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Roadster Conversion to J1772 Charging

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Update January 20, 2014

As documented below, it is possible to convert a Roadster to J1772 so that it can be charged directly from a standard J1772 charging station. Cathy and I developed a solution that is J1772 compliant (supports the proximity switch), is professionally manufactured, and supports full 70A charging.

Unfortunately, there are a number of pending issues that have caused us to halt work on the project.

  • When I asked for owners interested in doing the conversion in September, 2012, I got very few responses.
  • Henry Sharp has the compact CAN adapter which can be locked to the car. It's so much better than the Tesla adapter that the conversion has less appeal.
  • Because of the stupid "gas nozzle" shape recommended for J1772 connectors, it's hard to get a connection because of interference with the body panel below the port. With a lot of hacking on the mounting plate and cutting away part of the inlet wall, it kind of works with the ITT Canon 80A connector, but other J1772 connectors don't work as well.
  • The idea of switching public HPCs to standard J1772 stations so they are accessible to all EVs seems great, but I worry about the stations being taken by more prevalent 3.3/6.6 kW cars. Keeping the Tesla Roadster HPCs with the Roadster connector limits access to the few vehicles that can charge at 70A or more (Roadster and Model S). Obviously the equation may change if those HPCs go away and we start getting more public high amperage J1772 stations.
  • We haven't made any progress on a conversion cable for v2.x Roadsters. Although we thought the v2.x case would be easier than the v1.5 because of the much simpler connection to the PEM, sourcing a cable that matches the original Tesla cable (so that no PEM modification is needed) has proven difficult.
  • There's a little more work left to be done on the v1.5 cable. The folks at the cable company have been great, but the low expected volume is a barrier to getting it finished and into production.
So, we've made a lot of progress, have assembled the parts required, have designed and validated a circuit board for handing the proximity switch, and have a cable company that can produce quality cables capable of handing the sustained high current. This project can be re-activated if there's enough interest in the community to make it viable at some point in the future.

Original Post


Cathy and I, with help from Dave Denhart and many others in the Tesla and broader EV communities, have demonstrated a conversion method for our 2008 Roadster and Tesla High Power Wall Connector to use the new industry standard J1772 inlet and plug. This will allow us to charge without an adapter at the tens of thousands of Level 2 charging stations that will be installed in the US by the end of 2011.


What we have is functional and completely reversible, but not ideal; we view this as a version 0.9 conversion. As there are very few J1772 charging stations currently installed, and the numbers probably won't take off until late spring or early summer, we have time to develop a better solution before it actually becomes compelling for Tesla owners to convert in significant numbers.


I'm sure Tesla Motors could do a much better job of creating an integrated solution and I would prefer that to having the owner community develop a conversion solution.


Our next steps are:

1) Hope that Tesla Motors provides an official conversion solution before it matters to most owners, thus saving us the remaining steps.

2) Design a circuit to monitor the proximity pin and disconnect the pilot signal when the J1772 plug is unlocked.

3) Test with other J1772 plugs and possibly work on a better solution for cable clearance over the body panel.

4) The 2010 and later Roadsters have the inlet cable assembly connecting to the PEM in a different location. There may also be other differences. We haven't looked into it yet and don't know if it will be more or less difficult to convert than the 2008 Roadsters.

5) Before recommending an unofficial conversion to other owners, we'll need to find out how this will impact our warranty. Tesla Motors has been cooperative with our efforts: they sold our group an inlet cable assembly so that we could do the conversion reversibly. We hope they will continue to be supportive rather than forcing us to wait until our warranties expire before being able to effortlessly access standard J1772 public charging stations.

For more details on our project and what still needs to be done before we can recommend that other owners do the same, see my blog.
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Can you still charge at full HPWC/HPC current levels through your converted 'solution'?

Seems likely based on this part of your blog:
...we finally obtained an ITT Canon 75A UL-approved inlet and plug pair from Clipper Creek. The plug cord is intended as a replacement cable for Clipper Creek's model CS-100, and carries the same power and signal wires as the TS-70 aka Tesla's High Power Wall Connector (HPWC, formerly the HPC)...
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That's amazing Tom. Thanks for doing all of that work. Did you remove the Tesla plug somehow and install the J1772 plug (it's fixed in place)? That would be great if Tesla provided an officially supported solution but I'm glad people like you are looking into a solution as well. Thanks again.
In 1.0 can you tilt the socket back a bit so the cable does not rest on the car?

We had to tilt it back to get the ITT Canon plug to almost clear. There's more detail, and an image of the bracket on my blog.

