Setting Amp level on control panel

[haroldo]

Dumb questions from a newbie...
What setting should you use for amps in control panel/charging?
I've read that you're supposed to set the amp level to 80% of the charger's rated level, is that right? If my local generic charger is 32A, I assume I'm supposed manually adjust the car to 26A. If I forget to change it, and go to a Tesla Supercharger, presumably a lot higher amp, will the car know to adjust up the level (because it's a Tesla facility), of will it be limited by what is set on the control panel?
Thanks!

 

[RTPEV]

Several issues with your statements.

The 80% restriction applies to the car's (and EVSE's) continuous current draw compared to the breaker rating in your panel. For example, if you had a 40A breaker, 80% of that is your 32A continuous power draw limit. This limit should be set in the EVSE itself, and then the EVSE communicates that limit to the car. You don't have to do anything special in the car as long as your EVSE is set up correctly. Sometimes EVSEs can be "programmed" (via DIP switches or similar), other times they just specify that you need to use a 40A breaker for example, and they are hard-wired to 32A limit (or whatever the numbers happen to be for that specific EVSE).

The current limit that you set in the car (at least in North America, I can't speak to other geographies) only applies to L1 (120V) charging, and would be useful to people that are plugging their portable connector into a domestic outlet that has other things plugged into the same circuit (e.g. a fridge). You might want to cut down the charge current from the default of 12A (which is already 80% of the typical 15A breaker, see how that's already taken care of for you?) to something lower like 8A so you don't trip the breaker when the fridge kicks on. Don't worry about that limit affecting your charging at regular L2 charging stations, destination chargers, or Superchargers. That limit doesn't apply to those charging stations. It's only there for 120V charging.

 

[haroldo]

Okay, thanks. I only charge at work (free 32A charging stations) and Supercharger if/when I go on a long trip. I am not set up to charge at home.
Assuming I already played around with the amp limit on the charging control panel page, where should I set it (again, work is 32A). If I never do home charging, I assume I should never bother with this setting, right?

 

[srs5694]

For the most part, you shouldn't need to set it. The 80% rule applies to the circuit in the house, and the EVSE should already handle that. That is, a 32A EVSE is probably installed on a 40A circuit, so it's already running at 80% of the 40A circuit. Your car then negotiates its charge rate with the EVSE and automatically draws 32A or less. (Your Model 3 LR is capable of pulling 48A, but it will only pull 32A on your 32A EVSE.)

The ability to adjust the amperage in the car is handy if you know the circuit is dodgy, if you're using adapters that hide the circuit's true limits, if you know the circuit has other devices on it (which would mainly apply to 120V L1 charging), or if you want to slow down charging for some reason. Most of these are situations that you'd want to avoid, especially for your primary charging source; but you might run into them in the real world from time to time when traveling, hence the ability to adjust the L1/L2 charge amperage.

Don't worry about Supercharging amperage. AFAIK, you can't manually adjust the amperage at a Supercharger, so even if you do override your L1 or L2 charge rates, that won't affect Supercharging. The amperage is set by negotiation between the car and the Supercharger, much like with an L1/L2 EVSE; but with Supercharging, the amperage varies over the course of the charge to obtain what Tesla engineers believe is the best compromise between charge speed and battery health. In particular, the amperage will be higher at a low battery state of charge (SoC) and drop over time, to avoid overheating and damaging the battery.

 

[srs5694]

Okay, thanks. I only charge at work (free 32A charging stations) and Supercharger if/when I go on a long trip. I am not set up to charge at home.
Assuming I already played around with the amp limit on the charging control panel page, where should I set it (again, work is 32A). If I never do home charging, I assume I should never bother with this setting, right?

If you've already dropped it down, just increase it back to the maximum in the same screen.

 

[mociaf9]

Okay, so what you're talking about is the duty rating for electrical circuits. And the issue is that continuous loads are derated to 80% of the max allowed load on a circuit. For example, let's say you installed a NEMA 14-50 receptacle in your garage. It's on a 50A circuit breaker and has been properly wired to deliver 50A. Then for any normal, non-continuous load you can plug in and get 50A. But charging an EV is considered a continuous load, so the max you should charge at when plugged into that outlet is 40A (80% of 50).

