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Mysterious shut down

Greengolfer

Member
Aug 12, 2016
275
116
Highland,CA
Sooooo... My wife and I took a short vacation to Las Vegas this weekend. About 10 miles from our hotel(30 miles left in the tank), my car showed that it was starting to shut down and I needed to pull over in a safe place! I still had 12% power left. It also said that I needed to replace my 12 volt battery. Has anyone experienced a shut down when you still had power left?
 

Ostrichsak

Active Member
Sep 6, 2018
3,626
4,196
Colorado, USA
I had nearly exactly this happen to me two weeks ago on a road trip to Moab. No warnings to lower my speed to make it to my destination beforehand either. My distance to the next scheduled Supercharger was 7.6 miles and I had 13 miles of range displayed. Then, w/o warning, Bam! Car was coasting and warnings to pull over safely as the system had shut down.

P85D
 

cduzz

Member
Jun 6, 2019
427
562
boston ma
I wonder how many of these situations are from a pooched traction battery and how many are from a dying 12v battery?

Follow this:
  • Car runs many systems from 12v battery
  • car normally charges 12v battery from traction battery propping up a dying battery
  • car stops charging traction battery below 20% of traction battery
  • marginal 12v battery runs down before traction battery runs down
  • car dies
It would be really nice to see the 12v battery health from the MCU; perhaps "charging duty cycle" or some other graph.

Lead acid batteries have an interesting issue in that their chemistry is greatly aided by being warm but they're killed by being hot. As a result, you will kill the battery in the summer but not notice that it is dead only when you get the battery cold.

Also, dead lead acid batteries put quite a bit more load on the charging setup, I wouldn't be surprised if driving a tesla with a deeply marginal lead acid battery harms the charging circuitry, but I'm also speculating wildly; I'd love for someone to post correct information.
 

Big Toys

Member
Jan 19, 2019
611
589
Florida
In my discussion elsewhere about what % to charge the battery, I posited that the range meter is probably not an accurate reflection of charge. Actual voltage under load would be a more useful display. If you own a golf cart, this is a never-ending problem/discussion.
 

Ostrichsak

Active Member
Sep 6, 2018
3,626
4,196
Colorado, USA
In my discussion elsewhere about what % to charge the battery, I posited that the range meter is probably not an accurate reflection of charge. Actual voltage under load would be a more useful display. If you own a golf cart, this is a never-ending problem/discussion.
Apparently I own a $150k golf cart except with harder to get parts.
 

Big Toys

Member
Jan 19, 2019
611
589
Florida
Apparently I own a $150k golf cart except with harder to get parts.

HA, you'd think engineering could solve that problem on a $50K+ car, let alone a 48V cart. Really, the $10 digital voltmeter installed tells you exactly how much voltage you have left. Experience golf cart owners know that 48V carts generally have about 50 - 51V at full charge and never let it get down below about 48.xV at rest. Simple, eh?
 

Greengolfer

Member
Aug 12, 2016
275
116
Highland,CA
My car is a 2014 P85. Ostrichsak, I didn't get any warnings either! cduzz, My 12 volt has 40,000 miles on it, You might have given me an answer as to why I couldnt get to destination when my computer said I could. Fortunately, the Las Vegas service center got me in and out on saturday morning with a new 12 volt(warrented replacement).
 

ajdelange

Active Member
Dec 10, 2018
1,077
638
Virginia/Quebec
This is a huge clue! I have been puzzling over this extensively for the past week or so and, as has cduzz, wondered whether it was the 12V battery that was responsible. If replacing it solved the problem then it certainly looks as if this thesis has some validity.
 

cduzz

Member
Jun 6, 2019
427
562
boston ma
This is a huge clue! I have been puzzling over this extensively for the past week or so and, as has cduzz, wondered whether it was the 12V battery that was responsible. If replacing it solved the problem then it certainly looks as if this thesis has some validity.

The frustrating thing is that I want to replace my 12v battery (just) before it causes a reliability issue with my car, not just after.

With my ICE I can watch the voltage drop when starting the car, because my ICE has a volt meter. I can't (easily) monitor the 12v battery behavior in a tesla, can I?
 

Ostrichsak

Active Member
Sep 6, 2018
3,626
4,196
Colorado, USA
My car is a 2014 P85. Ostrichsak, I didn't get any warnings either! cduzz, My 12 volt has 40,000 miles on it, You might have given me an answer as to why I couldnt get to destination when my computer said I could. Fortunately, the Las Vegas service center got me in and out on saturday morning with a new 12 volt(warrented replacement).
The Tesla rep who I talked to on the phone logged into my car remotely and at first said he found noting abnormal. Then, after further digging said he was getting an error about the 12v battery but there were about 12 errors at this point so I'm not really buying that my 12v battery just completely crapped out shortly after leaving a Supercharger. It's not like the car hadn't been plugged in in days/weeks. I hope for your sake that permanently fixes your problem but I've read others who have had a similar story end up with their battery pack being replaced under warranty.
 

ajdelange

Active Member
Dec 10, 2018
1,077
638
Virginia/Quebec
The really frustrating thing about this is that the Teslas are supposed to have a sophisticated monitoring system on the 12V battery. As I've seen people report driving around for moths with a warning to get the 12V battery serviced I assume that it is very good at detecting the normal aging in a lead acid battery. But sometimes lead acid batteries fail abruptly without a hint that anything is wrong. I remember one case where I jumped in my truck, started it right up, drove to work and parked. When I got out I saw that I had done a really lousy job of parking and figured I'd correct that. Battery was stone dead.
 

