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MCU/FSD Upgrade, 12V Battery Dying Repeatedly in 2017 Model X

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What a timely posting...just had my 2017 August build Model X upgrade to MCU 2 this past Tuesday...and today the car is bricked. No lights turning on when clicking the fob, door won't open.

I don't have any of those app (TeslaFi) connected to my car. Just a usb hard drive for dash cam.

I took delivery of this car September 2017 and have not received the warning of replacing the 12V battery.

Roadside assistance will be towing my car to the service center...will see what the reason is for this failure.

Hi Shaz,

If your issue is like mine, a jump of the 12V system will bring it back to life. They needed to do this in order for the car to release the lock on my wall charger. After that the car seems perfectly normal (for how long I cannot say). I was able to drive the car out of the garage, down my driveway and on to the flatbed truck with no issues.

I'll keep this thread updated with the results of my car's diagnostics. As it stands I'll be connecting with them again on Tuesday to see what they know at that time.

Good luck!
 
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Service center notified me today that my issue was due to a faulty 12v battery and they have now replaced it. It's interesting that I never got any warnings about replacing my 12v battery. I think going forward I will not rely on waiting for the 12v battery warning and be proactive by replacing my battery every 3 years. This is our only family car and can't afford to have it die on me especially on roadtrips...or at least try to prevent this as much as possible.

Will report back if this happens again with the new battery.
 
It's interesting that I never got any warnings about replacing my 12v battery.

Here's hoping it lasts beyond the month for you. Then you're probably safe.

For me, they just slapped in a new battery with zero diagnostics the first two times.

I'm a bit pessimistic because you say you didn't get the warning, that seems like the battery went pretty suddenly...
 
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Here's hoping it lasts beyond the month for you. Then you're probably safe.

For me, they just slapped in a new battery with zero diagnostics to first two times.

I'm a bit pessimistic because you say you didn't get the warning, that seems like the battery went pretty suddenly...

Yeah totally sucks what happened to you, really hope they figure it out. Keep us posted on the progress.
 
After multiple battery swaps in quick succession I'd suspect the DC-DC converter, or a related sensor or wire, is bad. Kind of like the alternator on an ICE car going out. There may be nothing charging the battery. A wiring problem could also cause a problem, though I would expect more randomness or permanent symptoms. The DC-DC converter will activate periodically as needed to charge the 12V battery. A moderately larger vampire drain should not be a problem. A partial short in the new computers might cause a drain that was unexpectedly fast, but that seems unlikely.
 
I'd suspect the DC-DC converter, or a related sensor or wire, is bad.

Hi Animorph,

The onboard charging system is definitely their focus. They say there appears to be a messaging fault which is causing the system to disengage from the 12V battery (and some other symptoms). They have been monitoring the car's network to trace the source of that fault.

Most of the time it seems things work just fine, but when they don't (the fault manifests) they don't in a reasonably big way.

At least that's how I'm understanding their approach so far.

So you've got the right system, and the cause looks like it will be more software related than physical.

Getting closer...
 
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Hi dailo,

If you're confident that your car isn't sleeping and that none of the apps you may be using are keeping it awake, I suggest you get it in to the SC and have them diagnose and repair it. The loaner cars I've had over the past month are showing me what a properly sleeping car *should* be like. It's unnecessary power consumption (range reduction) and almost certainly a symptom of something potentially more serious with your car. Definitely something to address before the warranty runs out if it's not too late.

In my case it appears the sleeplessness has an underlying cause in a fault in the on board charging system.

Service center got back to me and said that apparently it is a known issue and will be fixed in a future software update. He mentioned he did look through the logs and see the car was constantly waking up due to a known fault. Not sure if it is just canned response they have for issues like this, since it seems like others aren't having the problem. Guess I'll just have to wait for a future software update.
 
