Porsche working on making SoH available to owners - Article

[Sace]

This is a rabbit hole for sure. The moment a displayed SoH drops by one half of one percent, Porsche will have angry customers lined up at their dealerships with pitchforks demanding “justice”. No good can come from this….

Probably why they wan't to come up with a more "stable" SoH reading than the one you can get from the OBD canner. That one jumps up and down depending on usage and is only really useful if you track it over time.

You can see the same on computers. My MacBook Air reports 86% of original battery capacity in the OS. If I use a third party app to evaluate the battery it reports between 80 and 87% SoH depending on various things.

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[Murph7355]

This is a rabbit hole for sure. The moment a displayed SoH drops by one half of one percent, Porsche will have angry customers lined up at their dealerships with pitchforks demanding “justice”. No good can come from this….

Except that they warranty SoH levels over time.

Ergo they must know how to measure it (or they are making it up as they go along).

Ergo they should be able to let the customer view this freely (otherwise they stand to be accused of making things up as they go along to suit their needs).

It's not like VAG have history of making things up to suit their needs....

 

[whitex]

“We’ve hardly seen a [Taycan] battery that has lost more than 5 per cent, 8 per cent (of its original capacity),” he said.

I am the only person who is having a problem parsing this? Does this mean they haven't seen a drop of 5% which would put it below 8% of original capacity?

 

[whitex]

They haven't seen mine ?.
(Dropped to 92 within a year, recovered to a now-steady 93.3. So he's technically correct, as 92 is not "more than 8".)

My SoH, 16 months after delivery, was 93.726% (my recent reading), so definitely more than 5% less than 100%, but under 8%. I couldn't parse the original Porsche statement. It reminds me of my kid's teacher stating "you paper must be a minimum of 5-8 pages long".

 

[RAHRCR]

Except that they warranty SoH levels over time.

Ergo they must know how to measure it (or they are making it up as they go along).

Ergo they should be able to let the customer view this freely (otherwise they stand to be accused of making things up as they go along to suit their needs).

It's not like VAG have history of making things up to suit their needs....

I haven’t bothered to read the weedy details of the battery warranty but I suspect that it is related to the health of the battery at the end and very little to do with where it is along the way. Get your pitchforks ready…

 

[Murph7355]

I haven’t bothered to read the weedy details of the battery warranty but I suspect that it is related to the health of the battery at a end and very little to do with where it is along the way. Get your pitchforks ready…

I believe they warranty it to be greater than 70% original capacity by the 8yr mark.

So at any point prior to that they should be able to see where it's at - if it was 70% at 5yrs I'd want mine replaced.

Either way, there must be a measurement method. So why the secrecy from them. "But you simple customers wouldn't understand" doesn't cut the mustard

It's this sort of thing that makes the market nervous about EVs. The manufacturers need to tackle it head on. Not doing so is contributing to piss poor residuals, which will damage Porsche more widely if they aren't careful.

 

[Dr Bob]

So at any point prior to that they should be able to see where it's at - if it was 70% at 5yrs I'd want mine replaced.

Either way, there must be a measurement method. So why the secrecy from them. "But you simple customers wouldn't understand" doesn't cut the mustard

The problem is that there is no one measurement to assess SoH. The first post says that Porsche aren't finding it easy to define.
Yes, we all see the SoH value via an OBD but that is not the full state of health. It is a measure of what capacity we have in the battery today- and that is not an easy calculation. It cannot be measured directly from say a multi-meter. The capacity is important in the overall state of health but you also need to consider the condition of the cells and module. Are the cells changing in internal resistance? Are we getting thermal damage to the cells? Is the BMS having to do excessive work in balancing as we approach 100% SoC, etc? There are many, many specs that need comparing but capacity is the most important. Not all those cell related specs would show up in reduced capacity (but many will). I could have a battery with a good capacity but is about to die. It's health therefore wouldnt be very good. Trouble is, we all think SoH is just the current capacity.
Think about it - if you loose a cell (due to a voltage variance from the other cells) and get the red screen of death, your SoH is unlikely to be any lower than the time just before the cell failled.
I guess Porsche wouldnt want to change the SoH to 'Capacity today' as then peeps would be calling them on a half % drop.

 

[BullitX]

I believe they warranty it to be greater than 70% original capacity by the 8yr mark.

