12V Battery, Mobile Service and other Qs

12V Battery, Mobile Service and other Qs

Using Google to searching this forum is just neat (sarcasm). Plus I am a bit ill-tempered having been on hold for over 40 minutes trying to get a live person for support questions. Maybe the forums can beat support response times here.

I have a few related questions to those who have had their 12V battery fail enough to where the message displays in notifications and in the instrument cluster.

1) My vehicle is a 17 S with under 10,000 miles. Is the 12V battery under warranty? Google seems to only provide search results on the big battery. Grrr.
2) How long can you drive with a 12V issue assuming you saw it on the first day and the car is able to be driven still?
3) It is 4:00pm CDT roughly. Chat is a opaque button on the site. The recording talks about Chat being an option so I guess it is a live feature. Does chat on the Tesla support website really work?
4) How do you select mobile ranger / mobile support via the web page? Edit: I did find it on the Tesla app but still have not found it online. But it may be because the app actually has items to select to qualify the issue. I can only select physical service centers and there is no issue description other than a generic entry text field.
5) How can I ask mobile support for more items to cover since they are making a onsite visit? e.g. bring new wipers


cmichael | 2019年6月12日

I now realize that my second question could be answered with "until it dies, duh", but I meant is there any signs that this is becoming serious so do not drive unless you want to Uber/Lyft home.

hammer @OR-US | 2019年6月12日

Battery will be under warranty. I drove three weeks with a 12v warning. Typically you request service through a service center and they will farm it out to mobile if possible or requested.

johncrab | 2019年6月12日

The battery IS under warranty. Much easier to replace on the newer cars and yours probably falls into that group. You can drive safely for a short while but don't push it. By the time you get the warning, the battery is pretty much kaput. Warning signs are excessive vampire loss. Mine was up to 10 miles/day lost just bringing the main battery online to charge the small battery. That's about 2.5 kWh/day. Normal loss is about 3 mi/day. Get it changed. It's $250 or so with tax and labour. Don't buy into the people selling lithium-ion replacements. This is a small deep cycle AGM battery for a reason. That battery tech will take a beating. These 12v batteries will usually make it 28-30 month and then that's it.

As for communicating with Tesla, you are more likely to get a meaningful response out of the IRS on a holiday weekend. Communication from T has become steadily worse in recent years and they see customers as a nuisance rather than as a vital link to staying in business. So good luck with that.

murphyS90D | 2019年6月12日

My car is 42 months old with no problems reported for the 12 volt battery.

redacted | 2019年6月12日

@hammer hit it on the head. I went most of a month on a battery warning without problem. I believe if you request mobile service in your appointment, the service center will call to set up mobile service. When they call to set up a time you can ask for wipers. Car has a 4y/50K warranty and 12v is covered by it.

dougk71 | 2019年6月13日

There are many parameters. I had both the 12v battery and the charging circuit for the 12v battery ( the main traction battery periodically charges the 12v battery) fail. Which one failed first is unknown.The 2018 ModelS 100D was rendered immobile and needed to be towed. Because of the interdependence of the 12v battery and other in car systems I'd get it seen to ASAP. | 2019年6月13日

@doug - While I can't state for sure, it's very likely the DC-DC inverter that charges the 12v battery died. After that, you have less than a day before the 12v battery discharges and dies. Similar to any ICE car, when the alternator dies, the battery is no longer charged and the car is not going to go very far. Luckily the DC-DC inverter rarely fails - likely far less than alternator failures on an ICE car (but more expensive should the inverter fail).

Tesla actually has an additional hardware 12v battery monitor to detect when it is starting to fail (I think Honda also has this feature in some of their cars). That detects weeks before it totally fails. Few other automakers include the extra tech, so when the 12v battery goes on those cars, there is very little warning - maybe a day or two.

p.c.mcavoy | 2019年6月13日

@TT - I baffled why you continue to view Tesla's 12V battery monitoring capability as something so unique.