Guess I'll just have to wait for a future software update.

dailo,

If it helps, they believe some of the issues I'm dealing with are also due to a firmware bug. They didn't have a timeline for a fix as of when I spoke with them yesterday but they are supposed to pursue it and have some kind of ETA when we speak again on Tuesday.

So, if it's a canned response, then we're both getting it :)

But I'm confident it's legitimate and hopeful that the purported fix really does fully address that issue.

I will post as I learn more.
 
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dailo,

If it helps, they believe some of the issues I'm dealing with are also due to a firmware bug. They didn't have a timeline for a fix as of when I spoke with them yesterday but they are supposed to pursue it and have some kind of ETA when we speak again on Tuesday.

So, if it's a canned response, then we're both getting it :)

But I'm confident it's legitimate and hopeful that the purported fix really does fully address that issue.

I will post as I learn more.

Did you ever get a fix? Was hoping new firmware update would help but doesn't look like there is any fixes for this issue.
 
Did you ever get a fix? Was hoping new firmware update would help but doesn't look like there is any fixes for this issue.

Hi dailo,

As a matter of fact, I went to the SC this past Tuesday and spoke with the service manager along with their chief engineer and two other folks. They had worked with the California engineers and the long-awaited firmware fix was to be pushed down this week after which they wanted to monitor the car for a couple more days prior to releasing it.

They contacted me this morning and the firmware was pushed down today and they will monitor today and tomorrow and, if all remains stable, they'll drop the car off on Sunday morning. This fix should be whatever is presently being pushed out to the rest of the fleet starting today.

They appear to be confident that the 12V battery dying was caused by an interesting combination of things, foremost among these being the MCU upgrade - apparently this checked the 12V battery status in a manner that is inconsistent with the battery monitoring system that is in my car (HW 2.0). It was expecting the battery monitor system that is in the newer models. This is part of what the firmware is supposed to correct.

- There were a couple of items in the mix that I genuinely cannot repeat how they were interacting, but the long and short of it was that if my car was at the specified maximum charge level AND it was plugged in and... something else... this would generate a fault. The fault led the system to believe there was some issue with the 12V battery so the charging system would disengage. Normally the system can reset itself but the battery monitoring issue was apparently interfering with that and this led to the 12V battery NOT being recharged indefinitely until it just died. There are a couple of other things in this mix but the Firmware fix is supposed to allow the system to reset when the somewhat rare situation would present itself.

I get the sense there is still some uncertainty but they are hopeful that this is enough to resolve the issue. I get this feeling due to the provisions being made to ensure I don't get stuck again should the car brick itself again. i.e. I'm going to hang on to the loaner for a week or so until we're all satisfied the issue's been addressed.

The phantom drain issue is less certain. We disabled EVERYTHING that was talking to the car, even the Tesla App, by not only signing out of them explicitly (so they didn't give dumb readings on my smartphones) but also changing the password. Between the third party apps and my aftermarket Dashcam (DR750S-2CH) constantly pulling a bit of current they tell me it's VERY difficult to ascribe a cause. So I'm going to keep EVERYTHING disconnected and see what becomes of the phantom drain and then introduce each item one-by-one (again, I've done this before) to see when/if the drain resumes.

Frankly, I expect that if the car is finally able to sleep - and it's clear what this is like from the past 3 loaners I've had - I fully expect the phantom drain to minimize regardless of what goes on with the apps/dashcam. So I'll be looking for this first. If I find something that stops the car sleeping, I'll have my culprit. Almost certainly though, it will be a combination of things that will cause this it it happens at all..
 
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Just wanted to make note of an observation I've noticed ever since getting the MCU 2 upgrade and 12V battery getting replaced. I have noticed that vampire drain is no longer occurring for my car. I have been setting my charge limit to 80% and prior to the MCU 2 upgrade I would notice battery drain every day (maybe 2-4%...not too sure as I never really cared for the drain...never had any third party apps). But now whenever I check the Tesla App I can see the state of charge holding at 80% the whole day.

