Don Breaks His Taycan - The Saga of the 12v Battery

[chrisk]

The problem is that Taycan's 12v battery is not depleted at all, so the moment the dead relay is activated again it can feed a lot of current back to the jump starter which has a little Li battery that can blow or catch fire.
Typically that is not an issue when jumping an ICE car with a dead 12v battery since that battery has not enough juice to feed back.
The latest generation of jump starters is supposed to have overcurrent protection but I am not sure if it protects both directions.

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[wmras]

The senior tech from my dealership is was not worried about the Taycan battery... he was worried about the li-ion booster blowing up b/c the Taycan might backfeed through the 12v batter to the booster and overrun what the booster battery was able to handle. I was happy to not take the chance.

Not going to happen with any well-designed jump battery booster. The jump battery would be protected from both reverse or higher voltage connections.

 

[H@wk]

Off topic, but.... I just find it amusing that while we discuss our shared problems with the 12v battery, I get that "deer caught in the headlights" look at the dealer when the topic arises. I'm a patient man, but I'd expected a bit more from THE premium German brand... At least that the mother company would keep their dealers up to speed on it. Oh well....

 

[Chuck J]

This may have already been written about, but just in case;

Pcarwhisperer
1 day ago
Hi Michael! There is a Technical Bulletin (TI) "2706 Discharged 12-Volt Battery After Charging the High-Voltage Battery" from Porsche that states when charging on a 120V at 6amps there could communication errors between the high voltage charger and Taycan which results in increased power consumption of the 12V battery which in turn can kill the 12v battery. The document recommends to keep the power output to no less than 8 amps when charging on a 120v in a pinch. There will be a software update sometime early this year to fix the error but it is not out yet.

Chuck J

 

[snstevens]

This may have already been written about, but just in case;

Pcarwhisperer
1 day ago
Hi Michael! There is a Technical Bulletin (TI) "2706 Discharged 12-Volt Battery After Charging the High-Voltage Battery" from Porsche that states when charging on a 120V at 6amps there could communication errors between the high voltage charger and Taycan which results in increased power consumption of the 12V battery which in turn can kill the 12v battery. The document recommends to keep the power output to no less than 8 amps when charging on a 120v in a pinch. There will be a software update sometime early this year to fix the error but it is not out yet.

Chuck J

In spite of the fact that my car has been a champ and has not presented me with these problems, I can't help feeling uneasy based on this last post, and feel vaguely like I'm a participant in a science experiment for which I'm not prepared. Perhaps I'm too accustomed to having vehicles that don't require me to tap into my EE background.

But for the record - God I love this car...

 

[MonkeysRock]

This may have already been written about, but just in case;

Pcarwhisperer
1 day ago
Hi Michael! There is a Technical Bulletin (TI) "2706 Discharged 12-Volt Battery After Charging the High-Voltage Battery" from Porsche that states when charging on a 120V at 6amps there could communication errors between the high voltage charger and Taycan which results in increased power consumption of the 12V battery which in turn can kill the 12v battery. The document recommends to keep the power output to no less than 8 amps when charging on a 120v in a pinch. There will be a software update sometime early this year to fix the error but it is not out yet.

Chuck J

Thanks for posting this. Our pretty much brand-new Porsche Taycan Turbo S just conked out after we had it plugged into a household current (6 amps) overnight. It stopped charging, then the doors locked themselves and we could not get into the car to do a thing. The service guy came, was able to open the door, start up the 12V battery again; but he just took the car to the local Porsche dealership (here in LA for the winter) to have it checked out.

I will report back with their findings.

 

[NC_Taycan]

There is a TSB about 6A being too low of current. Assuming this is a 110V outlet, you really should switch to a 220V outlet if at all possible in your place. If it's already 220V, increase from 6A to the appropriate lowest limit for the wiring gauge, breaker, and receptacle.

 

[BlueShoes]

There is a TSB about 6A being too low of current. Assuming this is a 110V outlet, you really should switch to a 220V outlet if at all possible in your place. If it's already 220V, increase from 6A to the appropriate lowest limit for the wiring gauge, breaker, and receptacle.

Just to add a note for anyone that doesn’t realize the terms get used interchangeably, the circuit is 120v or 240v. When you see someone reference 110v or 220v they’re generally referring to 120v and 240v.

 

[MonkeysRock]

There is a TSB about 6A being too low of current. Assuming this is a 110V outlet, you really should switch to a 220V outlet if at all possible in your place. If it's already 220V, increase from 6A to the appropriate lowest limit for the wiring gauge, breaker, and receptacle.

I did learn that 6A was inadequate from the Porsche technician at the dealership yesterday. However, we are staying in an AirBnB for a couple of months and I don't want to mess with their electrical circuitry.

The technician also said that our Max Charge rate was set at 25%, which was NOT the case. It must have reset itself to that Charge Rate because we had it set for 85%. Very concerning, if the Max Charge rate set itself to 25% somehow.....

 

[daveo4EV]

6 amp's is a conservative value for a 120 volt 15 amp circuit - 12 amps would be the 80% continuous use limit - but Porsche like other automotive manufacturers is choosing not to "tax" the average residential home's 120 volt wiring/breaker…which is a good choice - cause where household outlets are concerned you simply don't know the quality of the wire, how old it is, and if it was originally properly specfied - also with household outlets the plugs are more likely guaranteed to be a shared 120V/15 amp circuit rather than dedicated - so while your EV is charging someone might fire up the microwave (another high demand appliance) and be on the same "circuit/breaker" as the EV currently charging.

Chevy with their Bolt default to 8 amps for 120 volt charging sessions, but you can override and set it to 12 amps - but it will "forget" that setting for the next charging session - Chevy being very familiar over the years with liability law suites saw fit to make this a standard feature of the Bolt's charging software - and again this is a very conservative and reasonable approach.

