Charging on NEMA 5-20 at 7mph!

[Rocky_H]

Wow, you guys have gone off the rails.

Let’s go back to specifically what was said and why I corrected it:

16A might be slightly more efficient than 12A but 240v is ~10% more efficient than 120v.

So he was dismissing the difference in charging speed from 120V 12A to 120V 16A as so small a number it’s not even worth mentioning, but comparing it to a 10% increase in efficiency from just a voltage change, which he was considering very large. This needed clarification, because it’s extremely overly absolute, conveying a false impression to people that increasing current is meaningless and doesn’t do anything for efficiency, while voltage is the only thing that matters. That’s not correct.

Some of you seem to have gotten all out of the ballpark on this, attacking things I didn’t say.

You're cherry picking your science.

Yes, of course I am—that’s the point. It only takes one contrary data point to disprove any absolute statement. We wouldn’t really need to be talking about this if we were talking about 10kW or 20kW power levels, because they are all so efficient up there that there isn’t much difference, or if comparing two situations of the same power level, where you're isolating voltage versus current effects. But those weren't this point. When it’s around 1kW, and you’re losing a third of fourth of your power, increases to current or voltage both make a big difference. That’s what this topic was.

You all are ranting and insulting me to point out that voltages makes a bigger difference. Great—I never said it didn’t. I just wanted to make sure people do get the helpful information that at very low power, on 120V circuits, being able to increase the current significantly helps charging speed and efficiency and shouldn’t be dismissed as having negligible effect.

Several people are trying to “disprove” what I was saying with the “at a given power level” paradigm. But that wasn’t the context Yes, that’s obvious that if the power calculates to the same, the increased voltage does have innate efficiency advantages. I am aware of that, and yes, my electrical engineering degree is plenty of “background in electrical science” to know that, @aydyn. The point was NOT “at a given power level”, but if you are stuck using a 120V low power circuit, the current increase increases power and efficiency significantly and shouldn’t be dismissed.

 

[AWDtsla]

So he was dismissing the difference in charging speed from 120V 12A to 120V 16A as so small a number it’s not even worth mentioning, but comparing it to a 10% increase in efficiency from just a voltage change, which he was considering very large. This needed clarification, because it’s extremely overly absolute, conveying a false impression to people that increasing current is meaningless and doesn’t do anything for efficiency, while voltage is the only thing that matters. That’s not correct.

Lots of rehashing of things that are already known. Model 3 charging seems about the same as S/X. Expect the car to draw 300-400W as overhead (Not including very hot or very cold pack temps). Any increase above that ~400W is direct increase to charging rate. 12-16A is a massive improvement at 120V.

You can approximate charging rate as

MPH = (V*A*0.92 - 350)/RM

Where RM is probably 230 for Model 3.

 

[AWDtsla]

Additional note: the UI rounds up. So my EQ gives 6.18, which the app will show as 7

 

[nwdiver]

You all are ranting and insulting me to point out that voltages makes a bigger difference. Great—I never said it didn’t.

.... Really?

You're misinforming people by saying that voltage changes have more efficiency impact than amperage changes. The charging speed and efficiency of charging of the car is based on power, which is the product of volts times amps. So increasing either one, which gives more power, is what helps efficiency.

The internal charging characteristics vary car by car but from a pure physics standpoint increasing voltage vs current is not the same. The point I was trying to drive home is that you can increase POWER by increasing VOLTAGE without increasing losses. This is not true of current. Double Voltage and your losses don't change. Double Current and your line losses increase 4x. Line losses for 16A are 77% higher than for 12A. BUT if you were to send the same 1.9kW (16A @ 120v) at 240v and 8A your losses are now ~75% lower.

L1 charging needs to be viewed as a band-aid... not a solution. It'll do in a pinch and it's better than nothing but it shouldn't be encouraged as any kind of long-term solution. That's the point.

 

[SigNC]

Additional note: the UI rounds up. So my EQ gives 6.18, which the app will show as 7

agreed, i checked Remote S and it shows 6.2.

 

[Snow Drift]

How common is the 5-20 outlet? I don't think I've ever seen one.

 

[VT_EE]

How common is the 5-20 outlet? I don't think I've ever seen one.

Not very common at all. It does however allow you convert a standard 120V circuit with a simple change of outlet and breaker. Assuming the wire is the correct 12AWG romex

 

[nwdiver]

Not very common at all. It does however allow you convert a standard 120V circuit with a simple change of outlet and breaker. Assuming the wire is the correct 12AWG romex

5-20 is still 120v. 6-20 is 240 or 208v. 5-20 just gives you ~33% more amps and more than likely your car won't let you pull them because of the voltage drop... so probably not worth it. 6-20 on the other hand definitely worth it.

5-20 is much more common commercially than with residential. I think ~90% of the outlets were I used to work were 5-20. 6-20 is super common with hotels. Most of the AC units are 6-20.