Though, I do notice that now whenever opening the Tesla app it indicates that it is "waking up". I remember prior to the upgrade there used to be a "energy saving" mode and always connected mode. Usually when those were enabled and I checked the app , I would get a similar "waking up" message. It would seem that this is now enabled by default?

Now is this all because of the upgrade to MCU 2 and 12V battery replacement? Maybe....but it could also be due to software updates as I have had a few already. Anyways just wanted to make note of it if in case anyone is experiencing the same thing.
 
Hi dailo,

As a matter of fact, I went to the SC this past Tuesday and spoke with the service manager along with their chief engineer and two other folks. They had worked with the California engineers and the long-awaited firmware fix was to be pushed down this week after which they wanted to monitor the car for a couple more days prior to releasing it.

They contacted me this morning and the firmware was pushed down today and they will monitor today and tomorrow and, if all remains stable, they'll drop the car off on Sunday morning. This fix should be whatever is presently being pushed out to the rest of the fleet starting today.

They appear to be confident that the 12V battery dying was caused by an interesting combination of things, foremost among these being the MCU upgrade - apparently this checked the 12V battery status in a manner that is inconsistent with the battery monitoring system that is in my car (HW 2.0). It was expecting the battery monitor system that is in the newer models. This is part of what the firmware is supposed to correct.

- There were a couple of items in the mix that I genuinely cannot repeat how they were interacting, but the long and short of it was that if my car was at the specified maximum charge level AND it was plugged in and... something else... this would generate a fault. The fault led the system to believe there was some issue with the 12V battery so the charging system would disengage. Normally the system can reset itself but the battery monitoring issue was apparently interfering with that and this led to the 12V battery NOT being recharged indefinitely until it just died. There are a couple of other things in this mix but the Firmware fix is supposed to allow the system to reset when the somewhat rare situation would present itself.

I get the sense there is still some uncertainty but they are hopeful that this is enough to resolve the issue. I get this feeling due to the provisions being made to ensure I don't get stuck again should the car brick itself again. i.e. I'm going to hang on to the loaner for a week or so until we're all satisfied the issue's been addressed.

The phantom drain issue is less certain. We disabled EVERYTHING that was talking to the car, even the Tesla App, by not only signing out of them explicitly (so they didn't give dumb readings on my smartphones) but also changing the password. Between the third party apps and my aftermarket Dashcam (DR750S-2CH) constantly pulling a bit of current they tell me it's VERY difficult to ascribe a cause. So I'm going to keep EVERYTHING disconnected and see what becomes of the phantom drain and then introduce each item one-by-one (again, I've done this before) to see when/if the drain resumes.

Frankly, I expect that if the car is finally able to sleep - and it's clear what this is like from the past 3 loaners I've had - I fully expect the phantom drain to minimize regardless of what goes on with the apps/dashcam. So I'll be looking for this first. If I find something that stops the car sleeping, I'll have my culprit. Almost certainly though, it will be a combination of things that will cause this it it happens at all..

Thank you for all the details! I am hoping it's a firmware update that I don't have yet, but did install one yesterday. The drain issue isn't a big deal now that I am home, but would hate to be on a trip and have it drain so much overnight.
 
Just wanted to make note of an observation I've noticed ever since getting the MCU 2 upgrade and 12V battery getting replaced. I have noticed that vampire drain is no longer occurring for my car. I have been setting my charge limit to 80% and prior to the MCU 2 upgrade I would notice battery drain every day (maybe 2-4%...not too sure as I never really cared for the drain...never had any third party apps). But now whenever I check the Tesla App I can see the state of charge holding at 80% the whole day.

Though, I do notice that now whenever opening the Tesla app it indicates that it is "waking up". I remember prior to the upgrade there used to be a "energy saving" mode and always connected mode. Usually when those were enabled and I checked the app , I would get a similar "waking up" message. It would seem that this is now enabled by default?

