12v battery must be replaced soon

[israndy]

So it's hard to tell if the battery is actually bad if you have devices hooked to the battery that take power all the time.

 

[neurocutie]

Of course, the car rolls down the windows when the battery dies. Why doesn't it also pop the frunk?

Can the battery die *while* driving? prolly don't want the frunk opening when driving...

 

[ACofNY]

My M3 started with the 12v replace soon message. 45,560 miles. I set up an appointment for replacement. Phone rep said it would not be under warranty. I cancelled and went to the service center to purchase one myself. Rep came out and asked why I wanted to buy one considering that it would be covered under warranty. I explained that the phone rep said it would not be covered. He said come in tomorrow and we will replace for free. He made me an appointment and it showed up in my app.

I show up the next day and check in for my appointment with the scan image process they have. I get a welcome message and we will be with you shortly. 1 hour later, I go looking for people. None to be found during my wait. Rep calls me on the phone! and says we cannot see you today. Someone forgot to check me in and they have placed several walk ins ahead of me. I get the usual leave your car and we will give you uber credits. Problem is I live out in the country about 55 miles away and leave for work at 4am. Good luck getting an uber at that time.

I schedule mobile service for two days later. Mobile service comes out and replaces battery. When I leave work my windows do not roll down when opening the door. I can roll them down but when I roll them up, they bounce back down about 3-4 inches. Both front windows. When I park, I have to roll them down a little to clear the seal. Then I have to climb in from the back and roll them up. They will bounce down twice before staying up.

In addition, my steering wheel will not adjust more than an inch in any direction. Presets or manual adjust. Up, down, in or out. Mobile service is trying to diagnose remotely.

UGH

Tesla seems to notify you on the repair charge regardless if it is under warranty. I was told by the Rep that the computer always provides the cost (for the worse case) if it was maintenance. My M3 (1 yo/3300 mi) all of a sudden spewed out Freon from the Frump area, I was quoted by the App to approve the $250 charge prior to my appointment. I did not approve the charge under confirmation by the rep that it does not affect my appointment.

 

[ACofNY]

So for this to work, you need to have a 9 v battery where? I don't carry one around. Is there a plastic flap under the body or bumper one could be stashed at, like a spare key?

I purchase two of these type of battery jumper for my ICE car. It was almost useless, in the winter time, you can not leave it in the car. The cold drains the battery and winds up useless when you need it. You have to carry it to your house every night. I tried to leave it plugged in the to 12v outlet in the car which only provides power when the car is on. But I stopped after it exploded one day while trying to jump a ride on mower. The other one I bought from Costco wasn’t a blue to jump my ICE car.

 

[Phlier]

So for this to work, you need to have a 9 v battery where? I don't carry one around. Is there a plastic flap under the body or bumper one could be stashed at, like a spare key?

Most all of the 12v battery failure posts state that the car rolls down the rear windows (at least partially) to allow vehicle access after the 12v battery is completely dead. I keep a 9v battery new in package in the bottom of the jockey box "just in case."

 

[smatthew]

Can the battery die *while* driving? prolly don't want the frunk opening when driving...

If the car is on, the PCS is supporting the 12V system. So no.

 

[israndy]

Most all of the 12v battery failure posts state that the car rolls down the rear windows (at least partially) to allow vehicle access after the 12v battery is completely dead. I keep a 9v battery new in package in the bottom of the jockey box "just in case."

How does it do this with no power? I have unhooked my battery several times and when my computer was swapped he even unhooked the 12v under the rear seat. Windows didn't drop for us. What sort of failure drops the windows?

 

[Sophias_dad]

How does it do this with no power? I have unhooked my battery several times and when my computer was swapped he even unhooked the 12v under the rear seat. Windows didn't drop for us. What sort of failure drops the windows?

These are just guesses...


I imagine if any of the doors are open(if you are screwing around under the rear seat), it knows there's no need to lower windows.

