Theft alarm = low 12v battery!

[kl98cwg]

I left the UK a few days before Christmas for a break and received this worrying notification from the Porsche app yesterday. Before heading off I’d locked the car in my garage, which is connected to the house alarm system - as that hadn’t triggered I was fairly confident this would turn out to be a false alarm..

When I called the security operation centre they said the alarm was due to low charge in the 12v battery, so I’d probably not be able to unlock the car from the fob and I might need to call Porsche for assistance. It’s sensible to alert if the battery is low and that’s going to stop the alarm working, but a more meaningful message in the app would be helpful!

I’m hoping the car will still be usable when I get home, but I’m not optimistic as I’ve left it for longer than this (pre-uPdate) without any issues.

I couldn’t find any similar postings on the forum, but wondered if anyone else has experienced this? Also, are there still issues with sourcing the 12v battery should it need replacement?

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[TAYC4S]

I left the UK a few days before Christmas for a break and received this worrying notification from the Porsche app yesterday. Before heading off I’d locked the car in my garage, which is connected to the house alarm system - as that hadn’t triggered I was fairly confident this would turn out to be a false alarm..

When I called the security operation centre they said the alarm was due to low charge in the 12v battery, so I’d probably not be able to unlock the car from the fob and I might need to call Porsche for assistance. It’s sensible to alert if the battery is low and that’s going to stop the alarm working, but a more meaningful message in the app would be helpful!

I’m hoping the car will still be usable when I get home, but I’m not optimistic as I’ve left it for longer than this (pre-uPdate) without any issues.

I couldn’t find any similar postings on the forum, but wondered if anyone else has experienced this? Also, are there still issues with sourcing the 12v battery should it need replacement?

I left the car for a number of weeks and returned before Christmas.

I could not unlock the car and had to call out the AA. Just for context I have not experienced any 12v battery related issues before.

I had unlocked the drivers door with the actual physical fob and when the AA arrived he plugged in the traditional battery into the emergency fuse, released the boot and within 5mins the car was alive - once the 12v was boosted.

In short, if leaving the car for extended periods it might be worth having a trickle charger connected - or get someone to switch it on every couple of weeks.

For me all is good and the AA seem to know exactly what to do. One tip - wait the extra time for an AA Porsche specialist - they you that option when you call.

 

[W1NGE]

I left the UK a few days before Christmas for a break and received this worrying notification from the Porsche app yesterday. Before heading off I’d locked the car in my garage, which is connected to the house alarm system - as that hadn’t triggered I was fairly confident this would turn out to be a false alarm..

When I called the security operation centre they said the alarm was due to low charge in the 12v battery, so I’d probably not be able to unlock the car from the fob and I might need to call Porsche for assistance. It’s sensible to alert if the battery is low and that’s going to stop the alarm working, but a more meaningful message in the app would be helpful!

I’m hoping the car will still be usable when I get home, but I’m not optimistic as I’ve left it for longer than this (pre-uPdate) without any issues.

I couldn’t find any similar postings on the forum, but wondered if anyone else has experienced this? Also, are there still issues with sourcing the 12v battery should it need replacement?

Not sure this explains the problem in all cases.

The HV battery will top up the 12v should it drop (software patch from last year). Have this checked by your dealer.

No harm leaving your car connected to your EVSE when away to enable trickle charging.

Check all doors, frunk and trunk were fully closed.

Do you have a dash cam installed?

 

[kl98cwg]

I left the car for a number of weeks and returned before Christmas.

I could not unlock the car and had to call out the AA. Just for context I have not experienced any 12v battery related issues before.

I had unlocked the drivers door with the actual physical fob and when the AA arrived he plugged in the traditional battery into the emergency fuse, released the boot and within 5mins the car was alive - once the 12v was boosted.

In short, if leaving the car for extended periods it might be worth having a trickle charger connected - or get someone to switch it on every couple of weeks.

