So, about that long-awaited "12v battery low" software fix...

[Sonic]

About 5 years ago I bought my lovely brand new 2012 Porsche Taycan Turbo S.

Fully electric, completely new platform, basically shipped straight to production to be “tested in the wild”. Fine, i accepted that. It’s a brilliant car… but it had one absolutely ridiculous flaw that has continually made it borderline unreliable when not used frequently.

The car sits at home plugged into the mains electric supply, with a 93kWh 800v battery that could run a big house for days, plus a smaller 12v battery that powers the electronics. In theory, the big battery keeps the small one topped up.

In reality, there’s clearly a bug. Every few weeks, if the car isn’t used, the 12v battery just dies. Completely flat, without notice.

Result:
• Alarm goes off waking neighbours up
• Tracker company calls you and wakes you off
• Car is totally dead - it won’t unlock, handles won’t present, alarm wont go off, nothing

At this point you get to enjoy the “premium Porsche experience”:

You remove the physical key from the fob, fight to pull out the recessed door handle just enough to get the tiny key in, then try to turn the tiny key in the stiff lock to manually unlock the door, disable the alarm, and then climb into a completely dead car with no power.

So now you either call recovery… or follow the well documented official unofficial workaround:

• Remove interior trim in the driver footwell
• Expose a fuse panel
• Pull a specific +ve fuse out
• Attach an external battery to it
• Run a cable to the nearest earth point (the door latch, the battery cables wont reach, naturally…)
• Which gives just enough power to pop the frunk

Then:

• Open the frunk
• Remove more trim
• Access the actual 12v battery
• Jump it with the same battery pack

That finally wakes the car up so it can realise its own battery is dead… and recharge itself from the massive 800v battery it’s been sitting on the whole time.

So naturally, I now carry a battery pack and an electrical extension cable in the passenger footwell at all times. Not the boot. Not the frunk. Inside the cabin. Because reasons.

All of this is just about tolerable… until it’s 4am in an airport car park after a long flight and you physically can’t even open the door wide enough to start dismantling the interior.

Anyway, after 5 years of extensive research, Porsche have finally released their long-awaited over-the-air software update to fix this, which as a vaguely competent engineer, I assumed would be a simple logic update: “If 12v battery low -> charge up from big battery”.

No.

The fix is: The app now sends you a notification saying the battery is low… and you need to go and turn the car on and off again so it can charge itself.

I wish I was joking.

The car knows the battery is low.
It tells you the battery is low.
It could fix the battery being low.
But instead, it asks you to come outside and reboot it.

Turns out the answer, even in a £100k+ electric Porsche, after years of research, is still: “have you tried turning it off and on again?”

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[Taycan4S_UK]

the max I've left it has been two weeks and not seen any issues. Many have said that it could be 12v battery issue.

 

[eddieterry]

I had this problem for a number of years but the 12 Volt problem was fixed recently with the 12 Volt switch firmware update. This has totally sorted it out for me - have you had that completed for your car Sonic ? If not then contact Porsche to get it done. They also fixed a phantom drain on mine. Taken them three years but finally no longer need my CTEC !

 

[Sonic]

the max I've left it has been two weeks and not seen any issues. Many have said that it could be 12v battery issue.

Yeah it's usually around 3-4 weeks of no-use to be fair - but even so... i have loads of vehicles that aren't a problem being left alone for a good few months.

I know the Taycan does a lot with updates, sensors, communication with servers, the app, remote monitoring, alarms, tracking etc... but even so it's bloody annoying to have it sat there plugged in, fully charged, with a flat battery.

It goes back to the dealer regularly, they've checked it a few times and said no issue... but maybe you're right and the battery has an underlying issue.

 

[Sonic]

I had this problem for a number of years but the 12 Volt problem was fixed recently with the 12 Volt switch firmware update. This has totally sorted it out for me - have you had that completed for your car Sonic ? If not then contact Porsche to get it done. They also fixed a phantom drain on mine. Taken them three years but finally no longer need my CTEC !

Yeah it was in barely 2 weeks ago for that (and wheel swap) - which is why i was so surprised to see the new notification after parking it up and not having moved it since, but having fully charged it up and left it plugged in.

I think i might need to get another ctek as it's not getting much use!

 

[eddieterry]

It might be worth getting Porsche to do a two day monitor of the 12 Volt to see if you have any phantom drain when the car is switched off over a period of two days. They did this on mine and had to raise a ticket with Porsche technical to solve the higher than should be drain I had (although the big battery should take care of that anyway).

 

[Sonic]

It might be worth getting Porsche to do a two day monitor of the 12 Volt to see if you have any phantom drain when the car is switched off over a period of two days. They did this on mine and had to raise a ticket with Porsche technical to solve the higher than should be drain I had (although the big battery should take care of that anyway).

Great idea thanks - they usually have the car for a couple of days a few times a year for various recall / warranty work, so i'll let them know then

 

[Tooney]

It might be worth getting Porsche to do a two day monitor of the 12 Volt to see if you have any phantom drain when the car is switched off over a period of two days. They did this on mine and had to raise a ticket with Porsche technical to solve the higher than should be drain I had (although the big battery should take care of that anyway).

