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'21 M3P, max charging 32a / 32a with a 40a box (and 50a circuit)

MaskedRacerX

Member
Dec 13, 2020
210
232
Vilano Beach, FL
Howdy Folks!

Loving the car so far, I mean, it's early into my ownership, but is has radically changed my perspective on vehicles.

So quick backstory, we scored a Wrangler 4xe, and wanted a L2 charger, shuffled through a few, but wound up - in expectation of a adding a Tesla to the garage - with a 40a Grizzl-E Smart (though not using any smart features at the moment). Great product, solid chassis, super heavy duty cables, 3 year warranty right out of the box, ~$479.

We got a new circuit installed, a 50a, with a short run to an N6-50 receptacle flush mounted, supposedly very reliable electrical contractor in town.

So it had been charging the Jeep at its max, 30a, works great, almost no issues, stays cool.

We added the M3P, and using the K1772 adapter, it fired right up, and charged the Tesla. However, at some point, like the 2nd time, I opened the Tesla app to check out the charging info, and it showed 32a/32a (around 237-238 volts). So it's like it's setting the max charge to 32a, vs. 40a. I tried it a few times, always the same, even confirmed the charging rate settings on the display.

Then I tried it a couple of times with the charging screen open, and I can see it actually starts at 40a, 0V, and 1-2 seconds later, switches down to 32a. FWIW, we have 250a service, and I've done this without anything else really running, just a few lights, maybe a TV or two (no washer/dryer, maybe AC[?]).

From a few posts here it sounds like maybe it might be a marginal install, and it's causing the Tesla to step down to the next level (as sort of a safety protocol). I have the same company sending over a service person on Friday, I guess they'll try a load test, maybe double check the grounding.

Anything else that could be passed on to them that might help with diagnosis?

I mean, I'm seeing 29 miles / hour, which is pretty solid, but I think I'm leaving another 8 miles/hour or so on the table by not utilizing the full 40a - plus, I have a small concern the lack of 40a may be indicative of an install that might have future issues.

Here's the setup, not really much to see, but I had a pic i posted at the Jeep forum handy :)


IMG_7776.jpeg
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,430
12,681
San Diego
Then I tried it a couple of times with the charging screen open, and I can see it actually starts at 40a, 0V, and 1-2 seconds later, switches down to 32a.
A few seconds of video (or pictures of the various states it goes through) of the start of the charge with the charging screen might be helpful. Or maybe not.

I don’t have an immediate likely explanation. There are no “smart” settings on the Grizzl-e which are causing it to redeclare its capability, for whatever reason? It seems to be declaring 40A capability to start with. But maybe it changes its tune for some reason?
 
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MaskedRacerX

Member
Dec 13, 2020
210
232
Vilano Beach, FL
A few seconds of video (or pictures of the various states it goes through) of the start of the charge with the charging screen might be helpful. Or maybe not.

I don’t have an immediate likely explanation. There are no “smart” settings on the Grizzl-e which are causing it to redeclare its capability, for whatever reason? It seems to be declaring 40A capability to start with. But maybe it changes its tune for some reason?

I'll do a screen recording of the app during the charging process (FWIW, the car display mirrors the same behavior). This morning I woke the car up - reset the breaker - made sure the adapter was pushed on firmly - then plugged in the charger.

It started at 48 (on the right, i.e., the "charger capability"), then in about a second and it showed 40, another second 32a where it stopped, and then the left ramped up 10 ... 20 ... 32a, charging away.

It's my understanding the Tesla does some kind of test, like uses current to determine if there's resistance at some amperage, so my assumption is the circuit, while probably fine to delivery up to 50a to a "dumb device", might have just enough resistance to trigger the Tesla's charge protection[?]

I guess I could pop up to a Supercharger and confirm the car charges faster than 32a with any charger, there's some jist 10 miles away (plus, get to drive the car, it's sad sitting in the garage :D)
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,430
12,681
San Diego
It’s possible there is some wiring problem but my understanding is that the “max” number is declared by the EVSE. It is declared by the control pilot line using PWM (Wikipedia): “The SAE defines the ampacity value to be derived by a formula based on the 1 ms full cycle (of the 1 kHz signal) with the maximum continuous ampere rating being 0.6 A per 10 µs up to 850µs (with the lowest 100 µs x .6 A = 6 A).”