Almost always this derating has been taken care of for you. In your example, where you're getting 32A from a charger, almost certainly that's because the charger is wired on a 40A circuit and 32A is the 80% allowable continuous load. If you're using the correct adapter plug for the outlet (and assuming a nominally powered outlet) with a Tesla Mobile Connector, then this derating is taken care of for you automatically by the hardware. Same is true when using a Tesla Wall Connector, when setting up the hardware the derating is taken care of. Same is true whenever you plug into a public charger, it's already been set up to take the 80% continuous load limit into account.

Needing to adjust the current limit in the car is really rare. I can only think of 2 times it's usually necessary. 1) If you're using a homemade plug adapter that will effectively trick the Mobile Connector into setting the wrong limit, e.g. using a NEMA 14-30 to 14-50 adapter because you don't have the 14-30 plug for your Mobile Connector and you do have the 14-50 one. 2) If you're plugged into a normal wall outlet somewhere that has other things already plugged in on the same circuit, so you need to lower the power draw so you don't overload the circuit; or where the the breaker trips after you've been charging for a few hours, in which case setting a lower current may help you avoid the breaker trips.

 

[LoudMusic]

Several issues with your statements.

The 80% restriction applies to the car's (and EVSE's) continuous current draw compared to the breaker rating in your panel. For example, if you had a 40A breaker, 80% of that is your 32A continuous power draw limit. This limit should be set in the EVSE itself, and then the EVSE communicates that limit to the car. You don't have to do anything special in the car as long as your EVSE is set up correctly. Sometimes EVSEs can be "programmed" (via DIP switches or similar), other times they just specify that you need to use a 40A breaker for example, and they are hard-wired to 32A limit (or whatever the numbers happen to be for that specific EVSE).

The current limit that you set in the car (at least in North America, I can't speak to other geographies) only applies to L1 (120V) charging, and would be useful to people that are plugging their portable connector into a domestic outlet that has other things plugged into the same circuit (e.g. a fridge). You might want to cut down the charge current from the default of 12A (which is already 80% of the typical 15A breaker, see how that's already taken care of for you?) to something lower like 8A so you don't trip the breaker when the fridge kicks on. Don't worry about that limit affecting your charging at regular L2 charging stations, destination chargers, or Superchargers. That limit doesn't apply to those charging stations. It's only there for 120V charging.

I believe this is incorrect - you can set the Amps for any non-DC charging. I know for certain I can set it on a 240v50a circuit.

If you're using a Tesla NEMA adapter it somehow informs the car of what type of adapter is being used and sets the maximum amps automatically based on the 80% rule, and can be adjusted DOWN from there. This also works with appropriately built 3rd party adapters that fit the gen 2 mobile charger. It works for my 30A marine locking style adapter I have for use at marinas.

NEMA Adapter Bundle

Maximize your charging options with the NEMA Adapter Bundle. Simply attach the appropriate adapter to your Mobile Connector, plug into the corresponding outlet and begin charging. With all seven Gen 2 NEMA Adapters in one convenient storage bag, you can charge at any available outlet, at home or...

shop.tesla.com

Unfortunately you can't manually adjust amps when DC fast charging. The point is to fast charge so theoretically you're wanting to get out of there as quickly as possible. But with congested charging locations they probably also don't want people just setting the speed lower so they don't have to pay idle fees.

 

[RTPEV]

I believe this is incorrect - you can set the Amps for any non-DC charging. I know for certain I can set it on a 240v50a circuit.

I think you are right...I have my limit set to 8A for charging when I plug into my in-laws' outlet, and I know for sure that I charge faster than that at home from my EVSE! I guess it maintains two different limits, one for 120V and one for 240V. It must only bring up the 120V limit when you're actually plugged in to 120V.

If you're using a Tesla NEMA adapter it somehow informs the car of what type of adapter is being used and sets the maximum amps automatically based on the 80% rule, and can be adjusted DOWN from there. This also works with appropriately built 3rd party adapters that fit the gen 2 mobile charger. It works for my 30A marine locking style adapter I have for use at marinas.