Now is this all because of the upgrade to MCU 2 and 12V battery replacement? Maybe....but it could also be due to software updates as I have had a few already. Anyways just wanted to make note of it if in case anyone is experiencing the same thing.
\

I too have noticed the “Waking Up” message in the Tesla App since the MCU2/HW3 upgrade I had a few months back. Prior to that, I never saw that message so you seeing the same behavior would seem to confirm it’s something with the upgrade.

That said, it’s a minor thing and I’m fine with it given all the other benefits with the upgrade. And...let me find some wood to knock on...no 12V battery issues for me yet!
 
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I too have noticed the “Waking Up” message in the Tesla App since the MCU2/HW3 upgrade I had a few months back. Prior to that, I never saw that message so you seeing the same behavior would seem to confirm it’s something with the upgrade.

That said, it’s a minor thing and I’m fine with it given all the other benefits with the upgrade. And...let me find some wood to knock on...no 12V battery issues for me yet!

Just wanted to mention that I have not yet upgraded mine (scheduling it for 2 weeks) but I've only recently been seeing the "waking up" message on my 2016 X w ap2, mcu1 which I was attributing to my mcu dying... So maybe another change Tesla made?
 
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TL;DR - Car is back, 12V battery dying issue appears resolved primarily by firmware update, Phantom drain appears much improved.

Honestly, I do have a life outside of my Tesla, but you wouldn't know it to read the following...

12V Battery issue/Fix

I'm not a mechanic or a Tesla System expert so this is how I understood the issue on consultation with the Tesla Service Center head engineer:

I've had my car back for a little over 2 weeks now.

The good news is, my 12V battery has not died yet (nor do I expect it to die prematurely again).

The car never sleeping appears to be a notable symptom/cause, but it was not the only one. As was described to me there were several links in that chain that all needed to be present to kill the battery. According to the SC the firmware fix that addresses how the new MCU checks the battery status is doing its job and the MCU is now receiving responses from the battery subsystem that make sense to it. I'm not fully clear on how the charge port no longer generates the fault that it was producing before (leading to what is described as "load shed"), I don't *think* that hardware there was replaced. I believe that some of the issue was that the involved components were unable to refresh or restart themselves which essentially ensured the 12V battery was being consumed but not charged.
Ultimately I believe that the firmware fix was the source of correcting this issue.

The jury is still out with respect to Phantom Drain

The car now appears to sleep frequently (it's supposed to)! So I'm losing maybe 1%-2% / day. For comparison purposes, the loaner Model X is losing about 7% over 11 days. My car *was* losing between 4% and 6% PER DAY.
So this is an very good improvement.

I've been closely monitoring the car's SOC without the aid of any of my beloved 3rd party apps. Basically observed the car for 3 days without ANY apps, not even Tesla's own app talking to it. 4 days after getting the car back I connected that app and saw no impact on SOC / sleeping. So a couple of days later I introduced the power adapter I use to allow my phones to fast charge while driving. Still Good.*Maybe 1%-2%/day.

A couple of days after that, I went to reconnect my dashcam (BlackVue DR750S-2CH) - it is always on so I was anxious to see the impact. Unfortunately Tesla has disconnected the power source so I will need to dig in to that later. I don’t blame them as I don’t hold them responsible for drain or impacts imposed by 3rd party hardware.

So, instead I reconnected TeslaFi, easily my favorite statistics collector and car monitoring software. This yielded some interesting results.
If you're familiar with TeslaFi you know that it tries to be careful to let your car go to sleep. With the tremendous variation across the Tesla Fleet's models, software and components there is no one-size-fits-all in terms of configuring what will permit the car to yield the greatest data while not impacting sleeping (and ultimately phantom drain). I now have a hybrid car in that It's no longer pure AP 2.0 since the MCU2 and FSD upgrade.
Tweaking TeslaFi's polling (and ignoring the fact that, for me, TeslaFi reports that during Deep Sleep mode (no polling) my car is Idling, not sleeping), I found that during non-deep sleep times, my car could range from alternating 6 minutes sleeping and 51 minutes idling to my best result of 11 minutes sleeping and 36 minutes idling. It would just cycle over and over again.
I pinged James of TeslaFi a couple of days ago to see if those results jive with what he sees generally for my class of car but have not heard back yet.
I also pinged Tesla and they *did* get back to me and said that my car would be expected to be more prone to sleeping/waking due to the 12V battery checking being done between the new MCU and the older Battery monitoring subsystem.

