12v battery dead....again ('23 CT)

[Fish Fingers]

So I took my dog out into the countryside for a walk.

10 miles there and back and when I got back and switched off I got a warning box saying PCM can't be used because battery is low.

I got out my new CTEK charger which showed the battery was >95% yesterday and it started charging and took around 40 minutes to get back to where it was yesterday, so on such a short journey it seems it is overall discharging, ie whatever the charge current from the HV battery DC-DC converter is is less than the battery is needing to supply running the car.

Impeccable timing buying that new charger !

Sponsored

 

[Tooney]

So I took my dog out into the countryside for a walk.

10 miles there and back and when I got back and switched off I got a warning box saying PCM can't be used because battery is low.

I got out my new CTEK charger which showed the battery was >95% yesterday and it started charging and took around 40 minutes to get back to where it was yesterday, so on such a short journey it seems it is overall discharging, ie whatever the charge current from the HV battery DC-DC converter is is less than the battery is needing to supply running the car.

Maybe you did not keep the car on long enough for that 35 minute OTA update in UK to complete - so battery depleted?

 

[f1eng]

Maybe you did not keep the car on long enough for that 35 minute OTA update in UK to complete - so battery depleted?

AFAIK no update has been done, I certainly haven't had the warning panel asking for agreement to do it.

 

[eddieterry]

Nor me !

 

[f1eng]

Impeccable timing buying that new charger !

Maybe but ignorance can be bliss...

 

[DJP]

Same issue last week -12v battery failed had to leave vehicle with boot open.

 

[BlackiceEV]

Going by others who have had this problem Porsche are unlikely to find any problem with the 12 Volt. My personal view is that this is a problem of the main battery only charging the 12 Volt for a max of 30 minutes for up to 8 times which seems a problem in cold weather if the 12 Volt has been drained for some software related intermittent problem.
I find that the use of a CTEC lithium maintainer if leaving the car for over a week or if getting the low 12 Volt message is a simple easy solution.
I asked Porsche Tonbridge to check both the 12 Volt and software related to it but they found no problem which is why I use the CTEC.

This is the way to go, I do the same with CTEK charger : maintainer. If the 12V battery low warning comes on I attach it overnight to CTEK and all’s well. Best solution is to drive the car regularly but if that’s not practical the CTEK is the solution.

 

[pony1982_]

Thought I'd give you an update on where the dealership have got to with the car. They called earlier today to say that there was a problem with the 12v system and they had to raise a case with Porsche in Germany, who suggested a bunch of diagnostics, a battery drain and also to update every component. Unfortunately this didn't solve the issue, so they've sent some logs back and are waiting for a response. I now have a wait until they diagnostics back and forth between the dealership in the Uk and Germany concludes, which is a bit frustrating. I've owned the car for 6 months of which it's now spent over 5 weeks at the dealership - it's not the dealership's fault - they're clearly doing the best they can to get this resolved.

On the rattle, they said they've replaced the top mount which seems to have fixed the issue (good news on this front at least).

 

[ItsNot AboutTheMoney]

Thought I'd give you an update on where the dealership have got to with the car. They called earlier today to say that there was a problem with the 12v system and they had to raise a case with Porsche in Germany, who suggested a bunch of diagnostics, a battery drain and also to update every component. Unfortunately this didn't solve the issue, so they've sent some logs back and are waiting for a response. I now have a wait until they diagnostics back and forth between the dealership in the Uk and Germany concludes, which is a bit frustrating. I've owned the car for 6 months of which it's now spent over 5 weeks at the dealership - it's not the dealership's fault - they're clearly doing the best they can to get this resolved.

I would recommend to review my previous posting (#12)
where I mentioned using a Bluetooth monitor device.

This would provide a simple way to determine:

1. Does the car go into sleep mode after minutes when parked?

2. Does the battery keeps its charge after one or two day when not used?

3. Or does the battery abnormally gets discharged after few hours or a day?

4. Does the battery charger gets activated when sleeping, and if so for how long?

From the comments above, it seems like maybe one particular component
is not going into standby mode, and as a result the whole car stays awake.

This could be for example a proximity sensor used to look or unlock the doors,

I have noticed the same type of low voltage battery issues on many forums,
for different manufacturers, where for some reason the battery get discharge
and someone get stranded as a result.

Back in the day, cars had a gauge to measure the battery voltage.

I think EVs should provide a very basic low voltage battery monitoring
allowing to prevent getting stranded without any warning.

 

[Scandinavian]

Back in the day, cars had a gauge to measure the battery voltage.

I think EVs should provide a very basic low voltage battery monitoring
allowing to prevent getting stranded without any warning.

There is a gauge in the settings for the instrument cluster, but obviously only working when the car is operational.