For me all is good and the AA seem to know exactly what to do. One tip - wait the extra time for an AA Porsche specialist - they you that option when you call.

Thanks for the advice, I’ll be getting home soon and that makes me a bit more optimistic!

 

[kl98cwg]

Not sure this explains the problem in all cases.

The HV battery will top up the 12v should it drop (software patch from last year). Have this checked by your dealer.

No harm leaving your car connected to your EVSE when away to enable trickle charging.

Check all doors, frunk and trunk were fully closed.

Do you have a dash cam installed?

My car was uPdated at the end of November so hopefully that included the patch you mention, but I will check thanks.

I left the car connected to the EVSE and I have a charging timer that runs every night to take the battery to the recommended 85%.

I know I left the car completely closed and don’t have a dashcam, so there shouldn’t have been any unusual drain.

I’ll post when I get home and let you know how it all turned out!

 

[DLP]

I left the car for a number of weeks and returned before Christmas.

I could not unlock the car and had to call out the AA. Just for context I have not experienced any 12v battery related issues before.

I had unlocked the drivers door with the actual physical fob and when the AA arrived he plugged in the traditional battery into the emergency fuse, released the boot and within 5mins the car was alive - once the 12v was boosted.

In short, if leaving the car for extended periods it might be worth having a trickle charger connected - or get someone to switch it on every couple of weeks.

For me all is good and the AA seem to know exactly what to do. One tip - wait the extra time for an AA Porsche specialist - they you that option when you call.

I had the exact same scenario, but was advised by Porsche not use a trickle charger. However, they also didn't advise as to what i should actually do!

 

[W1NGE]

I had the exact same scenario, but was advised by Porsche not use a trickle charger. However, they also didn't advise as to what i should actually do!

Advice is given in the owner's handbook - most dealerships are unfamiliar with the basics and certainly won't have read the manual.

The EVSE acts as a trickle charger and different to a standalone battery tender trickle charger. Care is needed with these as it must support 12v li-ion batteries.

OP has done the right thing procedurally but normally not required unless leaving the car unused for a number of months.

 

[DLP]

Advice is given in the owner's handbook - most dealerships are unfamiliar with the basics and certainly won't have read the manual.

The EVSE acts as a trickle charger and different to a standalone battery tender trickle charger. Care is needed with these as it must support 12v li-ion batteries.

OP has done the right thing procedurally but normally not required unless leaving the car unused for a number of months.

Correct, and Porsche confirmed that it was in the manual. However, they still advised against it for some reason? When i get chance i will check with the service guy i deal with

 

[TAYC4S]

I had the exact same scenario, but was advised by Porsche not use a trickle charger. However, they also didn't advise as to what i should actually do!

I think many on this forum use a lithium battery trickle charger and Porsche even sells them. I have not got one nor am I sure I will bother unless it happens again.

 

[DLP]

I have one from my motorbike days, but will check with Porsche before using it, should the need arise

 

[W1NGE]

I have one from my motorbike days, but will check with Porsche before using it, should the need arise

I have one I got for my Boxster which has a Li-Ion option on it and never had a reason to use it. Leaving the EVSE connected will serve the same purpose so if you can do that at home no need (really) to have anything else IMHO.

 

[simcity]

I had the exact same scenario, but was advised by Porsche not use a trickle charger. However, they also didn't advise as to what i should actually do!

See the fourth page in this extract from the e-Tron GT reference...."external charging" ?

 

[simcity]

The EVSE acts as a trickle charger and different to a standalone battery tender trickle charger. Care is needed with these as it must support 12v li-ion batteries.

OP has done the right thing procedurally but normally not required unless leaving the car unused for a number of months.

Yep. Ordinarily 95 times out of 100 the advice to leave the car plugged in when away for a period would be completely fine and the 'little' 12V battery gets recharged from the 'big' 800V battery. Happy days.

