22KW OBC FAILURE INSIGHT & POSSIBLE SOLUTION

[whitex]

I both love and hate the fact that all these failures in reliability inevitably come down to $0.05 parts…

They cost a little more than that, even in volume, but the point remains - Porsche seems to spec out the absolute minimum/cheapest parts that will barely meet the spec. This is in line with the thin Porsche EVSE wires story and lack of thermal sensor in the plug, designed for industrial spec outlets. The other story about not being able to detect isolation breakdowns sounds similar too - lack of sensing capabilities. Heck, even the rear seat belt warning which always pops up whenever I start driving, is also Porsche cheaping out in occupancy sensors for rear seats. And yet they haven’t gotten their OTA solution despite building it for a decade now (since Mission E) or longer (other models need it too) - that would have saved them more money than cheapest parts (which actually cost then money).

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[ze_shark]

Porsche does not spec out that stuff. Suppliers do. And again, we do not know whether the component or the design is at issue.
But surely, Porsche has failed to detect these issues in its verification/validation protocols.
OBC, HVAC, all the same.

PCM is a whole different cluster because that is developped in house.

 

[ct14garage]

Sensible form fit function fix

Form Fit Function IMO is king when it comes to car repairs. Particularly, EVs of course. We do this a lot, not only Taycan.

For example second gen hybrids Cayenne Panamera we take the original 2014 Samsung battery modules and replace them with 2024 CATL battery modules with same size, voltage but higher capacity of course. When this battery was developed in 2014 the CATL modules didn’t even exist. This is a commercial repair solution already well tested by us which we have sold over 80 batteries with very good results.

Second gen hybrid Cayenne Panamera brand new electric range 20km. With our battery 45km, same as the third gen hybrids ??

In Taycan we have also done an experiment where we empty the original Taycan modules, empty them of the original LG pouch cells and reassemble them using CATL prismatic cells, welding them to make the same voltage as the original module with LG cells, welding the in module BMS voltage sensing wires… Done

I have built an experimental test Taycan battery (for my own test use only) in this way with CATL prismatic cells as opposed to LG pouch cell. Obviously this is not a commercial solution because I have no resources to perform the calculations and risk assessment etc that such a repair would need to be deemed safe and in this case as a matter of fact I have no way to guarantee it. So I cant sell it.

But just as a experiment, I think I’m the only person in the world who has driven a Taycan powered by CATL prismatic batteries LOL

Remember Fit Function is king when it comes to repairs. Whenever you repair anything the goal should be to replace whatever failed with an improved/stronger component reusing all the infrastructure which was designed for the previous component without having to make any changes whatsoever to that infrastructure (be it a circuit, a BMS etc)

For context:
- the Nexperia reference which OP (@ct14garage) claims to be using as a replacement to the STM SCTH40N120 is an early 2024 part.
- the original STM SCTH40N120 is an April 2021 part.
SIC parts are fairly recent.

I wonder whether the RDSON spec (100m Ohms vs 40 typ 60 max for Nexperia) plays a larger role in this application than the current rating itself IF the Metasystem design is borderline on thermal dissipation.

I do not think it’s a thermal problem, because I have experience with 22KW OBC blowing up within seconds of starting a charge, where everything still is cold.

That’s why I wanted to find a part with a bigger Amperage rating. I suspect the limiting factor is the Amperage.

But I don’t have the data or analysis to back up my suspicions, the repair works and that’s very great. But now remains to be seen whether the Nexperias will fry again. If they do, the flaw is within the circuit that drives the MOSFETS.

If it doesnt fail again or not as much I may have been right about amperage being the limiting factor.

 

[whitex]

Porsche does not spec out that stuff. Suppliers do. And again, we do not know whether the component or the design is at issue.
But surely, Porsche has failed to detect these issues in its verification/validation protocols.
OBC, HVAC, all the same.

PCM is a whole different cluster because that is developped in house.

Actually, Porsche failed to root cause the issue. If someone in a 3rd party garage can do it, why couldn't the mighty Porsche have figured out which part is failing and why. How many years had they had this charge fail? Rather than root cause, they chose to just stop selling it. Are there any competent engineering leaders who are empowered to make decisions left at the company? Or is it all just ran by bean-counters, trying to squeeze the last bit of profit out of the company before it sells its branding to some other compan? Perhaps we should look forward to a new PORSCHE brand, just like there is now an AUDI brand, which is not Audi, but related?

 

[whitex]

I do not think it’s a thermal problem, because I have experience with 22KW OBC blowing up within seconds of starting a charge, where everything still is cold.

My 19.2kW (US version of 22kW OBC) blew up when it was cold outsides, and also shortly after starting the charge in my garage, which has 19.2kW capable EVSE. My Taycan is charged whenever it's in the garage, so a lot of shallow battery charge cycles (20% or less), with an occasional 60% cycle (25% to 85%). The time it dies, it was starting at ~70% with target of 85% and it died once it got to 72%. Of course the part might have just been heat damaged from 2 years of usage. who knows.

Out of curiosity, what do you see the car (PIWIS) report as the error? When mine died, the error was saying something about being unable to read some temperature of the OBC (which prevented not just AC charging, but also DC charging). Since the car is under warranty, I just let Porsche change it out for free, but curious if it's the same failure more you're seeing.

 

[ct14garage]

Porsche failed to root cause the issue. If someone in a 3rd party garage can do it, why couldn't the mighty Porsche have figured out which part is failing and why.