The Tesla mobile connector negotiates the maximum charge rate with the car, and in turn, the Tesla mobile connector sets its limit based on which adapter you are using (as you say). I imagine it's some kind of jumper in the adapter that sets this. Pretty smart solution.

Unfortunately you can't manually adjust amps when DC fast charging. The point is to fast charge so theoretically you're wanting to get out of there as quickly as possible. But with congested charging locations they probably also don't want people just setting the speed lower so they don't have to pay idle fees.

Once you get past the constant-current stage of fast charging (which is when the taper down happens) it's the physics of the battery itself that controls the amps anyway. So even if you could set a charge speed limit, it would only work until you reached 20-50% SOC anyway, although I suppose if you set it low enough, it could take awhile to reach that SOC. That said, it's usually about wanting to go as quickly as possible at a Supercharger.

 

[srs5694]

the Tesla mobile connector sets its limit based on which adapter you are using (as you say). I imagine it's some kind of jumper in the adapter that sets this. Pretty smart solution.

Here's an article that goes into all the technical details of how this is done:

For Tesla End-To-End Charging, There's Supercharging & Destination Charging. For Everything Else, There's The Mobile Connector — Part I - CleanTechnica

Sign up for daily news updates from CleanTechnica on email. Or follow us on Google News! Put your propeller caps on folks because it’s time to take a deep dive into the magic behind the charging cable that came in the trunk of your Tesla Model S/X/3. The notion behind ... [continued]

cleantechnica.com

 

[Rocky_H]

I think you are right...I have my limit set to 8A for charging when I plug into my in-laws' outlet, and I know for sure that I charge faster than that at home from my EVSE! I guess it maintains two different limits, one for 120V and one for 240V. It must only bring up the 120V limit when you're actually plugged in to 120V.

It's not two different limits by voltage. You are plugging in at your in-laws' house, which is a different location. When you charge at a place and turn the amps down from the maximum, it sets a memorized amp level tagged to that GPS location, so when you charge there again, it will use that same amp level again.

 

[srs5694]

It's not two different limits by voltage. You are plugging in at your in-laws' house, which is a different location. When you charge at a place and turn the amps down from the maximum, it sets a memorized amp level tagged to that GPS location, so when you charge there again, it will use that same amp level again.

This is my understanding, too; however, I'd caution against relying on the car to remember such a setting, if it's important. My Tesla occasionally records my GPS coordinates as being slightly off (like at my next-door neighbor's house rather than my own house), and it's always possible that a setting like this would be lost or corrupted in the computer's storage. Thus, if you know that running at too high an amperage would cause problems, it's best to double-check the setting when you begin charging (or before; I don't recall offhand when the car shows the changed amperage -- before or after you plug in).

 

[HBDesiato]

It's not two different limits by voltage. You are plugging in at your in-laws' house, which is a different location. When you charge at a place and turn the amps down from the maximum, it sets a memorized amp level tagged to that GPS location, so when you charge there again, it will use that same amp level again.

Hm. I've been charging for a few years at home with my mobile charger (32amps max) which is great - I'm getting a "corded mobile connector" that can do more amps but I don't want to do more amps and risk flipping a breaker, I just want the mobile charger in the car and to avoid plugging and unplugging at my cheapo NEMA 14-50 outlet.
I've been playing around with this setting - changing it to 27amps at my home location but when I plug in I always get 32amps and every time I return from a drive this setting is 48amps until I plug in and get 32amps. It doesn't save my preference for charging and ignores what I specify.

I pull into the garage,
bring up the charging screen,
change it from 48amps to 27amps
get out and plugin the charger
I get 32 amps

Am I setting it wrong?

 

[LoudMusic]

Hm. I've been charging for a few years at home with my mobile charger (32amps max) which is great - I'm getting a "corded mobile connector" that can do more amps but I don't want to do more amps and risk flipping a breaker, I just want the mobile charger in the car and to avoid plugging and unplugging at my cheapo NEMA 14-50 outlet.
I've been playing around with this setting - changing it to 27amps at my home location but when I plug in I always get 32amps and every time I return from a drive this setting is 48amps until I plug in and get 32amps. It doesn't save my preference for charging and ignores what I specify.

I pull into the garage,
bring up the charging screen,
change it from 48amps to 27amps
get out and plugin the charger
I get 32 amps

Am I setting it wrong?

