Taycan 12V drain issues - caught in the act?

[daveo4EV]

I caught the Taycan the other day I think on it's way to dying while plugged into my Tesla chargers - I've shared extensive data with Porsche via my local service advisor - what I saw was the main charging user interface on the lower center console "looping" - it would start a 48 amp charging session - stop 30 second later, literally sit & spin for a while - then start a session again - stop, sit & spin - start, stop, spin- the whole time the 12V data on the dash was bouncing between 12.9V and 14.7 volts on the dash…

the only fix eventually was I unplugged the charging cord & TeslaTap - and reset the Tesla chargers by throwing the breaker - then I plugged in again - and all was well and a normal/happy 48 amp charging session ensued - and I finished at 93% SOC and drove home....

I'm convinced but can not prove my car was on it's way to dying - and I interceded and captured some data that may or may not help porsche identify bugs in their charging software that may lead to the vehicle spinning itself to death…

I've shared a detailed write up and additional data with Porsche - I do not expect to hear back from them - but one can hope…

Scenario Description

• Drove the vehicle 45 miles from point a to point b - started at 85% SOC - previous charge session via 40 amp PMCC - no issues
• Parked at my point b home
• point B home has a 3 chargers shared load Tesla Generation 2 wall chargers - 1 master, 2 slaves configured to share a 100 amp circuit
• Tesla wall chargers had been on for several weeks and have experienced light charging loads over the past several weeks - we are moving out of this home so charging is not happening that often any more, and typically only one vehicle at a time
• I attached a Tesla Tap to the Tesla Wall charger connector and plugged into the Taycan
• After about 30 seconds the Taycan acknowledged the charging cord/plug and began charging - I verified the charge rate was 48 amps (10.46 kW shown on the charging UI in the Taycan lower center console) - and I walked away
  • At the time the Taycan was the only vehicle plugged in or charging to the 3 charger shared load configuration
• I walked away from the vehicle and proceeded about my business
• 10 to 15 min later (I don’t know I wasn’t paying attention) I walked into the garage - and noted the Tesla charger had “stopped” the green lights were not animating
  • Warning bells went off - this was the exact scenario where the car will die - short charging session truncated and then dead 12V sometime later
• I immediately unlocked the vehicle with he key fob - entered the vehicle and pressed the power-on button on the left
  • The vehicle was indeed _NOT_ charging
  • And the main dash I have the 12V battery voltage status “on screen” - it indicated the 12V status was 12.9V - this is significant because it’s normally 13.3-13.5 volts - this is significantly lower than normal usage
• I immediately began capturing data of what the main charging software was doing - and what I saw was one very confused Taycan - it would loop start charging for like 15 seconds then quit and do it all over again - I left the car plugged in the entire time and did not unplug the charger cord
  • During the data capture I observed the 12V fluctuate between 12.9V and 14.6V - and the car was never able to stop trying to charge or successful maintain a charge.
  • data shows the continuous looping of the Taycan charging software and start/stop nature of the charging session and at various points in time I record the the 12V dash read out which clearly shows loads/charging going on with the 12V battery - the car was definitely in a “bad” funk and spinning out of control
• At some point in time I got a Porsche Connect app “charging error” message and the screen “went” red charging status - you might be able to pull porsche connect logs for my Taycan to corellate - the date was [blah]
  • Charging session started x:53 PM PST
  • I noted the charging fault at x+1:07 PM PST
  • I’m not certain when between x:53 pm and x+1:07 pm the vehicle stopped charging…
• I eventually logging the data
• Unplugged the Charger from the vehicle
• I threw the 100 amp breaker on the Tesla Chargers to “reset” them
• Restored “power” to the Tesla chargers
• Plugged back into the Taycan and it started a successful 10.46 kW (48 amp charging session) - I reached 93% SOC before unplugging and driving home.
• I’m fairly convinced I dodged a 12V battery death here - as the car was clearly confused by the state of an external charger - and it was in a bad bad bad software loop…

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[daveo4EV]

my experience with this issue convinces me this clearly just a random "funk" the charging software can get into - it seem to be cause by external factors with the charging EVSE hardware that can potentially confuse the Taycan's charging software - there is no "ACT" you can take as the driver/owner to cause or not-cause this situation - rather it's a combination of factors that can lead to the Taycan software looping continuously but making no progress on starting or giving up on a charging session…

there is nothing you can do to "cause" this problem
there is nothing you can do to avoid this problem

it will simply either occur or not occur - and clear appears to be a state where the taycan charging management software can get into a state where it will loop continuously - now clearly the Tesla chargers were in some soft of state where the Taycan didn't like them - but it didn't protect itself and just give up attempting to use them - rather it just looped for ever which I believe would've eventually lead to the 12V battery being drained and cut off…

a classic software bug and faulty error handling leading a looping condition which in this case drains a 12V battery powering the computer doing the looping - it might also be so focused on trying to start/stop the charging sessions that other parts of the system that would recover the 12V battery never given time to run because we're in a tight loop constantly starting and stopping the charging session.

but all this is pure speculation on my part.