As I've commented multiple times I've had equivalent capability on my 2011 Honda Odyssey for 8 years that provides me a text message alert on the dash with in my experience a 3-4 week window to replace it at my convenience. That's on a vehicle that was under half the prices I paid for my MS five years later. Given that was before Tesla even produced the first MS, it's hard to argue that what Tesla offers was somehow break-through technology.

GM started delivering on 2016 vehicles their OnStar Proactive Alerts, or prognostics system that provides 12V battery monitor along with starter motor and fuel pump monitoring.

You can find via simple google search videos on YouTube that talk about how to reset battery monitors on Ford vehicles all the way back to about 2012.

12V battery monitoring as Tesla offers is not new, unique, or novel in any way compared to commonly available systems.

NKYTA | 2019年6月13日

“12V battery monitoring as Tesla offers is not new, unique, or novel in any way compared to commonly available systems.”

No argument with your other assertions, but I have to disagree on this one.

Was Tesla not the first to top off the 12V from their traction battery? Does anyone else have a traction batt and that ability?

Does anyone but Tesla know that when the Model S came out that they would have to switch to a deeper cycle 12V? Nope, not even Tesla.

Even if that is the way the Volt/Bolt/vaporware EV does it, Tesla was first, because of the E, in EV. :-)

p.c.mcavoy | 2019年6月14日

@NKYTA - My statement has nothing to do with Tesla charging the 12V off the traction battery or the use of a deeper cycle 12V battery. As with the rest of all my comments, it has to do with the diagnostic monitoring, or more correctly prognostic monitoring, to alert the operator for the need to replace the 12V battery. You've applied it out of context. I would agree that I could have worded that statement to say "12V battery prognostics..." to make is less prone to applying it out of my intended context.

MilesMD88 | 2019年6月14日

@cmichael. Schedule it with SC. I did just that. It will get kicked to mobile if possible. Happened yesterday. I haven’t heard from them so I used “chat” earlier today. Worked great, no waiting. He said it takes 1-2 business days to schedule.
Yours will be covered under warranty. Mine went out of warranty 3 weeks ago. They said they will cover under “goodwill” since the current failing battery was installed 1 yr 5 months ago (8,600 miles).
Original 12v lasted 2 1/2 yrs, 20k miles. 2nd mentioned above.
Seems like the more an S is driven, it’s healthier for the 12v. The less driven, takes more of a toll on the 12v. I average 7K a yr. | 2019年6月14日

@p.c.mcavoy "TT - I baffled why you continue to view Tesla's 12V battery monitoring capability as something so unique."

Not so much unique, but I bet less than 10% of cars on the road have such a system. I did point out that Honda also uses the system, and I'm sure more are using it in higher-end new cars. For those of us with an older ICE car, very few have such as system and when the ICE 12v battery dies, your car is dead too, usually with little warning.

MilesMD88 | 2019年6月14日

How many miles a year do you drive?
What % do you charge your S to and do you leave it plugged in all the time when not driving, even though it’s charged.
Or, like, hit a SuperCharger and top off to 90%, then it sits in garage unplugged for a few days.
Just wondering what your charging habits are to achieve 4 yrs with no replacement. Mobile tech told me they generally last 2 to 3 yrs.

murphyS90D | 2019年6月15日

About 3000 miles a year.
Charge to 90% at 50 amps using an HPWC and unplug when done. 50 amps puts 25 amps through each of the two chargers in the car.
Supercharge about 6 to 9 times a year. The nearest supercharger to my house is 35 miles away so I only supercharge on trips.

Outside of two or three trips to a destination that is 270 miles away a year I typically drive twice a week for a total of 50 miles.

I see no point in leaving the car connected because the EVSE is off which means there is no connection to the car.
The 12 volt battery is always charged from the HVB even when connected to the wall.

If the 12 volt battery is kept topped off by an external smart battery charger there is no loss of charge in the HVB.
I did that for a week or so to prove the point but pulling the nosecone to connect the 12 volt charger was a pain.

