The charging battle btw Big Brother 800V and little Sister 12V

[BigApple]

Here are my $0.02 on the 12V EV issue my car was (is) plagued with.
A few weeks ago, my car had to be towed to the Dealer as the 12V battery was dead. (consequently, also damaged).

At that time no one knew what caused it. I was told i had a bad cell in the 12V battery.
Well now i have a new battery and it seems it is going slowly in the same direction.
To be fair i have to say now i have a dashcam installed so now i know for sure i have a draw during Parking. But i also have an additional 12V battery B130X for my Blackvue system to take the strain off the Porsch battery a little.
Either way here is what i came up with in regard to how my Porsche handles its little 12V "sister" battery.
It only charges the 12 Volt battery during...
1. Driving or when the engine is on (highest Charging power) 14-15V
2. DC or AC Charging of the big battery charges the 12V also but not as intense as driving. ~ 13V
3. And i also think when you precondition the car it will give its 12V sister a charge.

I wish the Porsche app would give out a battery reading of the 12V SoC. luckily my Blackvue Dashcam (app) does that so i can tell what the SoC of the 12V is at anytime from anywhere.

So, my advice to anyone who wants to make sure their 12V side of the car is not dead when they come back home after a few days or weeks. (OfCourse a nice Trickle charge if your car is parked inside is a smart thing while being away for longer.) But not all have a Garage for the car.
Next best thing: You are parked outside your house and have a Level 1 or 2 charger nearby. Advice. Keep it plugged in and have the cars big battery at a lower SoC.
MY approach is to set my Charging power to a lower 20Amps or such that's roughly about 5kW (more or less). Then change remotely when you feel like you want to give your 12V a charge remotely drag you charge level gage in the App from let's say %30 to %50 the first time and if needed again %50-%80 it would take longer to reach that with 5kW and thus charge your 12V longer as the process takes longer. If you can't control your charge power, then try out what works best for you. Technically you can also charge it up full (or almost) fast and then preheat your car regularly and that also charges your car but will of course use (waste more 800V energy) but that's ok as you have it charged up . You could technically hover btw the save %80 and down to %50 and back up. A strange workaround but it is an option if needed.

Allll this because Porsche it seems has not build in a Voltage threshold where it would kick in a charge of the 12V system to maintain it or recharge it before it reaches a dangerous low SoC.
At least that is what i had come up with so far. I hope i am wrong and there is a silver lining but so far i have not seen it.
I am actually German and grew up in Stuttgart. But i must say despite the Beauty of this car and its speed and handling. I am disappointed that my fellow German engineers did not think this through. (as far as i can tell)
Disclaimer: I reached out to Porsche in Germany and the ones i get on the phone. No one knows. %50 of the time i get rerouted to Porsche North America. And they know even less. As the Germans don't see an importance sharing things with their partners oversees or elsewhere.
Everyone is left guessing around.

I set my Dashcam to a voltage cut-off @ 12.5V just to be safe. the Bluackvue default i think is 12.1 V. But with the car and no "build in" Safety net you have to keep it higher. Let's see where this all goes.

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[SteveInKirkland]

I've been thinking about whether I should leave my Macan always connected to the charger with the target charge set low to try to save the 12v battery. I haven't done anything because I haven't had problems yet and I think I'm replacing the 12v battery every 2 years any way.

 

[RickDCMD]

I’m not an engineer but I wondering the same, why the car system does not charge the 12V battery when is getting low if the HV has a good level of charging, is not only Porches, Hyundai, Tesla, also have same problems. For sure i’s an engineering issue more complex that we think it is.

 

[Greg McD]

Here are my $0.02 on the 12V EV issue my car was (is) plagued with.
A few weeks ago, my car had to be towed to the Dealer as the 12V battery was dead. (consequently, also damaged).

At that time no one knew what caused it. I was told i had a bad cell in the 12V battery.
Well now i have a new battery and it seems it is going slowly in the same direction.
To be fair i have to say now i have a dashcam installed so now i know for sure i have a draw during Parking. But i also have an additional 12V battery B130X for my Blackvue system to take the strain off the Porsch battery a little.
Either way here is what i came up with in regard to how my Porsche handles its little 12V "sister" battery.
It only charges the 12 Volt battery during...
1. Driving or when the engine is on (highest Charging power) 14-15V
2. DC or AC Charging of the big battery charges the 12V also but not as intense as driving. ~ 13V
3. And i also think when you precondition the car it will give its 12V sister a charge.

