Can the 12v battery wait a month for its replacement?

Can the 12v battery wait a month for its replacement?

Hi, I got a 12v low voltage service warning last week. I called Tesla and was given an appointment for its replacement on December 4th. Will the battery last till then? I will use the car probable only a couple of times till then since I will be on holidays. Any experiences?


Speedy P | 1 novembre 2017

It can wait indefinitely if you have a little battery tender hooked up to the 12v battery. Super easy if you have the original front end nose cone. Just pop it off gently using a teflon pry tool (or credit card) and you will see the posts for the alligator clamps. Clamp on and plug in the tender and you're good.

I had the exact same problem with waiting on an appointment and I did the above and was able to wait it out. Might have made it without the tender, but the peace of mind was nice.

You'll know it's working from either the LEDs on the tender (if present) and/or that you will no longer have any parasitic loss of charge to your main battery. The % charge or range (depending on your settings) will not decrease nearly as fast when the car is sitting parked and on the tender.

Now if you have the updated front end, perhaps someone can amend my directions because I haven't tried it on our P100DL, just our P85D.

Hope that helps!

Solarfan | 1 novembre 2017

How about requesting a mobile service visit to change the battery? Tesla has done it for years.

Speedy P | 1 novembre 2017


Of course! Good point. I had other issues so I had to take it in, but if the 12v is the OP's only issue, then yes definitely request a mobile service call. I'm on my THIRD 12v battery in our original P85 and both replacements were done via Ranger.

siropo | 1 novembre 2017

I tried to get a Ranger but I live in the highest, farthest, ski resort in Switzerland (4x4 + chains compulsory sometimes) and Ranges just do not come here. The car will be parked at the airport for 3 weeks (plugged). I hope it makes it....

Simpson5809 | 1 novembre 2017

I have a 2014 S85 with 45,000 beautiful miles on it. It still has the original 12V battery and never has had a problem with the battery. Last week I had the 50k service done and they tested the battery and said it was fine. After reading all the stories in the forum about batteries lasting a year I’m wondering how this is possible. Any others out there with 12V batteries with superpowers?

TranzNDance | 1 novembre 2017

@Simpson5809, My husband's battery in his Audi lasted from 2008 (he bought it in 2009), 50k miles. We were in disbelief but the service guys saw the label that confirmed that it was original equipment. It died (a slow death) this year.

Simpson5809 | 1 novembre 2017

@Tesla, thanks. I have owned other car makes (Mercedes and Lexus) that the battery lasted three or so years, but that does not seem to be the Tesla experience on the Forum. It also seems that most are covered by the warranty. Since my warranty expires soon I was hoping to get it replaced. It just won’t die.

KeepAusWired | 1 novembre 2017

I also have a 2014 S85 on its original 12v battery. Still going strong.

Nexxus | 2 novembre 2017

We got the message last Friday. I didn't drive it over the weekend because I was worried. I drove it to work and then just dropped in without an appointment on Monday. They replaced it on the spot, no worries. They also uncorked her for us. Wow! What a difference. Feels like a brand new car!

Rocky_H | 2 novembre 2017

@Simpson5809, Yep, I also have an invincible 12V battery. March 2014 car with 45K miles on it and the original battery.

mikepisko | 2 novembre 2017

I also have a 2014 S85 on its original 12v battery.

RichardKJ | 2 novembre 2017

Another per-AP 2014 S85 on the original battery.

Simpson5809 | 2 novembre 2017

So there appear to be many 2014 Model S with original battery still functioning. What then would account for all of the annual battery replacements in later cars? A change in battery supplier? More load on the 12V in later cars?

siropo | 2 novembre 2017

Something to do with temperature change maybe? My car has only 12K miles and need battery change...

Simpson5809 | 2 novembre 2017

@siropo, temperature may be a factor. I live in Dallas Texas with hot summers and mild winters. My car is always garaged at night.

Speedy P | 2 novembre 2017

The ranger who replaced my first 12V battery back in 2014 on my 2013 P85 said that Tesla recently switched battery suppliers because of all the trouble they had with the 12V batteries. He said at the time he was doing at least one battery swap each time he went out. Of course, this is 3-year old info. Also, Tesla might just have a knee-jerk replace the battery reaction to the 12V battery low warning because I had the 12V battery replaced in my 2014 P85D in 2016 as soon as the warning popped up. They happened to have it for a yearly service visit and swapped it out. I never even saw the warning myself.

I just appreciate that I don't have to spend a couple hundred bucks on a battery every so often. Tesla has been great about replacing them.

rdpatague | 19 settembre 2019

am an owner of late 2016 model s 60 & the 12v battery warning light came on. any idea how much tesla will charge me to replace/install new battery? if location matters, would have the car serviced in the SF bay area.

dougk71 | 20 settembre 2019

The 12v battery is an interesting insight into Tesla engineering. The traction battery is superior to any other traction battery. The 12v battery that feeds the electronics that manage what might be a 500,000 mile traction battery is just a 50,000 mile battery and often times less than that. The 12v battery is as critical as the traction battery for operation but the 12v battery is little better than found in any low priced ICE car.
Go figure.