Or how about rotating the inlet about 30 degree CCW (but not too far where the cable would interfere with the trunk open/close).

Actually, with the way the body flares out toward the back, I think it would be more effective to rotate it 20 or 30 degrees clockwise. Unfortunately, the mounting points (bosses) on the back of the cup interfere with being able to do that. Most significantly, the boss that supports the bottom center screw is where the bottom corner of the base wants to be when you rotate it.
I don't know if it makes sense to merge, but here is the "precursor" thread talking about J1772 charging using adapters:

I get a little tired of trying to find the interesting bits in a thread that goes on forever, and I thought the conversion was a sufficiently big update to warrant a new thread. But I'm open to merging if that's the preferred way to handle this sort of thing.
I think that would interfere with the drivers door opening/closing or maybe even with the chargeport door.

I don't think interference with the charge port door or the driver's door is a problem. The problem is mounting it to the rear of the cup in a rotated orientation. It's a lot easier to see in person, but that requires taking your car apart, so I'll try to do it in photos.

If you open the charge port door you can see five screws that hold the inlet in place. There are two on each side and one at the bottom center:


On the back of the cup, there's a raised mounting spot (a boss) for each screw. The Tesla inlet port and cable is attached to a plate with four screws (not shown). The plate is attached to the back of the cup on the bosses with the five screws.

The J1772 inlet has a square base and, much like the Tesla inlet, it is sized to nestle in between the bosses.


At first we thought we could just cut out a plate flat plate to mount the J1772 inlet, but then we had to angle the top of the inlet back to gain cable clearance, so Cathy designed an adapter in CAD and printed it out on a 3D printer. It's the blue piece in the photo below. You can also see two of the bosses corresponding to the two screws nearest the camera and the raised rib that runs between them.


The bottom of the inlet base is flush with the top of the bottom center boss and pressed against the back of the cup to get the inlet as low and outward as possible for clearance. If you rotate the inlet, the edge and corner of the inlet base is obstructed by the bottom boss. If you were to mount the inlet rotated with the bottom corner behind the bottom center boss, it would be too far into the body to attach the cable and would make the cable clearance problem even worse. To mount it flush, you'd have to remove the bottom boss (or the bottom corner of the inlet base) and also remove the vertical ribs that join the two pairs of bosses on the sides.

Now we get to the real problem: the inlet cup is glued to the body panel. It's not only difficult to remove, it's really difficult to glue a new one to the panel. So replacing the cup with something designed for the J1772 inlet would be difficult. Also, if you do something dramatic like removing the bottom center boss, you've removed the ability to easily restore the charge port to factory condition.
I guess converting the HPC was trivial. I would want to convert my UMC since it is very useful for many locations outside of metropolitan areas and for friends homes when I visit them.

Obviously, the more invested you are in the Tesla plug the less interested you'll be in switching to J1772. I know some owners have multiple HPCs and mobile connectors. For those people, the conversion won't make sense as soon as it will for others, if ever.

I haven't examined a UMC, so I don't have any idea how easy it would be to swap the cable. The UMC packaging is pretty neat and compact, maybe not so easy to modify. At the very least, you could cut off the Tesla plug and splice in J1772 cable instead. Of course modifying the UMC will void the UL approval, just as it will for the HPC.

You could use the Tesla inlet to build a Tesla-to-J1772 adapter so you maintain access to any EVSE with a Tesla plug.

I'll bet with all the Leafs and Volts hitting the road, there will soon be a market for the J1772 equivalent of the UMC which will get satisfied by multiple vendors. It will be awesome to benefit from the economies of scale applied to hundreds of thousands or millions of EVs instead of being stuck in a 1,000 car niche.
Tesla said inan email reply that they're working on an adapter to UMC for next quarter.

I thought they were working on a stand-alone adapter, not related to the UMC. Is this a second adapter strategy, or have they decided to require the UMC to use their adapter?

The whole point of the UMC is to take power from a dumb outlet and generate the appropriate pilot signal. Since a J1772 charger generates the proper pilot signal, it seems wacky to run it through the UMC box.

It sure would be awesome if they'd just announce their plan for J1772 support, even the time frame and pricing can't be set in stone immediately. It's frustrating that they are so hush-hush about something as basic addressing a obvious need on the minds of many current and potential owners.
It sure would be awesome if they'd just announce their plan for J1772 support, even the time frame and pricing can't be set in stone immediately. It's frustrating that they are so hush-hush about something as basic addressing a obvious need on the minds of many current and potential owners.

It is nice to see you thinking in terms of the plan for other Roadster owners. You personally have solved the 'problem' on your own for yourself at least!