It wasn't until I saw that e-teron GT self stuffy doc, and this jumped out:

Re-charging concept
If the 12 V LiFePO4 battery is discharged while the vehicle is stationary, a specific re-charging concept is implemented under certain conditions.
Example: The vehicle is stationary and has entered bus sleep mode. If the 12 V LiFePO4 battery is discharged so much that its usa ble charge drops below 8 Ah and the state of charge of the high-voltage battery is higher than 10 %, the high-voltage network is activated and the 12 V battery is charged. This process continues until the 12 V battery has reached a capacity of 20 Ah or 30 mi nutes have passed. The high-voltage network is then deactivated again and the vehicle enters bus sleep mode. This process can be repeated 8 times per terminal 15 cycle.

The last bit is the killer - per terminal 15 cycle. In other words every time the car is switched off - this recharging concept will repeat up to 8 times.

Problem: if the car is stood for a very long time, even if plugged into an EVSE to charge the big battery, unless you actually turn the car "on" periodically to reset the 12V charging cycle count - it will only attempt to top-up / recharge the 12V battery up to eight times. After that. Nada!!

So even though 8 top up cycles (and that is only up to 50% SoC or a grand total of 4 hours of charging!!) sounds like plenty, its easy to imagine scenarios how the 12V battery could go flat eventually if there was enough parasitic drain on it and/or you simply ran out of 12V battery top-up cycles before the car was next switched on.

They talk about connecting a trickle charger to the 12V battery during workshop or diagnostics work to stop it from completely discharging - this is because the big battery to little battery recharging concept isn't quite as "infinite" as we possibly may be led to think.

 

[W1NGE]

Yep. Ordinarily 95 times out of 100 the advice to leave the car plugged in when away for a period would be completely fine and the 'little' 12V battery gets recharged from the 'big' 800V battery. Happy days.

It wasn't until I saw that e-teron GT self stuffy doc, and this jumped out:

Re-charging concept
If the 12 V LiFePO4 battery is discharged while the vehicle is stationary, a specific re-charging concept is implemented under certain conditions.
Example: The vehicle is stationary and has entered bus sleep mode. If the 12 V LiFePO4 battery is discharged so much that its usa ble charge drops below 8 Ah and the state of charge of the high-voltage battery is higher than 10 %, the high-voltage network is activated and the 12 V battery is charged. This process continues until the 12 V battery has reached a capacity of 20 Ah or 30 mi nutes have passed. The high-voltage network is then deactivated again and the vehicle enters bus sleep mode. This process can be repeated 8 times per terminal 15 cycle.

The last bit is the killer - per terminal 15 cycle. In other words every time the car is switched off - this recharging concept will repeat up to 8 times.

Problem: if the car is stood for a very long time, even if plugged into an EVSE to charge the big battery, unless you actually turn the car "on" periodically to reset the 12V charging cycle count - it will only attempt to top-up / recharge the 12V battery up to eight times. After that. Nada!!

So even though 8 top up cycles (and that is only up to 50% SoC or a grand total of 4 hours of charging!!) sounds like plenty, its easy to imagine scenarios how the 12V battery could go flat eventually if there was enough parasitic drain on it and/or you simply ran out of 12V battery top-up cycles before the car was next switched on.

They talk about connecting a trickle charger to the 12V battery during workshop or diagnostics work to stop it from completely discharging - this is because the big battery to little battery recharging concept isn't quite as "infinite" as we possibly may be led to think.

Understood but in the real world most people would not leave their car unused for a very long period to encounter the above scenario. Layups as long as this would require other arrangements to be made as you would with an ICE vehicle.

 

[kl98cwg]

I finally arrived back home last night and, as expected, the car was dead. It went exactly as TAYC4S described and Porsche Assistance/AA had the car up and running again in no time at all.
The AA chap said he‘d dealt with a number of calls like this and he also suspected a software issue.

The app was still showing ‘theft detected’ today, but I called the Security Operations Centre and they resolved that straight away.

The car is in for a service soon so I’ll get it investigated.

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