12v battery problems - again

[rb33gl]

The 12v battery has let me down twice before, requiring call outs from Porsche Assist. The big update was supposed to sort it, but I've just got in the car to be greeted with '12v battery low, connect to suitable charger'. The last time I drove it was 11 days ago.

It's been in to Silverstone to check it over, but they could find nothing. Either there's an issue with the battery in my car, there is something draining it or it needs a battery with a higher capacity.

I don’t want to put it on charge between uses – I had to do that to my 964 but that was expected on a 30 year old car!

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[Scandinavian]

The 12v battery has let me down twice before, requiring call outs from Porsche Assist. The big update was supposed to sort it, but I've just got in the car to be greeted with '12v battery low, connect to suitable charger'. The last time I drove it was 11 days ago.

It's been in to Silverstone to check it over, but they could find nothing. Either there's an issue with the battery in my car, there is something draining it or it needs a battery with a higher capacity.

I don’t want to put it on charge between uses – I had to do that to my 964 but that was expected on a 30 year old car!

I have just returned from a long trip with the car parked at the airport. My car has had the big update last year and worked fine since. Now the car has been standing for about 5 weeks without being hooked up to power. There were no chargers at the airport parking, so not possible to plug in. The main battery still had 74% charge and had about 77% when we left it. . I have nothing extra fitted like dash cam etc.

At our return the car was completely dead. So clearly a 12 volt issue. . By checking the app the car had reported in the last time on the 23rd of December. I never checked the car during the time away to avoid any issues. Still did not help.

Thanks to the advise here on the Forum, I had a battery booster in the cabin and could get the frunk open and the 12 volt battery kick started.

Very disappointed that this still is an issue with the Taycan after all the uPdates etc. . Our Tesla that has been standing parked at home without being plugged in, had no problems whatsoever. That only had 60% charge when leaving it and had consumed some 12% from the main battery.

I need to discuss this issue with Porsche service to see what has happened.

 

[Raphie]

This is concering, this means you can’t leave your car alone for a couple of weeks?
what’s the 12v level?

 

[Scandinavian]

This is concering, this means you can’t leave your car alone for a couple of weeks?
what’s the 12v level?

You should be able to! In the Good to Know app Porsche seem to indicate that the car should be fine without being plugged in for up to 3 months! This problem was quite common in 2020. Since then it has been addressed by SW updates.

It could well be that I have a faulty 12 volt battery, but I have never left the car standing for such a long period before? Will take it to the dealer to have it checked if possible.

Not sure what you mean about the 12 volt level. When I had kickstarted the car and put the cover back in place , the instrument cluster indicated 13.0 volts. Normally I have had 13.4 volts and there was a warning in the display.

It drove ok but I probably should drive it much longer to have it fully charged again.

 

[Raphie]

With the level i mean your 13.4, not sure what it’s supposed to be, might be your battery has become lazy and needs some longer drives to charge properly, might be it’s a dud and does no longer hold it’s charge as well.

 

[Speuk]

Which battery booster do you have?

 

[rb33gl]

I told OPC that is was difficult to understand why a small 12v Lithium battery could go out of charge when it's sitting on a 93kWh battery. I didn't get a clear understanding of how it charges up when you drive either. It obviously doesn't have an alternator so how does it charge?

 

[tigerbalm]

It obviously doesn't have an alternator so how does it charge?

It charges from a DC-DC converter between the main HV battery and the 12-volt.

 

[tchavei]

I told OPC that is was difficult to understand why a small 12v Lithium battery could go out of charge when it's sitting on a 93kWh battery. I didn't get a clear understanding of how it charges up when you drive either. It obviously doesn't have an alternator so how does it charge?

That made me chuckle. You're so right.

Anyway, @800v explained it perfectly here:

https://www.taycanforum.com/forum/threads/dash-cam-and-12v-battery.13972/post-210566

What I believe Porsche should do is just not limit it to 5 cycles and keep draining the main battery until it reaches the critical 10%. That way you could have the car parked for a year and still be able to drive off to the nearest public DC charger. My two cents.

