Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register
  • Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
  • The final cut of TMC Podcast #29 is available now with topics time-stamped. We discussed the Tesla Cybertruck's expected 1 MW Ultra-Fast Charging capability, the Tesla Semi Delivery Event, the coming Model 3 refresh (project "Highland"), and more. You can watch it now on YouTube.

Model 3 will only charge at 32A on home charger

Reif

New Member
May 16, 2022
3
2
WA, USA
I've had a charger installed for awhile, but recently had the breaker upgraded to be 60A. I then went in and changed the wall charger settings to be 48A max. However, the car still maxes out at 32/32A. I've updated all software, turned the charger off and on again, even factory reset the car.

Here is an image out of the wall charger's settings:
Any ideas? Thanks!!!
 
However, the car still maxes out at 32/32A
The onboard charger for a M3 SR or RWD is limited to 32A. The LR or P can handle up to 48A.

 
Ah, guess I need to buy a performance model then. :p

Thanks!
Just so we're clear about this:
The actual AC->DC conversion is done by these blocks. Each one can handle 16A. The SR's get two of them, the LR's and P's get three. On my 2018 LR RWD one can actually see them kicking in, one at a time: First, the current ramps up to about 16A; then, after a pause, it dips a bit, then ramps to 32A; then, another pause, and it ramps up to 48A.

My understanding is that these AC-DC blocks are, or at least were, used in Large Quantities at Superchargers. That may have been true for the 72kW, 120 kW, and 150 kW variants; I'm not sure if that's true for the 250 kW types.

And it all makes a bit of sense. The SR has a smaller battery so it takes less time to fill it up at 32A than it would for a LR or P; part of the reason the SR cost less is that (a) there's less battery in there and (b) the charger is smaller, it being sized for the battery.
 

ATPMSD

Active Member
Mar 12, 2021
1,788
1,730
Atlanta, GA
recently had the breaker upgraded to be 60A

Did you also need to upgrade the wire? If you have #6 romex, which is very common, you cannot run a 60-amp circuit. You can use a 60-amp breaker but need to set the WC to a 50-amp circuit (40-amp maximum output current). BTW if this is the case a 50-amp breaker is a better idea.
 
Just so we're clear about this:
The actual AC->DC conversion is done by these blocks. Each one can handle 16A. The SR's get two of them, the LR's and P's get three. On my 2018 LR RWD one can actually see them kicking in, one at a time: First, the current ramps up to about 16A; then, after a pause, it dips a bit, then ramps to 32A; then, another pause, and it ramps up to 48A.

My understanding is that these AC-DC blocks are, or at least were, used in Large Quantities at Superchargers. That may have been true for the 72kW, 120 kW, and 150 kW variants; I'm not sure if that's true for the 250 kW types.

And it all makes a bit of sense. The SR has a smaller battery so it takes less time to fill it up at 32A than it would for a LR or P; part of the reason the SR cost less is that (a) there's less battery in there and (b) the charger is smaller, it being sized for the battery.
This is some interesting info. My MY used to be fine at 32amps (could have done 40 but didn't desire the extra speed and slight efficiency drop) then had a couple random interruptions so I dropped to 26ish amps... then got them again a couple weeks later so tried 22amps, got again and I'm down to roughly 18 but maybe even 16. This is wall connector. On mobile charger it did the 32 max amps for a bit but changed itself to 16amps and won't allow an increase but at least doesn't get charging interrupted. How do I tell for certain it's my on-board charger? Wiring is 4 gauge copper to sub panel, 6 gauge to industrial Hubbell 14-50. All tight connections.
 

srs5694

Active Member
Jan 15, 2019
1,545
2,069
Woonsocket, RI
This is some interesting info. My MY used to be fine at 32amps (could have done 40 but didn't desire the extra speed and slight efficiency drop) then had a couple random interruptions so I dropped to 26ish amps... then got them again a couple weeks later so tried 22amps, got again and I'm down to roughly 18 but maybe even 16. This is wall connector. On mobile charger it did the 32 max amps for a bit but changed itself to 16amps and won't allow an increase but at least doesn't get charging interrupted. How do I tell for certain it's my on-board charger? Wiring is 4 gauge copper to sub panel, 6 gauge to industrial Hubbell 14-50. All tight connections.
Try another EVSE. It sounds like you have tried both a Tesla Wall Connector and the Mobile Connector that came with the car, so you may have already done this, but if I've misunderstood or if you want to triple-check, take the car to a public Level 2 EVSE that can do at least 30 amps and try it there. If the problem persists, then it's almost certainly an issue with the car, and you should schedule a service appointment. If the problem goes away with a second/third EVSE, then the problem is likely with your EVSE, and you may need to get it repaired or replace it.
 
