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

Mysterious shut down

  • Like
Reactions: David99
Great info. Thanks!

What does Tesla charge to replace the 12V battery past the original 4 year warranty?
I think at the time I had it done it was $250. My two Model S were both CPO though and still under warranty so the bill was $0 for me so I'm not 100% but I believe that would have been the cost at the time.
 

TIppy

Active Member
Jul 8, 2016
1,914
1,722
Tampa, FL
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

The car doesn't stop charging the 12 volt battery below 20% of the traction battery.

From the manual:

To protect against a complete discharge, Model S enters a low-power consumption mode when the displayed charge level drops to approximately 0%. In this mode, the Battery stops supporting the onboard electronics and auxiliary 12Vbattery. Once this low-power consumption mode is active, immediately plug in Model S to prevent a jump-start and 12V battery replacement.
 
  • Like
Reactions: David99

ucmndd

Well-Known Member
Mar 10, 2016
10,103
19,833
California
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".

This sounds completely and unabashedly 100% totally made up.
 
  • Funny
Reactions: ‘Merica
This sounds completely and unabashedly 100% totally made up.

I stand corrected!

I can't find where that bit of information in my brain came from, so perhaps it is made up. I think I may be mixing up "the car is stationary, off, and not connected to shore power; when the traction battery reaches a threshold it stops recharging the 12v battery" which I think I read somewhere (though can't find right now) with how the car behaves while underway.

The manual states:
Discharging the Battery to 0% may result in damage to vehicle components. To protect against a complete discharge, Model S enters a low-power consumption mode when the displayed charge level drops to approximately 0%. In this mode, the Battery stops supporting the onboard electronics and auxiliary 12V battery. Once this low-power consumption mode is active, immediately plug in Model S to prevent a jump-start and 12V battery replacement.

But of course, the manual doesn't say "under some situations the gauge will go from 7% to 0% in less than 10 seconds"

Is the 12v subsystem voltage available via the api to things like teslafi?
 

Attachments

  • Screen Shot 2019-10-21 at 9.35.22 AM.png
    Screen Shot 2019-10-21 at 9.35.22 AM.png
    69.3 KB · Views: 23

doghousePVD

My grandfather’s car
Dec 3, 2018
701
644
New England, USA
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?


Voltage is a very poor indicator of remaining energy (kWh) in a battery. Especially with lithium chemistries that have abrupt discharge life curves.
 

winb

New Member
Dec 30, 2019
3
3
94062
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?

2015 Model S 85D shut down with 30% Charge and 12V battery warning

On Christmas Eve, I was driving home when I received a Service required notification and then a 12 volt warning. I drove home and unloaded the vehicle. A few minutes later when I tried to drive to Tesla Service 2.5 miles away, it would not start and I had a new message: "Car needs service, Unable to start car". Tesla Service could not get to it on Christmas Eve so I arranged to have it towed the day after Christmas. Do to the busy schedule, Tesla Service was unable to look at the vehicle Thursday but they were able to late on Friday when they were unable to communicate with the the vehicle. Logs were requested and Monday roles around. I am informed that the problem is the High Voltage Battery Heater has failed along with the 12 volt battery. The 12 volt battery is less than 6 month old, having been replaced by Tesla Service. No heating or defrosting in use in the passenger compartment.

Should a High Voltage Battery Heater issue cause the vehicle to shut down on a day in the upper 50s?
 
  • Informative
Reactions: David99

MP3Mike

Well-Known Member
Feb 1, 2016
20,376
51,590
Oregon
Should a High Voltage Battery Heater issue cause the vehicle to shut down on a day in the upper 50s?

If it fails the HVIL, High Voltage Isolation, tests yes. I don't know if Tesla will shut the vehicle down if it just isn't working. (They would probably have to limit regen/power/charging longer since they couldn't actively heat the battery.)
 
Funny, but my car displayed a notice, "12 volt battery needs replacing" back a few months. I live 115 miles from service, could have replaced it myself, but figured I'd just drive over to the service center the next day. I have 97,000 miles and five-plus years on that old battery, and what I usually see is that a PbA battery only lasts a few years. Five years shows exceptional charging control by Tesla.

As to driving 115 miles, there was no problem. In my experience, Tesla doesn't wait to give a warning until the last moment. My guess is that some Tesla drivers want to ignore warnings until it gets serious. Or something.
 
If it is a high voltage fault the car can't close the contactors to pull power from the battery so it has no way to use the power in the HV battery.
I had this happen: car dead in garage (wouldn't turn on). Mobile service looked at it remotely and said it needed to be looked at by a service center because of a fault isolating the HV battery. Suggested that I put a trickle charger on the 12 V while arranging transport, which I did.

Short story:
The problem turned out to be a corroded wire to the charge port. Apparently that threw a fault that wouldn't let the contactors close, although I don't know why that would happen.

Longer story:
Since I was out of warranty Tesla Roadside got me a quote of $1400 from a tow company for the 300 mile transport across the mountains. They suggested that I check with my insurance company to see if they would pay for some of the tow. To my surprise, my State Farm tow insurance covered the tow because the service center was the nearest place the car could be repaired. They arranged everything. Since it was the end of quarter delivery push (last few days of March 2019) the service center couldn't look at my car right away but kept me well informed. They got right to it on April 1st. Told me that it took them nine hours to find the problem, a corroded wire to the charge port (they comped me all but one hour of service time).

I haven't ever read of this problem before or since, but it does suggest that there are a number of things that can cause a Tesla to die.
 

winb

New Member
Dec 30, 2019
3
3
94062
If it is a high voltage fault the car can't close the contactors to pull power from the battery so it has no way to use the power in the HV battery.
According to Tesla Service, no faults, just a bad High Voltage Battery Heater which may have caused the 12 volt battery to fail. No one seems be able to explain why this would cause the 12 volt battery to fail. Basically a really easy fix if your mechanically inclined but Tesla doesn't allow the owner to find out the problem without in my chase towing to the Service Center. I was quoted $1200 for what I could repair for less than $200. (Don't forget that towing from my driveway 2.5 miles to the Tesla Service Center costs $250, after being quoted $125.) I thought I would be able to access the logs but after going through a couple of departments at Tesla, I am informed that logs are only available to owners who have been involved in an accident and only regarding the accident. I know I'm out of warranty, but this seems kind of nuts.
 

David99

Well-Known Member
Supporting Member
Jan 31, 2014
5,055
8,090
Nomad (mostly US)
The only thing I can think of is this. There are two high voltage 'outputs' from the main battery. One goes to the drive unit to power the motor. The other one goes to the front of the car where it powers the AC compressor, the coolant heater and the DCDC converter which converts the 400 Volt to 12 Volt for the 12 Volt systems and the 12 Volt battery. If the battery heater has an issue, there is a risk of 400 Volt to 'leak' out. I assume the car noticed an issue with the coolant heater and for safety reasons shut down the entire high voltage string going to the front of the car disabling the DCDC converter and thus power supply to the 12 Volt battery which then dies rather quickly as it is small.
 
  • Like
Reactions: MP3Mike

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.


SUPPORT TMC
Top