I wish the Porsche app would give out a battery reading of the 12V SoC. luckily my Blackvue Dashcam (app) does that so i can tell what the SoC of the 12V is at anytime from anywhere.

So, my advice to anyone who wants to make sure their 12V side of the car is not dead when they come back home after a few days or weeks. (OfCourse a nice Trickle charge if your car is parked inside is a smart thing while being away for longer.) But not all have a Garage for the car.
Next best thing: You are parked outside your house and have a Level 1 or 2 charger nearby. Advice. Keep it plugged in and have the cars big battery at a lower SoC.
MY approach is to set my Charging power to a lower 20Amps or such that's roughly about 5kW (more or less). Then change remotely when you feel like you want to give your 12V a charge remotely drag you charge level gage in the App from let's say %30 to %50 the first time and if needed again %50-%80 it would take longer to reach that with 5kW and thus charge your 12V longer as the process takes longer. If you can't control your charge power, then try out what works best for you. Technically you can also charge it up full (or almost) fast and then preheat your car regularly and that also charges your car but will of course use (waste more 800V energy) but that's ok as you have it charged up . You could technically hover btw the save %80 and down to %50 and back up. A strange workaround but it is an option if needed.

Allll this because Porsche it seems has not build in a Voltage threshold where it would kick in a charge of the 12V system to maintain it or recharge it before it reaches a dangerous low SoC.
At least that is what i had come up with so far. I hope i am wrong and there is a silver lining but so far i have not seen it.
I am actually German and grew up in Stuttgart. But i must say despite the Beauty of this car and its speed and handling. I am disappointed that my fellow German engineers did not think this through. (as far as i can tell)
Disclaimer: I reached out to Porsche in Germany and the ones i get on the phone. No one knows. %50 of the time i get rerouted to Porsche North America. And they know even less. As the Germans don't see an importance sharing things with their partners oversees or elsewhere.
Everyone is left guessing around.

I set my Dashcam to a voltage cut-off @ 12.5V just to be safe. the Bluackvue default i think is 12.1 V. But with the car and no "build in" Safety net you have to keep it higher. Let's see where this all goes.

I'm assuming the Macan Electric has the same setup as the Taycan where there is a safety cut-out level of 50% SOC for the 12v Battery. If you leave your car unused for several weeks (months), the 12v battery will only run down to 50%SOC before disconnecting itself. This remaining charge can then be used to get the vehicle started but there is a manual switch process that needs to be used to allow this. Your service team can show you how to do this.

 

[BigApple]

I'm assuming the Macan Electric has the same setup as the Taycan where there is a safety cut-out level of 50% SOC for the 12v Battery. If you leave your car unused for several weeks (months), the 12v battery will only run down to 50%SOC before disconnecting itself. This remaining charge can then be used to get the vehicle started but there is a manual switch process that needs to be used to allow this. Your service team can show you how to do this.

I wish this was true. The battery reader that is connected to the actual 12v terminals says otherwise . It says numbers like 20% or down to 10% I connected to battery when it was down to 10% to a charger to avoid damage to the battery. What you describe sounded like a lithium battery that has an internal cutoff. That will shut off prior to going dead and that leaves a precentige of power reserved to be used when needed. I have one in my M3 where I press a little remote that will then release the reserved 20% to give me a few more emergency starts.

 

[rcomeau]

It would be nice if someone had an official word on this. It is common (expected, really) that the BCM (battery control module) manage the 12v by charging it when necessary regardless of whether yo are driving or charging or just sitting in a parking lot.

 

[BigApple]

It would be nice if someone had an official word on this. It is common (expected, really) that the BCM (battery control module) manage the 12v by charging it when necessary regardless of whether yo are driving or charging or just sitting in a parking lot.

Yes that is how it would make the most sense. I currently have to run the heater remotely to trigger the car being charged when it goes below 12v. No BCM doing anything. I wish that were the case. It seems we need to watch it ourself. Makes no sense.

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