Introduction: DIY J1772 EVSE

To begin with this is not for the feint of heart as you will be working with 220V at possibly as much as 80A. That being said, I TAKE NO RESPONSIBILITY FOR YOU ELECTROCUTING YOURSELF. If you don't have experience with High Voltage/High Current I'd advise you not to even attempt this. (Dire warning, I know. BUT I don't want to hear about anyone earning themselves a Darwin Award for attempting this. There is too many of those these days resulting from copper theft.) 

>>>I take no responsibility for you "bricking" your car for your not wiring things properly. <<<

Designing an EVSE, or charger as some say, is a great learning experience as well as having control of the form factor make it well worth the time and trouble to make one.


I also assume that you know how to work safely, and how to wire things in reference to a schematic.

Step 1: Tools and Supplies

What you will need:
J1772 EVSE control board - Open EVSE project (should be in Google Code, and they have great diagrams for EVSEs.)
J1772 Plug & Cord assembly - TucsonEV
Contactor/Relay/SSR - Electrical Supply
Box - Home Depot
12v PSU - Electronics Shop
Strain Relief for J1772 cable assembly - Electrical Supply
CR Magnetics 8420-1000-G - DigiKey
Heat-shrink tubing - Electronics Shop

Volt Meter
Electrical Tape
Knife/stripping tool
Diagonal Cutters
Micro Torch/Heat Gun

Step 2: A Little Background

From Wikipedia: SAE J1772

SAE J1772 is a North American standard for electrical connectors for electric vehicles maintained by the Society of Automotive Engineers and has the formal title "SAE Surface Vehicle Recommended Practice J1772, SAE Electric Vehicle Conductive Charge Coupler”.[1] It covers the general physical, electrical, communication protocol, and performance requirements for the electric vehicle conductive charge system and coupler. The intent is to define a common electric vehicle conductive charging system architecture including operational requirements and the functional and dimensional requirements for the vehicle inlet and mating connector.

Step 3: Design

First thing that you want to do when making your EVSE is layout the parts in the case and make sure that the case that you have gotten is big enough. (If you want to mount this outside get a NEMA approved water tight case.)

I thought that I'd be different and mount most of my hardware in a case that is designed to be a flush-mount with the wall.

When you have all of the parts, position them in the enclosure so that you can visualize the locations of where they are going to be mounted. It is also good to note that you may want to make a HV/HP(High Voltage/High Potential) and a LV/LP(Low Voltage/Low Potential) side. This allows for troubleshooting with a reduced risk of electrocution. Be sure to mount the GFCI Doughnut (the CR magnetics current transformer) close enough to the control board so you can reach it with the leads.

When you get everything the way you like it, mark the holes. This'll come in handy later. 

The file below will give you a general idea as to what we are doing and it should be referenced as it is the design we are going off of. It is also the exact wiring diagram for using a contactor. (Thanks go to the Open EVSE project for the file.)

Step 4: Got Control? (Mounting the EVSE Controller)

The controller board functions as our GFCI and as our COMMS board that communicates with the vehicle to close the contactors or SSRs.

EVSE control boards usually have 2-4 mounting holes. The best way to mount one is to lay the board into the case and mark the holes with a sharpie. Then Drill and tap the holes. (I don't mean tap with your finger either.) Once you get your control board mounted you should be connecting wires as you go along.

IF an LCD is wanted it can be purchased and installed in the case. Just be sure to cut a hole big enough for you to be able to mount the LCD that you chose. 

This is the time to configure the control board for what amperage setting that you want. Use a setting that is under your breaker size by at least 20%. This is to accommodate NFPA and NEC electrical requirements. Follow the instructions that are on the Open EVSE site for configuring your control board using the Arduino IDE.

Step 5: HV Ahead (mounting the Contactor)

A contactor is basically a GIANT relay capable of switching high amperage at high voltage. When mounting the contactor try to mount it close to where you are wanting your EVSE cable to come out. The mounting depends on how big your contactor is. For this application you should get a 12v Automotive relay as some of the contactors require 120/240v to close. This automotive relay is used to bump the voltage up to the correct voltage for closing the contractor and as such the contractor leads should be mounted to the N/O side of the relay. 

A SSR does the same thing as a contactor but it is solid state and in general requires smaller voltage to complete the circuit. The SSRs need to be mounted on a heatsink with a fan to keep them cool. Again mounting varies with each, but I'll give a general idea of how to mount them.

Wether mounting SSRs or a contactor, mark and drill your holes. Tap each hole and thread a screw from the BACK of the EVSE's enclosure. This allows you to use just nuts on the inside of your EVSE. Tighten them down to hold them into the EVSE.

Wire the SSRs or contactor up to the EVSE controller board. (I assume you know that + is positive, - is negative, and ~ means AC voltage.) 

At this stage it might be a good idea to connect power leads for the PSU of your choice. These leads will be discussed further in the next step.

Step 6: The Low End (12v PSU)

The Power leads you connected to the Supply side of the SSRs or contactor in the last step are going to be put to use now in the powering of the control board. "But," you say, "the control board uses 12v DC not AC." That is what the power supply is for. It converts 120/240v AC into 12v DC.

Mount the PSU into the enclosure. There are typically 2-4 screws that hold it into place. (NOTE: 3M Moulding Mount Tape can mount your PSU to the case instead of using screws.)

Hook up the leads from the supply side of the SSRs to the AC side of the PSU. The 12v Output from the PSU goes to the EVSE control board. (Again, I assume you know that + is positive, - is negative, and ~ means AC.)

Step 7: Cables, Cables, Cables Where Would We Be Without You? (mount and Attach the J1772 Connector)

Now that you have the contactor mounted and the control board mounted, you need the J1772 cable with connector.

Now there are many ways to attach the cable, this I will leave up to you. BUT before you do put the Current Transformer onto the 2 120v lines. The cables run through the center of the transformer. Then attach the end to the load side of the SSRs or contactor.

The ground line connects to the chassis ground bolt.

The J1772 pilot line connects to the EVSE control board. 

Step 8: Breaker One-Nine (Circuit Breaker Selection and Installation)

According to NEC and NFPA, you should select a breaker with a rating of at least 20% over what you'll be pulling. So, if you configured the EVSE board for 70A you need at least a 90A breaker. Follow the instructions that came with the breaker for install. (They typically rock-in.)

Step 9: Ouch, Shocked Myself (testing)

As implied by the title, use the volt meter to check the voltage during testing. The 220v side of things will show something around 208-240v. Don't be alarmed if you see 240v, most EVs can handle this voltage without incident. Have an electrician come out if the voltage is any higher (i.e. 250v), because you may be shortening the life of fuses in your EV. (I have had this happen and it is an expensive repair.) If you have close to 250v have a licensed electrician do a Power Quality Analysis and look specifically for transients as they kill fuses.

Remember this though, "One Flash and you're Ash". That is a principal you should always work by. Check every connection with a volt meter BEFORE you handle anything on the HV/HP side. Make DOUBLE sure that there is no voltage and that the circuit breaker going to the Mains is turned off. If a disconnect is required, lock the enclosure with a padlock after you turn it off. (That way some kid doesn't turn the Mains back on while you're working.) Then check the connections. 

IF all went well, you should have a working EVSE. If not follow the troubleshooting instructions on the Open EVSE page.

(Sorry for no photo, having a dispute with some as to the cause of a fuse failure and am not wanting to give them ammo.)

Step 10: Finish IT! (WE ARE DONE!!)

Coat of Paint anyone?? Then maybe some clear coat. 

Other than that you are done with construction. Now you need to mount the thing, which would be another instructable entirely.