Plug it in before you change anything and see what happens. If you are using the included Tesla mobile connector, the car should set that amp draw automatically based on the plug type that is attached to the mobile connector.

 

[Rocky_H]

I pull into the garage,
bring up the charging screen,
change it from 48amps to 27amps
get out and plugin the charger
I get 32 amps

Am I setting it wrong?

Basically, yes, but it's understandable you wouldn't have known. Anything you are changing while the car is not plugged in yet is not going to create a saved entry. It has to get plugged in and start to charge, and THEN you dial it down, that it will know it is for the actual charging at that location, and it will create a saved setting there. I know that's not necessarily intuitive, and I don't think that exact detail is described in the manual anywhere, but that's how it has always worked on all the cars.

 

[HBDesiato]

Thanks for the help! This time, after setting 27amps I got out and left the door open while I plugged it in! Currently charging at 27amps, Yay! When the door closes the screen goes black so it probably doesn't save the amp setting. Plugin then set makes more sense now but seems backwards.
I'll know tomorrow if the setting has been remembered.

 

[Rocky_H]

Thanks for the help! This time, after setting 27amps I got out and left the door open while I plugged it in! Currently charging at 27amps, Yay! When the door closes the screen goes black so it probably doesn't save the amp setting. Plugin then set makes more sense now but seems backwards.
I'll know tomorrow if the setting has been remembered.

After plugging it in, why wouldn't you go back to the screen and dial it up or down? That way you know it would save it.

 

[LoudMusic]

Thanks for the help! This time, after setting 27amps I got out and left the door open while I plugged it in! Currently charging at 27amps, Yay! When the door closes the screen goes black so it probably doesn't save the amp setting. Plugin then set makes more sense now but seems backwards.
I'll know tomorrow if the setting has been remembered.

Don't do anything on the screen until after you plug it in. The car talks with the plug and figures out what the charging rate should be.

It also knows how to turn it down or off if there are any detected problems.

 

[RTPEV]

Don't do anything on the screen until after you plug it in. The car talks with the plug and figures out what the charging rate should be.

It also knows how to turn it down or off if there are any detected problems.

I used to plug in at work where they had 4 120V outlets, one of which was on a 20A circuit breaker. There were 4 reserved spots for EV parking, but probably about 10 EVs that were trying to share the outlets, so it was fairly common for Volt owners (that could turn down their charge rate to 8A) to both plug into the pair of outlets on the 20A circuit (of course they would get this wrong as well, often plugging into a different outlet, or failing to turn down their charge rates).

Anyway, it's no longer a concern for me because I no longer work there and probably wouldn't need to charge my Tesla anyway, but if I did, it would be necessary to be able to turn down the charge rate prior to plugging in if there was another vehicle already plugged into the same outlet, not after.

And you wouldn't want to make this a permanent saved setting because it was only when you had to plug into the one outlet that could be shared that you needed to turn down the charge rate.

It may not be a huge deal, but I do agree that if you set the charge rate down on the screen, it ought to remember that until the next time the car is actually started and put in drive. It's counter-intuitive that it would just forget the setting after you exit the vehicle and shut the door.

 

[HBDesiato]

After plugging it in, why wouldn't you go back to the screen and dial it up or down? That way you know it would save it.

Mainly because it seems dumb to exit the car, then get back in to adjust the setting. If, after what I've done, the setting has not been retained, I'll do as you say for the next time.

 

[Rocky_H]

but if I did, it would be necessary to be able to turn down the charge rate prior to plugging in if there was another vehicle already plugged into the same outlet, not after.

It wouldn't have to be done before. Have you seen how long it takes to detect that it's plugged in, and then say it's preparing for charging, and then begin to slowly count upward as it ramps up the number of amps? It's not instant like the snap of your fingers. It's a pretty solid minute. So there is time to get in the car and turn it down as it's going through all that.

Mainly because it seems dumb to exit the car, then get back in to adjust the setting. If, after what I've done, the setting has not been retained, [...]

It won't be. *sigh* So you're going to intentionally do a method that won't work because you think it's "dumb" how it actually works? That's one school of thought, I guess.