The one thing I can say with confidence is that my car now was ticking down by a solid 2% / day on days that it wasn't used.
Since I obviously can't say what my car is doing in such detail without having the TeslaFi app monitoring and giving me such detailed information I really can't draw any conclusions as to whether or not it has any impact on my phantom drain but my gut is telling me it's having a small effect.

A couple of days ago I again disabled TeslaFi (deleted token, Changed Tesla password) to get back to a baseline (which crudely appears to be closer to a little over 1%/day).

Yesterday I enabled Sentry Mode and excluded home (where the car is currently located) and was pretty surprised to see the car had lost 4% charge in 24 hours. I knew to expect *some* impact by enabling Sentry mode but I'm suspecting it interferes with sleeping even when its not actively sensing - need to do more with this. I've disabled it in horror now and will re-enable when I'm confident in a monitoring app for objective measures. Although there is no doubting that the impact was noticeable.

I'm actually going to enable the Stats App on its own now and see how it reports phantom drain. It doesn't have the detail of TeslaFi for car state, but it has some very useful things to say about battery use.
 
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Hi @EagleOne ,

You might want to check this one out:

Since my MC2/HW3 upgrade, the car will not sleep when plugged in

I have had similar wacky sleep to you: 36 minutes awake and 12 minutes asleep...
I have also contacted James at TeslaFi.

@BlueBird is on to something - That the cars (including mine Original MCU2 upgraded to HW3)
Sleep great when fully (80% for me) charged and unplugged.
But when charged to 80% (or your favorite charge number) and left plugged in, they alternate
with the 36 minutes idling and 10 minutes of sleep or 12 minutes idling and 10 minutes sleep
all night long...

The fortunate circumstance for us is we are not yet exhausting our 12 volt battery to replacement...

Weird,

Shawn
 
Hi @EagleOne ,

You might want to check this one out:

Since my MC2/HW3 upgrade, the car will not sleep when plugged in

I have had similar wacky sleep to you: 36 minutes awake and 12 minutes asleep...
I have also contacted James at TeslaFi.

Thank you Shawn,

I did a bunch of testing with the "Polling Delay After Waking Up" setting and it got me most of the way to where I want to be.
At least I can now use TeslaFi with confidence again. I was *this* close to just discarding the app since it was clear it was impactful on my car's sleeping prior to James making that option available.

Feeling a bit bummed that I had TeslaFi disabled while I did a recent Blue Ridge Parkway trip but.. I was at least confident that I wasn't losing power right, left and center so... I guess the trade-off was worth it..
 
Overall, to round out this posting:

1) 12V battery issue is resolved
2) Phantom Drain issue is manageable - it's worst when plugged in but then.. it's plugged in so the car tops off during scheduled charging each night when plugged in.
3) TeslaFi is still my favorite app and my confidence in it has been restored since it now seems to deal with the new MCU2/AP2.0/HW3 hybrid configuration properly
4) Still need to wait for Tesla Firmware upgrade to address the sleep/idle cycling when plugged in.
5) Sentry Mode is not at all worth the phantom drain for the primary use I would have for it which is longer term parking.
6) My "holiday party" is working after all these trips to the SC. They finally figured out what ultrasonic sensor's & mounts needed to be fixed. It's not a critical thing but.. It's fun to show people and disappointing when it just stops 1/4 of the way through.
 
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