Since my car spends most of its time in my garage I should be the classic case for 12 volt battery failure.

My car visits the Service Center once a year for the prepaid maintenance. None of the invoices have mentioned the 12 volt battery. I have never seen the 12 volt battery warning.

The HVB was replaced at 920 miles for an internal failure that dropped the maximum range to 100 miles. It was considered serious enough that I was told not to drive the car. They came 21 miles to my house and picked it up I got it back a week later after they had a new battery shipped to the east coast from California.

MilesMD88 | 2019年6月15日

Ok. Doing same. Rarely use SuperChargers. Charge at home or work to 85%. Home 240v work 115v. Rarely drop below 40%. May not plug in at home for a couple days for your reasoning.
Maybe just unlucky with 2nd battery. anything to add? | 2019年6月16日

@Miles - Nope :)

NV4NV | 2019年6月16日

2015 70D with 49,600 miles. Two 12-volt batteries replaced at about 20,000 & 40,000 miles. In both cases, notification on dash gave advance notice of need to replace. In both cases, Ranger replaced with about a 3-week wait for service.

Car always plugged in when in home garage. Charge at slow rate of 15 amps - 11 mph - to about 75% to 80% SOC. Maybe 4 supercharge sessions per month.

The main problem that I have had with failure of the 12-volt battery is that when the battery replacement needed notification is on the dash, no software updates will be made. When a software update is available, I get the notice asking permission to download and install the software at 1:00 AM or whenever, but the software is never installed. It is annoying to get the software download failed notice every freakin' morning and then the request to install the software again every freakin' evening. This annoyance continues daily until the battery is finally replaced.

cmichael | 2019年6月17日

As an update.

1) Service said my 12V issue is covered by warranty. Whew.
2) Service said it varies. The nice lady at the other end of the phone didn't give me confidence as she related a "recent story" of someone else she was working with who became stranded due to this issue. You mileage may vary seems applicable here.
3) Service said chat does work, they did not understand why it wouldn't work for me. Let's blame Chrome or Windows 10.
4) Service mentioned that the pull down on the Tesla app does "route" certain items automatically to mobile service if other qualifiers (like mobile service coverage map) are met. It was mentioned this is manual when using the website.
5) Service was not able to modify the appointment. I was told to ask as there is supposed to be a confirmation about 24hr prior to the service appointment. Let's see how far I get asking about wipers and the yellow band issue I have on the S, and a loose interior panel on the 3.

Bonus. Despite getting a SMS text confirming the appointment, the Tesla website does not show a scheduled appointment 5 days later and after logout/logins. Grrr.

bryan.hopkins | 2019年6月18日

@cmichael, not sure if you're appointment is a mobile ranger appointment or not, but if it is, my experience is the appointment doesn't show up on the app or website. Appears the mobile ranger appointments are initiated via the app but once they setup the appointment, it isn't reflected in the app.

txakoli | 2019年6月18日


In my case, I scheduled a SvC appointment via the app to perform the airbag recall. I was soon contacted via text message, and the appointment was rescheduled as a Mobile Service. It's being performed this coming Thursday. The website reflects no scheduled appointments, but the appointment appears in the app.

MilesMD88 | 2019年6月18日

Tesla is a fantastic vehicle. Not being able to call & talk to someone about service will be Tesla’s undoing. Texting sucks!! You don’t know who your talking with, no names are given, no phone # are offered. Your completely left in the dark with who you are communicating with. Terrible way to conduct business.

cmichael | 2019年6月20日

Final update.

Mobile visited and my 12V and wipers have been changed out. Delightful mobile technician.

The appointment has not shown on the Tesla website. Everything handled via text and click to accept links.

Only nitpick is that I thought payment was authorized when you accept the agreement, but they needed the credit card.

It was mentioned that I could have kept driving the vehicle in his opinion. It was mentioned that service centers have been crazy busy but its getting attention and is getting better.

8 days between first notice and replacement.