Bill_75D | 20 settembre 2019

@rdpatague - If you are under 50,000 miles it should be covered by warranty.

Bighorn | 20 settembre 2019

My 12V has almost 240k miles with no signs of needing a replacement. It’s not a 50k mile battery obviously and it’s lasted longer than my traction battery which didn’t quite make 200k.

rdpatague | 20 settembre 2019

Bill_75D - thank you for your comment. Mine is well under 50,000 miles, so it should be covered by warranty then! Yeay!!

Mathew98 | 20 settembre 2019

@rdpatague - Request for a mobile ranger for the task. They replaced mine in my driveway in under an hour. | 20 settembre 2019

@rdpatague "any idea how much tesla will charge me to replace/install new battery?

$0 if under warranty. Maybe $200 out of warranty.

@doug - Actually the 12v battery is considerably better battery than most ICE cars at any price. The use case is totally different than in an ICE car, where it's used to start the car and little else. The Tesla AGM battery is used to power far more electronics than in an ICE car and must be charged from the main battery (no alternator). Generally, they appear to last about 3 years on average in the Tesla. Some ICE vehicles only last a year, but most get about 4 years of battery life. The battery life in these different use cases has little to do with the quality of the battery.

dougk71 | 20 settembre 2019

It remains that the engineering prowess that went into the design and manufacture of the traction battery to give high charge density and durability seems absent in the 12v battery. Now if all the 12v battery did was to illuminate the cabin it wouldn't be as interesting. The 12v battery is mission critical since it provides power to the electronics that manage the car and if it fails the traction battery is of little use. Often the mission critical elements are given as much or more attention by the engineers.
I'm not too unhappy with this since my 12v did fail and was replaced under warranty it is just that the traction battery seems so advanced and the 12v so ordinary.

bwb1 | 20 settembre 2019

Just had mine replaced this week. Out of warranty 2015 MS 70D with 65k miles. Ranger provided service for $266 all inclusive.

PrescottRichard | 20 settembre 2019

There’s a Lithium phosphate battery sold by Ohmmu that is lighter and should last longer. Seems like a solid biz here in AZ, but I haven’t used one yet.

Yes, it costs more up front but hopefully it lasts long enough to make the investment worthwhile. Anyone here try one? | 20 settembre 2019

For a lot more on the 12v battery:

It really is the right battery for the application. Tesla also included battery monitoring electronics to identify when the battery is going to need replacement. Very few ICE cars include battery monitoring (Honda is one), so when the battery fails in an ICE car, you might get a day or two warning, or perhaps no warning.

@PrescottRichard - Very bad idea. They are likely to last about a year or less. They are designed for ICE cars, and again a very different use case. Since the battery in the Tesla is deep discharged 3-5 times a day, that Lithium battery will not last long. In addition, the charging profile Tesla uses will be wrong for that battery. Since the battery is not temperature managed, it may fail completely in very cold/hot weather or life dramatically shortened. Not sure why you'd want to pay double the cost for 1/3 the life.

rschulze | 20 settembre 2019

I had my 2017 X 12v. battery replaced today after 10 days of battery warnings. SC was initially out of stock, but they found a new battery fairly quickly. I was pretty worried as I had 3 upcoming weekend trips. Each one over 300 miles round trip. They said it should last 2 weeks after warning and they said if I got stuck they would flatbed it and give me an Uber voucher, but it could possibly be jumpstarted to get me home. The ranger said usually they get 3 years and I was at 2 1/2. Battery seemed small, but he says the X is bigger than the S.
Battery is AtlasBX 60B19RS 12v. 40ah. Ranger was very great.

Bighorn | 20 settembre 2019

Mine is over 5 years old.

PrescottRichard | 20 settembre 2019

TT- I should have mentioned I pointed out your article to them back on the 10th, here is the reply. Keep in mind I’m not looking to start trouble :)

Hi Richard, thank you so very much for reaching out! Yeah, we’ve seen the Tesla Tap article, it is quite old by now. It fits into a certain way of thinking about batteries, especially Lithium, it is sort of a “one size fits all” approach and we don’t feel it accurately represents our batteries at all. Our batteries are built with LFP (Lithium Iron Phosphate) cells, LFP is a very robust battery chemistry and it behaves differently than than the other Lithium chemistries due to the fact it has the heavier Iron component to it. LFP is well-known to be safer than even Lead-Acid batteries and also more robust and longer lasting than the other Lithium chemistries. It has its trade-offs for that robustness tho, it is not as energy dense (small/lightweight) as the other Lithium’s and it is also much more expensive (more materials go into manufacturing and the worldwide manufacturing volume is much smaller). These trade-offs wouldn’t be acceptable for an auto-maker (where range and cost are EVerything) but for a premium 12V offering they are acceptable. We started this journey of developing the best 12V battery specifically for Teslas almost 5 years ago, we are passionate about these vehicles and driven by that passion to provide the very best possible solution. Our batteries are battle-tested and although we have had to rebrand our name twice due to a bad business deal we foolishly entered we have been selling our batteries for almost 4 years now. We have shipped to every climate in the world and have had less than 1% failure rate. When a customer has an issue with their battery we have found it is almost always the fault of the vehicle and not the battery (DC/DC needing reset is common issue, especially with the Model 3). To give a more concise answer;Not to discredit Tesla Tap but they say “the frequent deep charge/discharge cycles would greatly shorten the life of a lithium-ion”; if you do research you will find this is incorrect, frequent deep cycles are where Lithium is best suited, Lead-Acid doesn’t like deep-cycles. They actually got that backwards for some reason, I’m guessing naivety of the technology. I hope you find all of this helpful! Thank you again for reaching out to us!

