Forums

Tesla Wall Charger limited charge question.

Tesla Wall Charger limited charge question.

Hello hello. I recently received an error while charging about reduced charging speed. My 48amp charger was reduced to 32amps (LR RWD). I tested at the Tesla dealership at 40amps and its fine so I think it's an issue with installation in my home. I did it myself. It's a longer run (whole length of the house into the garage) and I used normal to low quality items honestly. Home depot stuff. It used to work fine, but now I get the error so I'm betting the car has changed criteria and was sensitive to power fluctuations to limit amperage.

My question is, is there a probable/easy solution to fix this? I was told it was probably the run length and would need larger wire to prevent this issue. Could it be a bad breaker? Loose connection in unit? If its too troublesome, I'll stick with the 32amps cause I'm not buying $200 of cable to save an hour charge time.

andy.connor.e | 13. september 2019

What size wire did you use? Whats an estimated length (one way) that you're running from the breaker to the charger?

shawncordell | 13. september 2019

I’m also curious to know what size wire you ran. My setup is similar to yours at 125’ and I used 6 gauge wire. Works fine with no problems

Lorenzryanc | 13. september 2019

I have to double check the gauge when I get home, but I thought I went large enough, stressing "thought". I'd say 40-50 feet maybe straight from the box.

andy.connor.e | 13. september 2019

Thats no issue at all for the run length. When you can check let us know what the wire size is! Also whats the breaker size?

Its also possible that the car is pulling current in increments. So perhaps it can only pull 32A or 40A, in which case it would not pull 40A because you might not have a 50A breaker, maybe the car is smart enough to know that??

Lorenzryanc | 13. september 2019

6/2 NM-B (Non-Metallic) ROMEX Simpull (60')

So I'd guess about 50-55 Feet total run.

Lorenzryanc | 13. september 2019

60 amp breaker, DIM switch set to 48amps

Lorenzryanc | 13. september 2019

ugh... DIP :/

andy.connor.e | 13. september 2019

In the off chance you respond when i am on the road or on the lake this weekend, your wire size should be 8 AWG. If its less than #8's, i would upsize it to 8 AWG. If you are trying to run 48A through the wires though, you will need to upsize to 6 AWG.

Again to make sure i ask, what size breaker do you have in your panel for this charger? Didnt ask before and dont think you provided it.

andy.connor.e | 13. september 2019

Thanks @Lorenz.

Not sure what the DIP switch set does as i have only ever had thermal mag breakers. Your breaker size and wire size is perfect for what you're doing. Not sure, but perhaps set the DIP switch back to 60 or 'max'? The car itself can limit current which is easier than trying to limit it at the breaker.

Lorenzryanc | 13. september 2019

Thanks for the verification with my hardware. The DIP is in the charger itself. The manual says goto "9" for 60amp breaker and 48amp output. Is it possible a cheap breaker could cause fluctuations or anything like that? Possible a poor connection of the wire inside the charger could cause the issue? I know when I installed the cable, it was a real pain to fit it in, so maybe it loosened up?

shawncordell | 13. september 2019

The DIP switch is on the wall connector. Mine is also set at 48 which is what the manual suggests for my Model 3.

shawncordell | 13. september 2019

I’d check all that you mentioned about AFTER you kill the power.

Lorenzryanc | 13. september 2019

Maybe try to find a neighbor with a 48amp+ charger to test it out again? If I max my car charging to 33amps (or anything higher) it'll give me the error and drop to 32amp. The Tesla store had 40amp chargers and it worked fine.

andy.connor.e | 13. september 2019

I wouldnt know if its a problem at the breaker, but it seems like that would be the source of the problem.

