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Convert NEMA 5-20 to 6-20?
- Thread starter ratsbew
- Start date
I think this is good info but just want to add a qualifier about cold temps. I am sure this works well most of the year most of the country but temp starts dropping below freezing and it is unlikely to work well. Not sure of M3 amperage draw for battery heating but tonight at 37f my S was pulling 15amps at 240volts just to warm the cabin when I sat down to run nav routes.
In the dead of winter 10f and lower with a 30amp outlet battery/interior warmup could consume a few miles.
In the dead of winter 10f and lower with a 30amp outlet battery/interior warmup could consume a few miles.
You are correct. The ampere draw is the same...
But double the voltage.
Nice, thanks for the clarification. Enjoy your Tesla.
So 6-20 charge should be around double the charging rate of a 5-20?
eprosenx
Active Member
Correct (when on 240v residential service). And actually a faster charge than double since there are fixed overhead losses while charging (cooling pumps, etc) and so any boost in energy input goes direct to the battery since fixed losses are already covered.
davewill
Active Member
Actually a little more because charging has a fixed overhead of 3-400W or so:
5-15: 12a * 120v = 1440W - 300W = 1140W net charge rate
5-20: 16a * 120v = 1920W - 300W = 1620W
6-20: 16a * 240v = 3840W - 300W = 3640W
As you can see with a conservative overhead (I think the overhead might be bigger), the 6-20 is over triple the speed of a 5-15, and 2.25 times a 5-20. Any extra overhead (like from cold weather) will make this even more pronounced.
jgs
Active Member
As long as you don't run the cabin heater while the car is parked overnight to charge (who would do that?) it should be just fine. Last winter I had to charge my S on a mere household plug for a few weeks. It was well below freezing the whole time, car outdoors, not in a garage, and I didn't have a problem getting the expected 3 mph or so of charge. I think the 6-20 solution sounds just great.
nwdiver
Well-Known Member
Correct. 6-20 and 5-20 each use 3 wires. To upgrade a 5-20 to 6-20 you're repurposing the neutral as a hot you just need to ensure that there are no other outlets on that circuit. I'm a little surprised this doesn't happen more often since it's by far the most cost effective solution to charging at home. You're increasing your charge rate 2.6x and increasing charge efficiency >5%.
davewill
Active Member
Yes, it can be that easy if you have a 15a or 20a 120v circuit that has a single outlet on it (or can be rewired to have only one outlet). Unfortunately, that situation isn't very common. It mainly happens when an outlet was installed for a specific purpose like an AC or water heater.
OP here. This 6-20 setup has been amazing for me. Almost 14 months and I've never needed faster charge rate. The only benefit for me would be since I'm on a time-of-use plan and I could gain more miles during the absolute cheapest hours of the day if I had a HPWC...but it would never pay for itself since I only spent $15.00 for this.
According to TeslaFi, I've pulled 3,984kWh through this outlet.
According to TeslaFi, I've pulled 3,984kWh through this outlet.
Watts_Up
Well-Known Member
I looked at your video, but I would be interested to see also your breaker panel.
I am just curious how many 15 A, 20 A, ... breakers do you have.
In particular, I wonder if you might have at least two 20 A breakers?
In general those 20 A plugs are dedicated for kitchen appliances, such as Fridge, Garbage disposal, microwave, toasters...
Also if you are in a house where the dryer uses natural gas, this dryer might have instead a 120 V 15 A or 20 A plug.
I was thinking then, while visiting some relatives or living in a rental place where you don't want to make any electrical circuit changes.
If you can localise two 20 A plugs not caonnected to the same phase, and if there is only ONE plug connected to this circuit,
then it would be interesting to make a kind of "Dryer Buddy" but I call it "Appliance Buddy" in this case to provides 240 V 20 A plug.
The point is that if at any momemt an appliance starts, such as a fridge, the "Appliance Buddy" would stop the EV charger.
This is a little bit like combining two "Dryer Buddy" to make one "Appliance Buddy" to have a NEMA 6-20 without making any electrical changes.
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Watts_Up
Well-Known Member
This why I would be interested to see the picture of the main panel from theOP.
I noticed in few older built home, that there was a tandem 30 A for an oven range, several 15 A for the rooms, and two 20 A for the kitchen.
If the kitchen is not too far from the garage, you could easily share the two 20 A plugs (if they are not on the same phase)
using some extension cords and an automatic disconnect like used for making a Buddy Dryer.
It is fairly dangerous to do what you are thinking of in homemade fashion. However there is already a device called a "Quick 220". It has the necessary circuitry (e.g., several relays) for relatively safe operation. But won't work on GFCI-protected circuits.
M3BlueGeorgia
Active Member
12 gauge will work for 5-20 (120v-20A) but not for 6-20 (240v-20A).
You are going to be pulling twice as many watts, so go with thicker wire. At least 10 gauge.
What are you talking about? The amount of current is the same, so heat wasted in wire losses is the same. 12 gauge wire is 100% acceptable (and code compliant) for a NEMA 6-20 outlet. You need 10 gauge if you want to move up to a 30 amp outlet.
Correct, wire gauge required is a function of the amperage on the circuit. Voltage is irrelevant.
Where voltage becomes a concern is in the insulation on the wire, but all THHN or Romex is rated to much more than standard household voltages. I usually see a 600V rating.
A handy way to think about it is like water going through a pipe. You need a thicker pipe to accommodate more gallons per minute but it doesn't matter if you are expecting 100 gpm at 5 psi or 5000 psi. What does matter in that case is the thickness of the pipe material.
Where voltage becomes a concern is in the insulation on the wire, but all THHN or Romex is rated to much more than standard household voltages. I usually see a 600V rating.
A handy way to think about it is like water going through a pipe. You need a thicker pipe to accommodate more gallons per minute but it doesn't matter if you are expecting 100 gpm at 5 psi or 5000 psi. What does matter in that case is the thickness of the pipe material.
M3BlueGeorgia
Active Member
The equations are a bit more complex that this, because it depends on the wire run length.
However, 10 gauge will have less electric loss than 12 gauge, and for anything but a short cable run, it may start to heat up at 240v-20a (240v-16A continuous) whereas it wouldn't at 120v-20a.
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