Consensus on proper maintenance of the 12V battery while on vacation?

[SergeyIndy]

This is excellent and direct source to hopefully everyone agrees we need to follow.
I am not happy that as owners we need to worry about this and need to remember or set reminders for ourselves to babysit the 12v battery, but I can tell you after my Cayenne 12v battery discharged while a shop was working on a door hinge and then relay closed to make it totally dead, seeing the $5K+ estimate to replace it, would make anyone pay attention to this topic.
My 15-year-old exceptionally cared for Acura could not start due to the battery, so I jumped it, and an hour later, the Acura dealer got me a new one for $175 with a 100-month warranty << - that I can live with.

This is proof, the cost of 2020 Cayenne 12v replacement, before all taxes/shop fees.
Diagnostics and quote below.

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[tchavei]

This is proof, the cost of 2020 Cayenne 12v replacement, before all taxes/shop fees.
Diagnostics and quote below.

This is totally insane.

Being the Taycan my first Porsche and recalling that my MB is on its 3rd battery over the years (at $200 each), I'm definitely having a "second thought" moment.

People are actually paying 3.5K each 5yrs to have their batteries replaced on their Porsche cars?

Jfc

 

[Scandinavian]

Left my 4S last year for six weeks when i was in europe with an SOC of 85% and after I returned it was 84% and the lithium battery had not changed at all and was 12.4 Volts like it always is.There is so much nonsense being written about this lithium battery that I laugh everytime time i see a post on this issue because in my opinion there is no problem leaving your car unused for months at a time.The state of charge number is also irrelevant as long as it is above 30-40% to be safe

I assume there is a missprint that your battery was 12.4 volt, because then the car would be dead! I guess you mean 13.4 volts

Seems there is some limit like like 6 to 8 weeks when the battery will survive just fine. There is a very good article on here about the training manual for the Audi e-tron GT where the 12 volt battery charging is described. Excellent reading so search for that.

I have frequently left my car for 2 weeks and up to 4 weeks without any problems. The main battery charged to ca 60% and extremely little drain on that battery during the absence. Huge difference to a Tesla over same period.

I have experienced one occasion where the car was left for 8 weeks, and then the battery was dead! From the Porsche website it looked like the last communication from the car had taken place after 6 weeks, so then it seemed ok. Why it had reported in I will never know, but it did. But after returning after 8 weeks absence the car was dead at the airport. It was not plugged in or on any trickle charger as that is not possible there.

There is some drain on the 12 volt battery over time, alarm system running, listening to the mobile connection in case you want to use the app, etc etc. Normally it gets charged by the main HV battery but these cycles seem to be limited to a low number. Why we do not know.

so leaving it for 2 weeks should not give any problems, but 2 months + , I would recommend trickle charger and also car plugged in.

 

[Scandinavian]

I'm going on a vacation and my Taycan will be sitting in the garage for a little over 2 weeks.

The manual states:

• Make sure the charge level is at 20-50% while the vehicle is left standing (e.g. via charging profile)
• If possible, connect to the "mains supply" (EVSE) for trickle charging.

However, the service department at my dealer suggested to use a trickle charger and strongly advised against the manual's advice of leaving it plugged in at 20-50%. To get clarification on this, I called Porsche and they also repeated my dealer's suggestion of using a trickle charger for that period of time.

I searched the forums and saw a mixed bag of suggestions - from leaving it plugged in at 20-50%, to leaving it unplugged around 50%, and also to using a trickle charger. I'm inclined to go with the manual's suggestion, but now I feel even more unsure due to the conflicting advice from my service department and PCNA.

Just trying to avoid coming home to a dead 12V battery. Anyone have thoughts or experience on this?

Leaving the car for two weeks should not present any problems at all, as stated in this thread.

If would follow the manual if you feel unsure. Leave it at 50% plugged in.

I you leave it in your garage you could also leave the frunk open, just in case.

With all belts and braces also plug in a trickle charger, but for such a short time I would regard it unnecessary. I have frequently been away with the car left for up to 4 weeks and have had no problems with that. Only once when I left it for 8 weeks did I get into trouble with a dead car.

It also is quite simple to revive the car, should the relay have disconnected the 12 volt battery, so do not loose any sleep over this issue. There are very good instructions on the forum for this so do a search.

 

[bilM]

I've now got a Porsche Lithium trickle charger (looks like the CTEK one) and will use that next time we're away.

It is important to note that trickle charging is not acceptable for lithium batteries. "Trickle charging" means that a certain current is forced into the battery even when full. Trickle charging is used in lead acid, NiCad, and NiMH batteries to keep them topped off. The Li-ion chemistry cannot accept even a trickle overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous.

 

[Tooney]

I have experienced one occasion where the car was left for 8 weeks, and then the battery was dead! From the Porsche website it looked like the last communication from the car had taken place after 6 weeks, so then it seemed ok. Why it had reported in I will never know, but it did. But after returning after 8 weeks absence the car was dead at the airport. It was not plugged in or on any trickle charger as that is not possible there.

What was the fix for the dead battery after this situation? How was the car restarted? Did the battery need to be replaced?

 

[rb33gl]

It is important to note that trickle charging is not acceptable for lithium batteries. "Trickle charging" means that a certain current is forced into the battery even when full. Trickle charging is used in lead acid, NiCad, and NiMH batteries to keep them topped off. The Li-ion chemistry cannot accept even a trickle overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous.

Not what my OPC said. I've been in discussion with them for several weeks about the lithium 12v, after it failed twice with 2 weeks non-use.