Tronguy | 13. september 2019

@Lorenzryanc: I agree with @andy.connnor.e: You're using 6 GA, which should be fine, and the DIP is set for 48A charging, which should also be fine.
This leads us into the fine art (or not) of troubleshooting. I'm just taking pot shots at the wall, now, so YMMV.
1. It's a dual breaker. They're ganged. You've done the turn-it-off, then turn-it-on again at the breaker end, right?
2. The TWC has blinky lights it lights when it detects Something Gone Wrong. Got any of them?
3. When my LR works its way up to 48A, it always appears to do so in stages. First it does one or two amp, ramps up to 10A or so, goes back down, gets up to 24A, fiddles a bit and maybe goes back down again, then hits 24A, then ramps monotonically (finally) up to 48A. What's yours doing? Does the amperage get up to 48A (on the screen) then back off to 32A?
4. Screws. My old chief petty officer, back in the day, told us tweets that, "90% of your problems are going to be with the wires." Wise man: He's been right over 50+ years of troubleshooting hardware. Hit the breaker on the breaker box, verify with a voltmeter that the power is _really_ off, take off the cover with the special Allen wrench you didn't lose, right? And go look at the screws that clamp down the power _and_ _ground_ wires in the TWC and make sure that they're tight. While you're in there, inspect: Dirt, bugs, spiders, water? Tug on the big honking wires going into the Tesla cable and make sure they're tight.
5. Speaking of grounds: Tesla cars tend to be sensitive about ground currents, which should be non-existent. Make sure your ground wire is good and properly connected to the appropriate (I believe) green screw. If you ran your wire from a sub-panel, make double-sure that there's no weird grounding involved between the sub-panel and the main panel. I've heard Stories about people who put ground stakes in their houses on both the sub-panel and the main panel and, as a result, got funny currents flowing on grounds within the house. I'm not really an electrician but this is the place where doing things to Code can make a difference.
6. If nothing is found above, hit the mains breaker on your breaker panel, pull out the 60A breaker, and double-check the connections, especially for any loose ones. And make sure that the ground wire is properly bolted down to the correct bus.

If all the above fails, you might actually have something-or-other busted. Bad breaker, snapped wire in your cable, bad TWC. In my experience, everything fails eventually. Along these lines:
1. With everything put to rights, haul out an AC voltmeter and make sure that, in the breaker box, you've got 125 VAC between neutral/GND (they're the same in the breaker box, if said breaker box is wired right) and each feed wire on the output side of the breaker. They should be the _same_ voltage: So, if you've got 124.5 on feed A, you should have 124.5 on feed B, and 249 between the two. If there's an imbalance, check on the _other_ side of the breaker and see if the imbalance is there, too. No imbalance on the bus bars inside the breaker panel but an imbalance on the breaker output side.. Bad breaker.

At this point I'm out of ideas.

Final point: If you're uncomfortable/inexperienced with high voltage and/or voltmeters, no offense, but quit screwing around and hire an electrician. 120 VAC may kill: 250 VAC has dead bodies lying around. I was trained up back in the day on radars which had a couple of kilovolts floating around and know the safety tricks (one hand in rear pocket, for example) when messing around. And I still hire an electrician if I think what's going on is far enough outside of my job description. Don't you be the next dead body.

andy.connor.e | 13. september 2019

It takes 5000V to kill at normal skin resistivity. Utility ahead of the transformer is 4160V or higher. 120V wont kill but it wont feel good. It also would do much more damage if you had a ground fault which is probably the biggest concern.

But i agree with @Tronguy.

Check NEC 310.15(B)(16) for conductor sizes and ampacity.

Last note. Make sure you're using a minimum 10 AWG size ground for this. Like @Tronguy mentioned, Tesla's are very sensitive to proper grounds.

Lorenzryanc | 13. september 2019

I've been zapped by plenty of 120... never 240 :) I always try to change outlets without cutting power and without fail, shock myself :/
Thanks for thorough plan of attack!
1) Yes, turned off over night and back on. Also reset the charger.
2) no blinkies
3) It used to slowly trickle up to 48 amps... maybe within 45 seconds or so. Now, nothing happens for about 30 seconds, then the error pops up and it moves up to 32amps. I also see the voltage on the car screen is bouncing around a bit as its charging which I'm sure the car hates. Its like it knows somethings up right off the bat, spends some time to see if it resolves, then gives up and says, "you gots a problem, here's 32amps".
4) I'm honestly thinking this may be the issue. When I installed the two wires, it was quite hard to get them to goto their home and maybe the screw wasn't tight enough. Its so cramped in there so I'll dig out that special wrench and test that next.
5) Grounds also couldn't hurt to be checked. No Subpanel.

If I see nothing wrong with this list, I'll drop my car to 32amps and home and call it a day. I primarily charge at work and the difference between 32 and 48 amps is not worth going crazy over. Just wondering if there was something I was missing. It used to work fine and stopped one day. I also forget the ground size, but I think it is 10 AWG.

bjrosen | 13. september 2019

It feels like a ground problem to me but it could also be the Tesla EVSE.

andy.connor.e | 13. september 2019

I think its safe to say its either the breaker or the charger itself. You have all the correct hardware.

kevin_rf | 13. september 2019

What is the car screen showing the voltage as? I'm voting something is loose somewhere that needs to be reclamped. Have you inspected the charging cable and port for any debris or scorch marks?

Tronguy | 13. september 2019

@andy.connor.e: Yup. And one more thing: The car itself can also be at fault. SC's usually have a TWC around for this purpose or you may know somebody else with one. In any case, if you can find one, plugging the car into said TWC and verifying 48A may be Yet Another Troubleshooting Step.

