Hi all, we just picked up our Model 3 LR a few days ago and I noticed that when I plug it into my garage outlet that it seems to charge at 5 miles per hour rather than the usual 2-3 miles per hour that most people get. Is something wrong here? It is a standard 120v wall plug with vertical receptacles and no horizontal slots. In the app, I'm showing that it is recharging at 12/12A 109V and replenishing 5 miles per hour. It seems awfully high which makes me start to wonder how accurate it is or if it's pulling too much? The cable, charger, and outlet do not feel hot at all but since this house was built in the 70's, should I be worried?
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5 miles per hour on 120V 15amp outlet?
- Thread starter Nessal
- Start date
5mi/hr is not that uncommon for a 15 amp outlet. 12 amps times 120V is 1440w. Lose a few hundred to keep the car awake and efficiency losses through the charging circuit, and you'll be right below five, rounded up to five for display.
Most people get four or five. I've seen three only on occasion, but my garage outlet is on 14 gauge wire back to my main panel around 60 feet away, and I doubt the builder used the most direct route. I commonly saw 112V at the car or even less, at least until the electric company replaced the pole transformer outside my house(!)
You should not be worried at all.
Most people get four or five. I've seen three only on occasion, but my garage outlet is on 14 gauge wire back to my main panel around 60 feet away, and I doubt the builder used the most direct route. I commonly saw 112V at the car or even less, at least until the electric company replaced the pole transformer outside my house(!)
You should not be worried at all.
rexus31
Member
Yeah my SR+ would drift down to 5 mph sometimes during the charge, but was almost always at 6mph. I think most of the people talking about 2-3 mph are either people who are remembering something they read (because they themselves charge at higher amps), or perhaps they are people who have older, or bigger Teslas…
ucmndd
Well-Known Member
Miles per hour depends on the efficiency of the car. Model 3 is pretty efficient.
The only measurement that matters is power. 12 amps at 109 volts is 1300 watts, 1.3kw, which is pretty normal.
That said, 109v is getting a little low for a 120v circuit. What voltage does the car show immediately after you start charging? If it starts around 120v and then drops to 109-110 after a few minutes you could have some high resistance somewhere in that old 70s lights and plugs circuit.
The only measurement that matters is power. 12 amps at 109 volts is 1300 watts, 1.3kw, which is pretty normal.
That said, 109v is getting a little low for a 120v circuit. What voltage does the car show immediately after you start charging? If it starts around 120v and then drops to 109-110 after a few minutes you could have some high resistance somewhere in that old 70s lights and plugs circuit.
ATPMSD
Active Member
Assuming this is a dedicated circuit, which it should be, you can use a GFIC breaker and a standard outlet, or a standard breaker with a GFIC outlet.
ATPMSD
Active Member
Here is the math: 12A * 109V = 1,308 watt * 80% (20% loss due to AV to DC conversion) = 1,046 usable watts. To convert to miles you divide this by the EPA consumption used by Tesla, which for the M3 I believe is either 240 Wh/mi or 250 Wh/mi based on model. So you should be seeing 4-miles per hour. But, if you AC/DC conversion is just a little better, or the voltage is a little higher, you get the 5 miles per hour you are seeing.
ucmndd
Well-Known Member
ATPMSD
Active Member
You may well be right as I know it varies by model and year. I wish people would refer to charging and vampire drain in kWh, which is constant instead of miles, which varies by model and model year. But each to their own.
davewill
Active Member
Well you would actually have to refer to them in kW not kWh.
... and since the car doesn't report in kW, people report the number they do get.
ATPMSD
Active Member
This always dive me nuts, thank you! But I believe the car will report in kW if you select to display SOC as a percentage instead of miles.Well you would actually have to refer to them in kW not kWh.
AlanSubie4Life
Efficiency Obsessed Member
As you said, depends on the model, and whether you’re talking about displayed rated miles or the rate displayed on the charging screen.
For 2021 Model 3 SR+, it’s about 203Wh/rmi, or 194Wh/rmi displayed.
53.5kWh/263rmi, and then multiply by 0.955.
For 2021 Performance Model 3 it is:
80.6kWh/315mi ~= 255Wh/rmi
Or 244Wh/rmi (displayed).
For 2021 (and maybe 2022) LR AWD it is:
77.8kWh/353rmi or 79kWh/358rmi
220Wh/rmi or 210Wh/rmi (displayed)
For my vehicle it's 245Wh/rmi, 234Wh/rmi displayed.
These numbers can be checked for the fundamental constant for any vehicle by exactly aligning average consumption with the line and subtracting 5Wh/mi (line is always 5Wh/mi too high), or just taking Projected Range * Recent Efficiency / (Rated Miles remaining )(no confusing subtraction using that second formula).
And then multiply by 0.955 if you want to know energy content of each displayed rated mile, which removes the buffer energy.
I think the displayed rates when charging are calculated with the fundamental charging constant so will be lower than what you actually get, but I am not sure about that. You can always compare actual results vs. displayed rate over a fixed time period and see whether they align (I’d expect 4.7% more miles added than predicted).
Anyway, can all be easily checked in the vehicle.
There's a thread for this, which used to be stickied, but it's out of date now, so was removed from stickies, and I'm a bit too lazy to update my spreadsheet (and it also requires soliciting data from user vehicles for more recent models). And I would want to link to all the data from pictures of people's cars, which would be a project! Maybe someday. Just a little pointless since any user/owner can easily determine the constant, right from their own vehicle. Still, if I wrote it all up with the degradation threshold covered and stuff it would probably be helpful. Meh...
2020, 2019, 2018 Model 3 Battery Capacities & Charging Constants
I should have done this a while ago, but I've finally compiled all the data that Tesla provides to the EPA, and put it into a spreadsheet. The detailed 2020 test data is now available, so we can see why things are rated the way they are. Through formulas, I've also tried to capture what...
teslamotorsclub.com
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You guys rock! Some of this stuff flies over my head but it's good to know that this is OK and won't burn my house down.
AlanSubie4Life
Efficiency Obsessed Member
As someone mentioned, that 109V is quite possible and fine in SOME circumstances but could be worth investigation as to the root cause. This suggests that about 130W of heat are being lost somewhere. (Dial back the charge current to 5A and see what the voltage drop is there to extrapolate open circuit voltage, or just watch what the voltage is when the current is just starting its ramp right after the relay on the UMC closes (have to be quick).)
130W assumes your open circuit voltage is actually 120V (it isn't always).
That's kind of a lot. If it's a long run of 14AWG wire, it's no big deal, normal. However, if it's a short run, it could be due to contact resistance in the outlet. These can get very hot and melt due the long charging events.
It's well worth spending a couple bucks and replacing the outlet if it is loose, old, etc., removing the back-stabbing connectors, etc. It does require good ability to do such (simple) work yourself so that you don't make matters worse. But it is extremely simple.
Barring replacement, keep an eye on the outlet, check it for excessive heat after an hour of charging (feel it - it should be warm but should not be burning hot).
The UMC has a temperature detection in the plug so in theory will shut down if it detects too much heat but it's best to not rely on these things, since thermal conductivity to the plug can also be compromised by bad connections.
Not saying there's a problem - it just should be double checked to make sure it is all good. Again, a reasonable length run will also result in this voltage drop - and that's fine because that heat is distributed over a lot of material and it just means things get warm, and is the cost of low voltage and long runs with small gauge wire.
El joe
Active Member
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