 

[daveo4EV]

there also was _NO_ Porsche Connect activity prior to the charging sessions for at least several weeks - although during the "event" I eventually got a push notification reporting a charging error - but I did not initiate any control/changes to timers/profiles or charging via the iOS app...

this furthers my opinion that the porsche connect app usage is coincidental to the 12V battery drain problem and may not help - but that app's usage alone is insufficient to cause or prevent these issues.

 

[H@wk]

Thank you for your thorough writeup @daveo4EV. As a senior software engineer with over 30 years in the business, I’m inclined to agree with you here, - this sounds like a rather mundane fault in the programming logic. And that worries me. That this has been and still is a bug a year and a half since @louv and others took ownership of their “release version” Taycans, with all the reports Porsche _must_ have received by now....

I’ve had the 12v drain happen 3 times in the last 3 months now, on the same charger that I use almost daily (one of the most popular ones over here used by all kinds of EV owners), with no upgrade of the charger nor car (granted; the dealer ”ran the October update again“ on my car 2 weeks ago - but that was already on there anyways).

These days, I pop the frunk, plug in the charger, keep my booster topped up, and use the PCM app whenever I feel like it - just in order to see what conditions may provoke the issue.

Hopefully by summer, when this awful virus thing is beaten and one can have a “normal” vacation by car again this issue will be resolved. But truthfully, I’m not holding my breath....

 

[feye]

I use the Porsche charger and haven't had the issue. Is it charger related?

 

[bootsie]

I use the Porsche charger and haven't had the issue. Is it charger related?

I was just wondering the same thing. There’s all sorts of handshaking going on between the charger and the car when it’s plugged in, right? It’s not just a 2-wire AC connection to the power?
Who’s to say what’s going on between the two, but I bet Porsche hasn’t testing charging with non-Porsche AC chargers anywhere near as much as they have with their own.

 

[feye]

I was just wondering the same thing. There’s all sorts of handshaking going on between the charger and the car when it’s plugged in, right?

Certainly not. The Porsche Charger should be able to recognize the car and charge it automatically even when the charger has a pass code set. Plug & Charge at home, so to speak.

 

[Taycanturbolondon]

Certainly not. The Porsche Charger should be able to recognize the car and charge it automatically even when the charger has a pass code set. Plug & Charge at home, so to speak.

My Porsche charger keeps asking me to type the pin every single time I connect the car.....my charger is in a shared underground car park hence the need for a pin

 

[feye]

My Porsche charger keeps asking me to type the pin every single time I connect the car.....my charger is in a shared underground car park hence the need for a pin

Yes, mine too, but the charger should be able to recognize the car to offer plug & charge. Next time I charge, I try to get this going.

 

[bootsie]

Certainly not. The Porsche Charger should be able to recognize the car and charge it automatically even when the charger has a pass code set. Plug & Charge at home, so to speak.

Exactly my point, though maybe I didn't word it well.
There's more going on between the charger and than car than just a supply of power from an AC socket though, right? There's communication between the charger and the car, some logic at both ends negotiating how the charge is going to happen, I guess?

 

[Iben]

I`m experiencing the same (i need the pin for safety in shared garage).
I thought the car was able to sense the Porsche connect charger, making the charger only work on my car without the pin.

Maybe we need the new update (late feb.)?

 

[feye]

Exactly my point, though maybe I didn't word it well.
There's more going on between the charger and than car than just a supply of power from an AC socket though, right? There's communication between the charger and the car, some logic at both ends negotiating how the charge is going to happen, I guess?

I am sorry, I cut too much in your post. I was referring to:

It’s not just a 2-wire AC connection to the power?

 

[feye]

I wonder if that helps?

 

[Iben]

I'm going to try.
Thank you

 

[daveo4EV]

I think people have had the vehicle die with the PMCC connected, but i could be wrong

I however have always speculated that there is some “out of band” communication that porsche attempts with their own chargers - and when talking to a charger that isn’t one of their own their software might be confused and cause the 12V drain issue…

the simple fact is Porsche must fix this (if it is in fact a contributing factor to the 12V issue) - the Taycan will not always be charged “at home” and it could encounter this problem at any number of public J-1772 chargers across north america - assuming the vehicle will only ever speak to a Porsche AC charger is not a valid assumption and one I hope Porsche is not making…

no response from Porsche as this time as to my “findings” - but sent the eMail late in the day yestereday - and I really do not expect much other than possibily a “thank you for your feedback we are of course working to resolve this issue but have nothing to report at this time”.

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