Tronguy | 13. september 2019

@andy.connor.e: About 250 VAC/120 VAC/and generally getting zapped.
Yup, at "normal skin resistivity" You May Not Be Killed. But I have a comment and a true story.
The comment: Be a little sweaty and normal resistivity takes a nosedive. Besides being somewhere warm, being worried can make (almost undetectable) cold sweats appear. Enough said.
The story: We were having problems one day with unplugging and plugging stuff in. Couldn't make the field fault happen come heck or high water. ONE person in our crowd decides to fumble around with the hardware - and the fault was recreated.
I came down, fumbled identically: Couldn't make it happen. It was like Arthur and the sword: A crowd showed up, everybody's doing the fumble dance, nobody can do it, just this one person.
Haul out an ohmmeter. Measure skin resistance. Most of us are 9 kOhm to 20 kOhm. Our hero, the person who could Make Things Die, measured infinite. A little close questioning revealed that said person was one of those people who, on an ESD test station, _always_ had to put some hand lotion on the wrist so the wrist strap had connectivity.
Further testing of $RANDOM people revealed that roughly one in five people had, well, high-resistance skin. And this matched up with what was going on in the field. Sheesh. ESD.
But my argument is that it appears, upon the evidence, that literal skin resistance (not the copper wire kind) varies wildly among individuals. Find somebody with low skin resistance and they may be the person who gets knocked flat by a 12V battery, never mind 120 VAC. High resistance, and they can probably hang onto 400 VAC without getting more than a tingle. But, ahead of time, how would one know?
So: Don't take unnecessary risks. The electricians I've watched in action _never_ do.

andy.connor.e | 13. september 2019

+1 @Tronguy

Lorenzryanc | 13. september 2019

The car looks fine. In fact, when I brought it in, they had a service bullietin to change the "dead posts" or something like that. Those are the top 2 prongs in the charge port. They tested the system after and it all worked fine. I tried at home with the same 32amp error. I'll have to check the voltage, but I think I recall 212 or something like that.

andy.connor.e | 13. september 2019

Thats actually quite a bit low.

Lorenzryanc | 13. september 2019

I don't remember exact number, so I'll verify when I get home, but yes, I do recall thinking that number was indeed low.

kevin_rf | 13. september 2019

I would vote it is current limiting because the voltage is low, especially if it is starting at 240v or something.

Again points to something working loose or arching.

andy.connor.e | 13. september 2019

+1 @kevin

Tronguy | 13. september 2019

Yup, get out that old-tyme voltmeter, put it across the contacts in the TWC, and see what you've got. 212 is rediculously low. Further: If you've got 250 VAC across the buses in the breaker box at the other end of the house, you're dropping some 35-odd volts somewhere. Some of that would be across the wire you strung (but, usually, not that much since it's 6 GA wire), but that would imply there's a spot somewhere with 20V or so across it and 32A. That, my man, is around 600W in a little bitty spot, and, wherever said spot is, it's going to be HOT.
Be careful, watch what you're doing, and start thinking fire/safety hazard. I AM NOT KIDDING. And if you've got 250 VAC at the breaker and 212 V at the TWC under load, STOP CHARGING YOUR CAR UNTIL THIS IS FIXED, YOU COULD BURN THE HOUSE DOWN.

Lorenzryanc | 13. september 2019

I'll crank up the voltmeter when I get home to very the breaker and the bus to make sure everything right there... then I'll move down the line to see where it could be losing. Pretty simple run so I can't imagine anything wrong with the run itself. It'll hopefully be an obvious loose screw.

andy.connor.e | 13. september 2019

Its possible that your incoming utility feeder is not sized properly, giving you that massive voltage drop.

Lorenzryanc | 13. september 2019

So my voltage looks good. 238-241. Car does no charging as soon as you plug in, about 30 seconds the error pops up "Charge speed reduced, unplug and try again". It'll then go up to 8kW 32/48A 238V.

I'll try to find some time this weekend to disassemble and verify some screws and grounds. Thanks for all your help!