Ostrichsak

Active Member
Sep 6, 2018
3,626
4,196
Colorado, USA
As stated that is not always going to be the problem. So, out of curiosity, what was the resolution when it happened to you?
Called Tesla Roadside and was informed that a tow truck would be 2.5+ hours away. He advised me to call the local constabulary who would put me in contact with tow services that were out of Tesla's "network" and I could pay them and be directly reimbursed. To truck arrived in 20min and towed me that last 7.6 miles to the next Supercharger stop. Plugged in, waited a good long while for the car to come back to life and start charging which it finally did. Filled up and continued our journey as if nothing had happened. Other than "jack mode" randomly coming on at 75mph on the trip back there have been no other indications that we ever had an issue to begin with. I seriously doubt the 12v battery had anything to do with it but it was in the list of dozens of errors so I could see where a phone rep remotely viewing this log would infer this.

Weeks later we're still waiting for someone to get back to us about reimbursement even though we were "pre authorized" to do so.

Once that's done I will push to get the battery pack replaced under warranty because I never want that to happen again. I've been driving 25 years now and have NEVER run out of means of energy.
 

cduzz

Member
Jun 6, 2019
427
562
boston ma
The Tesla rep who I talked to on the phone logged into my car remotely and at first said he found noting abnormal. Then, after further digging said he was getting an error about the 12v battery but there were about 12 errors at this point so I'm not really buying that my 12v battery just completely crapped out shortly after leaving a Supercharger. It's not like the car hadn't been plugged in in days/weeks. I hope for your sake that permanently fixes your problem but I've read others who have had a similar story end up with their battery pack being replaced under warranty.

The traction / high voltage battery supplies power to the 12v subsystems while the car is underway until it is at 20% at which time you're left with only the 12v battery alone running all the computers, fans, defrosters, seat heaters, displays, and other "accessories". The 12v battery on the S is relatively undersized and not well managed according to random untrustworthy bloggers on the intertubes. I personally have seen ordinary 12v batteries behave totally normally until they're under load when their capacity suddenly falls through the floor. If your car suddenly fails while the traction battery has less than 20% but more than 5%, especially if there is no surge in load on the traction battery (steep up hill, passing a prius, rolling coal on a taycan) I would suspect the 12v battery first.

You may have one of several gremlins in your car, but one of them could easily be the 12v battery.

Frustratingly there is no real feedback as to where the 12v battery is in its lifecycle; I would love it if the voltage of the 12v system were exposed in any of the existing APIs.
 

BrokerDon

Active Member
Aug 23, 2014
1,418
1,348
Newport Coast, CA
I had nearly exactly this happen to me two weeks ago on a road trip to Moab. No warnings to lower my speed to make it to my destination beforehand either. My distance to the next scheduled Supercharger was 7.6 miles and I had 13 miles of range displayed. Then, w/o warning, Bam! Car was coasting and warnings to pull over safely as the system had shut down.

P85D

How old and how many miles were on your P85D when this happened?

What mileage / age have other Model S owners had to replace their 12V lead acid batteries?

My March 2015 built (4.5 year old) P85D just turned 50,000 miles and is still on its first 12V lead acid battery... and starting to worry its going to need replacement any time now. Fortunately it is plugged into a Tesla High Power Wall Connector when it is our garage so the 12V lead acid battery should be staying charged. I also rarely run our HV battery below 20% SoC.
 

Ostrichsak

Active Member
Sep 6, 2018
3,626
4,196
Colorado, USA
How old and how many miles were on your P85D when this happened?

What mileage / age have other Model S owners had to replace their 12V lead acid batteries?

My March 2015 built (4.5 year old) P85D just turned 50,000 miles and is still on its first 12V lead acid battery... and starting to worry its going to need replacement any time now. Fortunately it is plugged into a Tesla High Power Wall Connector when it is our garage so the 12V lead acid battery should be staying charged. I also rarely run our HV battery below 20% SoC.
November 2014 production and 67k miles on the odo at the time of incident.

We had two Model S previous to this and had to have 12v battery replaced in both. The first was a 2013 that had the original battery fail at about 85k miles. The second (in my sig below) was a newer 2015 70D with 85k or so miles.
 
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BrokerDon

Active Member
Aug 23, 2014
1,418
1,348
Newport Coast, CA
November 2014 production and 67k miles on the odo at the time of incident.

We had two Model S previous to this and had to have 12v battery replaced in both. The first was a 2013 that had the original battery fail at about 85k miles. The second (in my sig below) was a newer 2015 70D with 85k or so miles.

Great info. Thanks!

What does Tesla charge to replace the 12V battery past the original 4 year warranty?
 

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