I'd bet that normal drain on the 12V is quite slow and fairly predictable. There's plenty of power available to spin a small window motor even when the voltage has dropped below "you can use the car normally" levels. If you remove the 12V battery connection, there's no time for the computer to notice a problem before there being no power at all available.

 

[smatthew]

must be a gradual failure - like "oh no there's only 6V we're in trouble"

I wish that once the car detected pending 12V failure it went into a failsafe mode where the car doesn't go to sleep, and the PCS keeps everything running. You'd waste a few electrons, but then you wouldn't have the problems people are experiencing. Maybe even automatically alert service to get a 12V battery ready for you?

 

[Avid]

There is probably a capacitor dedicated for this one job.

 

[RayK]

That would have to be one hell of a capacitor. Maybe a flux?

 

[Phlier]

I have zero proof of this, but since guys say that the windows roll down *very* slowly when this happens, I think it's getting the power to do this directly from the DC/DC converter.

We know that the DC/DC converter is used to charge the 12v battery. If the system says, "yup, this battery is toast" while trying to charge it with the DC/DC converter, it's final acts before shut down is to set the appropriate error flag, roll down the windows, turn off the DC/DC converter and power down the car.

Pure speculation, but possible.

If you just yank the 12v battery cable off, the code that detects 12v battery failure while charging never gets a chance to run, and that part of the code is what runs down the windows. Besides, an open circuit is a lot different than a battery failing (most of the time).

 

[Avid]

That would have to be one hell of a capacitor. Maybe a flux?

Too much power, instructions say only for time travel.

 

[RayK]

Too much power, instructions say only for time travel.

So... something like this? Maxwell Technologies 16 Volt Large Modules Ultracapacitors General Purpose Modules

 

[smatthew]

So... something like this? Maxwell Technologies 16 Volt Large Modules Ultracapacitors General Purpose Modules

Oh no. $140 in quantity, and stores an impressive 2.1 watt hours! And with 24mA (at 16 volts, that's .4w) leakage current, it can only hold it's power for like 5 1/4 hours.
To put it in perspective, that battery holds about 1/250th of what the current 12v battery holds.

 

[RayK]

Well @Avid said a flux capacitor is too much power. The datasheet I'm looking at for the Maxwell BMOD0500 P016 B01 module says it's 500F at a rated 16V, a total of 18Wh; 3.2Wh/kg and it's 5.5kg so that's really 17.6Wh; they must round up. Leakage current is 5.2mA @25C. So, yes it's not the same as a regular 12V battery, but it's a little bit better than what your specs says. No price on their site.

A little bit more Googling shows this: https://www.amazon.com/Maxwell-Durablue-Capacitor-ultracapacitor-Amplifier/dp/B07T4NNWB4

Looks like a custom module built with Maxwell 3000F 2.7V Supercapacitors.

 

[Sophias_dad]

Oh no. $140 in quantity, and stores an impressive 2.1 watt hours

I think you misread the datasheet. It seems to say 3.0 wh per cell, and there are 6... so its 18 wh for the entire unit(also shown a bit later in the datasheet). Its still only a small fraction of the conventional 12V battery. Also not seeing your 24ma leakage current....

 

[smatthew]

Oops. Went to Mouser and only found 1 16 volt module. Most be a different one. But if the 2.1 watt hour model is $140 bucks......

Yeah, the model linked earlier is almost $1,400. Yowzah!

 

[Altes]

service center wich 300 miles away

Why in gods name did you buy a tesla.....

 

[yessirrom]

Mobile service comes out and replaces battery. When I leave work my windows do not roll down when opening the door. I can roll them down but when I roll them up, they bounce back down about 3-4 inches. Both front windows. When I park, I have to roll them down a little to clear the seal. Then I have to climb in from the back and roll them up. They will bounce down twice before staying up.

In addition, my steering wheel will not adjust more than an inch in any direction. Presets or manual adjust. Up, down, in or out. Mobile service is trying to diagnose remotely.

UGH

Mobile service came back out and was able to fix the windows / steering wheel issues in about 5 minutes. Just a more robust re-calibration it sound like. All good now.