I don’t quite picture Porsche taking an angle grinder and cutting opened failed OBCs as we do

Porsche’s position is that the OBC is one piece and unserviceable. They’re not gonna change this opinion.

instead they ditched the part when they got tired of it

 

[F1Ruaraidh]

Form Fit Function IMO is king when it comes to car repairs. Particularly, EVs of course. We do this a lot, not only Taycan.

For example second gen hybrids Cayenne Panamera we take the original 2014 Samsung battery modules and replace them with 2024 CATL battery modules with same size, voltage but higher capacity of course. When this battery was developed in 2014 the CATL modules didn’t even exist. This is a commercial repair solution already well tested by us which we have sold over 80 batteries with very good results.

Second gen hybrid Cayenne Panamera brand new electric range 20km. With our battery 45km, same as the third gen hybrids ??

In Taycan we have also done an experiment where we empty the original Taycan modules, empty them of the original LG pouch cells and reassemble them using CATL prismatic cells, welding them to make the same voltage as the original module with LG cells, welding the in module BMS voltage sensing wires… Done

I have built an experimental test Taycan battery (for my own test use only) in this way with CATL prismatic cells as opposed to LG pouch cell. Obviously this is not a commercial solution because I have no resources to perform the calculations and risk assessment etc that such a repair would need to be deemed safe and in this case as a matter of fact I have no way to guarantee it. So I cant sell it.

But just as a experiment, I think I’m the only person in the world who has driven a Taycan powered by CATL prismatic batteries LOL

Remember Fit Function is king when it comes to repairs. Whenever you repair anything the goal should be to replace whatever failed with an improved/stronger component reusing all the infrastructure which was designed for the previous component without having to make any changes whatsoever to that infrastructure (be it a circuit, a BMS etc)




I do not think it’s a thermal problem, because I have experience with 22KW OBC blowing up within seconds of starting a charge, where everything still is cold.

That’s why I wanted to find a part with a bigger Amperage rating. I suspect the limiting factor is the Amperage.

But I don’t have the data or analysis to back up my suspicions, the repair works and that’s very great. But now remains to be seen whether the Nexperias will fry again. If they do, the flaw is within the circuit that drives the MOSFETS.

If it doesnt fail again or not as much I may have been right about amperage being the limiting factor.

Great stuff.

The fact that a known solution from Porsche is to turn the current down in single phase mode shows that current rating is indeed the prob.

Great fix. Nice one on the CATL cells too. Was deeply unimpressed with LG cells when we did eSLS way back when.

 

[whitex]

I don’t quite picture Porsche taking an angle grinder and cutting opened failed OBCs as we do

Porsche’s position is that the OBC is one piece and unserviceable. They’re not gonna change this opinion.

instead they ditched the part when they got tired of it

This is wrong on so many levels. If a part keeps on dying on multiple cars, you don't just keep on swapping it and/or discontinue it. You root cause the issue. At least that is what I would be doing if I was running Porsche engineering (which I don't ). Porsche seems to be aging really badly in the 21st century.

 

[ct14garage]

PS: It’s not so much that they don’t care about it, but all the Electrical system of the Taycan wasn’t designed nor built by them. They relied on LG, MetaSystems, HITACHI and plenty others. Those are the ones really responsible so Porsche doesnt bother with it. It’s not their job to fix their mess.

When the OBC fails and Porsche repairs it for you for free, Porsche then claims this cost back from Metasystems. Every single time.

 

[Gru]

My 19.2kW (US version of 22kW OBC) blew up when it was cold outsides, and also shortly after starting the charge in my garage, which has 19.2kW capable EVSE. My Taycan is charged whenever it's in the garage, so a lot of shallow battery charge cycles (20% or less), with an occasional 60% cycle (25% to 85%). The time it dies, it was starting at ~70% with target of 85% and it died once it got to 72%. Of course the part might have just been heat damaged from 2 years of usage. who knows.

mine blew up while charging at the office at 3.2kW, underground parking, mild temperature. The office charger was damaged too after. So I don't know if the cause was the charger or the car.

I charge 99% of the time at 22kW or DC 270kW. Obviously temperature wasn't the cause when it broke.

 

[simcity]

Its probably best to keep this discussion strictly to OBC's and repairs rather than views on climate change etc.

 

[hifi239]

Home AC chargers above 11.5kW are rare in the US. I've seen Blink AC at 15kW, but 99% of public AC is 6kW. Would the MOSFET failure be less likely if I never charge at the higher rates people here have mentioned? I have the 19.2kW option.

 

[ct14garage]

Home AC chargers above 11.5kW are rare in the US. I've seen Blink AC at 15kW, but 99% of public AC is 6kW. Would the MOSFET failure be less likely if I never charge at the higher rates people here have mentioned? I have the 19.2kW option.

As I’ve seen no difference.

 

[hifi239]

As I’ve seen no difference.

Thanks. It is odd, however, that this is so random. I've AC charged 3x per week for three years with no problem. I wonder if it was a bad batch of MOSFETs.

 

[Chiu]

I can totally relate to this. When I use an AC charger with more than 11kW, it triggers a red error and fails to charge in less than 30 minutes. However, if I reduce the power to 9kW, the charging completes successfully up to 100%.

This issue has been bothering me for a while, especially since Tesla allows users to adjust the AC charging power directly from the screen, while the Taycan always draws the maximum available AC power.

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