Long Recovery from 12V Flat Battery

[Xenophon Christodoulou]

I had a planned business trip that required the car (Taycan Turbo MY21) to be garaged for 8 weeks. I phoned my OPC to seek advice to avoid flat batteries and was told by the Taycan Specialist Mechanic that there was no need for a maintenance charger on the 12V battery and that I should leave the HV battery with 50% charge and NOT connected to the wall charger. I also left the keys locked in a safe 25m away from the car and whilst abroad never used the "Porsche Connect" App to avoid waking the car up and using power. After 5 weeks I received a message on my phone through the connect app that the car failed to charge. (I suspect this is when the 12V Lithium battery shut itself down). On my return I could not open the doors. I called Porsche Assist and they sent an AA Mobile Technician. At this point I have to say that his first question when he saw the Taycan was to ask whether it was a hybrid or petrol, so was not particularly familiar with the vehicle. I had left the bonnet open before my departure to allow easy access in case I had a flat battery which allowed him easy access and he tried to jump start the car with his jump start kit. I was then able to open the doors but could not engage Drive or Reverse and lots of alarms came on. The car was towed to the OPC on November 15th for fault finding and repair. Following a long process of fault finding and replacement of various bits I got the car back yesterday on January 7th. Initial fault finding revealed that their was a leakage on the 12V battery and couldn't hold its charge. This was narrowed down to the E-Box (the electronics that control current delivery from the HV battery to the motor). A ticket was raised by the OPC BUT Porsche UK insisted on various checks and cheaper part replacements first. So after changing the DC Converter and onboard charger they finally authorised the replacement of the E-box CPU which seems to have resolved the problem. In the meantime I was given a loaner BMW series for 5 weeks by Porsche assist and then a Cayman S for two weeks and finally a Basic Taycan by my OPC dealer. End result was that I was deprived of my car for 8 weeks when this failure could have been rectified in two weeks. Also, it turns out that I was given the wrong advice as my OPC was not aware that there was a Porsche Advanced Technical Advice which requires the car to be connected to the wall charger as it keeps the 12 V battery charged. We believe that the problem was caused by the Porsche Assist technician jump starting the 12V Lithium battery and engaging Drive with the leads connected. Porsche should issue a new advice soon but be warned. Do not engage DRIVE with the jump start leads on. It could fry your electronics. Apologies for the long rant. I am now awaiting Porsche's compensation offer!

 

[W1NGE]

I had a planned business trip that required the car (Taycan Turbo MY21) to be garaged for 8 weeks. I phoned my OPC to seek advice to avoid flat batteries and was told by the Taycan Specialist Mechanic that there was no need for a maintenance charger on the 12V battery and that I should leave the HV battery with 50% charge and NOT connected to the wall charger. I also left the keys locked in a safe 25m away from the car and whilst abroad never used the "Porsche Connect" App to avoid waking the car up and using power. After 5 weeks I received a message on my phone through the connect app that the car failed to charge. (I suspect this is when the 12V Lithium battery shut itself down). On my return I could not open the doors. I called Porsche Assist and they sent an AA Mobile Technician. At this point I have to say that his first question when he saw the Taycan was to ask whether it was a hybrid or petrol, so was not particularly familiar with the vehicle. I had left the bonnet open before my departure to allow easy access in case I had a flat battery which allowed him easy access and he tried to jump start the car with his jump start kit. I was then able to open the doors but could not engage Drive or Reverse and lots of alarms came on. The car was towed to the OPC on November 15th for fault finding and repair. Following a long process of fault finding and replacement of various bits I got the car back yesterday on January 7th. Initial fault finding revealed that their was a leakage on the 12V battery and couldn't hold its charge. This was narrowed down to the E-Box (the electronics that control current delivery from the HV battery to the motor). A ticket was raised by the OPC BUT Porsche UK insisted on various checks and cheaper part replacements first. So after changing the DC Converter and onboard charger they finally authorised the replacement of the E-box CPU which seems to have resolved the problem. In the meantime I was given a loaner BMW series for 5 weeks by Porsche assist and then a Cayman S for two weeks and finally a Basic Taycan by my OPC dealer. End result was that I was deprived of my car for 8 weeks when this failure could have been rectified in two weeks. Also, it turns out that I was given the wrong advice as my OPC was not aware that there was a Porsche Advanced Technical Advice which requires the car to be connected to the wall charger as it keeps the 12 V battery charged. We believe that the problem was caused by the Porsche Assist technician jump starting the 12V Lithium battery and engaging Drive with the leads connected. Porsche should issue a new advice soon but be warned. Do not engage DRIVE with the jump start leads on. It could fry your electronics. Apologies for the long rant. I am now awaiting Porsche's compensation offer!

Thanks for the detailed post.

If you had popped your bonnet prior to your departure then the bonnet lights would be active and ultimately led to the draining of your battery is that not correct?

You have an emergency key to open the driver's door should all else fail and then a method described in the manual to open the bonnet / charge port door.

 

[JimBob]

Sorry to hear about this. It looks like a real effort to fix. The Agero tip sheet says to disconnect the the outside power when the instrument cluster restores. Now this is from memory and someone may have the proper facts. Somewhere I think I saw a stronger warning that you are not supposed to leave the outside power connected to prevent damage to the car once the car comes to life. I know when ever I had a dead 12v, as soon as the cluster lit up, I disconnected the booster.

 

[NoRPM22]

thanks for the detailed writeup. I will soon be getting delivery of the car and in a few months, I also plan to be away from home for several weeks. My car will be indoors parked in the house garage. If I am reading this right, is the best option to leave the car plugged into the EVSE with a certain SOC setting like 80%? And maybe leave it unlocked to avoid any random alarms?

 

[Xenophon Christodoulou]

Thanks for the detailed post.

If you had popped your bonnet prior to your departure then the bonnet lights would be active and ultimately led to the draining of your battery is that not correct?

You have an emergency key to open the driver's door should all else fail and then a method described in the manual to open the bonnet / charge port door.

Not really the point of the post but no, there is no bonnet light on when the bonnet is just left unlocked!

 

[JimBob]

thanks for the detailed writeup. I will soon be getting delivery of the car and in a few months, I also plan to be away from home for several weeks. My car will be indoors parked in the house garage. If I am reading this right, is the best option to leave the car plugged into the EVSE with a certain SOC setting like 80%? And maybe leave it unlocked to avoid any random alarms?

Here

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