I think the warning can be a bit more tricky since the voltage curve is very flat for that Lithium battery. And then the question is how well the car’s system read the voltage and starts the charge cycle. Perhaps temperature also has a big effect.

Have a look at some published graphs for the voltage curve on this type of battery chemistry. Very flat curve and not much difference in voltage at 25% or 80 %?

 

[Jagu]

Thought I'd give you an update on where the dealership have got to with the car. They called earlier today to say that there was a problem with the 12v system and they had to raise a case with Porsche in Germany, who suggested a bunch of diagnostics, a battery drain and also to update every component. Unfortunately this didn't solve the issue, so they've sent some logs back and are waiting for a response. I now have a wait until they diagnostics back and forth between the dealership in the Uk and Germany concludes, which is a bit frustrating. I've owned the car for 6 months of which it's now spent over 5 weeks at the dealership - it's not the dealership's fault - they're clearly doing the best they can to get this resolved.

On the rattle, they said they've replaced the top mount which seems to have fixed the issue (good news on this front at least).

Top mount of what?

 

[thefunkygibbon]

I swear, if i have a 12v battery issue on my Taycan, after having dealt with CONSTANT battery drainage issues on my previous 2 Porsches (911 & Boxster) I'm going to go completely flip mode.
its an electric car for crying out loud. in 2025. my previous cars were 15 and 20 years old respectivly. If Porsche havent sorted out the battery discharging issue in over 20 years there is literally no hope for them!

 

[Isaac]

I swear, if i have a 12v battery issue on my Taycan, after having dealt with CONSTANT battery drainage issues on my previous 2 Porsches (911 & Boxster) I'm going to go completely flip mode.
its an electric car for crying out loud. in 2025. my previous cars were 15 and 20 years old respectivly. If Porsche havent sorted out the battery discharging issue in over 20 years there is literally no hope for them!

Better get ready to flip then ! .... my Taycan 4S currently in for its second extensive visit to the dealer....I have bought a lithium trickle charger which I will fit when it comes back or ask them to do it... This said never had an issue with any other Porsche battery in ICE cars and I have had a few...But I do agree that its beyond belief that it can happen to an electric car which is plugged in ...which mine was.

 

[thefunkygibbon]

Better get ready to flip then ! .... my Taycan 4S currently in for its second extensive visit to the dealer....I have bought a lithium trickle charger which I will fit when it comes back or ask them to do it... This said never had an issue with any other Porsche battery in ICE cars and I have had a few...But I do agree that its beyond belief that it can happen to an electric car which is plugged in ...which mine was.

i had issues in that, if i didn't use the car for a couple of weeks, it would invariably be unusably depleted when i tried to start it. even went as far as buying a solar panel to trickle charge the car/s whilst it was sitting there but it didn't much help.

So is the setup of batteries in the taycan such that the main battery array doesn't charge the 12v? and the 12v is charged in the same manner as an ICE? ie an alternator is involved?

 

[Isaac]

i had issues in that, if i didn't use the car for a couple of weeks, it would invariably be unusably depleted when i tried to start it. even went as far as buying a solar panel to trickle charge the car/s whilst it was sitting there but it didn't much help.

So is the setup of batteries in the taycan such that the main battery array doesn't charge the 12v? and the 12v is charged in the same manner as an ICE? ie an alternator is involved?

Well there is a degree of mystery about the charging process as you will see from this forum. However the high voltage battery is meant to charge the 12 volt battery and there is a suspicion that a software update around Dec/Jan changed the recharging system so that for some reason the 12v battery is not charged as it was before. In one case my 12 v battery went flat after 2 days and in the other after 7 days but always with the car plugged in. I have had the car for 4 years so this problem is entirely new for me. However others have experienced strange flat battery issues before Dec/Jan but there appears to have been a noticeable uptick since Jan 25. The Porsche Assist folks confirmed this and Porsche dealer said some dealers were too buy to take the cars in... Also in Dec a letter arrived from Porsche warning owners not to put the car on charge in a garage due to fire risk before the software was checked by the dealer. My dealer knew nothing about this letter when I phoned the next day which is extraordinary. On the first visit to the dealer for the first flat battery they referred it to Germany who authorised a new control unit to be installed and software updates. But it clearly did not work. Luckily I have other cars but the level of inconvenience caused by this is seriously annoying. We also know from details released publicly when Porsche listed its shares that they had software issues that had or were expected to delay new models by a year. I wonder if the software update that might be causing the problem is related to the fire risk. As I said at the start its completely shrouded in mystery and Porsche are either not being open or dont know themselves what is going on. It will make me think long and hard before I buy another Porsche or VW group product as they appear to have some QA issues and customer service has fallen off a cliff....

Sponsored