The fact that it shows 48A is weird - it’s a 50A receptacle so under no circumstances should the EVSE think it can ever do more than 40A (80% continuous rule). Tangent: I am assuming the 50A receptacle is backed by 50A capable wires (typical but not actually required - 40A max “allowed” for that particular receptacle which would mean 32A continuous due to the electrical code exception), but still that would come down to config of the EVSE during the install.

Again, I wonder about the configuration of the EVSE. It definitely needs to know 40A is the limit (hard configured with switches or whatever).

For sure the vehicle and the station will be doing ground continuity checks, but that usually manifests differently, if there are problems there.
 
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MaskedRacerX

Member
Dec 13, 2020
210
232
Vilano Beach, FL
Thanks, good additional info.

Yeah, I confirmed the setting on the EVSE, an internal bank of dip switches (actually cycled them to the opposite setting then back to make sure they were fully in the proper on/off position).

I'm a software dev/architect, and fiddle with a lot of electronics, I'm usually pretty good at isolating the issue, but this is all sort of new to me - and I don't have another BEV or EVSE to cross check (that's normally what I'd do with other types of connectivity - swap cables/devices).

Right, when we spec'ed a 50a install, I would assume the proper AWG for the run, it's only like 18".

Doing some additional research to confirm this combo (Grizzl-E + J1772 adapter + 40a setting + 50a circuit :D)


[edit 1]

Yep, here's a video, a Model Y, a Grizzl-E, 40a as expected:



[edit 2]

Removed the receptiable cover, and it from the mount, looks like 6 gauge, connections were tight. I'm going to hit up the local Supercharger, and make sure my car isn't being janky.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,430
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San Diego
I'm going to hit up the local Supercharger, and make sure my car isn't being janky.

This is DC charging so will not really tell you anything, probably. It could rule out some problems, but not the likely problems. Maybe if you can find a high power L2 station (but these are basically non-existent)?

40a as expected:

Yeah, the x/40A is what I expect. You saw x/48A you said, going to x/40A, followed by x/32A. At least that is my interpretation. That is weird. To me if that is actually happening, it suggests the Grizzl-E is messed up or broken in some way so that the CP signal is misbehaving.
 

MaskedRacerX

Member
Dec 13, 2020
210
232
Vilano Beach, FL
Yeah, the x/40A is what I expect. You saw x/48A you said, going to x/40A, followed by x/32A. At least that is my interpretation. That is weird.


Exactly that, and like I said, I'm used to carefully watching system behaviors in my profession, so I'm definitely not misreporting the behavior.

I mean, there's 3 major components in this:

Car
EVSE
Circuit

So that's a lot of different variables - if we assume the car is working, either the circuit is faulty somehow (though still allowing for 32a charging), or there's some kind of funky control logic in the EVSE - if it's the latter, maybe a firmware update will make a difference (if it's not current), though, of course, their portal is down at the moment ... 😐

Thanks for the ongoing input!
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,430
12,681
San Diego
I mean, there's 3 major components in this:

Car
EVSE
Circuit

As far as the circuit goes, maybe there is a grounding problem (electricians do LOVE to leave it disconnected I have noticed (I think it is literally their favorite shortcut) - and it could explain a signaling problem - no reference potential). I would think that would have manifested in other ways though. Other than for safety continuity checks, it isn’t supposed to be used for powering anything, so maybe not. Not sure what the CP signal uses as a ground reference - I suppose the midpoint of the two line voltages (~0V) though I am not sure at all.

Basically, the duty cycle of the CP Signal being all over the map (which is apparently happening) can be caused by:

1) Car electronics are broken somehow and interpretation of CP is incorrect. This would show up at other L2 stations, perhaps.

2) Signalling from the EVSE is broken. This could be due to it being programmed or designed incorrectly, or it could be due to incorrect reference voltages (wiring issues).

I suppose your J-1772 adapter might be flaky as well (intermittent passing of the CP). Maybe plug/unplug and jiggle it around a bit gently.
 
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MaskedRacerX

Member
Dec 13, 2020
210
232
Vilano Beach, FL
So when I setup the WiFI on the box, there was of course SSID/password, and also a field for a URL of the remote OCP service, I left it empty, but it must actually default to the united chargers backend as when it finally was available, I logged in, setup a new charger station with my S/N, and it connected.