Depending on the home and the circumstance I would be comfortable dialing the charging session up to the full 12 amps one can expect from a 15 amp breaker (NEMA 5-15 plug) but I might attempt to evaluate the circuit before doing so by finding the breaker, flipping It, seeing what it affects, and trying to determine what is also on that shared circuit. You can also minimize the risk of circuit overload by charging from NEMA 5-15 at night while people are sleeping when there is unlikely to be competing demands (no one running the microwave while the car is charging if everyone it asleep).

the simple fact of the matter is you simply can't tell if a NEMA 5-15 plug has other high demand appliances "sharing" the same circuit/breaker (microwave, coffee maker, room heater, toaster oven, curling iron, hair dryer) - if an EV was charging even at 6 or 8 amps (720 - 960 watts) - and you fire up a 1000 or 1250 watt appliance on the same circuit -that would equate to (1720 - 2210 watts - 1.72 to 2.21 kW) - a 120 volt circuit with 15 amp breaker has a maximum rated load of 1800 watts or 1.8 kW - and only 80% of that load is rated for more than 2 hours if the load is continuous - that will be too much load for the breaker and the wire - and the breaker should pop - however if the breaker does _NOT_ pop - you are now pulling too much current across 120 V wiring that may overheat, melt, short and potentially catch fire…it's a serious issue.

 

[BlueShoes]

6 amp's is a conservative value for a 120 volt 15 amp circuit - 12 amps would be the 80% continuous use limit - but Porsche like other automotive manufacturers is choosing not to "tax" the average residential home's 120 volt wiring/breaker…which is a good choice - cause where household outlets are concerned you simply don't know the quality of the wire, how old it is, and if it was originally properly specfied - also with household outlets the plugs are more likely to be a shared 120V/15 amp circuit rather than dedicated - so while your EV is charging someone might fire up the microwave (another high demand appliance) and be on the same "circuit/breaker" as the EV currently charging.

Chevy with their Bolt default to 8 amps for 120 volt charging sessions, but you can override and set it to 12 amps - but it will "forget" that setting for the next charging session - Chevy being very familiar over the years with liability law suites saw fit to make this a standard feature of the Bolt's charging software - and again this is a very conservative and reasonable approach.

Depending on the home and the circumstance I would be comfortable dialing the charging session up to the full 12 amps one can expect from a 15 amp breaker (NEMA 5-15 plug) but I might attempt to evaluate the circuit before doing so by finding the breaker, flipping It, seeing what it affects, and trying to determine what is also on that shared circuit. You can also minimize the risk of circuit overload by charging from NEMA 5-15 at night while people are sleeping when there is unlikely to be competing demands (no one running the microwave while the car is charging if everyone it asleep).

the simple fact of the matter is you simply can't tell if a NEMA 5-15 plug has other high demand appliances "sharing" the same circuit/breaker (microwave, coffee maker, room heater, toaster oven, curling iron, hair dryer) - if an EV was charging even at 6 or 8 amps - and you fire up a 1000 or 1250 watt appliance on the same circuit - that will be too much load for the breaker and the wire - and the breaker should pop - however if the breaker does _NOT_ pop - you are now pulling too much current across 120 V wiring that may overheat, melt, short and potentially catch fire…it's a serious issue.

Well said. This is precisely why I've argued against people in forums saying "oh we can just install community charging plugs for EV's in dense areas and apartment complexes. 120v is fine for basic use." It's a much different beast to plan for EV charging than simply having a plug in the wall. Dedicated circuits become critical and at that point if you're running dedicated circuits, you might as well run 240v and properly evaluate the service panel. Mass charging of EV's in the wild will be an interesting problem that property owners and utility companies will need to figure out.

 

[chrisk]

Making sure that your circuit can handle X amps is a valid concern but that could be a warning screen or sticker on the charger. The same warning is needed even for 240v input.

The problem here is that the engineers who built the PMCC charger chose to allow/default 6amps without consulting with the engineers who build the car's charging system. I also suspect nobody tested that scenario either. This is not a 3rd party charger. This is the dedicated charger that comes with the car. The charger's settings should work for the car it comes with, so if 6amp is not enough it should not be an option when the plugged-in car is a Taycan.

 

[BlueShoes]

The problem here is that the engineers who built the PMCC charger chose to allow/default 6amps without consulting with the engineers who build the car's charging system. I also suspect nobody tested that scenario either. This is not a 3rd party charger. This is the dedicated charger that comes with the car. The charger's settings should work for the car it comes with, so if 6amp is not enough it should not be an option when the plugged-in car is a Taycan.

The rest about making sure that your circuit can handle X amps could be a warning screen or sticker.

wait a minute... are you suggesting the two groups of engineers aren't talking?? /S.

I bet you're right. Simple enough from the outside but classic forest for the trees problem. The joys of a first gen learning curve. With our first EV we learned our driving habits just didn't support L1 charging so I never have even tried to charge the Taycan like that but it's good to know because as has been noted elsewhere, sometimes like on vaca that's all you have!

 

[daveo4EV]

@chrisk I agree 100% - Porsche dropped the ball here - they should not be defaulting to a charge rate that will cause the vehicle to discharge/trip-offline the 12V battery - left hand didn't know what the right hand was doing - I think we can all appreciate and see the learning that is going on in the legacy automotive engineering departments here…

 

[daveo4EV]

The same warning is needed even for 240v input.

I'll quibble with this one slightly - the vast majority of 240 volt circuits "are" dedicated - they are typically installed to support a single and particular appliance - this is because the circuit is typically sized to exactly "match" the appliance it's being install for - there are few if any "shared" load use cases for 240 volt circuits, other than sub-panels.

but I see your point.

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