Electrical System Error (yellow) and 12V battery charger

[Stu Kan]

I've been reviewing the other posts on this subject and have some follow-up questions.

First, here's the sequence:

• While on road trip (in Taycan 4S 2025), I was charging to 60% at an Electrify America(EA) and suddenly at 59%SoC it stopped and Electrical System Error alert;
• Never experiencing it before, I unplugged then tried to plug-in again and charger button was red plus the EA screen said unplug;
• I got back in the car and soon the message that the 12V battery was low;
• Called Porsche and they said we needed to tow to nearest dealership (I was in a small town so nearest dealership was not nearby...);
• As I was talking with Porsche, everything started shutting down and car now stuck in park as the 12V battery lost its charge;
• A long time before tow truck arrived and we struggled to figure out how to get the 12V charged enough to open frunk and charged further to get car into neutral so we could roll it in position to get it on the truck's bed;
• Porsche dealership techs hooked up their jump charger to the 12V and were able to drive it off the tow truck and into the shop with the yellow Electrical System Error et al still showing on the displays; FYI: the SoC was still at 59% where it was at EA station;
• Porsche kept it overnight and said OBD showed only "infrastructure" errors and they guessed the EA charging station had some issue that threw the car into error; from what I could tell, service just let it sit and eventually it cleared itself...;
• Picked the car up and continued on my road trip without further issues;

And my follow-up questions:

• Would it be smart to buy a jump-starter like the one shown in vid in previous post (NOCO Boost...) to keep in the car for future emergencies like this?
• As mentioned, from what I could tell, the service guys were able to get it moving by using their own 12V battery jump-starter before they let it sit and clear up overnight; at the least, I could get the car moving to a safe place...;
• Other recommendations for figuring out what really happened? preventing same error in future?
• I've sent this same description to Porsche Support;
• Assuming this isn't related but will mention: the car was in service a few weeks prior to try to clear up issue(s) with Porsche Connect et al (MyPorsche iPhone app not working, CarPlay not working, SOS button showing red, Spotify PCM app not working, satellite maps and live traffic not working etc) where Porsche Service updated software via "campaign WRV3 scope 2" . . .; this service only partially successful: CarPlay now works and SOS button light now green, but separate Spotify app doesn't work, MyPorsche app still doesn't work, satellite maps/traffic still a no go etc;

Thx for reading and any advice!

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[ct14garage]

The 12V battery in the Taycan is laughably small — just 40Ah. Meanwhile, the car’s 12V systems draw a constant 67A, even more when the aircon blower’s on. Do the math: 40Ah doesn’t even last 20 minutes under that load.

Normally, the high-voltage (HV) battery takes over powering the 12V systems via the DCDC converter that steps down battery voltage 800V to 12V.

In your case, something triggered a safety shutdown of the HV system — maybe an isolation fault, maybe a fried component.

When that happens, the HV battery disconnects (contactor opens - like a circuit breaker tripping at home), and nothing recharges the 12V battery. It drains fast.

So no… your issue isn’t the 12V battery. It’s a high-voltage system failure.

 

[Stu Kan]

The 12V battery in the Taycan is laughably small — just 40Ah. Meanwhile, the car’s 12V systems draw a constant 67A, even more when the aircon blower’s on. Do the math: 40Ah doesn’t even last 20 minutes under that load.

Normally, the high-voltage (HV) battery takes over powering the 12V systems via the DCDC converter that steps down battery voltage 800V to 12V.

In your case, something triggered a safety shutdown of the HV system — maybe an isolation fault, maybe a fried component.

When that happens, the HV battery disconnects (contactor opens - like a circuit breaker tripping at home), and nothing recharges the 12V battery. It drains fast.

So no… your issue isn’t the 12V battery. It’s a high-voltage system failure.

Thanks for replying. I wasn't thinking the 12V battery was THE problem but when it is drained so quickly in a situation similar to mine, it might be helpful for to have a jump-starter at least get basic functions like frunks and screens going again, and prepare for the tow truck, if nothing else!

 

[ct14garage]

Thanks for replying. I wasn't thinking the 12V battery was THE problem but when it is drained so quickly in a situation similar to mine, it might be helpful for to have a jump-starter at least get basic functions like frunks and screens going again, and prepare for the tow truck, if nothing else!

When this happen the best you can do is switch off the car and lock it til the truck comes. This way consumption will be minimal and the battery will hold up

 

[LotusPhil]

I had exactly the same issue about a month ago. My car would charge for two minutes then generate a charging issue and stop the charger. The public DC charger then shut down and I moved to the one next door. Same thing happened so I tried charger number 3 whilst on the phone to the gridserve help line. I got enough charge inside to get home unplugged the car got the yellow electrical fault dashboard and awaited the tow truck. Left the car at Porsche for a fortnight and they reported no faults. They could see a log saying there was a problem but there were no details to identify the source…. I’ve had this happen three times now in two years… ?

 

[Stu Kan]

I had exactly the same issue about a month ago. My car would charge for two minutes then generate a charging issue and stop the charger. The public DC charger then shut down and I moved to the one next door. Same thing happened so I tried charger number 3 whilst on the phone to the gridserve help line. I got enough charge inside to get home unplugged the car got the yellow electrical fault dashboard and awaited the tow truck. Left the car at Porsche for a fortnight and they reported no faults. They could see a log saying there was a problem but there were no details to identify the source…. I’ve had this happen three times now in two years… ?

At Porsche service, do you know what they did, if anything, to revive it? Did they drive it off the truck as they did with mine? From what I could tell by what Porsche service told me, other than checking the codes/logs, they just let it sit for a while and it cleared itself. With this yellow electrical fault, it would be nice to know if we could revive it ourselves without it having to be towed away and all of that.

 

[LotusPhil]

On this last occasion the 12v battery died by the time the AA got to me but on the two previous occasions turning the car off locking it and leaving it for half an hour solved it. I only discovered this when on the first breakdown I called the AA locked the car to go and find a coffee… by the time I came back it was back to normal. I must have tried locking the car a dozen times on this last occasion but I couldn’t clear the fault. Once the AA had jump started the 12v battery to open the trunk the car was fine again and we drove it onto the low loader. What really confuses me is when the public DC charger fails… it’s as though my hi voltage battery is shorting out the charger but that’s only a guess??

 

[Stu Kan]

On this last occasion the 12v battery died by the time the AA got to me but on the two previous occasions turning the car off locking it and leaving it for half an hour solved it. I only discovered this when on the first breakdown I called the AA locked the car to go and find a coffee… by the time I came back it was back to normal. I must have tried locking the car a dozen times on this last occasion but I couldn’t clear the fault. Once the AA had jump started the 12v battery to open the trunk the car was fine again and we drove it onto the low loader. What really confuses me is when the public DC charger fails… it’s as though my hi voltage battery is shorting out the charger but that’s only a guess??

That’s good info about locking and letting it sit clearing it on the first couple occasions . But I get you—pretty strange that our HV battery or onboard charger bringing the public charger down!

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