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Home Charging
- Thread starter JB&JB
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Ron Burgundy
Member
It has been (in the past, maybe not now?) suggested that you only charge at 80% of the rated amperage of the circuit breaker that your home charger is connected to. So if your charger is connected to a 40A breaker, that would suggest your charge at 32A (set on your charging menu). I have this configuration, and get about 23-25 miles of charge per hour.
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I have a 60amp circuit so mine shows 48amps. Basically whatever your circuit is you should be @ 80% of that. Unless your scaling down for some other reason, i.e. not enough power in the house
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Thank all you guys for the reply, actually you all are correct, I was able to reach Tesla and the max for my charger is 40A, so I can actually charge up to the 40A or lower, also if it’s charging at a rate that is to high, I was told that the car would automatically lower it to a safe limit. Thanks again 
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From the supplied screenshot, 40A is the max charging rate, so that implies a 50A breaker. (80% of 50A is 40A).
Something not mentioned here is that it's less healthy for your battery to charge to 100%. It's recommended that you charge to what you need for your daily driving, and only go higher when you really need it.
You currently have the car set at 100%, and you really don't want to leave it sitting overnight at a high state of charge.
One last recommendation - change the display from "miles" to "percentage". Miles are inaccurate anyway.
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Thank all you guys for the reply, actually you all are correct, I was able to reach Tesla and the max for my charger is 40A, so I can actually charge up to the 40A or lower, also if it’s charging at a rate that is to high, I was told that the car would automatically lower it to a safe limit. Thanks again
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Brass Guy
Active Member
Eh, matter of opinion. I've been using the miles setting for many years and am used to it and usually close to match it.
Set to miles, I know how fast my battery is losing range, or if a "battery-gate" hits my car.
But on topic, I usually set mine to charge at 34A at home, though 40A capable.
If the car detects too much voltage drop, that's when it lowers the charge rate automatically.
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Why 34A? Why not 33A, or 29A?
I'm only asking because it seems arbitrary. If you can charge at 40A, why set it to anything lower?
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But this would be set at the EVSE (e.g. wall charger). So if the breaker 60A, the EVSE would be set to 48A.
You wouldn't adjust the amperage down to the 80% value in the app or car... otherwise those simple user settings could overload the wire and cause a fire.
Whatever your charging equipment lets you charge to you should be safe to charge to. If not, then your electrician did a Very Bad Thing™.
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the A is for the Amps that are used for charging. It is usually less than the breaker being used. In your case you probably have 40 AMP breaker, I would guess you are charging at about 32 to 33 MPH, my 50 amp breaker gives me about 40 mph.
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beenmb
Member
"The NEC (National Electric Code) defines safety electrical standards for homes. Since EV charging is relatively new, the NEC had to modify its existing safety load standards since EV charging can run continuously (defined as greater than 3 hours) for 3, 6, or even 12 hours straight–a situation that was not anticipated in the original safety code.
The NEC 80% rule stipulates that for EV charging, electrical circuits should not be continuously loaded to more than 80% of their maximum rated capacity…with a regular wall outlet and mobile charger you could dial it back from 12A to 9A on the charging screen. Still a lot of charging 4 miles per hour x 10 hours a day x 350 days a year = 14,000 miles a year at cheaper electric rates.
The NEC 80% rule stipulates that for EV charging, electrical circuits should not be continuously loaded to more than 80% of their maximum rated capacity…with a regular wall outlet and mobile charger you could dial it back from 12A to 9A on the charging screen. Still a lot of charging 4 miles per hour x 10 hours a day x 350 days a year = 14,000 miles a year at cheaper electric rates.
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My level 2 charging is 240v through a 40 amp breaker at the sub panel to a 50 amp breaker at the main panel. I use a gen 1 mobile charger that is rated for 40 amps.
When plugged in, the car shows 40 amps max draw. I've tried the 80% rule at 32 amps and the two inches of wiring running into and out of the charging brick does get noticeably warm after an hour or two of charging and thereafter. It's also somewhat warm about two inches into the charging handle too.
I've chosen to play it safe and roll with 24 amps since I plug my car in 24/7 set to 65% SoC max. My weekdays are only about 20 miles mostly so 65% is plenty. Besides, I don't want to burn my house down and being plugged in 24/7 allows the car to maintain hv battery as it needs.
My car also came with a gen 2 mobile charger but it only has a 5-15 plug and 32 amps max but I'd still be dialing it back to 24 amps.
When plugged in, the car shows 40 amps max draw. I've tried the 80% rule at 32 amps and the two inches of wiring running into and out of the charging brick does get noticeably warm after an hour or two of charging and thereafter. It's also somewhat warm about two inches into the charging handle too.
I've chosen to play it safe and roll with 24 amps since I plug my car in 24/7 set to 65% SoC max. My weekdays are only about 20 miles mostly so 65% is plenty. Besides, I don't want to burn my house down and being plugged in 24/7 allows the car to maintain hv battery as it needs.
My car also came with a gen 2 mobile charger but it only has a 5-15 plug and 32 amps max but I'd still be dialing it back to 24 amps.
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I assume this is in response to my post? If so, no worries. My electrician hard-wired everything for 50 amps. We chose a 40 amp breaker to match the mobile charger and to never allow it to draw more than 40 amps.
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