Intermittent red warning J1.2

[Speuk]

The battery gets always topped up when the voltage drops below a certain amount. You don't need any kind of trickle charger. In Drive the voltage converter is just forced on all the time, but as soon as the voltage drops below a set threshold it gets topped up anyway.


It does absolutely nothing to it. It's a Lithium battery and it gets topped up each time the voltage goes below a certain number. In fact, there would be more wear on it if you would have driven it in that time rather than let it sit.


Bad advice, the Taycan does not need any kind of CTEK charger. Don't waste your money. It's actually actively harmful for a Lithium battery to keep it 100% fully charged all the time and will reduce it's service life. The Taycan does not have any lead-acid 12V batteries.

You guys don't even have a clue what's wrong with the car. You don't know that it has anything to do with the low voltage battery. Buying random shit is not going to solve the issue, and is not helpful in the very least. Correct diagnosis and then solving the problem (by bringing it to the dealer's attention) will be the solution. In fact due to the voltage converter being force engaged in drive and the issue occurring during driving you can rule out the 12V battery.

I agree with most of what you say, but there is no need to adopt such an aggressive manner on this forum, members have good intentions.

I agree we have not a clue what's wrong but we all know that OPCs are often poor at properly addressing issues.

You are correct, in saying that the 12v battery is automatically topped up when the voltage drops below a certain level, this has been the case since the software was updated to cause this to happen. That said we still see issues with 12v batteries dropping to a level when they "trip" and need to be jumped to reset the relay so the automatic charging is not infallible

You say " In fact due to the voltage converter being force engaged in drive and the issue occurring during driving you can rule out the 12V battery." I do not think this is necessarily correct, just because the voltage converter is forced to engage in drive it does not mean there can be no fault with the 12v battery. However, I agree it is more likely the fault lies elsewhere. I had a similar error message on my first Taycan after the battery compartment pressure test campaign, this turned out to be a loose pin on the connection to the battery control unit, probably damage by the tech forcing the connector back in and resulted in the need for a new control unit and HV cable.

I did not suggest that the lithium battery be kept at 100% and I agree this would be harmful

You are correct in saying this is best resolved by the OPC as they have PIWIS and access to Porsche AG. I am tempted to say therefore no need to waste your time using third party software to read fault codes, just leave it to the OPC

Sponsored

 

[4sCT21]

Given the opc had my car in to diagnose the issue earlier this year, and there were no active or stored codes, my gut feeling is this booked visit will deliver the same, but who knows.

All I can do is give the OPC the chance to diagnose and repair.

At least they've now seen the warning light first hand, and how it behaves.

If they can not, then I will have to consider other avenues, consumer rights etc

I cant be having essentially check engine lights (sometimes multiple) illuminating every journey to and from work.

 

[prj]

That said we still see issues with 12v batteries dropping to a level when they "trip" and need to be jumped to reset the relay so the automatic charging is not infallible

Who are "we" exactly? Ever since this was fixed back in 2021 or so, I haven't really heard of any issues with 12V batteries outside of cell failures due to LGChem manufacturing defects, in which case your trickle charger will do nothing.

I did not suggest that the lithium battery be kept at 100% and I agree this would be harmful

Yet that's exactly what the charger will do. You don't need any trickle charger on any EV. It's like bringing water in a cup to the ocean because you're worried it's going to dry out.

 

[Speuk]

Who are "we" exactly? Ever since this was fixed back in 2021 or so, I haven't really heard of any issues with 12V batteries outside of cell failures due to LGChem manufacturing defects, in which case your trickle charger will do nothing.

Yet that's exactly what the charger will do. You don't need any trickle charger on any EV. It's like bringing water in a cup to the ocean because you're worried it's going to dry out.

Well for one my next door neighbour has just (in September 2025) had his 12v lithium battery replaced under warranty as it had developed a fault. I agree that charging failures have largely been eliminated since the first half of 2023 but not 100% eliminated.

I agree you shouldn't need to trickle charge a lithium battery and certainly not a regular basis but if there is a fault elsewhere it may not get charged by the car.

 

[prj]

Well for one my next door neighbour has just (in September 2025) had his 12v lithium battery replaced under warranty as it had developed a fault.

The trickle charger would have had exactly zero effect on this. As I said before, there are defects in the LG Chem produced 12V Lithium batteries, very widespread on the Cayenne.

I agree that charging failures have largely been eliminated since the first half of 2023 but not 100% eliminated.

In which the trickle charger will not save you because if the charging does not work you will not be able to drive the car, the battery will go flat in less than 5 minutes. The 12V battery has a BMS and it shuts itself off to protect itself before it gets damaged due to undercharging. Any fault with the battery is a faulty battery and nothing to do with charging (or lack thereof).

I agree you shouldn't need to trickle charge a lithium battery and certainly not a regular basis but if there is a fault elsewhere it may not get charged by the car.

In which case the trickle charger will not save you.

Hence me saying it is pointless - worse than doing nothing.

 

[4sCT21]

So a quick update, they've diagnosed a HV issue, 2 degraded cells.

They've not seen this on a J1.2 so far and have reported back to Porsche.

Given that ive been having these errors since around 800 miles on the clock, they've been bad since manufacture.

They are unable to release my car back to me, so let's see how this pans out.

 

[prj]

Hope this is a one off...

 

[4sCT21]

Its not the news I was expecting

 

[chun]

Hope this is a one off...

With similar hope the problems started on j1.1 in 2021, when they reported issues following first fire in 2020.

LG Chem strikes again?

 

[4sCT21]

So ive just picked up my car. Software updates and cell balancing carried out, they reckon its fixed.

We shall see.

 

[4sCT21]

Quick update, first long journey post repair, the warning is back.

I've had enough.

 

[4sCT21]

Have spoken now both with my local OPC and the supplying dealer. Both very sympathetic, totally understanding my position. The intention is to potentially have the car recovered to the supplying dealer, and ultimately for me to reject the car.

I need to speak to the head of service at the dealer first.

Not spoken with the finance company yet (VW).

 

[4sCT21]

Im dropping the car off at the supplying dealer prior to the new year. Ive told them I do so, expecting to not see it again.

They would like the chance to check the car themselves, which i totally understand.

I checked my mileage and the first fault occurred at 350 miles, and i'd hardly driven any of those myself, as the car was collected back to the dealer (90 miles return) twice to try to correct paint issues.

I will be obviously pushing for a full refund as the car was faulty at the point of sale.

Totally fed up of the whole situation, its ruined my Porsche ownership experience.

 

[D00notD00d]

They’ve had multiple fix attempts. Based on Uk Consumer Legislation, seems you have a strong case to reject the car.

 

[4sCT21]

Not what I wanted from my first Porsche

The car is with the dealer, will update when I have a resolution or more likely, issues.

Sponsored