 

[VT_EE]

5-20 is still 120v. 6-20 is 240 or 208v. 5-20 just gives you ~33% more amps and more than likely your car won't let you pull them because of the voltage drop... so probably not worth it. 6-20 on the other hand definitely worth it.

5-20 is much more common commercially than with residential. I think ~90% of the outlets were I used to work were 5-20. 6-20 is super common with hotels. Most of the AC units are 6-20.

My bad, I was seeing 6-20 in my brain. 5-20s are far more common. I have them in my kitchen.

 

[Snow Drift]

My bad, I was seeing 6-20 in my brain. 5-20s are far more common. I have them in my kitchen.

Is it a new build? Even our GFI aren't 5-20.

 

[VT_EE]

Is it a new build? Even our GFI aren't 5-20.

Renovated it 3 years ago. GFIs are 20 amp for both kitchen countertop circuits.

 

[gtmotor]

6-20 on the other hand definitely worth it.

6-20 is super common with hotels. Most of the AC units are 6-20.

Here's a little pro-tip... Many of the uh, lower priced, hotel/motels that have the room facing the parking lot have these outlets. If you're trying to save some money by not staying at a 5 star resort with the official Tesla chargers you can try your luck with one of these.

I called the front desk and asked if I could plug my car into the outlet outside and they said: "Sure! Go ahead!"

It has two problems though, one your charge cable is now a trip hazard and two, you won't have AC in your hotel room while it's plugged in

 

[theredviper]

Renovated it 3 years ago. GFIs are 20 amp for both kitchen countertop circuits.

My condo (finished in 2016) has 5-20 throughout the kitchen. It's nice for appliances, no more popping breakers for the toaster and microwave on at the same time.

I'm in Canada. I'm assuming it's code now, since the builder would have cheaped out if given the opportunity...

 

[nwdiver]

It has two problems though, one your charge cable is now a trip hazard and two, you won't have AC in your hotel room while it's plugged in

LOL been there... also slow is fast. If you're using a 14-50 adapter and not 'striiickly' limited to 16A like you would be with a 6-20 plugged into your UMC... you're, you're gonna be tempted to got to ~18A. That only works for a couple hours before the breaker pops

 

[AWDtsla]

My condo (finished in 2016) has 5-20 throughout the kitchen. It's nice for appliances, no more popping breakers for the toaster and microwave on at the same time.

I'm in Canada. I'm assuming it's code now, since the builder would have cheaped out if given the opportunity...

I believe it is code now, however they often cheap out on the outlet even if the circuit is 20A. Inspectors don't care, apparently.

 

[EfficientWatts]

My condo (finished in 2016) has 5-20 throughout the kitchen. It's nice for appliances, no more popping breakers for the toaster and microwave on at the same time.

I'm in Canada. I'm assuming it's code now, since the builder would have cheaped out if given the opportunity...

Note: While 5-20 is a good sign of a 20 amp breaker with proper wiring, you could have the same effect if the plugs were still 5-15. You can have 5-15 but with 12 gauge wiring and a 20 amp breaker, which would have the same effect (unless you had 5-20 appliances, though such an appliance would likely use up a good chunk of capacity). my kitchen for example is all 5-15 plugs but are on 5-20 breakers

 

[davewill]

Sometimes there will be 20a circuits in a home, but the outlets themselves will still be 5-15.

 

[MRT336]

Check your fuse box too. Sometimes you get lucky and find a dedicated 5-15 or 5-20 that was installed for a specific purpose. ie: I have an 80s house that had a "freezer" outlet installed in the garage, on it's own circuit, and already had a 20amp breaker (but only a 5-15 outlet). That type of labeling indicated it MIGHT be on it's own circuit, and turns out, it is. I don't have a freezer there, and was just using it to charge cordless drill batteries. I can now easily replace it with a 5-20 outlet to get a little more charge speed, and then possibly upgrade later fairly easily to a 6-20, assuming the wire gauge can handle it.

 

[nvesprini]

bringing an old topic back to life. for anyone charging off a 5-20 do you use a 5-20 extension cord, and if so what brand? need a short run to reach the car but having a hard time finding one. amazon has a few but a couple reviews showed they overheated when used for charging.

 

[jdcollins5]

bringing an old topic back to life. for anyone charging off a 5-20 do you use a 5-20 extension cord, and if so what brand? need a short run to reach the car but having a hard time finding one. amazon has a few but a couple reviews showed they overheated when used for charging.

What do you consider a short run? I use a 75 foot extension cord at my kids that is #12 wire, which is good for 20 amps. The 5-20 draws 16 amps continuously. Most extension cords are #14 wire which is only good for 15 amps, hence they will overheat. Add distance and voltage drop and you aggregate the situation even more.