  • Helpful
Reactions: GSP and Rocky_H

ATPMSD

Active Member
Mar 12, 2021
1,788
1,730
Atlanta, GA
This is some interesting info. My MY used to be fine at 32amps (could have done 40 but didn't desire the extra speed and slight efficiency drop) then had a couple random interruptions so I dropped to 26ish amps... then got them again a couple weeks later so tried 22amps, got again and I'm down to roughly 18 but maybe even 16. This is wall connector. On mobile charger it did the 32 max amps for a bit but changed itself to 16amps and won't allow an increase but at least doesn't get charging interrupted. How do I tell for certain it's my on-board charger? Wiring is 4 gauge copper to sub panel, 6 gauge to industrial Hubbell 14-50. All tight connections.

The problems you have sound like voltage issues. But I agree wing with @srs5694, that you should try a couple fo public charging sites. Also, if there is an RV park nearby you can trying a 14-50 outlet with the mobile connector and see what happens.
 
  • Helpful
Reactions: GSP
Just chiming in with everybody else. Current draw is set by:
  1. Car finds out how much the connector to AC/DC (L1, L2/ Supercharger) can supply.
  2. Car figures out how much it can accept. (More or less, looks at its navel.)
  3. Picks the lower of #'s 1 and 2.
  4. If, while charging, Stuff Happens, it may reduce the current. What little I know under this category includes:
    1. Drop in AC voltage. Happens when a Mobile Connector is being used with an extension cord (personal experience). The high current on an extension cord whose advertising (Heavy Duty!) may have gotten past its actual current capacity results in an I-R drop across the suspect cord. The cord, if left in this state, would heat up to the point of letting the smoke out, so Tesla's programmers reduce the current draw. Since they don't like smoke, either. Similar can happen with loose connections to the breaker panel/in the wall/in the socket (worn contacts, anybody?), and so on. And probably includes loose connections inside the car, although I haven't heard of somebody suffering through that one, yet.
    2. High temperature on the Mobile Connector plug that goes into the wall. Oddly enough, the Mobile Connector reports its temperature back to the Mothership (the car) and, if the temp starts getting Up There, the car will cut back or simply stop charging. This can be because of cheapie or mis-installed sockets reaching End of Life or even a bad temperature sensor.
    3. Battery getting full. This is Extremely Obvious during supercharging, when one's initial 120kW/150kW/240kW rate slows down once one gets past 30% state of charge or so. But if one is going for 100% charge on a L1/L2 charger, the charge rate also slows down when one gets higher than 90% or so. The last 1% take XXX more than the first 1%, and all that.
The odd part about @BLH17's post is that the car isn't throwing error messages left, right, and center. In my experience, the car's not shy about putting up error messages for items #1 and #2 above; not so much for #3, since that's not an error, that's expected behavior. Trying somebody else's Wall Connector might be in order. Looking for Destination Chargers (which are typically Tesla Wall Connectors (TWC)) and using one might be in order. Similarly, Tesla Service Centers have the things in the parking lot and, of course, if one is at a Tesla SC, they'll typically let one do a little self-checking.

Finally: If it turns out that everything is sweetness and light with your car at somebody else's TWC or whatever, then it might be a good idea calling Tesla's support line for the TWC. Back in the day, one of my co-workers got a Gen 2 TWC for his snazzy new Tesla. He was having an electrician do the wiring. Said electrician didn't read or pay attention to the entry in the manual for the TWC and therefore didn't follow the instructions that stated, "Do not adjust the switches on the TWC with the panel breaker on." Which resulted in the discovery, after the electrician left, that the TWC was toast.

My co-worker called the Tesla hot line in the manual and got a live body on the third ring (cue me falling over in astonishment). Who did a bit of troubleshooting and then drop-shipped a new TWC to our guy, without our guy having to pay.

Not sure if you'll get that kind of service these days, but one never knows. And I think the Gen 3 TWCs have internet connectivity; not sure, but there might be some logs in there.
 