Bighorn | 20 settembre 2019

Interesting. I thought they suffered in the cold as well. They seem to dispute that.

PrescottRichard | 20 settembre 2019

It’s not you grandpa’s old Lithium battery.

Still haven’t spoken with anyone who HAS one, but chances are I will at some point and if there’s anything interesting there I’ll post it.

MilesMD88 | 21 settembre 2019

Replaced in May 2019 by mobile service, 2 weeks out of warranty. Tesla replaced it goodwill since it was my 2nd battery. Original battery lasted 2 1/2 years. 1st replacement battery lasted 18 months & 2 weeks. (May 2015 delivery P85D)
Before they changed it to goodwill, price quoted was $216.
Technician at my house showed up in an S. Cool! Took about 30 minutes. Told me the 12v powers everything in the cockpit except for AC & Heat. Deep cycle battery, charges 5 - 7 times daily from main battery.
30,000 miles now. Seems like not driving a lot is detrimental to the battery’s life. | 21 settembre 2019

@PrescottRichard - Thanks, I wasn't aware they had designed it specifically for the Tesla/EV. The ones I looked at in the past were for the ICE market. I'll work on updating the article. Here's more on the chemistry they use:, which agrees with what they told you.

PrescottRichard | 21 settembre 2019

Sure TT, thank YOU for having an open mind and citing sources :)

That biz is very receptive if you’re interested in communicating with them. I didn’t post a link because I don’t want to be pushing their batteries here. There are plenty of those types of posts and until I have one for a couple years I wouldn’t feel comfortable recommending them. Hopefully I won’t need one for another year or so.

I’ll pass on that link to hear what the reply is for my own info. | 21 settembre 2019

@PrescottRichard - The page is updated with a new section on Ohmmu's batteries and links to batteries for the S/X/3:

Thanks for info! | 21 settembre 2019

Maybe I'll buy one and try it out when my battery needs replacement. I expect I have another 6-18 months on my current 12v.

No one has a problem with links when they are Tesla related and it helps others to evaluate if it may be of interest. It's the spam for crap that has nothing to do with Tesla or our cars that gets annoying :)

p.c.mcavoy | 21 settembre 2019

MilesMD88 | September 21, 2019 - “Seems like not driving a lot is detrimental to the battery’s life.”

I think there’s actually a pretty simple explanation to why not driving a lot is harder on the 12V.

When the car is being driving, the DC/DC converter provides the 12V power to run the necessary systems, not the 12V. That results in the 12V not being drained/cycles when the car is in use.

It’s when the car is not in use, the contactors are disengaged, preventing power being drawn from the HVB, that the 12V battery has to carry the load, gets drawn down, until contactors are engaged, power from HVB is drawn to recharge the 12V battery.

That’s why folks like BH, whose cars get driving almost constantly and rarely sit still, seem to have 12V battery last quite long time while others that don’t tend to drive as much have more issues.

I’m curious how I’m going to fare going forward as I’ll soon start spending quite a bit of time out of the country with my 2016 MS90D unused for couple months at a stretch.

MilesMD88 | 21 settembre 2019

Thanks p.c.

ChargeUp | 26 settembre 2019

I got in my 2018 Model S yesterday to find a Low Voltage warning, and Car Unable to Drive. Tesla remotely diagnosed it as the 12v battery having only 12.3 volts. He said it needs to see at least 12.7v. I fortunately had access to a trickle charger that brought it over 13v and the car became drivable. But question is why did the car allow it to get so low with the main battery not kicking in to charge. I checked it again today and it was over 14v on it’s own. Anybody else had this issue, and is the 12v battery the problem (the first being replaced once already after 10 months) or the system that keeps it charged?

murphyS90D | 27 settembre 2019

That 12.7 volt statement is nonsense. 12.7 volts is a fully charged battery. 12.3 volts is around 60% charged.

The car charges the battery to 100% when it drops to 50%. For a parked car that happens at least 4 times a day.

14 volts means the battery is currently being charged.

ChargeUp | 27 settembre 2019

I checked the voltage myself. 12.3v as they said, and next I checked it was 13v and the message went away, so there is something to their “below 12.7v” statement. My question remains why the high voltage battery did not charge the 12 volt as normal. I’m thinking it’s not the 12 volt battery, but rather a failure of the system that charges it. It’s been fine now for two days.

murphyS90D | 28 settembre 2019

What was the SOC of the HVB? Below a certain point it stops charging the 12 volt battery.

ChargeUp | 28 settembre 2019

It was at 37%. And the car was only parked for about an hour before coming back to the low voltage, unable to drive alerts.