NC_Taycan

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Clearly the problem is related to some kind of phantom drain on the 12v battery. But another issue is that it clearly doesn't keep the 12v battery charged using the car's main battery bank, which is baffling. You've got a bazillion kwh battery sitting there, and it may even be connected to AC power. Yet the 12v battery dies. Perhaps it only charges the 12v battery when the car is being driven, like an ICE car? Very odd.
What I've managed to gather - the 12V system will wake up the DC-DC converter and 800V battery to re-charge the 12V when it gets low. If this happens while charging, you will see charging pause while the 12V is being recharged. However after some limit is reached on the number of times this is done in some time period (don't know what those magic numbers might be) the wake-up to re-charge stops. I won't pretend I have any idea why it's designed this way. If 12V drain continues from that point, the 12V battery will eventually reach a low enough state of charge that it is disconnected from the vehicle (latched off) and the car is now completely dead. Once it gets to that state, you are "jump-starting" the 12V system. But yes there's 12V drain. Call it phantom, but it's coming from the charging hardware (in the car) and PCM both being active, and possibly the OTA communication module being active. These things can all be controlled by software, so it should be able to be fixed entirely in software. The charging hardware in the car is remaining on because there is some strange state where the external charger is waking up the in-vehicle charging hardware but not charging (e.g. because charging is paused, or because charging has finished but the handshake to shut down the external charger wasn't received or interpreted properly). This can happen with the Porsche charger (it happened to me) and it can happen with non-Porsche chargers. Only take-aways are to completely avoid using the Connect app once the car is connected to the charger until you are near ready to drive. Locking the car while charging may help. Keeping the key out of range of the car while charging may help. I don't think we have a report of 12V dying while the car is NOT hooked up to a charger.
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daveo4EV

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hmmm…so these drop outs are the charging being paused for the 800V to step in and charge the 12V?

that’s very very very interesting…looks like my Taycan dodged a bullet on Nov. 10th- 12V almost died 4 times?

Porsche Taycan Don Breaks His Taycan - The Saga of the 12v Battery A78B841D-8448-4D12-8930-A4FAF9FF6602
 

Dave T

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I won't pretend I have any idea why it's designed this way.
This is the million dollar question. Nice description! Where did you learn the part about the car stopping the 12v battery recharge after some mysterious number of tries? I hadn't heard that one before.
 

NC_Taycan

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This is the million dollar question. Nice description! Where did you learn the part about the car stopping the 12v battery recharge after some mysterious number of tries? I hadn't heard that one before.
What I *think* I know is from multiple sources - I've forgotten what came from whom at this point. I am not in any way affiliated with Porsche - just an owner like the rest of us. I am an engineer and work in tech/cloud so have some understanding of how things have to be done to work a certain way.

hmmm…so these drop outs are the charging being paused for the 800V to step in and charge the 12V?

that’s very very very interesting…looks like my Taycan dodged a bullet on Nov. 10th- 12V almost died 4 times?

A78B841D-8448-4D12-8930-A4FAF9FF6602.jpeg
I wouldn't characterize this graph as having almost died four times. More like it worked as designed. I didn't mean to imply "low" meant "almost dead" - just "time to recharge". I think you would have to see more frequent charging pauses. Keep in mind though I have no idea how many times or the time interval after which it gives up.
 

Vim Schrotnock

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OK, I have the answer (for now anyways...).

Evidently there is a setting in the Porsche Mobile Charger for a 'home energy manager', which I do not have. When this setting is active, the charger communicates every 4 minutes with the car, and that is evidently the cause of the 12V battery drain. This is not a setting that the user can adjust, it must be done by the dealer. They turned off this setting, and said this would resolve the problem.

I got this information directly from my service technician who was in contact with Porsche NA. He spoke to someone yesterday morning, and they could not tell him what the issue was. The same person got back to him yesterday afternoon and told him that this was the issue, and they had just discovered it.

