Tesla Wall Charger Throttling Current

[Artemus]

All,

I installed my Tesla Wall Charger in April when I received my MSP. I used 4ga wire which runs approximately 7 feet from the circuit breaker panel. The voltage reads 239 - 240 Volts as reported by my Tesla app.

I have noticed that if I increase the maximum charging current to 48 Amps, it will charge just fine, and the voltage is stble at 239 - 240V, however, the next time I check my Tesla app, either the app or the car has decreased the maximum charging current to 46 Amps. Essentially, it appears that either the app or the car prefers a 46 Amp charge limit. It would not surprise me to find out that for some reason, 46 Amps is the “preferred” maximum charging current, but I do not find any discussion when I search here or on Google.

Anyone see something similar on their Tesla Level 2 Wall Charger?

Thanks so much,

Artemus

 

[DerbyDave]

I have always had issues with my electrical knowledge, but it seems to me that you would need 240V or more to get 48A. 239V would likely be the difference down to 46 A. Mine is always 240V or more when I measure it. We got some good electric folks on this board, and I am willing to be schooled again. Wait for some further responses.

 

[golferguy]

Its not the 239V. When it throttles down to 46A, I suspect your voltage dropped to less than 239v. That's the piece of data thats missing.
If it did drop further, that is a sign of heat resistance issue. Although you used #4 wire, was it copper? Did you torque the screws per spec at the wall unit and breaker?

48A is what you should have at all times except 90% to 100%, it will taper down.

 

[LoudMusic]

I had the same problem for a while, though I'm maxed at 32A. It would sometimes go to 30 or 28 amps. As I recall, I tracked it down to a second mobile app (my wife's phone) at a different setting and when she would open the app on her phone it would adjust the car's charge rate.

Typically when a Tesla adjusts charge speed due to voltage sag, it will halve the amps. That trigger I believe is at 10% of the rated voltage. So you shouldn't see that happen until it dip to 216 volts.

Again, it's been a while since I've looked any of this up. You might want to search these forums and also the available Tesla user manuals for specifics.

 

[ATPMSD]

This is almost always a voltage issue. What voltage does the car show when it is charging at 46A? Can you raise the rate from 46A back to 48A and if so, what does the car show as the voltage when you do this?

The other potential issue is that the wall connector is overheating. Trip the break and check to ensure all the connections are copper, then re-torque all three to specs, which is 50 lbf . in (5.6 Nm). If you are comfortable opening the breaker box I would also tighten all three connections in there as well, you will have to check the breaker for the proper torque setting, or just snug them up a bit.

 

[mongo]

All,

I installed my Tesla Wall Charger in April when I received my MSP. I used 4ga wire which runs approximately 7 feet from the circuit breaker panel. The voltage reads 239 - 240 Volts as reported by my Tesla app.

I have noticed that if I increase the maximum charging current to 48 Amps, it will charge just fine, and the voltage is stble at 239 - 240V, however, the next time I check my Tesla app, either the app or the car has decreased the maximum charging current to 46 Amps. Essentially, it appears that either the app or the car prefers a 46 Amp charge limit. It would not surprise me to find out that for some reason, 46 Amps is the “preferred” maximum charging current, but I do not find any discussion when I search here or on Google.

Anyone see something similar on their Tesla Level 2 Wall Charger?

Thanks so much,

Artemus

The wall connector typically does not throttle current unless it senses an overtemperature situation.
If the charging display shows 46/48, the reduction is happening on the vehicle side of things. The second number is the max the wall connector supports. The first number is the amount the vehicle is drawing.

Regarding voltage, if the grid is above 240V, the vehicle may pull less Amps due to reaching the maximum power
240V * 48A = 250V * 48A = 11.5 kW

 

[Artemus]

Thanks so much for all the responses everyone.

I have never seen the voltage drop lower than 239V, but I suppose it could drop sometime during overnight charging. The 4Ga wires are tight in the wall charger, but I did not check the torque, but I will. Also, I will check my other device I use and make sure that I do not have the max current set to 46A on it. I would have never thought to check for conflicting parameters; thanks for the suggestion @LoudMusic.

By the way @ATPMSD , I suspect you mean 50 in lbs and not 50 ft lbs in your post above?

Artemus

 

[ATPMSD]

By the way @ATPMSD , I suspect you mean 50 in lbs and not 50 ft lbs in your post above?

This came straight of out the Wall Connector manual, page 20:

“3. Use a torque driver and the included 4 mm hex bit to torque the terminal screws to 50 lbf . in (5.6 Nm).”

 

[WilliamG]

I have always had issues with my electrical knowledge, but it seems to me that you would need 240V or more to get 48A. 239V would likely be the difference down to 46 A. Mine is always 240V or more when I measure it. We got some good electric folks on this board, and I am willing to be schooled again. Wait for some further responses.

No that won’t be it. My charging starts out at around 240V as the amperage counts upwards but settles in the 232-234V range when it hits 48A charging. Not been an issue, and is just standard/expected voltage sag. For me it’s worse in the hot summer or cold winter when the grid is being hammered by residential cooling/heating in the neighborhood. I never drop below 48A.

 

[mongo]

By the way @ATPMSD , I suspect you mean 50 in lbs and not 50 ft lbs in your post above?

This came straight of out the Wall Connector manual, page 20:

“3. Use a torque driver and the included 4 mm hex bit to torque the terminal screws to 50 lbf . in (5.6 Nm).”

"50 lbf in" is 50 pounds-force inches not 50 pound feet lb-ft.
Lbf being a disambiguation of pound-mass.

 

[ucmndd]

Regarding voltage, if the grid is above 240V, the vehicle may pull less Amps due to reaching the maximum power

This is the answer. The onboard charger is an 11.5kw charger, not a 48 amp charger, despite common nomenclature.

If the voltage is higher than 240 even briefly, which is pretty common in US residential service, the max amps will drop to 46-47 because 11.5kw is the max power output of the charger.

240v x 48a = 11.5kw

244v x 46a = 11.5kw

… and so on.

 

[mongo]

This is the answer. The onboard charger is an 11.5kw charger, not a 48 amp charger, despite common nomenclature.

If the voltage is higher than 240 even briefly, which is pretty common in US residential service, the max amps will drop to 46-47 because 11.5kw is the max.

240v x 48a = 11.5kw

244v x 46a = 11.5kw

… and so on.

Yeah, I typoed, 240 * 48 = 250 * 46