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FlatSix911
Porsche 918 Hybrid
If you are on a 240V/50A circuit, you should be getting 29 miles per hour charging rate. 
If you are on a 240V/50A circuit, you should be getting 29 miles per hour charging rate.
This chart only applies to the wall connector, right? I'm not using a wall connector, just the UMC to the outlet.
I think I'm on a 240V/40A circuit. The car says it's getting 40 amps, so I'm assuming it's a 40A circuit?
Just called customer service, and they had me change the settings in the car from 30 amp to 40 amp, and I'm now getting 26 mph. I guess the 30 amp was limiting the speed of my charge.
Does anyone know what is the benefit of charging at 30 amp versus changing the setting to 40 amp? Why not default at the faster charging rate at 40 amp?
Does anyone know what is the benefit of charging at 30 amp versus changing the setting to 40 amp? Why not default at the faster charging rate at 40 amp?
The car dropped amps from 40 to 30 as a safety measure when it sensed a problem with the circuit. You should be able to charge at 40A if it's wired properly. Get it checked before you try to use it again.
roblab
Active Member
When Tesla refined the charging software, back when a few f*res started, the car got a lot more picky. My charger dropped from 40 to 30 amps. I can raise it to 32 and it's OK with that, but higher, it will drop it back to 30. I really don't think there is anything wrong other than I have a longish run to the other side of the garage. But 22 miles per hour of charge still charges up overnight, and may be a tiny bit more gentle on the battery, so I haven't torn everything apart looking for the cause.
mikeash
Active Member
Note that when looking at charging speed, give it a few minutes. The displayed speed is an average for the entire charging session. Since the car ramps up gradually when it starts charging, the listed speed will be low at first. After five minutes or so, the value will be fairly close to the real long-term speed.
Skotty
2014 S P85 | 2023 F-150L
You should be able to charge at 30 or 32 amps on a 40 amp breaker, or 40 amps on a 50 amp breaker. Problems with wiring could reduce that amount. 30 amps is fine for overnight charging; that's what I use.
Yes, it was.
Higher amperage, higher charge rate. The car analyzes the circuit it is connected to and makes a determination about what is a safe amperage to charge at. It does not automatically charge at what you think is the maximum amperage the circuit can handle.
You likely have a problem with the circuit you are plugged into. You need to have a qualified electrician check it out ASAP.
What is the amperage of the circuit breaker of the circuit you are trying to charge from?
JSkrehot
Member
While prepping for my Model 3, there is no point to putting in a 80 amp circuit if I do not plan to get dual charging? Tesla does not currently offer faster charging at home than 29 miles per hour on a single charger? Thanks for your help.
one thing to remember is that for commercial power (which is 3-phase) you can only get 208 V which is roughly 1/6 less Volts than a 240 V outlet. and 208 is kind of a "best case" scenario, i have seen 196 V when charging at a ChargePoint J1772 plug. You obviously get much less miles/hr of charge from 208 V vs 240 V.
Not sure why the J1772 standard was not made for commercial installations (3-phase) in mind from the get go.
Not sure why the J1772 standard was not made for commercial installations (3-phase) in mind from the get go.
I am currently battling this issue. My 100amp service that runs to the house coupled with my 40+ year old box has forced me to limit my charging to 30A. I have wiring for 50, my breaker is 50, and i should be good... but without a box upgrade, I'm stuck for now.
How old is your main panel? What's its max service?
demundus, can you explain why this is an issue? I'm curious. I'm imagining that you have wiring to support 100A coming into your old load center, wiring to support 50A, and a new 50A breaker, then I don't see why the age of the load center matters?
I have been getting 29 or 30 mph charge on my UMC on 240v/50a (I always saw 29 on my old 60, but I always see 30 on my new 90D)
mikeash
Active Member
The "dual chargers" option is dead. Currently the default is a single 48A charger, and the upgrade option is to change that charger to a single 72A charger. They're identical hardware, and it's just a software change.
If the Model 3 follows the same pattern, which is a big if but is reasonable speculation, then by default you could use up to a 60A circuit. EV charging is a continuous load which can only use 80% of the rated capacity of the circuit, so a 60A circuit can support 60*.8 = 48A charging. As it currently stands, taking full advantage of 48A charging requires a wall connector (or suitable J1772 charger), as the mobile connector tops out at 40A.
With a Model S, 40A charging gets you about 29MPH, 48A would get you about 35MPH, and 72A would get you about 52MPH. A Model 3 should see slightly higher MPH numbers, since it'll be a more efficient vehicle.
It's rare that you need anything more than 40A charging (which, because of the 80% rule, means a 50A circuit). That's enough to fill the car up completely overnight, which is usually all you need. Some people need to make quick turnarounds at home, or at least be prepared for them, and higher amperage charging is useful for them, but most people don't need anything more than filling up overnight.
You can probably plan on a 50A circuit. If you're planning to install wiring ahead of time, see what the difference in cost would be. If a 90A circuit (needed for 72A charging) is not much more money, you might put that in just to be future proof. If you're just trying to figure things out in advance but won't do the work right away, plan on making a final decision once the final Model 3 specs and options are announced.
Long long long story short: My car started charging at a lower rate, then eventually stopped charging. My breaker was melted (slow burn) over the course of a year. I replaced the breaker and tried to charge at a full 40A and got smoke from the breaker. Dialed it down to about 30 and havent had an issue, but still uncomfortable with the idea. I had the electrician who did the work come out to inspect, he cleaned the busbar and load test the line. The breaker is getting pretty hot @ 40a on the bar side (not wire side). He wasn't really sure why, the line run is over engineered, as is the breaker. The panel is old, and while there isnt much load on the house (gas everything) he suggested to get a new box with upgraded service.
A few other opinions yielded a similar result. Some have indicated I should have used #6 copper instead of #8, but hindsight is 20/20 and he was within code and spec to use #8, so I can't rest on that as a fault.
davewill
Active Member
Whoa!!! Something is seriously wrong. I wouldn't use a circuit that acted like that if you paid me. Get someone who knows what they're doing out there to check it out. What brand is the panel?
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