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Help with High Amperage Charger

U.P.O.

Member
Nov 8, 2021
5
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Hi

I have a 2017 Model S which i have owned for almost 4 years. It has the high amperage charger upgrade (~17kW)

I have been charging it on a Telsa Wall Charger, on 3 phase, 240v, perfectly fine in all that time. (I am in Europe)

However, for the last 2-3 months when i plug the car in, the car initially ramps up to 17kW charging. It reads 3 phase, 24/24a and the volatage might be 238v. If i watch it for a bit, it will stay perfectly fine at 17kW until eventually, (it might take 1 minute, it might take 10 minutes) the voltage will briefly flick over 240v and then a message will appear on the dash saying "Unable to Charge. Disconnect Cable and Retry" and the charging speed will drop to 11kW.

A second or two later, the voltage will go back under 240v and the car will ramp up to 17kW again by itself. As soon as the voltage flicks over 240v again, i will receive the same message on the dash about being unable to charge, the charge will go back down to 11kW, however after the second time reducing it does not go back up to 17kW. It just remains at 11kW and stays charging at that rate.

If i unplug the cable or stop and restart the charge from either the screen in the car or the app, it will go back up to 17kW until the whole process repeats.

I plugged into a public 22kW charger to rule out my charger and the same thing happened. (Although that went up to 248v !)

The car had never tripped before. It's only happening in the last few months. I have effectvely lost the ability to charge at 17kW.

I spoke to the Tesla Ranger and he had never heard of that issue.

On goggling, i can't find much, except for someone saying usually charger errors are down to a little fuse that might just cost $10 to replace but Tesla wont repair chargers. They just swap them out for new ones that cost approx $2000 which seems crazy. The local Tesla ranger confirmed this to me.

Has anyone come across this before or can anyone offer an opinion on what might be the issue and if it can be fixed ?

Thanks
 

ucmndd

Well-Known Member
Mar 10, 2016
7,618
14,826
California
The 72 amp onboard charger is actually made up of three individual 24 amp (~5.7kw) charging boards. What you describe sounds like one of them is malfunctioning/failing and the car is falling back to using just two of the three.

You're right that Tesla's "fix" will almost certainly be to replace the onboard charger at a significant cost to you. Given the failure mode you describe I'm skeptical of the idea it's a fuse, as that would generally result in a binary failure, not the waffling between 11 and 17kw like you describe.
 
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U.P.O.

Member
Nov 8, 2021
5
0
I
The onboard charger is actually made up of three individual 24 amp (~5.7kw) charging boards. What you describe sounds like one of them is malfunctioning/failing and the car is falling back to using just two of the three.

You're right that Tesla's "fix" will almost certainly be to replace the onboard charger at a significant cost to you. Given the failure mode you describe I'm skeptical of the idea it's a fuse, as that would generally result in a binary failure, not the waffling between 11 and 17kw like you describe.
Thanks for the reply.

Yeah i was thinking one of the three onboard chargers was failing alright. I have no idea about fuses or possible causes or fixes though. I cant figure out why it will go to 17kW (so that charger will work) until the voltage goes above 240v though. And why can it restart itself once but not a second time ?

I dont even know how to identify which one of the chargers is the one thats failing.

Replacing the charger is a last resort. Heopfully it can be repaired
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,266
8,948
Boise, ID
Yeah i was thinking one of the three onboard chargers was failing alright. I have no idea about fuses or possible causes or fixes though. I cant figure out why it will go to 17kW (so that charger will work) until the voltage goes above 240v though. And why can it restart itself once but not a second time ?
I agree that it sounds like the onboard charger is failing. I've seen a few threads on this, and the intermittent, off-and-on behavior seems common to this. And I don't think it's necessarily related to the voltage levels moving. I think it's just dying.
I dont even know how to identify which one of the chargers is the one thats failing.
Well, no, you wouldn't. Those are just circuit boards inside a box. You can't get to see them directly unless the charger is removed and taken apart.
 

U.P.O.

Member
Nov 8, 2021
5
0
I
I agree that it sounds like the onboard charger is failing. I've seen a few threads on this, and the intermittent, off-and-on behavior seems common to this. And I don't think it's necessarily related to the voltage levels moving. I think it's just dying.

Well, no, you wouldn't. Those are just circuit boards inside a box. You can't get to see them directly unless the charger is removed and taken apart.
Thanks for the reply. This is not sounding too promising for a fix so !
 

U.P.O.

Member
Nov 8, 2021
5
0
I
There are used Gen 3 chargers for sale on eBay, but this is really pushing the boundaries of hobbyist tinkering.
Thats a pity. I was hoping it was just going to be something small like the volatage going over 240v tripping a fuse or switch or something that an auto-electrician or someone could maybe look at.

Looks like i might just have to carry on with 11kW charging so and hope it doesn't have a kock on effect on the remaining two chargers.
 

mongo

Well-Known Member
May 3, 2017
13,940
45,095
Michigan
Thanks for the reply.

Yeah i was thinking one of the three onboard chargers was failing alright. I have no idea about fuses or possible causes or fixes though. I cant figure out why it will go to 17kW (so that charger will work) until the voltage goes above 240v though. And why can it restart itself once but not a second time ?

I dont even know how to identify which one of the chargers is the one thats failing.

Replacing the charger is a last resort. Heopfully it can be repaired
The voltage change could be due to the change in current draw. When the charger module drops out, current is reduced and the voltage rises. Just like the change from charging to not charging. So the failure leads to the voltage change, not the other way around.
 
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