I'm not sure how this will impact anyone else that has the Porsche Mobile Charger, but for sure if you have it, I would check with your service tech that the setting is off. I'm not familiar with the 'home energy manager', and the service tech doesn't even know if it's something that is available in the US.
 


daveo4EV

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hmmm - well then there are multiple causes - cause my 12V battery “death” was while I was plugged into my Tesla Gen2 charger…

and yeah - as notes - a 12V battery drain problem caused by porsche’s back channel communication with the PMCC…

I’ll be very excited to hear more about this - but I’m dubious.
 

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hmmm - well then there are multiple causes - cause my 12V battery “death” was while I was plugged into my Tesla Gen2 charger…

and yeah - as notes - a 12V battery drain problem caused by porsche’s back channel communication with the PMCC…

I’ll be very excited to hear more about this - but I’m dubious.
Could it be so that the car ses a charger that is connected but does not find the Home Energy Manager in both cases. The PMCC did not have it connected and the Tesla charger obviously not either. Is the car continuously trying to communicate?
Sounds very peculiar reason but would mean this problem would occur at any AC charging station??
 

daveo4EV

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I would not be surprised if the vehicle has a software problem where it can get confused if it’s not talking to a Porsche charger Energy Manager
hmmmmm…
 


drjhyatt

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OK, I have the answer (for now anyways...).

Evidently there is a setting in the Porsche Mobile Charger for a 'home energy manager', which I do not have. When this setting is active, the charger communicates every 4 minutes with the car, and that is evidently the cause of the 12V battery drain. This is not a setting that the user can adjust, it must be done by the dealer. They turned off this setting, and said this would resolve the problem.

I got this information directly from my service technician who was in contact with Porsche NA. He spoke to someone yesterday morning, and they could not tell him what the issue was. The same person got back to him yesterday afternoon and told him that this was the issue, and they had just discovered it.

I'm not sure how this will impact anyone else that has the Porsche Mobile Charger, but for sure if you have it, I would check with your service tech that the setting is off. I'm not familiar with the 'home energy manager', and the service tech doesn't even know if it's something that is available in the US.
Are you saying I have to take my mobile charger to the dealer for them to turn off the home energy manager?
 

Vim Schrotnock

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Are you saying I have to take my mobile charger to the dealer for them to turn off the home energy manager?
I believe so.

I did a bit of research, and the 'Porsche Home Energy Manager' is not available in the US:

https://www.porsche.com/international/_iceland_/aboutporsche/e-performance/home-charging/

For some reason, my Porsche Mobile Connect (PMC) was set by the factory to 'look' for the Home Energy Manager (HEM) every 4 minutes. There was no HEM, so they corrected the problem by turning off that part of the PMC. This is nuts of course, since first of all, they should have turned it off to begin with if that is what caused the problem. Second is there should be a pretty simple solution that allows the PMC to be configured to interface with or without a HEM and not drain the battery.

Bottom line is that I would recommend anyone with a PMC to have their dealer check that it is not setup to 'look' for a HEM if you are in the US. This is not a very good reflection on Porsche and their ability to validate and control their software.
 

daveo4EV

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hmmm - I'm wondering why only the dealer can modify the PMCC - I see the energy manager controls on my PMCC - and mine has nothing listed…

I'm very interested in more details.
 

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Ok, thanks to everyone for the help to raise my 4S from the dead. My dealer was of no help at all. They sent a tow who had no idea and after he left --nothing no followup or help. Their service department closed on weekend, thanks a lot. Ordered a charger online but was going to take a week to get it. Went to NAPA auto parts and got a Pro-Logix 6/12 v 4.0 amp charger maintainer (lithium compatible).

Hooked it up and got and error light after a few seconds charging. After a few try's, was able to open frunk with key fob before flashed to error. Then used my wife's Cayenne to jump start the battery.

Got a message the 12 v was low to plug in immediately. I had unplugged from source electric the PMobile Charger. After the PMC rebooted, light was red (once it was jumped) then was able to unplug which then became green when I replugged. Charged for less than for 3 min but was running late for my golf game. Pulled the charger and away I went. All seems ok after the 20 min drive to and from.