They recommended trickle charging it if I wasn't going to use the car for prolongued periods - the manual says the same. I got a Porsche Charge-o-mat Pro Charger - 'with trickle charging and battery monitoring functions as well as two charging modes for Porsche 12V lead-acid batteries and Porsche 12V lithium-ion batteries'.

 

[mutanthands]

Not what my OPC said. I've been in discussion with them for several weeks about the lithium 12v, after it failed twice with 2 weeks non-use.

They recommended trickle charging it if I wasn't going to use the car for prolongued periods - the manual says the same. I got a Porsche Charge-o-mat Pro Charger - 'with trickle charging and battery monitoring functions as well as two charging modes for Porsche 12V lead-acid batteries and Porsche 12V lithium-ion batteries'.

On a related note, the charger is a re-branded CTEK, if you wanted to save a little money, just grab one of them

 

[rb33gl]

On a related note, the charger is a re-branded CTEK, if you wanted to save a little money, just grab one of them

I had a CTEK for the lead-acid 12v in my 964. Left it on all the time, great bit of kit (and easy to plug in). But it was no good for lithium batteries.

 

[eddieterry]

Not what my OPC said. I've been in discussion with them for several weeks about the lithium 12v, after it failed twice with 2 weeks non-use.

They recommended trickle charging it if I wasn't going to use the car for prolongued periods - the manual says the same. I got a Porsche Charge-o-mat Pro Charger - 'with trickle charging and battery monitoring functions as well as two charging modes for Porsche 12V lead-acid batteries and Porsche 12V lithium-ion batteries'.

I would not worry as although it is not recommended to use trickle charging on lithium-ion batteries this isn’t a safety issue Lithium-ion batteries have built-in safeguards designed to stop most damage or exploding if they’re left charging while at maximum capacity and the Cteck should monitor and go into maintenance mode anyway.

 

[Eric]

I wish that was always the case. You're basically saying that you crossed intersection XYZ without having an accident albeit that intersection is marked as an accident prone area.

It just means you didn't have an accident. Doesn't mean that nobody else will.

There are several reported cases of shorter absences where the car just died. There are also reports that a Porsche update somehow improved the situation but it isn't completely solved as long as they keep insisting on only charging the 12V 8 times max between states 15 (readiness to drive).

Scientifically it does not make sense that you would have a problem with a lithium battery which is charged all the time by a huge battery of 90 kwatts .As long as your main battery is charged halfway there should not be any problem with the 12 volt lithium battery.Most likely the people who have problems are dealing with a defective 12 volt battery.It is known in the boating world that 12 volt starting batteries are prone to defects.In my circle of friends who have Taycans none of them have had a problem after tens of thousands of miles

 

[Eric]

I assume there is a missprint that your battery was 12.4 volt, because then the car would be dead! I guess you mean 13.4 volts

Seems there is some limit like like 6 to 8 weeks when the battery will survive just fine. There is a very good article on here about the training manual for the Audi e-tron GT where the 12 volt battery charging is described. Excellent reading so search for that.

I have frequently left my car for 2 weeks and up to 4 weeks without any problems. The main battery charged to ca 60% and extremely little drain on that battery during the absence. Huge difference to a Tesla over same period.

I have experienced one occasion where the car was left for 8 weeks, and then the battery was dead! From the Porsche website it looked like the last communication from the car had taken place after 6 weeks, so then it seemed ok. Why it had reported in I will never know, but it did. But after returning after 8 weeks absence the car was dead at the airport. It was not plugged in or on any trickle charger as that is not possible there.

There is some drain on the 12 volt battery over time, alarm system running, listening to the mobile connection in case you want to use the app, etc etc. Normally it gets charged by the main HV battery but these cycles seem to be limited to a low number. Why we do not know.

so leaving it for 2 weeks should not give any problems, but 2 months + , I would recommend trickle charger and also car plugged in.

yes of course 13.4 volts.However it does not make a lot of sense that six weeks is ok and then suddenly after eight weeks you have a dead 12 volt lithium battery.I maintain as long as you have a decent charge in your main battery you should not have a problem with your 12 volt battery.A lithium battery can go through thousands of charging cycles without the battery failing so that argument also does not make sense.I am however with you that is puzzling that you battery failed after eight weeks

 

[Scandinavian]

yes of course 13.4 volts.However it does not make a lot of sense that six weeks is ok and then suddenly after eight weeks you have a dead 12 volt lithium battery.I maintain as long as you have a decent charge in your main battery you should not have a problem with your 12 volt battery.A lithium battery can go through thousands of charging cycles without the battery failing so that argument also does not make sense.I am however with you that is puzzling that you battery failed after eight weeks

Agree it should not be a problem, but it seems the 12 volt battery will only receive a charge from the main battery for 8

cycles. And perhaps I just ran out of cycles. I did not try to communicate with the car since I knew waking it up will take power out. But perhaps the car tried to send something to mothership from where it stood parked. And I have not checked for network coverage there either.

Have a look at the Audi trading manual which was posted here in the Forum.

 

[Scandinavian]

Here is a link to a thread and posts where this cycle issue has been discussed

https://www.taycanforum.com/forum/threads/theft-alarm-low-12v-battery.14264/post-215238

 

[XLR82XS]

I have frequently left my car for 2 weeks and up to 4 weeks without any problems. The main battery charged to ca 60% and extremely little drain on that battery during the absence. Huge difference to a Tesla over same period.

Owned 2 Teslas and now Taycan since May 2021. I can, and do, leave the Taycan over a month without powering on and it's fine. Leaving it at 50-65% SOC and it not only starts up with zero issues, but doesn't loose any % charge.

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