Lbanworth | 13. september 2019

@Lorenzryanc The first step in the troubleshooting process would be to locate and turn off the breaker that feeds the Tesla WC. Next, disconnect your Tesla WC from your charge port. Next, check incoming utility power before it goes through the main breaker. The multimeter should read somewhere between 230 - 240 VAC. If your meter shows a value within this range then proceed to the next step. The next step, while you're at the breaker panel already, would be to turn the Tesla WC breaker back on while still unplugged from your charge port. Check the voltage coming off of the breaker that feeds your Tesla WC. What is your voltage reading? It should be the same as what you measured on the main utility. If its the same, then connect the Tesla WC to your charge port. Now measure the voltage coming off the Tesla WC breaker again. It should be between 230 - 240 VAC. If not, then your Tesla WC is your problem. If the voltage measured at the breaker is between 230 - 240 VAC then the next step would be to check the voltage coming off of the Tesla WC. To do this you will need to remove the face plate. The voltage measured on the output terminals should be between 230 - 240 VAC. If it isn't, the problem lies in your Tesla WC. At this point, I would turn the power to the Tesla WC off and check the terminals for loose connections. The Tesla WC has inputs that monitor temperature, current and ground. If any of these inputs is not at its desired setpoint, the Tesla WC will momentarily come on and off. This will signal faults to the car's computer and to the Tesla WC. I hope this was helpful to anyone who reads it. Let us know what you find! Good luck!

kaffine | 13. september 2019

andy.connor.e

THAT IS WRONG. 120V kills more than any other voltage. I will say that is likely as more people are exposed to 120V than higher voltages but it can certainly kill.

M3BlueGeorgia | 13. september 2019

Set the car to not to try to pull more than 40A and see if you still have the problem, and then try 32A if you do.

Also watch the voltage while the car is trying to increase the amps to pull 48A. If the voltage drops as the amps ramp up, the car assumes resistance in the system is increasing because of overheating and steps back on the amps. So sit in the car and watch that.

BTW: I like people's thoughts on grounding. Worth having that double checked.

NOTE: Make absolutely sure the breakers are off before you mess with anything that potentially exposes you to an electric shock.

bigjools | 13. september 2019

It's amps that kill not voltage. For the same power, 120V requires higher amperage.

Consider standing under a power transmission line - you've got a few thousand volts between your head and your feet. You don't die because there's next to no current.

Tronguy is right - if you have that much volt loss on the cable run, you're going to burn down your house at some point. Volts don't just magically disappear, it's a result of power loss, and the loss is in heat.

Tronguy | 13. september 2019

@bigjools: For these purposes, Ohm's Law rules: Amps = Volts/Resistance. Yeah, current kills: But one doesn't get the current unless one has the voltage and resistance.
Further: Say one is standing in a pool and one's left arm hits 120 VAC. Current flows down the arm, down one's side, down the leg, and into the pool, and Smoke And Agony will occur - but it's very unlikely the person in question will die.
Next: One hand in the pool, other hand on 120 VAC. Current flows from the 120 VAC hand, through the chest (and heart), and out the other side. Chance of death: Really, really high, since the AC current going through the heart can seize the sucker up. Not to mention cooking critical muscles.
Safety tip: When working around live voltages, always do it one handed and keep the other hand in the rear pocket. And be very, very careful about just where one's hands are, at all times. Yeah: And make sure somebody else is around, too. And that that someone has access to a medium length of clothesline. (Documented cases of somebody freezing up solid on 220 VAC, helper grabs the frozen person, gets frozen themselves, both die.) Looping the clothesline around the frozen person and pulling on that is much, much safer. And non-intuitive.

bigjools | 13. september 2019

@tronguy Yeah, I have a degree in electronic engineering. I don't know a lot about biology though, but I do just tend to avoid anything that can place a potentially large current across my extremities :)

kevin_rf | 14. september 2019

This 120v argument reminds me of the argument that O2 isn't flammable and you can safely ignore the fire Hazzard it presents. ( Spoiler, it's an extremely hazardous fire hazzard in gaseous or liquid form. )

kevin_rf | 14. september 2019

Noticed something over on one of the TMC threads about melted J1772 adapters. (J1772's melting on bad third party chargers is not relevant, but...) Any truth to the cars charge port has temperature sensors on each pin?

If it is not the wiring, that might explain things...

You indicated your HPWC had been working, and now is suddenly limiting you to 32amps. Is it possible debris on the cable or in the connector is raising the temp just enough to trigger some sort of thermal limit? If this is the case, I would vote the cable since the car seems to charge just fine elsewhere. Check for corrosion, scorch marks, varnish, debris, melting.

nwatson | 14. september 2019

I have experienced something similar to this with my wall connector. P3D. My wall connector was professionally installed. Occasionally it will start charging up to 48 amps, and then drop down to 32 shortly after and stay there. Previously this happened a couple days in a row and I flipped the breaker and then reset the wall connector and the problem went away. Coincidentally when this happened I spontaneously "lost" 9 miles of range on my vehicle. Didn't happen again for a while, but happened again today and now when i charge it to 90% i have lost another 7 miles of range (264 miles @ 90%, used to be 279 originally). Only had the car since June and 4k miles on it. Wondering if you lost any range when this happened? I am wondering if my battery was somehow damaged during these events?