I did notice during the initial drive the 12 v reading on the dash was 14.1-14.5 v. After sitting in the parking lot for 4 hours the reading back to a more usual 13.4 v.

Before this entire episode the only thing I had changed the night before was check the direct charge box under charge. Also, I stopped looking at the P connect app for fear it was potentially the leak for the battery issue that I had never before experienced. Probably will take to the dealer next week......
 

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I'm curious if ANYBODY has had this problem who is simply plugging their car in and using the default charging profile.

IOW: Has anyone who is NOT using any of the software "magic" had this issue?

I'm not using any software, any added profiles, any timers, any magic at all. I expect I'm in the minority here, but I've not had any issues (knock on wood). There was speculation early on that this problem was specifically related to manipulating the charging profile while the car was charging (Remotely or via a Scheduled Timer).
I’ve had my 4S since July. Never used a profile or timer also. I know it’s not conclusive, but also have not had the problem.

I’ve never used the Porsche charger, only a Zappi2.
 
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evanevery

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I’ve had my 4S since July. Never used a profile or timer also. I know it’s not conclusive, but also have not had the problem.
Extended speculation is/was that the issue is software related and occurs when modifying charging parameters while the car is actually charging (via remote access or timer manipulation).

Just curious if ANYONE who charges as we do (no timers, profiles, or remote access) has had a dead 12v battery...
 

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You know your Taycan has a 12v battery, right? Do you know where it is? Do you what to do if it goes completely dead?

UPDATE July 30, 2020: tl;dr? Jump to Reply #297 for the Fixes to this problem.



I do. Now. I didn’t pay much attention to it until yesterday morning. I mean, I knew it was there... somewhere. Probably.

Go grab a cup of coffee... aw, hell, you are probably stuck at home, Sheltered in Place, so go grab a beer... and come along for a new (but hopefully NOT epic) adventure.

Two days ago I finally had a crew out to the house to install a new Charging Station in my driveway. I started that process last November, but by the time the electricians could schedule it, the ground had frozen (remember: Maine) and the couldn't trench my driveway. "We'll come do it after the spring thaw." Well, now I have a ChargePoint Flex, capable of charging at 50A (the Taycan can only handle 40A, or 9.6kW), I fired it up, connected it to my WiFi, name it, set it to know that it was connected to a 50A breaker, and therefore limit itself to 40A.

I connected up to the car, and set up my Profiles and Timers. My location-aware Profile creatively named "Home" was set to have a minimum charge of 50%, and preferred charging times of 10PM to 5AM. I set up a Timer, Target charge of 90%, 7 days a week, departure time of 3AM, no climate control. All went as expected. The car was at 40% when first plugged in at 4PM. It immediately charged it self to 50%, then stopped charging, as expected. Then at 10PM it started charging... slowed down a couple hours later, and then picked up again and finished charging at 3AM at the requested 90%. Odd that it charged and stopped and charged again... but whatever, the end result was As Requested.

That's the setup. Most of that is PROBABLY all coincidental to what comes next. I am not implying any connection, just setting the stage.

The next morning, yesterday, I wake up and check the iPhone app at about 7:30am: the car is nicely charged as requested.

At 9:51am, my phone rings from an unknown number. I answer, and it's the Porsche Connect Security Team. "There's a problem with your car." "What's the problem?" "First you need to answer your two security questions..." <redacted> "<laughter> Yup, that's right. OK, either your car was broken into or there a problem with the battery." "Uh... those are really different things. OK, I'm out at the car now. No problems. No windows broken, no damage." "OK, well, have a good day, Call us back if you have any questions."

At this point I notice the car hasn't automatically unlocked. Odd. I grab the remote from my pocket and press the unlock button. No joy. I think maybe it's the remote. I read in the "Good To Know" Manual, to place the key near the upper right corner of the rear window and press unlock. Nope. Nothing.