So at any point prior to that they should be able to see where it's at - if it was 70% at 5yrs I'd want mine replaced.

Either way, there must be a measurement method. So why the secrecy from them. "But you simple customers wouldn't understand" doesn't cut the mustard

It's this sort of thing that makes the market nervous about EVs. The manufacturers need to tackle it head on. Not doing so is contributing to piss poor residuals, which will damage Porsche more widely if they aren't careful.

They will only replace the cells that are below the threshold, until the total unit reaches or exceeds the threshold. So basically if you have 9 cells at 70% and one at 60%, they would just replace that single cell with a new one (if you are lucky) or with a spare cell (used?) that would be 70% or higher.

Edit:
For clarifiction: if you have multiple cells below the threshold, they could just replace enough cells to reach the total threshold. Which means you could end up with a battery pack that has a bunch of mixed cells, for example 4x 75%, 3x 68%, 1x 60%, 2x 80%. As long as the total average health is at or above the threshold.

 

[Dr Bob]

They will only replace the cells that are below the threshold, until the total unit reaches or exceeds the threshold. So basically if you have 9 cells at 70% and one at 60%, they would just replace that single cell with a new one (if you are lucky) or with a spare cell (used?) that would be 70% or higher.

How on earth are Porsche going to measure the capacity of an individual cell? You calculate SOC and hence track capacity by measuring the Amps in and Amps out and then running some algorithims that give you a % number. Amps in and out is also not easy when you have to factor in Peukert's equation. No way can you report an SOC or capacity on each cell. I was also understanding that Porsche were replacing modules not cells.
Cells will be replaced if the voltage varies outside given guidelines not on the capacity of a cell.
One essential of these batteries is that the cells need to be matched. Hence if you had most of the cells with a capacity of near 70%, ie the overall bank is old, tired and lost a lot of capacity over the years, you cannot go putting in a new cell with 90 or 100%. That would wreck the balancing of the bank. Cells with 20% difference in capacity will mean very big differences in cell voltage as the cells increase in voltage into the top knee when charging up to 100%. The BMS would not have time to rebalance and you would end up with cells at 100% SOC with others in the low 90's. Even the 5% (?) buffer Porsche put in would not prevent an overcharge which would then be a huge safety risk with chance of dendrite formation, thermal runaway and potentially fatal fire. Cells have to be matched for the battery to operate properly.
Today while the Taycan is still relatively a new model, its easy to replace a failed module with a new one as the battery is still likely to be at 90% capacity and the new one will soon be down to that. As we start approaching the 8 year old Taycan, it will be interesting to see how they replace modules where the battery SoH is down at 80%.

 

[BullitX]

How on earth are Porsche going to measure the capacity of an individual cell? You calculate SOC and hence track capacity by measuring the Amps in and Amps out and then running some algorithims that give you a % number. Amps in and out is also not easy when you have to factor in Peukert's equation. No way can you report an SOC or capacity on each cell. I was also understanding that Porsche were replacing modules not cells.
Cells will be replaced if the voltage varies outside given guidelines not on the capacity of a cell.
One essential of these batteries is that the cells need to be matched. Hence if you had most of the cells with a capacity of near 70%, ie the overall bank is old, tired and lost a lot of capacity over the years, you cannot go putting in a new cell with 90 or 100%. That would wreck the balancing of the bank. Cells with 20% difference in capacity will mean very big differences in cell voltage as the cells increase in voltage into the top knee when charging up to 100%. The BMS would not have time to rebalance and you would end up with cells at 100% SOC with others in the low 90's. Even the 5% (?) buffer Porsche put in would not prevent an overcharge which would then be a huge safety risk with chance of dendrite formation, thermal runaway and potentially fatal fire. Cells have to be matched for the battery to operate properly.
Today while the Taycan is still relatively a new model, its easy to replace a failed module with a new one as the battery is still likely to be at 90% capacity and the new one will soon be down to that. As we start approaching the 8 year old Taycan, it will be interesting to see how they replace modules where the battery SoH is down at 80%.

My bad, I meant modules. Not the individual cells. Battery packs contain modules and modules contain cells. They can check on a module basis, and replace that module.
Ergo akin a refurbished battery pack.
I apologise for the confusion.

Edit: That they could replace certain parts of the battery is also mentioned in their warranty, at-least here in europe.

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