are there, if you take out your frunk, you will see the entire coolant system. I will try to find the diagram and post it for you.


New Member
May 25, 2019
Hello folks, here are some updates.

Since the last service, even if I have been driving all this time with the old 12v battery, I had no warning messages anymore. I think they reset some kind of counter in the system. The battery is most probably perfectly fine, otherwise it would read a voltage drop and give me the warning again.

I still drive with the new 12v in the frunk and I still have the break in setup for my mask, so that I can remove it easily in case of need (I will make a video about it tomorrow). In the meanwhile I post you my amatorial dumb proof video on how to break into your frunk in case of a lockout. I'm not a youtuber, the quality is terrible but you get the important aspects in the clip, how to release the latch. I will make a better one as soon as I have time.


About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.