svp6

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Modification: _IF_ the vehicle is still plugged into the external charger (EVSE) one might consider removing the charging plug - since the vehicle is "dead" this will require that you access the manual release pull cords - please see Porsche's "good to know" information for these instructions.

Since we're dealing with electricity - safety pre-cautions should be taken and having a live power source plugged into he vehicle may not be the best plan...

this is an extra measure of safety - since in the US the J-1772 power requires a vehicle to be "alive" to talk to the EVSE - the EVSE should have cut power when the vehicle died - but better safe than sorry.
Dave,

Nice write up and I hope I never need to use it.

Re: if charger still plugged, why not unplug the charger from the NEMA 14-50 or alternatively disable the circuit from the house fuse box? Seems easier to do than the chord release
 

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To be painfully clear :
Never connect jumper cables directly to the 12 V
lithium battery or other electrical components.
Only connect jumper cables to the emergency
starting terminals
And those are where exactly?
 
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I"m not sure if in those circumstances the ODBII port will actually charge the LiON battery - nor how long it will take.

it might work and yes would be easier - but to date I'm unaware of any recovering the vehicle in this manner once it's in this state.

further testing would be required to actually verify the 12V battery is receiving power via the ODBII port when the car is in this state

once the vehicle is in this state - it’s really really really dead - the ODBII port may be electrically isolated from the 12V battery when the car is in this condition

we’d need to test it - and the amount of power/current would take a while to get enough power to the 12V battery to wake the car up - and while in this state there is no way to know if you’re making progress or how long it’s going to take.
 
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Re: if charger still plugged, why not unplug the charger from the NEMA 14-50 or alternatively disable the circuit from the house fuse box? Seems easier to do than the chord release
not all charges are "NEMA 14-50" - throwing the breaker is the best choice - if your EVSE is hardwired, unplugging it works if it's not hardwired -and is an excellent point.

thank you @svp6 that's a great idea.

Again I think we're safe, because the charger will cut out the second the J-1772 pilot signal goes away as it is designed to do - but safety first - making sure your EVSE is un-powered during recovery is a prudent safety step.
 

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Ok, but wouldn’t charging with the OBDII port and the proper 3 amp charger be easier than Dave’s “approach 2” above?
It is a matter of time and energy. The 12V battery has to be charged up to a level high enough for the system to come alive, and then the 800V battery takes over charging the 12V battery. Normally that works fine with 3-4 amps through the OBD port.

However, if the 12V battery is deeply discharged, you may need more current (amps) to bring it alive. That may be why Porsche recommends a jump battery or high amperage charger for 5 minutes (or the jump battery needs to power the 12V bus to reconnect the 12V battery through its relay).

Most importantly, whatever method is used to charge the 12V battery only has to be used until the system becomes alive and the 800V battery takes over the charging task.

2020-09-30 edit
 
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Your posting (and all previous postings) suggest I stop at step 1: Call Porsche and have them deal 100% with it, including providing me a loaner.

Having said that, I really appreciate knowing this information is nearby...just in case.
 

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And those are where exactly?
Both are under the cover in the frunk. Page 287 in owner's manual. The positive jump terminal is nearby the battery with a cover on it. The negative is further towards the passenger side of the car away from the battery.
 

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Thanks for bringing up the point that we need to carry the extra length of wire for the ground if we're using the battery booster. You say 16 gauge wire, but that's really thin. Do you mean 6 gauge?
 
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@Charlie no I meant 16 guage - remember you're only using this wire to power the "frunk" electronics - to open the frunk - you're NOT using the 16 gauge wire to "jump" the 12 volt - the amount of power need to open the frunk is trivial - and the whole process is "powered" for less than 30 seconds - so it's a trivial amount of power for a very very short duration.

if you want a comfort factor you could use some lower gauge wire (12, 10, 8) - but honestly I believe it would be overkill…we're not trying to power a Diesel engine starter motor - we need 12 volts and about 0.1 amps to provide power to the frunk electronics.

