Pt.2: Taycan lets you drive with shorted out battery modules [VIDEO]

[HellNo]

Another fire bomb on wheels at the shop. This car has the ARB6 update installed.

For the uninitiated among us, would you mind explaining a little about what we are looking at here? I get that it’s not good, but what is it - Is that corrosion? Heat damage? Leaking cells?

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[ct14garage]

For the uninitiated among us, would you mind explaining a little about what we are looking at here? I get that it’s not good, but what is it - Is that corrosion? Heat damage? Leaking cells?

pools of water under the modules and fully dead short circuit cells

 

[Tooney]

pools of water under the modules and fully dead short circuit cells

What symptoms originally brought that Taycan into your shop for repair?

Did driver get any warnings on instrument panel? (Such as the supposed ARB6 yellow warning "service necessary"?)

Any internal diagnostic codes?

In other words, did the car's driver warning system or internal codes provide warning before you removed the HV battery?

 

[ct14garage]

Did driver get any warnings on instrument panel?

Yes sure, there was a yellow electrical system fault in the dash that occasionally turned red....... BUT, a car with a battery in this condition shouldn't be driving, let alone CHARGING....

 

[ct14garage]

a car with a battery in this condition shouldn't be driving, let alone CHARGING....

Speaking of which, a question I have been asked many many times.... Let's clear it up once and for all.

Many people in the past have seen this frequent statement of mine and immediately asked,
but Cris, these batteries discharge at 600-700KW under fast acceleration, while they only charge at like 350KW maximum, isn't discharging more likely to cause thermal runaway?

The reality is a bit more nuanced than comparing KW. During charging ions are being intercalated (pushed) into the anode of the cell. Whereas during discharge (fast acceleration) those very same ions simply leave the anode and move towards the cathode.

Then we have to factor in the cells that Taycan uses, which are LG pouch cells LG66... It is very well known and acknowledged by LG/Porsche in multiple bulletins that some of these cells suffer from internal defects. These internal defects over time lead to plated Lithium, which during charging, and specifically during charging at high SoC may suddenly pierce the separator, resulting in an internal short.

This internal short will of course cause a ton of heat which the cell is unable to dissipate and at some point that heat starts a thermal runaway chain reaction.

This is the exact reason why Porsche's solution is to limit the charging to 85%. Because in bad LG pouch cells the biggest risk of thermal runaway is during or right after charging at high SoC (> 85%)


Discharging on the other hand, even at peak power merely generates heats by means of I2R loss (the internal resistance of the battery). There are no documented runaway cases of LG pouch cells under discharge (this is not say it can't happen but yeah)....


So yeah.... in the case of Taycan and other EVs which use LG Pouch Cell.... The real danger for the car burning itself to ashes really only comes when charging specially at high SoC



Remember, Taycan fire usually follows these steps

Cell Internal short (a lot of heat generated) -> Heat causes thermal runaway -> Thermal runaway spreads (the heat spreads) to nearby cells and modules -> The car is burned to ashes

 

[Tooney]

So yeah.... in the case of Taycan and other EVs which use LG Pouch Cell.... The real danger for the car burning itself to ashes really only comes when charging specially at high SoC

Does it matter whether the charging at high SoC is being done at AC Level 2 or DC fast chargers?

 

[Jasper4S]

Call me stupid if it is a dumb question, I really have no clue how batteries work exactly. What is the worst thing that can happen if you keep driving with the batteries as in your picture? High voltage shock hurting me? Shock that could fry other electronics in the car? Fire? Decreased range? Power loss? All?

 

[ct14garage]

Call me stupid if it is a dumb question, I really have no clue how batteries work exactly. What is the worst thing that can happen if you keep driving with the batteries as in your picture? High voltage shock hurting me? Shock that could fry other electronics in the car? Fire? Decreased range? Power loss? All?

High voltage shock hurting the occupants is a possibility. I have several customers who have experienced this. Another possibility is EV fire.

Decreased range is basically a given. Frying other electronics in the car is not possible

 

[ct14garage]

Does it matter whether the charging at high SoC is being done at AC Level 2 or DC fast chargers?

These defective LG cells just have issues with being charged at high SoC, regardless of the speed.