Then I flashed new firmware, like a minute 2-stage download to the box, rebooted, came back online.

**BOOM**

40a/40a :D

Hopefully this will provide some debugging info for someone else, even if they're using a different EVSE.

Heck, the WiFi version is worth it just for the easy of updating, I'm not even sure the non-WiFI version has an end user provision for updating the firmware.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,430
12,681
San Diego
So when I setup the WiFI on the box, there was of course SSID/password, and also a field for a URL of the remote OCP service, I left it empty, but it must actually default to the united chargers backend as when it finally was available, I logged in, setup a new charger station with my S/N, and it connected.

Then I flashed new firmware, like a minute 2-stage download to the box, rebooted, came back online.

**BOOM**

40a/40a :D

Hopefully this will provide some debugging info for someone else, even if they're using a different EVSE.

Heck, the WiFi version is worth it just for the easy of updating, I'm not even sure the non-WiFI version has an end user provision for updating the firmware.
Yeah, this makes sense. That limit is set by the EVSE (what people call the charger, which is fine, but which actually just a glorified switch - the true “charger” is in the car…), not the vehicle.

Glad you sorted it out.
 
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elptxjc

Member
Dec 15, 2019
833
168
El Paso, TX
I have a 14/50 circuit, with 50A breakers, and 60A wiring (super short run, like a foot), and it also charges at 32A/32mph. But in my case, I think it's the Tesla (mobile) cable. My guess is if it's charging at exactly 32A too, it has to be Tesla limiting it to that, for some reason. Maybe the adapter that connects to the car? But I really doubt it's anything wrong with the circuit, but checking it for peace of mind is not a bad idea. Good luck.

By the way, it's been near 110F+ here lately, and my garage gets super hot (probably like 100F, but feels hotter), and my charger feels very hot even without charging, so I'm using the (free) supercharger 2 miles from my house often. I'm curious if such heat has any risk of damaging the 14/50 Tesla adapter. Does anybody know at what temperature it shuts down? Or it just decreases the charging rate below 32A? Thank you.
 

Braumin

Member
Mar 5, 2021
54
53
Canada
I have a 14/50 circuit, with 50A breakers, and 60A wiring (super short run, like a foot), and it also charges at 32A/32mph. But in my case, I think it's the Tesla (mobile) cable. My guess is if it's charging at exactly 32A too, it has to be Tesla limiting it to that, for some reason. Maybe the adapter that connects to the car? But I really doubt it's anything wrong with the circuit, but checking it for peace of mind is not a bad idea. Good luck.

By the way, it's been near 110F+ here lately, and my garage gets super hot (probably like 100F, but feels hotter), and my charger feels very hot even without charging, so I'm using the (free) supercharger 2 miles from my house often. I'm curious if such heat has any risk of damaging the 14/50 Tesla adapter. Does anybody know at what temperature it shuts down? Or it just decreases the charging rate below 32A? Thank you.
The mobile connector is limited to 32A max even on a 14-50 circuit because code allows a 14-50 plug on either a 40A or 50A circuit, so to be safe, Tesla limited the Mobile Connector to 32A to avoid a fire.

If the sensor on the Mobile Connector detects the receptacle is getting hot, it will limit charging to I 50% in my experience. It won't stop altogether.
 

Gasaraki

Active Member
Oct 21, 2019
2,010
1,255
Syracuse, NY
The mobile connector is limited to 32A max even on a 14-50 circuit because code allows a 14-50 plug on either a 40A or 50A circuit, so to be safe, Tesla limited the Mobile Connector to 32A to avoid a fire.

If the sensor on the Mobile Connector detects the receptacle is getting hot, it will limit charging to I 50% in my experience. It won't stop altogether.
OP is not using the mobile connector.
 

MaskedRacerX

Member
Dec 13, 2020
210
232
Vilano Beach, FL
I have a 14/50 circuit, with 50A breakers, and 60A wiring (super short run, like a foot), and it also charges at 32A/32mph. But in my case, I think it's the Tesla (mobile) cable. My guess is if it's charging at exactly 32A too, it has to be Tesla limiting it to that, for some reason.

See post #9, it was EVSE firmware on the Grizzl-E, a flash resolved it and the Tesla is charging at 40a :)
 
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