How to prevent 12v battery from dying when stored for 6 weeks without trickle charger or charging station?

[W1NGE]

No need. The car automatically tops off the 12v with power from the HV if the 12V starts to lose voltage.

Only for a limited number of times - so be careful with this advice nor is this documented by Porsche in the Owner's Manual. There is a post with quite some technical detail explaining how the process works and the finite number of top ups that will be performed - this is significant given the varying duration of layup times.

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[f1eng]

No need. The car automatically tops off the 12v with power from the HV if the 12V starts to lose voltage.

Sadly not, as several people have experienced, including myself.

HV battery at 76% after 9 days not used over Christmas 12V battery so flat the central locking didn't work.

 

[rb33gl]

This one, perhaps:

"...it's looking for specific science things..."

Obviously the latest Porsche engineering terminology

 

[W1NGE]

It means that it shows 13.6 if it is fully charged?
When I started my car, it seem to regulate between 13.4 and 13.6 when standing still

I'm not sure precisely as the car is powered on at that point so it could "charging". The value can be 13.4v.

 

[whitex]

This one, perhaps:

Interesting. They missed the fact that there is a button inside all US car frunks which opens it. The video is from 2 years ago, I wonder if Porsche has fixed this since then. I have left my 2023 Taycan once for 3 weeks plugged into an EVSE, no issues. It was also parked at service for over 2 weeks awaiting a new onboard charger, I checked it via the app every couple of days, no issues.

Last but not least, if you're worried about the HV battery not topping off the 12V after a some number of attempts. perhaps set a departure timer to preheat the car every few days. Preheating the car will always enable the HV battery, which should reset any 12V re-up counters. If you have you car plugged into the EVSE, it will also top off the HV battery when needed.

 

[whitex]

AFAIK, there is not a consensus on the forum about how many times the HV battery will recharge the 12 V when the vehicle is stored. I think I’ve seen 6 times when the main battery is stored at over 50%, with a caution not to store at much high percentages, so as to permit the battery management system to rebalance to individual cell, so say 50% - 60%. I kind of wish we had a firm rule we could count on. Don’t use the app, keep the key away, and 50-60% seem to be the only guides, but they don’t always work, based on my own experience.

I've kept my Taycan at 85% daily charge per Porsche recommended daily limit, even if stored for few days. I've kept my wife's Q8 etron at recommended 80%, same thing. I've had 4 Teslas which I charged to 90% recommended level, he oldest one was 3 months shy of 7 years when I sold it with minimum degradation. My Taycan SoC after near 2 years and under 14k miles reads 93.7%. All 4 Teslas had minimal battery degradation, oldest being almost 8 years old with <5% degradation (I think it was 3.x%, but it was a while back so don't remember specifics). I don't have specific numbers for the eTron, but I did not notice any significant degradation after over a year. I've left my Taycan for 3 weeks while plugged into an EVSE (worth noting, I have a 24/7 dashcam drawing power around the clock). The only times I've drained my 12V batteries on Tesla was when I removed the infotainment computer (which also controls the 12V top-off) - all my Teslas also had a 24/7 dashcam setup (independent of Tesla's sentry mode). I honestly stopped worrying about it long time ago - charge to recommended daily max, watch for 12V warnings to replace the 12V battery. I have trickle chargers I could connect to my car when leaving it in the garage, but it doesn't seem to need it. If it does, I can open it using the physical key and jump start it to open the trunk, will deal with it if it happens.

 

[PorscheCH]

I fear by the time the right tube display is switched on the HV battery has already started charging the 12V so what is displayed is the charger output.
Mine read 13.4 immediately after my car was jump started by Porsche assist even though in fact the 12V battery did not have enough voltage to unlock the car 30 seconds previously.

Same here. Right tube showing 13.4 right after jumpstart. And for the following 1h+ of driving also showing a "12v low. charge immediately. right port impaired" message.

Also, I find it hard to believe the car hv battery topped up the 12v for 8 times (?) during the 12 days the car was parked and not driven. How would the 12v be then totally flat after such a short time?

 

[Dee]

>14V: battery is charging
13,5V: battery is charged.
<13V: battery is dying, you're lucky to even see this number...

 

[exilen94]

>14V: battery is charging
13,5V: battery is charged.
<13V: battery is dying, you're lucky to even see this number...

So 13.4 - 13.6 means it is charged?

 

[W1NGE]

So 13.4 - 13.6 means it is charged?

Yes - at the correct level

 

[Dee]

So 13.4 - 13.6 means it is charged?

Yes.

Funny thing: when my car was being recalled, my loaner Taycan stayed constantly on 14,0-14,1V.
I notified my dealer but I don't know if this is changed over the years, I assume not.
My car is 2020 TS, loaner was a 2023 CT.

 

[Art]

Looks like I may have the storaging record here as my 4S was put in garage 30.8.2024. So it has now stayed there ca. 5 months. Charged once from 65 to 70%.
Powered on 2-3 times just to check there's no errors and reset the 12V charging cycles. It has no warming in the garage so temp. has been all between +25C to -25C.
No problems with the 12V since converter and charger changed.
Earlier I had several 12V flatouts.

 

[exilen94]

Looks like I may have the storaging record here as my 4S was put in garage 30.8.2024. So it has now stayed there ca. 5 months. Charged once from 65 to 70%.
Powered on 2-3 times just to check there's no errors and reset the 12V charging cycles. It has no warming in the garage so temp. has been all between +25C to -25C.
No problems with the 12V since converter and charger changed.
Earlier I had several 12V flatouts.

How much battery did HV loose after months?? I left my car 57% for storage for 6 weeks, it is currently 1 week now

 

[Art]

I don't have exact figures but during this 5 months it dropped from 80 to 65 because I let it circulate the coolant, heat the cabin and battery for two times. Then charged from 65 to 70 - just for testing.. Still showed 70% today.
If the key is not nearby and you don't wake it remotely - it does not use much.
My Porsche connect has ended long time ago.

 

[simcity]

Only for a limited number of times - so be careful with this advice nor is this documented by Porsche in the Owner's Manual. There is a post with quite some technical detail explaining how the process works and the finite number of top ups that will be performed - this is significant given the varying duration of layup times.

Yes. Not Porsche Taycan - but from Audi e-tron GT, somewhat wordy 'self study' manual (I guess for their service tech's). Anyway same under the skin....

"terminal 15 cycle = basically ignition-start button on/off"

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