I look at the Porsche Connect App now... It looks like this:

52BFD3FE-984B-4C5E-A0EA-B1E12E48EA74.png


OK, let's try the Emergency key.
1) Pull it out of the remote.
2) Lift the driver's door handle, look underneath
3) Insert key, and turn.
Door unlocks and opens.

Car is still dead. No dash lights. Nothing. Press Start button. Nothing.

OK. This is all I know how to do. Time to call Roadside Assistance. And get my car towed.

Before the car can be towed, I have to unplug from my Charging Station. Hmmm. The car is locked. The car won't let go of the charger plug. There *must* be an emergency release somewhere. Back to the "Good To Know" app, to read the manual.

To Remove the Charging Stations' plug from the car:
1) Open the front door, on the side where you are plugged in.
2) Look for a round button at the top of the front body panel.
3) Pull on that knob, which is connected to a cord, which will release the lock on the charging station plug.

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Tow truck arrives 20 minutes later. But, since the car is completely powerless, it can't be put into neutral. And he says, "I don't have dollies in this truck, and there's no way I'm going to drag that beautiful car up onto the truck." So, he goes away.

I call my local dealership's service department. They send out their head technician to my house.

Since the Tech is coming from his house, where he'd been sheltering in place, he had to go to the shop, get some tools, and then drive to my house, I know I have some time. So I read further into "Good To Know".

I discover instructions for applying power to the 12v system, so that the Frunk can be opened (and then the 12v Battery can be accessed directly). I go in the house, grab a spare 12v battery, and some charger clips and go back outside.

To Apply 12v Power to the car, when the car's 12v Battery is dead:
1) Open the fuse panel (to the left of the driver's side footwell)
2) Find the Red 12v Positive Terminal, and pull it out about 1/2 inch.
3) From your spare 12v Battery, Attach 12v Positive to that terminal.
4) From your spare 12v battery, attach negative to the hinge of the car. (bare metal)

At this point, I hear relays switching on and off... kinda like it was trying to connect, something was failing, and then it would try again. After 10 seconds of that, I disconnected. Never mind. I don't know what's really wrong, so I'm just going to stop.

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Soon after, the technician arrives.

He connects a bigger batter to the same places. And tries to turn on the car. No joy. We wait a few minutes. Still nothing.

6C9CA70C-D0F5-452F-8C3B-F3E5A3E074DD.jpeg


Then he says he needs their Lithium Ion Battery Charger. So a quick, 10 minute run back to the shop, he grabs the big charger. Meanwhile, I run a 100 foot extension cord so he can plug in the charger.

When he returns, and attaches the big charger, the car wakes up enough that we can pop the hood. Now we have access to the actual 12v Lithium battery, so the charger can do a better (read: faster) jobber-charging the 12v Battery.

4BB6ABE6-AD00-41CC-8339-17B331DA347D.jpeg
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After charging for about 5 minutes, the valiant Technician attached their diagnostic computer to the ODB-II connector, and collects some diagnostic data from the car.

We let it charge, and download data for another 10 minutes or so, and now everything seems fine.

We remove the brick from under the front wheel. (in case we needed to put it in neutral... I didn't want the car rolling downhill into the street). And he drives the car back to the Dealership, leaving me with a nice silver Cayenne loaner.

Later that day they asked for more details on the charging sessions, to try and analyze what happened when. I was able to send charge session logs from ChargePoint, and via security camera footage, identify exactly when the battery went dead. (the charge port blinking light turned red, and the went out)

That's where this chapter ends.
Stay tuned for more adventures in "Don Breaks His Taycan" (again).

A7CAC624-235C-4054-94E5-A96244FE493F.jpeg
Thanks so much for your so helpful post. I was able to use your directions to talk the Porsche Roadside service person and get my dead Turbo S running and out of the garage to the flatbed. Would have been quite a challenge otherwise.
Now, after getting the car to Porsche of Beverly Hills service, they still don’t know what’s wrong. It appeared to be the 12volt, but then maybe the main electric battery...
Thanks again.
 
 




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