CCS Failure Question / Discussion

[Bill Carlson]

I have ~22k miles and no PCS issue (yet) although my PCS is on the "bad" list. My home charger is 60->48A 240VAC and I can charge at work at 240VAC 30A.
I rarely supercharge as the other 2 are free. I *can* set these down to 24A charge rates if needed.

I'm aware that the recommendation to avoid/delay CCS failure is a lower charge current (24A)... Do we have any paperwork to back that up? Sounds like all we know is that there are a bunch of potential FET issues cold solder joints in affected lots/parts. I can trim back charging rate but quite honestly I'd rather fail fast and wait as opposed to drag my feet and hit 50K miles and then be past warranty. I'm interested in hearing thoughts on this as I don't want indefinitely be feel like I need to charge at 24A ...... ...... ......

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[mongo]

I have ~22k miles and no PCS issue (yet) although my PCS is on the "bad" list. My home charger is 60->48A 240VAC and I can charge at work at 240VAC 30A.
I rarely supercharge as the other 2 are free. I *can* set these down to 24A charge rates if needed.

I'm aware that the recommendation to avoid/delay CCS failure is a lower charge current (24A)... Do we have any paperwork to back that up? Sounds like all we know is that there are a bunch of potential FET issues cold solder joints in affected lots/parts. I can trim back charging rate but quite honestly I'd rather fail fast and wait as opposed to drag my feet and hit 50K miles and then be past warranty. I'm interested in hearing thoughts on this as I don't want indefinitely be feel like I need to charge at 24A ...... ...... ......

We don't "know" anything other than it reports a MOSFET health fault.
Keep charging as you were, people with lower charge currents have failed PCS also.

 

[CyberGus]

SAVE US SANDY MUNRO

 

[yohst]

I have ~22k miles and no PCS issue (yet) although my PCS is on the "bad" list. My home charger is 60->48A 240VAC and I can charge at work at 240VAC 30A.
I rarely supercharge as the other 2 are free. I *can* set these down to 24A charge rates if needed.

I'm aware that the recommendation to avoid/delay CCS failure is a lower charge current (24A)... Do we have any paperwork to back that up? Sounds like all we know is that there are a bunch of potential FET issues cold solder joints in affected lots/parts. I can trim back charging rate but quite honestly I'd rather fail fast and wait as opposed to drag my feet and hit 50K miles and then be past warranty. I'm interested in hearing thoughts on this as I don't want indefinitely be feel like I need to charge at 24A ...... ...... ......

Tesla has made no statement as to the causes of the failure - so all stated reasons are speculation. That said, as an EE I feel I can speculate a bit more specifically (grin) if that makes sense? Also there is this msg: https://www.cybertruckownersclub.co...d-info-on-pcs-issue-04-21-26-ai-answer.57114/. "reports from owners and service tech that MOSFETs blow"

Silicon part degradation have a strong relationship with junction temp. Additionally, board solder joint issues (if there are any) are 'exercised' by board flex (unlikely in this case) and board temperature cycling. If these issues are indeed the cause, then lowering AC charge will lessen the future chance the PCS lets go of the holy smoke. Of course, past degradation may have taken place already hence the possibility that it goes on a lower charge exists.

Getting that thing cooked and replaced is something I thought of also, but with current part shortage and future upcoming trips, I rather like to stretch my runway and lower my AC charges. I put a request in for the SC to monitor the state of my truck/PCS which they have under consideration (I don't think they will do anything with it, or if they can, but perhaps it helps to document where I am now and may be they proactively get the part going, who knows).

As others have said, it is sad that Tesla has not better planned this considering they knew of the 'bad series' for a while. They either think the problem is not as wide spread as we think it is (totally possible, we mostly hear of the bad ones) or think it is manageable (through free DC super charging) or ...

my 2ct

 

[Gigahorse]

I have ~22k miles and no PCS issue (yet) although my PCS is on the "bad" list. My home charger is 60->48A 240VAC and I can charge at work at 240VAC 30A.
I rarely supercharge as the other 2 are free. I *can* set these down to 24A charge rates if needed.

I'm aware that the recommendation to avoid/delay CCS failure is a lower charge current (24A)... Do we have any paperwork to back that up? Sounds like all we know is that there are a bunch of potential FET issues cold solder joints in affected lots/parts. I can trim back charging rate but quite honestly I'd rather fail fast and wait as opposed to drag my feet and hit 50K miles and then be past warranty. I'm interested in hearing thoughts on this as I don't want indefinitely be feel like I need to charge at 24A ...... ...... ......

You are halfway through your warranty. 48A it up

 

[CyberGus]

You are halfway through your warranty. 48A it up

I'm gonna charge at 48A all night, and then PowerShare the house all day until the PCS melts

 

[UberNoob]

Use it how it was intended if they wanted you capped at 24a they would software update that. Not looking forward to having to buy the replacement as mines out of warranty.