BUT naturally, fast charging will heat the cells more thereby reducing the window to thermal runaway point. Making it easier for the cell to reach the critical temperature if that makes any sense.

 

[Fish Fingers]

@ct14garage

How many of these repairs have you done and how many Taycans are there in Thailand (approx)?
Just wondering what the frequency is and if there are any circumstances which affect Thai fleet differently to elsewhere?

Second question, how bad are the HV shocks people have had?

 

[D00notD00d]

I’m confused:

-The HV battery compartment seal is pressure tested to prevent air and moisture ingress.

- The HV battery is voided if the vehicle has been damaged by external causes or influences (e.g. accident, hail, flooding, animal bite).Animal bite?

- Contradictoraly, the HV battery compartment has drain holes. These are not/cannot be one-way.There’s a servicing requirement to check & clean the drain plugs. And a service bulletin to remove the drain plug filter if it becomes blocked.

Regular monsoon flash floods will be a factor in Thailand. But nevertheless you’d expect the Porsche safety design to detect short circuits and shut down the battery.

Have any flooded j1.2s been seen so far? Does this problem also affect the RS e-Tron?

 

[ct14garage]

The HV battery compartment seal is pressure tested to prevent air and moisture ingress.

When it leaves the factory yes, but any seal deteriorates over time. And some even have defects on the sealant (there is an active recall for this)

Contradictoraly, the HV battery compartment has drain holes. These are not/cannot be one-way.There’s a servicing requirement to check & clean the drain plugs. And a service bulletin to remove the drain plug filter if it becomes blocked.

This means nothing, those drain hole are in the exposed center part of the battery, where it's not sealed and totally exposed, not even covered by the lids where the drain holes are.

those drain holes have nothing to do with the sealed inside of the battery

 

[ct14garage]

Second question, how bad are the HV shocks people have had?

I've had several customers report being shocked in the lower calf of the legs when exiting the car. One of them was a woman and she reported each time it hurt quite a lot making her almost not want to drive the car.

I haven't experienced it myself, nor can I scientifically explain how it happens.

BUT different unrelated customers have reported the same thing, and each customer who reported it their batteries were leaking electricity so there must be some truth it.

 

[D00notD00d]

@ct14garage - thanks for the info.
Is it only if the lid sealant has failed that water ingress via the drain holes into the module compartments could occur?
Is blocked drains therefore secondary rather than a cause of water entry?

Coincidentally I came across this today

It covers battery removal, module replacement and cell balancing.
A few things that were surprising to me:
- a cell balancing error can occur if the vehicle has been idle for a while (perhaps that’s why Porsche say that if idle for 2 weeks or longer a SOC of between 20-50% should be maintained, plus if not connected to a mains supply, the car should be charged to 50% before parking). Not all Porsche dealers are aware of this and apply it to their stock.
- the quantity of thermal paste used is specific and variable in each module compartment.
- the battery compartment lid isn’t reused.

Lid sealant is discussed around 10min in.
The Porsche tech says Porsche AG advice is that the lid is (designed & tested to be) ’watertight’ not ‘waterproof‘.
I wasn’t previously aware that there’s a difference, but whereas watertight will keep water out as long as the seal remains intact, apparently waterproof provides sustained protection even when submerged and in harsh conditions. He also says we shouldn’t believe the stuff we read about leakages on the internet….but maybe the floods in Florida aren’t as bad as those in Thailand.

 

[ct14garage]

- the quantity of thermal paste used is specific and variable in each module compartment.

Yes, hence why in the batteries I rebuild we don't use thermal paste and instead use thermal pads of equivalent w/mk that don't need specific measuring due to the slightly curved module beds....

I get why in an automated manufacturing process liquid TMI makes a lot of sense over thermal pads as a robot can very easily and accurately apply the liquid TMI. But for us it makes no sense whatsoever to measure the quantity of old TMI and apply exactly the same weight of the new one...

Also this liquid TMI Porsche uses Polytec VP2106 absorbs humidity so any water inside the battery will always end up in the thermal interface right under the modules... not good...

Polytec VP206-408 thermal conductivity: 2.7w/mk
CT14 pad thermal conductivity: 3.1w/mk

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