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If your car detects a possible issue when charging, it will lower the amps by 25%. For example, if you charge at 40 amps, it will lower it to 30 amps to be safe. 75% of 72 amps is 54 amps. There a several threads which discuss this drop. Here's one: Charging Reduced From 40A to 30A
Thanks! I just did a reset of the charger and the car is now back to full charge. Never knew about the 25% reduction.
BigMskiman
Active Member
You shouldn't have to reset the charger. When the car is not plugged in & at the location with the charger, set the current limit back to the max.
But notice what the rest of this thread is saying; it probably isn't your wall connector that has a problem. The car will lower the amps to 3/4 of the set level if it detects that there is an unexpected voltage drop somewhere in the circuit upstream (Bad Thing). So you should get that checked to see if there is a loose connection somewhere.
I would check your settings. There are dip switches that could be set incorrectly to 54A. Pull cover off and you will see the setting for 72A settings.
It's definitely not the switch settings inside the wall connector. If it were set for that, it would ONLY feed that current. He is saying that sometimes it will run at 72A for a day or two, and then revert to a lower level.
What kind of volt drop are you getting? You may not have enough amperage feeding your house to charge your car at 72A and run everything else in your house. If you see a 10+ volt drop I would suspect this to be the problem. I do believe the volt drop will also cause your HPWC to charge at a lower amperage.
Run everything in your house that could possibly be on anytime your charging your car then you can plug your car in and watch the volt drop when you ramp-up to 72A. I see around 5 volt drop when I reach 72A and my vehicle will keep that charge rate the entire duration of my charge.
Run everything in your house that could possibly be on anytime your charging your car then you can plug your car in and watch the volt drop when you ramp-up to 72A. I see around 5 volt drop when I reach 72A and my vehicle will keep that charge rate the entire duration of my charge.
Looks like your car is detecting only 54A available. I would call Tesla tech support as it appears your car is reading or interpreting a message from your HPWC that only 54A is available from the HPWC. My guess is that your root cause is the HPWC or upstream supply. Also, your voltage is a tad on the high side and that may be triggering something in the HPWC to cause it to reduce available charging current.
The car has no way to detect how much power is available. It relies on the wall connector to tell it how much power it can supply. As a safety feature the car will drop the charging current if it detects a voltage drop as this can be an indicator that it is pulling too much power through an inadequate supply, but there can be other reasons for a voltage drop too.
just got my New X and don't even know how to post a new question on this site?
NEED EXPERT ELECTRICAL ADVICE
I'm trying to rig a 100' extension cord FOR OCCASIONAL EMERGENCY USE. i have a 220v /30A outlet on the outside of my house. 3 pin twist lock type. BUT the tesla cord either has a FOUR PIN 240v plug or whatever is left when NO adapters are used.
how do i get from a 3pin (with conduit as ground) to 4 pin to use this extension cord???
I'm no expert and Tesla says you shouldn't be using extension cords but you said "Occasional Emergency use" so:
I have this for emergency use when travelling but haven't needed it yet: Heavy-duty NEMA 14-50R extension cord for Tesla, 20 ft.
It will fit in 14-30, 14-50 and 14-60 outlets. You do need to manually adjust the amps in the car if you are using in a 14-30 outlet. However, you said that you only have 3 pins. Can you take a picture and see how the socket is labeled?
Based on the "twist lock" description, I would guess it was actually a 6-20 outlet. Tesla doesn't make native 6-20 twist lock adapters but they did just come out with a standard 6-20 adapter for the new UMC. Of course you could buy or make an adapter but you need to be sure of the outlet, wiring and breaker you are using first.
For expert advice, you should learn the specific names of the types of outlets you're asking about, so we can give helpful answers. The naming system for outlet types is called NEMA. Here is a page that shows the most common types and what they're used for, but you can Google for NEMA outlets, and find charts of every single kind.
NEMA connector - Wikipedia
He said it's a 30 amp outlet, so not L6-20 obviously. Very likely an L6-30, though.
The "4 pin" you're talking about is called a 14-50. The site evseadapters.com sells several types of adapters for the Tesla charging cord 14-50 plug to other outlet types. This one should be the one you're looking for, which is the L6-30.
NEMA 14-50R to L6-30P Twist-Lock Adapter
Please do take a look at your outlet, though, to see if it is an L6-30. There are also L14-30 and one or two others that have different numbers and arrangements of pins.
Also, VERY important note. If you are using something like that, you WILL need to dial down the current in the car. The car gets a signal of how many amps to use by what real Tesla plug is on the end of your UMC. You're using the 14-50 plug, and if you use a 3rd party pigtail to switch it to some 30A outlet type, the car can't detect that. It will try to draw too much current, and if you're lucky, the breaker will trip to save you from a problem. The rule is that you can only draw up to 80% of the circuit rating, so for a 30A circuit type, set the car for 24A or less, etc.
However, back on your original question, I would highly recommend against a 100 foot cord. That is going to have a lot of voltage drop to it, and that length is likely way overkill. I have a 30 foot, and 50 foot may be useful, but I wouldn't recommend higher than that. Also, have you experienced how stiff, bulky, and especially heavy official 14-50 extension cords are? 30 foot is borderline, but for any longer, I would recommend a custom one. The reason is that real 14-50 cords are made to offer both 120V and 240V capability, which your Tesla charging doesn't need both of. So the cord has one extra unnecessary thick wire included, which is extra cost and dead weight.
Read these couple of threads about making a custom extension cord that doesn't have the extra wire. You can do one that's very light and flexible if you just need up to 30A capability, or a little heavier if you want 50A.
How to build a 30 Amp Extension Cord for 24 A, 240 V charging
How to build a lightweight 50A extension cord
Or, the EVSEAdapters site does make those thinner extension cords without the extra wire that you can buy.
Adapters for Tesla
Before you spend a lot of time and effort on this you might want to figure out exactly what sort of “occasional emergency” you would have that would require the use of such a cord. You’re probably looking at several hundred dollars for the wire and plugs and it would only be useful for whatever type of plug you put on it, so depending on where and when you need it in that emergency it might not even work for you. At that point you might be better off using a regular 115V plug or driving to a public charger instead.
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