I would not recommend 16 gauge wire for the actual "jumping" of the 12V battery (phase 2 of the instructions) - but the wire is also un-necessary because the jumper clamps easily reach the positive/negative posts in the frunk - no extra wire required

in fact when I was done with this whole affair I plugged my 12V booster back into the wall power to charge it back to 100% - and it didn't even indicate it needed the charge…

getting the Taycan back online from a dead 12V requires a trivial amount of power - which makes the problem even more frustrating and embarrassing for Porsche in my opinion - we are bricking a $150k to $240k automobile because the LiON battery tripped off line due to a lack of less than 1 amp of power - a few milli-amps in reality…an amount of power less than static electricity on a door knob in winter.

It is literary ridiculous.

if you are planning to carry extra wire around to extend the jumper clamps for "generic" vehicle duty (maybe starting other ICE vehicle) then yes by all means you need some more beefy gauge wire (8 or 6 gauge should be sufficient) -but as a bridge to getting a Taycan to wake back up there really isn't much power being transferred here - as I noted the booster wouldn't even take a charge when I was all done with this.
 
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@Charlie no I meant 16 guage - remember you're only using this wire to power the "frunk" electronics - to open the frunk - you're NOT using the 16 gauge wire to "jump" the 12 volt - the amount of power need to open the frunk is trivial - and the whole process is "powered" for less than 30 seconds - so it's a trivial amount of power for a very very short duration.

if you want a comfort factor you could use some lower gauge wire (12, 10, 8) - but honestly I believe it would be overkill…we're not trying to power a Diesel engine starter motor - we need 12 volts and about 0.1 amps to provide power to the frunk electronics.

I would not recommend 16 gauge wire for the actual "jumping" of the 12V battery (phase 2 of the instructions) - but the wire is also un-necessary because the jumper clamps easily reach the positive/negative posts in the frunk - no extra wire required

in fact when I was done with this whole affair I plugged my 12V booster back into the wall power to charge it back to 100% - and it didn't even indicate it needed the charge…

getting the Taycan back online from a dead 12V requires a trivial amount of power - which makes the problem even more frustrating and embarrassing for Porsche in my opinion - we are bricking a $150k to $240k automobile because the LiON battery tripped off line due to a lack of less than 1 amp of power - a few milli-amps in reality…an amount of power less than static electricity on a door knob in winter.

It is literary ridiculous.

if you are planning to carry extra wire around to extend the jumper clamps for "generic" vehicle duty (maybe starting other ICE vehicle) then yes by all means you need some more beefy gauge wire (8 or 6 gauge should be sufficient) -but as a bridge to getting a Taycan to wake back up there really isn't much power being transferred here - as I noted the booster wouldn't even take a charge when I was all done with this.
Thanks. 16 guage makes it a lot easier to manage.
 
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thanks to another thread we have a great photo of a "bare" Taycan front end (wow it's soooo complex) - I've modified that photo and highlighted just the "jumper posts" as requested by some on this thread…

see photo below - the blue highlighted box is the location of the two posts you would use to "power" the 12V system for the vehicle - red = positive, bare-silver-metal = negative

1601479312679.jpeg
 

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thanks to another thread we have a great photo of a "bare" Taycan front end (wow it's soooo complex) - I've modified that photo and highlighted just the "jumper posts" as requested by some on this thread…

see photo below - the blue highlighted box is the location of the two posts you would use to "power" the 12V system for the vehicle - red = positive, bare-silver-metal = negative

1601479312679.jpeg
I might have missed it in the lengthy discussions earlier, but is there a way to open the hood if the battery is dead?
 
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@Dave T steps 3-14 on the first post of this thread - instructions to do just that is the sole reason this thread exists.

the trunk no - I retrieved my 12V booster by folding down the rear seats.

but now that I think about it - it's not clear - but I don't think so - I haven't tried.
 

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@Dave T steps 3-14 on the first post of this thread - instructions to do just that is the sole reason this thread exists.

the trunk no - I retrieved my 12V booster by folding down the rear seats.

but now that I think about it - it's not clear - but I don't think so - I haven't tried.
Ah ok, thanks. I hadn't read it all the way through. I thought the post was talking about charging when you made that first battery connection down in the foot well. I'm still hoping OBDII charging would work. Hoping even more that I never have a dead 12V battery in the first place!
 

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