 

[_Brian_]

FWIW, here is another data point. Last November/December, our Taycan was held hostage at the local Porsche dealership for over 4 weeks to get the big update. I monitored the car a few times a week before the update. During the 4th week, they did the update. The history shows they moved the car into the shop and then it went off line. In the end, no issues with the 12 volts battery and by the time they turned the car over to me, the 12 volt battery/system voltage was in a normal range. They car has hd no modifications/additions. I'm assuming Tacans vary in off-line 12 volt load demand.

 

[simcity]

That made me chuckle. You're so right.

Anyway, @800v explained it perfectly here:

https://www.taycanforum.com/forum/threads/dash-cam-and-12v-battery.13972/post-210566

What I believe Porsche should do is just not limit it to 5 cycles and keep draining the main battery until it reaches the critical 10%. That way you could have the car parked for a year and still be able to drive off to the nearest public DC charger. My two cents.

Yep the system only charges the 12V battery up to 50% or for 30 minutes (whichever comes first) during a charge from the HV battery - up to a grand total of 8 such cycles - between key off's.

So the very most your 12V battery will ever get is 4 hours of recharge between key-off cycles - whether you have the car connected to an EVSE or not. That might be enough or it might not be if there is additional parasitic drain on the 12 V system (say with accessories fitted by user) or a weak or aged 12V battery.

LiFePo4 battery discharge profile is very flat, so it's everything, everything....then nothing very quickly as they roll off the cliff edge.

Switch the car on from time to time if you're not using it. Perhaps think of getting a lithium maintenance charger and hooking it up if the car will sit around for ages.

 

[Scandinavian]

Which battery booster do you have?

I have one like this one. Noco booster but not sure if it is exactly this one.. Worked very well.

https://www.amazon.fr/NOCO-GB50-Ult...tomotive&sprefix=noco+50,automotive,84&sr=1-3

 

[rb33gl]

Anyway, @800v explained it perfectly here:

https://www.taycanforum.com/forum/threads/dash-cam-and-12v-battery.13972/post-210566

What I believe Porsche should do is just not limit it to 5 cycles and keep draining the main battery until it reaches the critical 10%. That way you could have the car parked for a year and still be able to drive off to the nearest public DC charger. My two cents.
[/QUOTE]


That's really helpful, thanks. Shame we have to learn about it from Audi though.

I've contacted Silverstone and will try to get an explanation as to why a small £1000 battery discharges in less than 2 weeks, when I have no ancilliaries that might contribute to it.

The Taycan is a fantastic car but it could be even better without these daft gremlins.

 

[Scandinavian]

My cars is left unused for weeks from time to time. And had this from another that I sold. https://smartercharger.com/collections/accessories/products/ctek-ctx-battery-sense Looks like car is waking up like once a week to charge 12V battery.

This was from a different thread about the 12 volt issue. Interesting to see that the car wakes up at regular intervals to charge the 12 volt battery from the main battery. But limited to a certain number of times???

However more concerning was the information from my Service guy this morning. He recommended to not leave the car more than 10 days to avoid having the 12 volt issue. He stated they had that experience from a lot of Taycans in the workshop. In such case there seems to be a SW issue that the cycles are not performed as they should?? 10 days is a very short time and I certainly have left mine for more days than 10 days without any issue.

Seems we are not fully out of the woods as yet regarding the 12 volt issues??

 

[tchavei]

Apparently it's 8 cycles now (I wrote 5 earlier by mistake) after the software update so indeed it's strange how that car was flat after 10 days. I still think the manufacturer shouldn't limit the cycles. I'd rather return to a functional albeit low charged car then find it with main battery full but dead and unusable.

I've been following most 12v related threads as I plan to install a dual dashcam when mine arrives and that will be a constant 500-600mah draw in parking mode (6-7w) so it's concerning how cars without any accessories can go flat like that.

I guess I'll have to keep a booster somewhere inside the car just in case.

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