Did the higher than normal battery drain get resolved? If so, what was done to fix it?

 

[chun]

Turns out the answer, even in a £100k+ electric Porsche, after years of research, is still: “have you tried turning it off and on again?”

What if you park underground with no signal? That would be the worst solution, but I think that is not the actual solution. Preaty sure that notification is supposed to come up only if the SoC of the car is below 25% and the 12v battery loses power. So I have a feeling it’s a bug with the app

From my own experience, while traveling for a few months, the way I’ve been told by dealers to avoid 12v drain is:
- plug it into charger with a 60% limit, and make sure the timer has the preconditioning option on - because the preconditioning turns on the car and the HV electrical, which in turn charges the 12V.

Has always worked for me.

And I think around 2024 maybe, or early 2025(?), they configured an internal timer that starts the HV battery up as long as it’s above 25% every few days, which charges the 12V.

I also know from the guys working on the app in Cluj that the biggest 12V drain was the communication module / app. Every refresh in the app would trigger a check on the server side that would send a request to the car for its status, which would of course use power from the 12v - pair it with constant app checking, and you got a dead 12v. - they just addressed this in 2026/ late 2025, where the app no longer triggers a request to the car with each refresh, in turn it only brings the latest data from the server, and the server only pings the car when you refresh at quite a few minutes apart from one another.

 

[gnr3312]

About 5 years ago I bought my lovely brand new 2012 Porsche Taycan Turbo S.

 

[Sonic]

Back when money was cheap in UK

 

[eddieterry]

Did the higher than normal battery drain get resolved? If so, what was done to fix it?

Yes - Not sure exactly how but something to do with software / firmware. Eventually Porsche technical told them what to re-update which solved the problem.

 

[tycanmt]

Interesting to see many comments on this thread along the lines of "12V battery problem, what 12V battery problem -- you're doing something wrong". This syndrome is extremely well documented and there is a fix to the 12V battery firmware (WSS6), and apparently now a "workaround" that the app notifies the owner. So it does exist and you all can stop posting that it doesn't. Unfortunately my vehicle drops all contact with the app service after a day or two of not being driven.

 

[AutoX]

About 5 years ago I bought my lovely brand new 2012 Porsche Taycan Turbo S.

Fully electric, completely new platform, basically shipped straight to production to be “tested in the wild”. Fine, i accepted that. It’s a brilliant car… but it had one absolutely ridiculous flaw that has continually made it borderline unreliable when not used frequently.

The car sits at home plugged into the mains electric supply, with a 93kWh 800v battery that could run a big house for days, plus a smaller 12v battery that powers the electronics. In theory, the big battery keeps the small one topped up.

In reality, there’s clearly a bug. Every few weeks, if the car isn’t used, the 12v battery just dies. Completely flat, without notice.

Result:
• Alarm goes off waking neighbours up
• Tracker company calls you and wakes you off
• Car is totally dead - it won’t unlock, handles won’t present, alarm wont go off, nothing

At this point you get to enjoy the “premium Porsche experience”:

You remove the physical key from the fob, fight to pull out the recessed door handle just enough to get the tiny key in, then try to turn the tiny key in the stiff lock to manually unlock the door, disable the alarm, and then climb into a completely dead car with no power.

So now you either call recovery… or follow the well documented official unofficial workaround:

• Remove interior trim in the driver footwell
• Expose a fuse panel
• Pull a specific +ve fuse out
• Attach an external battery to it
• Run a cable to the nearest earth point (the door latch, the battery cables wont reach, naturally…)
• Which gives just enough power to pop the frunk

Then:

• Open the frunk
• Remove more trim
• Access the actual 12v battery
• Jump it with the same battery pack

That finally wakes the car up so it can realise its own battery is dead… and recharge itself from the massive 800v battery it’s been sitting on the whole time.

So naturally, I now carry a battery pack and an electrical extension cable in the passenger footwell at all times. Not the boot. Not the frunk. Inside the cabin. Because reasons.

All of this is just about tolerable… until it’s 4am in an airport car park after a long flight and you physically can’t even open the door wide enough to start dismantling the interior.

Anyway, after 5 years of extensive research, Porsche have finally released their long-awaited over-the-air software update to fix this, which as a vaguely competent engineer, I assumed would be a simple logic update: “If 12v battery low -> charge up from big battery”.

No.

The fix is: The app now sends you a notification saying the battery is low… and you need to go and turn the car on and off again so it can charge itself.

I wish I was joking.

The car knows the battery is low.
It tells you the battery is low.
It could fix the battery being low.
But instead, it asks you to come outside and reboot it.

Turns out the answer, even in a £100k+ electric Porsche, after years of research, is still: “have you tried turning it off and on again?”

This is because Porsches are designed for you to engage with the car. If the car fixes itself, then it with rob you of the joy of interacting and bonding with your taycan.

 

[aryuthere]

Sitting here reading this thread while my taycan won’t start due to a dead 12v battery even though the car was plugged in and nearly full at 85%.
Funny thing is my porsche app does show the starter battery has a low charge state except at no point did I get a notification from the app. Well unless said notification is meant to be the car’s theft alarm randomly deciding to ring without letting you do anything about it….

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