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Fast charging from 120V

vfx

Well-Known Member
Aug 18, 2006
14,790
40
CA CA
This 120 Doubler rig solves a problem and I use it every day.

Not everyone can access a 240V circuit no matter how much they desire. "Fast" is a relative term but I assure you, those that are still forced to 120V sites will take notice. :wink:

This device is useful for Tesla owners living, (or visiting) apartment buildings and condos. For road trips it can significantly cut wait times at charge stops.

With 120V at 12 amps I get about 3.5 Miles Per Hour Charge (MPHC) (the Tesla charge manual lists that as a from-empty 70 hour charge) Very slow because the temperature control pumps and fans consistently draw power first.

With 120V and the VDS set to 16 amps I get about 4.8 MPHC, (the Tesla charge manual lists that as a from-empty 36 hour charge) a huge difference.

With the 120Doubler rig at 16 amps, charge time is now 11 MPHC (the Tesla charge manual lists that as a from-empty 18 hour charge) Any increase of amperage from this point show much smaller gains in charge time. With this setup, charging is basically overnight!

It consists of:
A MC240 or Roadster Foundry cable
A Quick 220
Various Adapters (user wired)
Long heavy duty extension cord(s) to find an out of phase 120V circuit. Mine is 130 feet:eek:

220from2120s-2.jpg

The image shows the setup outdoors but this is an indoor rated device. Also note the coiled cord shown is an unsafe practice and no power is present in the picture.
 
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TEG

Teslafanatic
Aug 20, 2006
21,771
8,748
How do you tell it to draw no more than 16amps ahead of time?
Do you have to set that on the VDS before plugging the MC240 into the Roadster?

I imagine if you let it try to draw 24amps (MC240 default) it would likely blow both breakers on the two 120V circuits.
 

vfx

Well-Known Member
Aug 18, 2006
14,790
40
CA CA
The GPS memory overrides the MC240.

That is, at least in this case, the car already knew this site was a 16amp draw from when I only had a MC120V and when I went to a MC240 it stayed there.
 

TEG

Teslafanatic
Aug 20, 2006
21,771
8,748
OK, so you have to be careful when hooking that "contraption" up in new locations. Is there a way to pre-program the GPS ampacity setting for a new location before you plug it in?

I wonder how many locations the GPS can store?
 

vfx

Well-Known Member
Aug 18, 2006
14,790
40
CA CA
OK, so you have to be careful when hooking that "contraption" up in new locations. Is there a way to pre-program the GPS ampacity setting for a new location before you plug it in?

I wonder how many locations the GPS can store?

Our list of questions about the GPS knows no end.:rolleyes:

I will test the rig at another site this week.
 

donauker

Member
Sep 5, 2006
798
86
When you open the charge port door on the Roadster the charge screen is shown on the VDS. You can then go in and set the max current for this location before connecting the cable, or you can connect the cable but not slide the switch forward. The car ignores the cable until the switch is closed.
 

vfx

Well-Known Member
Aug 18, 2006
14,790
40
CA CA
I did test the current setting at another location.

Before hooking up I set the current at 10A. Then I bumped it up to 16(15) A. Worked great. I never went back but I will assume the GPS will remember the current at that site.
 

DaveD

EVs Kick Gas!
Aug 18, 2007
642
242
Redmond, WA
I'll probably feel stupid for asking, but what's unsafe about the coiled cord shown?

A wire carrying current will heat up, and coiling the wire will concentrate the heat, possibly causing materials (like the insulation on the wire) to overheat and melt. Bad things can then happen.
 

ra-san

Member
Dec 26, 2008
296
5
San Diego, CA
both points true, but given the loose and few coils in the picture neither effect would be even close to the order of magnitude required to raise a concern... right? Just being in the sun would be more heat. As for magnetic field, well doubt it's noticeable next to the much stronger stuff in the car charging system.

I've felt the HPC charging cord going full blast, and the mobile foundry cord (not going full blast). Neither get particularly warm (good thing!)
 

doug

Administrator / Head Moderator
Nov 28, 2006
16,898
1,018
SF Bay Area
Coiled wire can act as an inductor as well...

HowStuffWorks "How Inductors Work"

That's not much of an issue here. There's current going in both directions within the cable, so they cancel out.
Also realistically speaking the diameter of that loop is so large and since there's only air within the coil (no field enhancing core), any inductance would be quite low.


.
 
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BBHighway

Member
Feb 2, 2008
224
0
About a year ago there was a house fire near where I live.

The cause of the fire was an extension cord to a space heater coiled up inside a metal bucket with a pile of rags on top.

They probably didn't know any better, but that was a seriously bad idea.
 

vfx

Well-Known Member
Aug 18, 2006
14,790
40
CA CA
I was talking about heat buildup. Someone once showed me a picture of a similar cable loop to what I had set up for the photo (with some more loops) that was burned to a crispy critter.

It's just a bad idea to coil loops that are running this much power and I did not want to propagate the idea that it was ok.
 

Todd Burch

Voltage makes me tingle.
Nov 3, 2009
7,888
29,238
Smithfield, VA
Just curious: Why isn't Tesla selling something like this?

I'm an ME--not an electrical engineer--so my knowledge of electricity is relatively limited...sorry if I'm restating the obvious...But from what I can tell, VFX's setup is essentially finding two 120V outlets that are out of phase, combining them to build a 240V outlet, and using that to charge, right?

Since you're doubling the voltage, you're essentially halving the charge time, and doing so without requiring special installation of a 240V outlet.

Seems like this would be a pretty popular charging accessory (avoiding the hassle and cost of installing a 240V circuit), so why isn't Tesla selling it?

Is it because it's difficult to find two nearby outlets that are out of phase?
 

TEG

Teslafanatic
Aug 20, 2006
21,771
8,748
I think you understand the concept. I also think Tesla had made some of those cables for their own internal use, but (for whatever reason) decided not to 'productize' it. Perhaps it is a code or UL thing, or just too hard to find convenient outlets that are out of phase with each other.
 

vfx

Well-Known Member
Aug 18, 2006
14,790
40
CA CA
I'll put one together for anyone who want but nobody expressed an interest. It's a pretty unique set of circumstances that put you in the place to need the speed of charge but not willing to spring for a rewire upgrade.

I only know of one other person who put one together. Sometimes people build these things and don't post though.

Finding a second out of phase circuit usually takes a long (50' min) 10G extension cord.

At my home I went from 3 to 4 MPHC to 10 to 11 MPHC amps stayed at 16.
 

Tdave

Member
May 16, 2008
760
80
Owings Mills, MD
I'll put one together for anyone who want but nobody expressed an interest. It's a pretty unique set of circumstances that put you in the place to need the speed of charge but not willing to spring for a rewire upgrade.
Visiting friends or family for an overnight visit is the situation for which I would find this most useful.

How much?
 

vfx

Well-Known Member
Aug 18, 2006
14,790
40
CA CA
Exactly what I thought. You are the first to ask, Dave.

Let me crunch some numbers.
 
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