Just chiming in with everybody else. Current draw is set by:
  1. Car finds out how much the connector to AC/DC (L1, L2/ Supercharger) can supply.
  2. Car figures out how much it can accept. (More or less, looks at its navel.)
  3. Picks the lower of #'s 1 and 2.
  4. If, while charging, Stuff Happens, it may reduce the current. What little I know under this category includes:
    1. Drop in AC voltage. Happens when a Mobile Connector is being used with an extension cord (personal experience). The high current on an extension cord whose advertising (Heavy Duty!) may have gotten past its actual current capacity results in an I-R drop across the suspect cord. The cord, if left in this state, would heat up to the point of letting the smoke out, so Tesla's programmers reduce the current draw. Since they don't like smoke, either. Similar can happen with loose connections to the breaker panel/in the wall/in the socket (worn contacts, anybody?), and so on. And probably includes loose connections inside the car, although I haven't heard of somebody suffering through that one, yet.
    2. High temperature on the Mobile Connector plug that goes into the wall. Oddly enough, the Mobile Connector reports its temperature back to the Mothership (the car) and, if the temp starts getting Up There, the car will cut back or simply stop charging. This can be because of cheapie or mis-installed sockets reaching End of Life or even a bad temperature sensor.
    3. Battery getting full. This is Extremely Obvious during supercharging, when one's initial 120kW/150kW/240kW rate slows down once one gets past 30% state of charge or so. But if one is going for 100% charge on a L1/L2 charger, the charge rate also slows down when one gets higher than 90% or so. The last 1% take XXX more than the first 1%, and all that.
The odd part about @BLH17's post is that the car isn't throwing error messages left, right, and center. In my experience, the car's not shy about putting up error messages for items #1 and #2 above; not so much for #3, since that's not an error, that's expected behavior. Trying somebody else's Wall Connector might be in order. Looking for Destination Chargers (which are typically Tesla Wall Connectors (TWC)) and using one might be in order. Similarly, Tesla Service Centers have the things in the parking lot and, of course, if one is at a Tesla SC, they'll typically let one do a little self-checking.

Finally: If it turns out that everything is sweetness and light with your car at somebody else's TWC or whatever, then it might be a good idea calling Tesla's support line for the TWC. Back in the day, one of my co-workers got a Gen 2 TWC for his snazzy new Tesla. He was having an electrician do the wiring. Said electrician didn't read or pay attention to the entry in the manual for the TWC and therefore didn't follow the instructions that stated, "Do not adjust the switches on the TWC with the panel breaker on." Which resulted in the discovery, after the electrician left, that the TWC was toast.

My co-worker called the Tesla hot line in the manual and got a live body on the third ring (cue me falling over in astonishment). Who did a bit of troubleshooting and then drop-shipped a new TWC to our guy, without our guy having to pay.

Not sure if you'll get that kind of service these days, but one never knows. And I think the Gen 3 TWCs have internet connectivity; not sure, but there might be some logs in there.
I will be trying a friends Wall Connector in town at some point in the near future. I know my voltage goes between 235V and 250V (245-250V when my solar is pumping out energy) so that is a wide range but shouldn't stop charging at all. I usually charge off peak hours so no solar going and it goes about 237-239V and stays consistent there as long as I'm not trying to do 40 amps which I never do anyway. This is just nuts to me because nothing is warm/hot, nothing is burning/smoking, nothing is loose at all but it just stops charging all the time. I wish the logs in the car gave some real info on WHY it chose to stop charging my car.
 
My understanding is the new Lithium Iron Phosphate (LFP) batteries support a higher Model 3 RWD charging rate. I was told by Tesla that when I receive delivery of my Model 3 next month, it will be from the Freemont factory, which has recently switched from the older Nickel Cobalt batteries to the new LFP batteries for the Model 3 RWD. I've heard from several sources that Model 3 with LFP batteries supports a faster charging rate. Just not sure if that would translate to me seeing a difference the a 40 AMP Mobile charger with a built in 14-50 plug. If it does, I will then purchase the 40 AMP version of the Mobile charger. Does anyone now if the latest Model 3 RWD with Lithium Iron Phosphate batteries will support 40 AMP charging with the 14-50 Mobile charger that is designed to support 40 AMP charging.
 

Rocky_H

Well-Known Member
Feb 19, 2015
8,627
11,211
Boise, ID
Just not sure if that would translate to me seeing a difference the a 40 AMP Mobile charger with a built in 14-50 plug.
No it won't. Faster or slower charging capabilities for the battery have to do with really fast DC charging, like from Superchargers or CCS stations. Those are talking about 200 kW or so power levels.

At home charging from AC circuits in your house are on the level of like 7 to 9 kW. That has nothing to do with the battery's capability. That is limited by the piece of equipment in the car that is the onboard charger. That is what converts the AC electricity to DC, and that is already limited in the car to only be able to accept 32A maximum. On the larger battery models, Tesla CHOSE to build them with a larger capacity charger, so they can accept up to 48A, but the model you have only has the 32A one.
 

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top