"Taycans drive with shorted out battery modules"

[Tooney]

First of all, where my shop is based there are a lot of Taycans, over two thousand of them. Most of them are grey import cars which have been shipped all the way from the UK. They of course don’t have any sort of warranty… So we repair them daily and very often see a potentially dangerous situation which I will detail below:​

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Once again a waterlogged disaster - several fully shorted out modules… Factory battery seal…imagine driving around with this ticking time bomb while merrily DC-charging it. It’s like playing EV fire roulette! ?​

. . .

Porsche’s BMS (Battery Management System) is often blissfully unaware tho, letting you drive around with modules that have the electrical isolation of a soggy potato? (yep, I’ve seen even 0.2MΩ!!!). Yet the bloody thing’s as clueless as a GPS in a concrete jungle.​

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When the safety systems do finally kick in (after many days), it’s not even the BMS that’s doing the saving—it’s the voltage converter (DCDC) that realizes somewhere there is a MAJOR electricity leak and requests safety shutdowm of car’s HV system (the equivalent of “tripping the breaker at home”). Seen it happen so many times, I could write a book about it.​

Google search for: Taycan shorted out battery
https://rennlist.com/forums/taycan/...ive-with-shorted-out-battery-modules-wtf.html

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[laua]

Holy shit. Well - I’ve got my popcorn out. I’d love to hear others with more tech experience chime in.

 

[Caraholic]

Have a feeling this is what happened to my car for its battery replacement. There was a comment made by the tech that the chassis had current flowing through it. So it had to be shipped off to another dealer. This is a bit scary as I was driving around a month with that error waiting for the shop time

 

[r553]

My 2020 4 S got a replacement re-manufactured battery installed in July of this year.
I brought my car to the dealer because I noticed a loss of range in one week. While the car was at the dealer being checked out the battery shut down. The car gave me no error messages. It took about a month all together. Getting the battery was about three weeks. I was told the re-manufactured battery was a 2023 model. The replacement battery restored my range loss and then some.

 

[Dr Bob]

First of all, where my shop is based there are a lot of Taycans, over two thousand of them. Most of them are grey import cars which have been shipped all the way from the UK. They of course don’t have any sort of warranty… So we repair them daily and very often see a potentially dangerous situation which I will detail below:​

​

Once again a waterlogged disaster - several fully shorted out modules… Factory battery seal…imagine driving around with this ticking time bomb while merrily DC-charging it. It’s like playing EV fire roulette! ?​

. . .

Porsche’s BMS (Battery Management System) is often blissfully unaware tho, letting you drive around with modules that have the electrical isolation of a soggy potato? (yep, I’ve seen even 0.2MΩ!!!). Yet the bloody thing’s as clueless as a GPS in a concrete jungle.​

​

When the safety systems do finally kick in (after many days), it’s not even the BMS that’s doing the saving—it’s the voltage converter (DCDC) that realizes somewhere there is a MAJOR electricity leak and requests safety shutdowm of car’s HV system (the equivalent of “tripping the breaker at home”). Seen it happen so many times, I could write a book about it.​

Google search for: Taycan shorted out battery

I consider myself to be an expert on Li batteries but that is on the battery chemistry rather than the battery module construction and BMS design (of which I know little on the Taycan). What is certain though is that a fully functioning BMS system cannot manage each cell and module (voltage, internal cell resistance & isolation, etc) the way it needs to – too many wires, instrumentation and complexity. I can see what the guy in Thailand is saying – thanks for posting it Tooney – and I think there is probably a lot of credibility in that. If a module is not isolated and is allowing current to flow to the chassis then you would have thought that the BMS would pick up a voltage drop in the module but then would it, if there is a fault in the BMS? How robust really is the BMS? Battery packs are failing and the spotlight is normally falling on cell malfunction – I know I have commented on how cells fail and relationship to balancing and overcharging – but is the BMS one of the root causes allowing cells to go badly out of balance (and hence overcharging) due to it not monitoring module performance properly? I'll watch the comments coming out of the guy in Thailand with more interest now!

 

[chun]

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Google search for: Taycan shorted out battery

Can you... perhaps, copy+paste the link?

 

[Tooney]

Can you... perhaps, copy+paste the link?

https://rennlist.com/forums/taycan/...ive-with-shorted-out-battery-modules-wtf.html

 

[kurand]

so, what is actually being measured to get these 200KΩ readings and how are they being measured? you can’t just take a multimeter in resistance range and measure an active component like a battery; any residual charge in the battery will invalidate the reading. also, 200KΩ is still a pretty big resistance.

 

[WasserGKuehlt]

I reckon anyone equipped with a basic understanding of Kirchoff’s laws would be able to detect a “fully shorted” module, so I am skeptical of the claim of incompetence or even that it’s a prevalent fault. Having read the RL thread (oh, RL, you’re unchanged), the OP over there does advance the possibility that the car/BMS does not overreact on purpose (so as not to brick the car on noise, given that there is an eventual protection). But it’s hard (for me) to understand what is the claim here: is it that batteries aren’t sealed properly, or that the car’s safety systems aren’t? I don’t think we can infer much from one waterlogged battery, except perhaps that even in that case the battery did not self-combust..?

 

[chun]

But it’s hard (for me) to understand what is the claim here: is it that batteries aren’t sealed properly, or that the car’s safety systems aren’t? I don’t think we can infer much from one waterlogged battery, except perhaps that even in that case the battery did not self-combust..?

He is saying the car is giving errors to late, and you end up driving hundreds of kilometers with the battery being on the brink of a fire before you get an error from the DCDC that shuts it all down.

He is saying the BMS should inform the driver something is not ok much sooner.

He is also saying smallest breakage of the sealant for the battery enclosure will guaranteed result in this sooner or later, as water is being forced in there while driving; and the of course refurbished batteries / batteries that were worked on are much more likely candidates for issues.

 

[ct14garage]

so, what is actually being measured to get these 200KΩ readings and how are they being measured? you can’t just take a multimeter in resistance range and measure an active component like a battery; any residual charge in the battery will invalidate the reading. also, 200KΩ is still a pretty big resistance.

Who ever measures isolation of High Voltage component with a multimeter in resistance range? ROFL

iso is measured with a Fluke 1508 or similar insulation meter which sends a signal of either 500V DC or 1000V DC and makes up the isolation measurement from that.

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