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Good point, I had read it was rated for 55... I can't find where I read that now, but when I find it again I'll link it. Other searches are yielding 40a. Even so, if its rated for 40, and all I'm ever drawing is 40, why would there be an issue?
Even still, I can just re-run the #8 with #6 myself if this turns out to be the problem. I'll try to find a Tesla certified electrician... a year ago I couldn't even get one to call me back about an install
Edit: Reference this thread Wire Gauge Size for 50 Amps
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mikeash
Active Member
Because circuit ratings are for intermittent loads, while EV charging is a continuous loads. Continuous loads can only use a maximum of 80% of the rating. To charge at 40A, you need a 50A circuit. With a 40A circuit, you can only charge at 32A.
More correctly, you can charge at 40A on a 40A circuit, but there's a good chance of tripping the breaker or worse if you do, and it's against code.
AndreSF
Member
If the breaker is 50Amp and tripping at 40Amp load, I would definitely look into it ASAP.
A question to you on your original post. Is 22mph rated range charging not fast enough for you to have your car ready for the next travel window? The breaker tripping issue aside (which could be a sign of a serious issue), if the lower rate is satisfactory in terms of not waiting for the car to be ready, why would it not work for you?
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djgabriel2004
Member
first week when I bought My MS 70 I was charging it at the dryer's outlet with a 30 amp breaker and I had to set the car at 20amps because the breaker couldn't handle 30 amps Continuously.
If you have a 50 amp breaker you should be fine buy maybe the wires are too thin and they are overheating.. sometimes the overheating happens in a few minutes/hrs. and the breaker trips immediately after it. don't forget that the "best" thing that can happen is a breaker trips, that means the breaker is doing it's job, I highly recommend you to call an electrician, a bad Breaker/Wiring can Cause Fire in your home.
If you have a 50 amp breaker you should be fine buy maybe the wires are too thin and they are overheating.. sometimes the overheating happens in a few minutes/hrs. and the breaker trips immediately after it. don't forget that the "best" thing that can happen is a breaker trips, that means the breaker is doing it's job, I highly recommend you to call an electrician, a bad Breaker/Wiring can Cause Fire in your home.
That is sufficient, but if I can get it to work properly at a higher rate of charging, why not charge it at the higher rate? Is there a downside to that? I found out from my electrician that I had a faulty breaker, which he has replaced.
AndreSF
Member
Lower draw rate obviously puts less stress on the wiring/electric system overall. That was the point. But if problem is found and resolved, that's great!
I see the point now, thanks. Yes, it is supposedly fixed. I will find out tonight when I actually try it. I think I would still try it at 40 amps just to make sure it works fine, and if it does, then I would charge regularly at 30 amps unless I need a faster charge for some reason.
strider
Active Member
What voltage is the car showing when you charge at 40A vs 30A? If the voltage sags too much the car will dial back the current on the assumption that something is getting hot and resistance is rising causing the voltage sag . It sounds like you need a new panel. If the bus side of the breaker is getting hot that is a bad thing.
cman8
Member
One theory I have about charging amperage, particularly in winter, is to do it at the highest amperage possible. Because the car is using energy to keep the battery at a temperature satisfactory for charging, you should get the charging done ASAP.
mspohr
Well-Known Member
You haven't mentioned what voltage you are getting in the car. This is displayed on the charging screen. My guess is that it's dropping down from 240.
You may have undersized wiring somewhere giving you a voltage drop.
In the home we just sold I got was 31 miles per hour. In our current home it's 30 miles per hour. 1st home was built in 2008. Our current home was built in 2016.
wcalvin
Member
If the problem develops gradually, suspect contacts or screws not tightened. If it always cuts out before reaching 40A, the extra resistance that is dropping the voltage at the car below about 190V may be a long run of too-small wire. I've encountered that twice with 120V outlets; they were rated 15A but I could not draw half that without dropping the voltage at the car below the minimum acceptable. The electrician probably skimped on the wire.
JDaniel
Member
I used 3C #6 copper and a 50A SqD QO. Mine charges at 40a. It's in 3/4 plastic conduit in the garage and stapled to the joists in the house. Only 12'-15' total run. The Tesla wires get very warm which scared me at first. I don't feel any heat on my #6s or the breaker.
Acrono
Member
This is INCORRECT. Going from a single 48A onboard charger to the upgraded 72A single onboard charger is NOT a software upgrade. I took delivery of a MS 90D that was an inventory car on 9/26/16, and I wanted the upgraded charger option. Prior to delivery, they had to remove the old charger and install the new one that had been ordered from Fremont. They then physically showed me the old charger and said, "hey, this is what we took out of your car."
What I've been told is that it's a software upgrade for most newer production but a hardware upgrade for some production time blocks. I actually thought it was mostly some earlier Xs that needed a hardware upgrade, but I don't think which cars are which has been clearly spelled out.
mikeash
Active Member
Thanks for correcting and clarifying. Some do have it as a software upgrade, but clearly not all. I'll try to remember that for next time!
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