The DIY J1772 Charging Adapter

Not long after I purchased the Vectrix, I started wondering “If it’s an international vehicle, what would it take to charge on 240V (instead of 120V) and from a public J1772 Level 2 EV charging station?”.

Everything I had heard lead me to believe that the charger on the bike is much like a modern computer power supply – it will run off AC power from a range of somewhere between 100-250V or so. I already have a 240V electric outlet in my garage, used for a welder. It’s a 30-amp twist lock connector. I looked around, and sure enough, I actually already had all the parts I needed to build an adapter that would physically connect the 30 amp twist lock to a typical 120V electric outlet.

So, I sat down in my living room one night last week and built the adapter. Afterwards, I went out to the garage, plugged everything in, crossed my fingers, and flipped the circuit breaker on. A moment later, the Vectrix booted up into charge mode, exactly as it normally would. It worked! I just charged the cycle on 240!

For some of you hard-core DIY electric car folks out there, you’ve been running on 240V for years, but I’ve never had a 240V charger before. So, it’s still pretty exciting.

The other part of this is that there is a shocking LACK of 120V charging available. Some of the few public chargers that appeared in my area originally had both 120VAC power AND a 240V J1772 connection, but the more recent ones ONLY have J1772. That doesn’t help out a person with a Hymotion Prius with a standard plug on it OR most electric motorcyclers.

But getting my bike to charge from a plain 240V outlet is one thing, and charging from a “smart” Level 2 EVSE is another! Electric Vehicle Supply Equipment actually communicates with the vehicle and only activates power after a handshake and confirmation that everything is connected. It goes something like this..

“Hi, how ya doing. I’m an EVSE.”
“Uh, good. I’m an electric car. Can I get some juice?”
“Sure thing, let me turn that on for you….”

Ok, perhaps I’m anthropomorphizing a bit, but the point is that it’s not JUST as simple as plugging in a cable. On the other hand, it’s not rocket science either. I browsed through a few forums and asked a few friends for advice. After an evening of research, I had a pretty good sense of what I needed to do.

For me, pictures always help, and one of the best ones I found was over on the EVTV blog. http://evtv.me/2011/01/j1772-2009-charging-for-your-ev/  I also found another good article and diagram at: http://www.aprs.org/charging-DIY.html

In a nut shell, the magic of the J1772 connection is just a diode, two resistors, and a switch. Pin 4 of the connection carries a signal from the EVSE. It goes through the diode, through a 2.7K ohm resistor, and then to ground. A second resistor, of 1.3K ohms is connected in parallel with the first when a switch is connected. When that happens, the total resistance is 877 ohms. Pin 4 on the EVSE responds to 2.7K ohms as “Hey hello there” and 877 ohms as “Okay, sure, let me turn the power on for you.”

I set to work by first removing the power inlet power from my salvaged Mitsubishi iMIEV. Yes, that’s still sitting in my garage. Needs parts? I’ll give you a good deal, but you can’t buy the power inlet because I just built an adapter from it.

I had already hit the hardware store and purchased a 4″x4″x4″ marine grade electrical junction box. I drilled a hole in it’s lid with a hole saw that matched the J1772 connector.

I also purchased a regular old 120V electric outlet, except that this one happened to be rated for 20 amps and was only a single outlet instead of two. I didn’t need a second plug, and it saves space inside the box. I drilled a hole in the side of the box to fit that single outlet.

I cut the very end off the wire harness of the Mitsubishi power inlet. I stripped the end of the two hot wires, and then connected them to the two main connections of the electric outlet. I did NOT connect the third pin to the ground on the electric outlet. It would act as the electronics/communications ground as well, so I added a short pig-tail to the electric outlet ground, knowing that there would be several other wires going to it as well.

Next, I had to tackle the electronics – if you can call a diode and two resistors electronics. Of course, I didn’t actually have two resistors of those exact values, so I had to put several together to come up with those total values. That meant I had 5 resistors instead of 2. Oh well. Since I was going to have several connections, I first tested it all out on a bread-board. Only after I had it all worked out did I transfer the components to a small project PCB board and solder them. On one side of the board was a 1N4003 diode, going to 2.7K ohms of resistors. On the other side was 1.3K ohms of resistors, the a switch, and then the parallel connection to the end of the other half of the circuit.

I soldered Pin 4 from the J1772 connection to the front of my circuit board, going to the diode. On the back end of the circuit, I soldered on a ground wire, then wire nutted that to the Pin 3 on the J1772 and the ground wire on the electric outlet.

I drilled a small hole in the side of the box, pushed the toggle switch through, and mounted it in place by tightening the nut.

I mounted the circuit board inside the box, against the side, with hot glue. The J1772 connector was hot-glued to the inside of the lid, and the electric outlet to the side of the box.

With the components all mounted in place, the next trick was to fit all the wiring inside. The J1772 connector still had several feet of wire on it. Part of the reason why is that there was already some properly done splicing of a ground cable part way down. Also, who knows, maybe I will need some longer wire for a different version of this adapter. The point is I still had several feet of wire to wind around and squeeze into this four-inch-square box.

Once I wrangled it in there, I attached the lid with the four screws that went with it. The last step was to add labels, so I would remember which direction was ON and OFF for the switch, and a warning that the 120V electric outlet would actually have 240V going to it.

I hopped on the Vectrix and zipped over to a friend’s house, several miles away, who has a home electric car charger right on the side of her house. I opened my truck, plugged the Vectrix cord into the adapter, and then plugged the EVSE cable into the box. On the EVSE, a light turned on, indicating that it registered that it was plugged in, but not yet providing power.

I flipped the switch on the box. KA-THUNK!

Yipes! I thought for sure something was wrong, that the EVSE faulted out. Nope. It took me a moment to realize that it was just the contractor inside the EVSE turning on. It sure sounded loud though, and I guess I just wasn’t expecting the noise. In all that time that I’ve been working on electric cars, I realized that I have never even ONCE plugged in a car to a commercial 240V EVSE.

Of course, a moment later, the Vectrix booted right up into charge mode and began charging as usual.

I played around with the position of the adapter box in the trunk of the Vectrix. I was able to arrange it so that I could have the adapter in the trunk with the EVSE plugged into it AND fit my helmet in there, AND close and lock the trunk. The cord goes out through a notch in the edge of the trunk designed for such a purpose. The EVSE cable is thicker than the regular charging cord, so it’s tight, but it does fit!

I let the bike charge for a few minutes, and then flipped the switch on the adapter box back to off. The bike stopped charging, and its fans spun down.

So, the adapter box worked! The best part is that it worked the first time! No building/fixing/tinkering/makingversion2 and THEN having it worked.

Sometimes things just work the way they are supposed to.

Stay charged up, I know I will.
-Ben

 

Tagged as: adapter, charging, DIY, electric motorcycle, ev, J1772, SAE, Vectrix