 

[mongo]

As others have said, it is sad that Tesla has not better planned this considering they knew of the 'bad series' for a while.

Please expand on this 'bad series' concept.

 

[yohst]

Please expand on this 'bad series' concept.

Affected series (PWA or SNR of MOSFETs/boards). Must admit I can't find the dang reference where I read it or how I came about it.

 

[Gigahorse]

I'm gonna charge at 48A all night, and then PowerShare the house all day until the PCS melts

YUPPP Not getting caught at 50,001 miles

 

[RoboTaxi]

The majority of my charging is at 110v and a little super charging. I have a PCS failure. I was under the impression lower AC rates wouldn’t cause the failure but…….

 

[mongo]

Affected series (PWA or SNR of MOSFETs/boards). Must admit I can't find the dang reference where I read it or how I came about it.

At one point an article came out that conflated the 2024 inverter recall and the PCS failures. Inverter did have specific VIN tracking. Maybe that is what you are thinking of?

 

[gtgarner]

My CT beast wouldn't charge via AC.

2 weeks at Tesla to replace something in the PCS and now it works.

 

[HaulingAss]

Tesla has made no statement as to the causes of the failure - so all stated reasons are speculation. That said, as an EE I feel I can speculate a bit more specifically (grin) if that makes sense? Also there is this msg: https://www.cybertruckownersclub.co...d-info-on-pcs-issue-04-21-26-ai-answer.57114/. "reports from owners and service tech that MOSFETs blow"

Silicon part degradation have a strong relationship with junction temp. Additionally, board solder joint issues (if there are any) are 'exercised' by board flex (unlikely in this case) and board temperature cycling. If these issues are indeed the cause, then lowering AC charge will lessen the future chance the PCS lets go of the holy smoke. Of course, past degradation may have taken place already hence the possibility that it goes on a lower charge exists.

Getting that thing cooked and replaced is something I thought of also, but with current part shortage and future upcoming trips, I rather like to stretch my runway and lower my AC charges. I put a request in for the SC to monitor the state of my truck/PCS which they have under consideration (I don't think they will do anything with it, or if they can, but perhaps it helps to document where I am now and may be they proactively get the part going, who knows).

As others have said, it is sad that Tesla has not better planned this considering they knew of the 'bad series' for a while. They either think the problem is not as wide spread as we think it is (totally possible, we mostly hear of the bad ones) or think it is manageable (through free DC super charging) or ...

my 2ct

I don't think lowering the charge current would reduce the chances of failure because the PCS is highly modular. First, there are two 24 amp Power Conversion Units, charging at half power (24 amps) will still run one of the PCUs at full power. Secondarily, each Power Conversion Unit has multiple MOSFETs in banks (not sure of how many). So at the current increases towards the maximum of 24 amps it's likely that each MOSFET is fully loaded before the next one kicks in.

Charging at a lower amperage just means you will be charging for more time, giving heat more time to build up in localized areas.

Personally, I think either you have bad MOSFETs in your PCS, and they will eventually fail, or you don't. I'm hoping I don't but, even if I do, it's not a big deal because Tesla has reduced the price of replacement with an updated part number to only $1,000. I don't expect mine to fail but, if it does, it's not going to be a big deal.

 

[yohst]

I don't think lowering the charge current would reduce the chances of failure because the PCS is highly modular. First, there are two 24 amp Power Conversion Units, charging at half power (24 amps) will still run one of the PCUs at full power. Secondarily, each Power Conversion Unit has multiple MOSFETs in banks (not sure of how many). So at the current increases towards the maximum of 24 amps it's likely that each MOSFET is fully loaded before the next one kicks in.

Charging at a lower amperage just means you will be charging for more time, giving heat more time to build up in localized areas.

Personally, I think either you have bad MOSFETs in your PCS, and they will eventually fail, or you don't. I'm hoping I don't but, even if I do, it's not a big deal because Tesla has reduced the price of replacement with an updated part number to only $1,000. I don't expect mine to fail but, if it does, it's not going to be a big deal.

I am no Tesla design engineer so this is speculative; Yes there are two parallel 24A units. I speculate/expect these to work in parallel each take a portion of the charge so _not_ one takes it up to 24A, then the other kicks in. In a former life I did a triple redundant PSU design (a little different but has similarities) and load sharing was the way to do this. There are a few topologies fairly common that basically all do some form of load sharing with a regulation so that the common output bus is the desired charge. So lowering charge setting to 24A I expect each unit to carry about half of that. A lower charge is a meaningful change to the MOSFETs junction temp and thereby failure rate.

Right now I have free super charging as a result of this issue. Nice though a little in convenient at times. But where I go I often have to rely on AC charging and then I would like the speediest possible. So my strategy now is to only use AC charging when I have no other option until the truck is serviced.

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