Dreaded Red Electrical System Error & Poll

[D00notD00d]

My understanding is that failure of one module will affect the balancing procedure. There is a maximum permitted variation between cell voltages.
The State of Health/capacity is only as good as the least healthy module\cell.

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[Sace]

It's very good questions. But since they can't repair a module a single failing cell requires replacement of the module it sits in. But why we typically see multiple module replaced is indeed odd. It seems that the cells are generally quite prone to failure

 

[tonycolin]

theres a guy over at rennnlist, whos a wizard with these batteries.

https://rennlist.com/forums/taycan/1387965-diy-taycan-battery-module-replacement-2.html

quote from him

"No doubt. C modules (2020) have a defective chemistry which was later upgraded in G modules (2021).

This causes at least one of the cells inside the module to suddenly drop voltage to 0.00V and cause the battery to fail with a Cell Voltage difference too high error.

This fault is basically exclusively to 2020 model. And quite common. I dare to say every single 2020 car will have this issue sooner or later.

2021s, 2022s, 2023s, 2024s experience battery issues as well. But its isolation problems, or temperature sensing problems, etc."

very interesting

 

[Dr Bob]

@Avantgarde - First, I agree with your comment that we are missing specifics as to why modules fail, and at what point module failure leads to total battery replacement. It seems to me that there are three possibilities --

• Manufacturing Defects in Modules -- Each module is manufactured by a third party (LG?) and every manufacturing line experiences some small degree of variation which can lead to occasional failures.
• Catastrophic Failure -- In this case an event occurs during Taycan use that causes the electronics, or cooling system to not support the HV battery, causing battery failure. While I have not heard of examples of these, they are certainly possible if Porsche didn't design robust and redundant systems, or if you are in an accident and the car is damaged.
• Usage-based Wear & Tear -- As it happens, there are optimal ways to keep your HV battery healthy, and if you don't follow these guidelines it can lead to individual module failure, or simply lower levels of maximum State of Charge. The recommendations are at this link and are a summary of a video in the same link that discusses battery chemistry.

Perhaps over time some of those affected will be able to share specific reasons why a battery module has failed. Personally, I doubt that a single module failure would lead to a spreading impact across multiple cells, but I could be wrong on that. Perhaps @whitex has some insights since he has been an EV owner across Taycan and Tesla.

There is a load of c$£p talked about batteries on the internet but the quote from Sam above is pretty accurate with the 3 methods of cell failure. Let's look at them in a bit more detail.

The manufacturing defects are probably the most likely when looking at cell failure. Cells are manufactured to exacting standards but QC can fail and batteries with specific weaknesses can make it to the car makers. Are the cells well matched (ie same capacity), are the cells the same internal resistance, are they made properly, have they the same chemical material in them etc etc? At a conference I went to pre Covid, I saw slides of a Li-ion battery made in China (aren't they all?) with pieces of copper wire in the cells – just waiting the give a thermal runaway on overcharging. How can a battery be made that badly? Out of spec cells when fitted in a battery pack will likely work quite well to start with but can then start to go out of balance (more than the BMS can fix) and so you end up overcharging cells which in turn destroys the mechanical integrity (and chemistry) and so even more out of balance. Once cell voltages vary too much in a module it will shut down and a new module is required. Some cells not constructed properly can me prone to mechanical issues when stressed with temperature (high and low) which again change the internal resistance and hence all the above problems. There are many other reasons why a cell will fail if it is not in spec – but most follow the above route.

The previous post by Tony which quoted:

"No doubt. C modules (2020) have a defective chemistry which was later upgraded in G modules (2021).

This causes at least one of the cells inside the module to suddenly drop voltage to 0.00V and cause the battery to fail with a Cell Voltage difference too high error.

is interesting but some of this is a load of rubbish. Ok, the cells are ending up showing 0.00V and so the module fails because of cell voltage difference. That delta voltage will certainly mean the BMS takes the module out of circuit. However, battery chemistry will never cause a sudden voltage drop to zero. Far more likely is a hardware failure with a conductor in the cell not conducting. Failing chemistry would be a gradual change. Maybe this is why the C type module have been failing and that then is down to poor QC and the faulty cells have been supplied (but not battery chemistry). I know why Tony is worried it will happen to every battery but that is perhaps a bit pessimistic. Certainly many cells may have failed that way but it is only a small fraction. Maybe 95% of those made were in spec on that specific issue and so will not fail as the other have. It is possible they are all bad and everyone will fail eventually.

The second area is down to the environment the cells are in – how they are cooled and heated, how the BMS operates (and particularly how it balances the cells). This is then down to Porsche and we just dont know how many failures are down to say BMS failures. A stone hitting the bottom of the car and affecting the cooling system is certainly Porsche's problem in poor design.

The third area (wear and tear) is something that can we can do something about. Our charging regime will have an effect on the batteries. Someone who charges to 100% every time and then drives to below 5% will stress their battery more than someone who is sensible and keeps to the normal charging limits. The stress on the battery will affect cells in a different way if the cells are not perfect. Cells which are borderline good and borderline on balancing will not survive as well if stressed. The variation in how people look after their batteries will skew the results when looking at cell performance across all the peeps on here. I've said it before on here and I am still of the view that the ability to charge the Taycan very fast (ie at 3C – over 270Ah) is really pushing the limit of battery stress and hence the need for top quality cells.

Maybe the above can help Avantgarde understand the mystery he sees in why batteries are being replaced.

 

[Dr Bob]

It's very good questions. But since they can't repair a module a single failing cell requires replacement of the module it sits in. But why we typically see multiple module replaced is indeed odd. It seems that the cells are generally quite prone to failure

One theory as why we see individual cells failing in a module and thus writing it off, then seeing this happening in a number of modules, could be that a only small number of cells have manufacturing defects (as per my post above) and so only a small number of cells are failing and spread out over different modules. Single cells failing is as sign that the cells are not quite prone to failure - the exception rather than the rule. The problem is that one cell failing has a dramatic effect for us - ie the need for the car to go back to the service centre... again.

 

[baboum68]

My CT4S MY2022 is at the garage for its second HV charger replacement. First one was replaced in July 2023 and I was told at the time that the part had a new ref. Number. My serviceman called me today saying the new part has arrived and when asked, it sounds like it is the same ref. Number as when replaced in 2023. Bottom line is that I am going to have a car that is most likely to get the same problem again. I can’t believe that after 3 years of know issues with this, Porsche doesn’t seem to have any fix for this problem.

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