Direct wiring Universal Connector, should I be concerned

[artsci]

I'm in the process of building a new curbside charging station to replace my current one, which was designed for charging my Volt but has been also been set up to work with the Model S. Now that I've used it for more than a year, I want to make some important improvements that will ensure that it's more convenient to use with my Model S when it's delivered in the spring.

The set up will basically be the same concept -- a Hubbell pin and plug system that will make it portable so I can move it from the curbside when it's not in use. However, this time I'll be using a 7" wide bollard cover with a lockable hinged door. That way I can install the UMC permanently inside the bollard so I don't have to keep plugging and unplugging the 14-50P connector and hanging the UMC on the side of the post, where it's exposed to the weather. I can also keep the cable inside the bollard and extend only what's needed to reach the Tesla when I want to charge. The cable will thread through an opening at the bottom of the hinged door. The inspiration for this approach came from this product in the UK called StreetServ.

I've already ordered an extra UMC from Tesla for this purpose. My concern is about direct wiring the UMC. To do this I'll have to cut the adapter end off the UMC and direct wire the leads to the Hubbell plug and its 240v 50 amp connections. The actual wiring should be easy to do but as I've not seen the adapter end of the UMC I'm not sure how it's set up. I assume it must have a least three pins, one for ground and the others for neutral and hot. Am I correct in this assumption?

I know this will void the warranty but I'm not concerned about that. Any thoughts or advice? A photo of the end of the UMC without an adapter attached would be much appreciated. I've assembled all the materials for this and will begin work in a few weeks.

 

[Zextraterrestrial]

I think you only use 2 wires. but confirm with others

 

[andrewket]

I've already ordered an extra UMC from Tesla for this purpose.

How did you do this? It's not listed as an accessory on Tesla's website.

A

 

[tezco]

I would assume there are the two two hot power leads (one from each side of the 240V mains) and a ground, but the neutral is probably not be connected since the Roadster adapters included several without neutral connections. The neutral would only be needed if there was something that needed to run at 120V. My AV J1772 EVSE is wired without a neutral, and works.

The only question I have is whether there is any sort of a sensing circuit that informs the brains of the UMC as to what type of plug is attached, and thus what it's current limits are (so you don't over draw the circuit.) Perhaps some of the Roadster owners can tell us if switching out the ends of the Roadster cable changed the charging rate. If so, there might be some sort of circuit that you would have to duplicate to get the UMC to work. Might be safer to install the standard receptacle inside your post and leave the standard plug on the UMC.

Here are a couple of photos of the adapter and end of the UMC cord. There are four pins, the smallest of which is opposite the ground on the NEMA 14-50. This pin is very tiny, so I suspect it would not be up to code to carry the necessary ground current in the event of a fault. (I think the ground can only be one wire size smaller than the hot wire size, and this is less. I assume that any neutral tap would also have to be larger that what is implied by the size of this pin.) So, the wiring doesn't appear to be inline from front to back of the adapter.

 

[adelman]

The only question I have is whether there is any sort of a sensing circuit that informs the brains of the UMC as to what type of plug is attached, and thus what it's current limits are (so you don't over draw the circuit.) Perhaps some of the Roadster owners can tell us if switching out the ends of the Roadster cable changed the charging rate. If so, there might be some sort of circuit that you would have to duplicate to get the UMC to work. Might be safer to install the standard receptacle inside your post and leave the standard plug on the UMC.

None of those pins are connected to the neutral. There is some sort of sensing going on, and I'd speculate that it involves that tiny pin. Maybe something like a
resistor to ground whose value encodes the current??? I haven't investigated further, but you definitely don't want to "hack" the end off your cord.

Ken

 

[tezco]

None of those pins are connected to the neutral. There is some sort of sensing going on, and I'd speculate that it involves that tiny pin. Maybe something like a
resistor to ground whose value encodes the current??? I haven't investigated further, but you definitely don't want to "hack" the end off your cord.

Ken

J1772 standard uses resistance to set maximum charging current: "The function of the Proximity Pilot PP allows the car to control the maximum charging current of the charging station by adding a resistor on the PP-PE loop." http://en.wikipedia.org/wiki/SAE_J1772
The lower the resistance, the higher the current. So if you connected the small pin to neutral, you might not have any limit on charging current (if Tesla uses a similar scheme).

We have seen reports of reduced charging currents when the cord is not fully inserted into the charging port. Presumably, a weak connection would cause a higher resistance in the sensing circuit, and this would help protect the charging port in case the main leads are also less than fully connected.

 

[artsci]

How did you do this? It's not listed as an accessory on Tesla's website.

A

Made the request through the DC Service Center. I may have a long wait but hopefully it will arrive before the car.

- - - Updated - - -

I would assume there are the two two hot power leads (one from each side of the 240V mains) and a ground, but the neutral is probably not be connected since the Roadster adapters included several without neutral connections. The neutral would only be needed if there was something that needed to run at 120V. My AV J1772 EVSE is wired without a neutral, and works.

The only question I have is whether there is any sort of a sensing circuit that informs the brains of the UMC as to what type of plug is attached, and thus what it's current limits are (so you don't over draw the circuit.) Perhaps some of the Roadster owners can tell us if switching out the ends of the Roadster cable changed the charging rate. If so, there might be some sort of circuit that you would have to duplicate to get the UMC to work. Might be safer to install the standard receptacle inside your post and leave the standard plug on the UMC.

Here are a couple of photos of the adapter and end of the UMC cord. There are four pins, the smallest of which is opposite the ground on the NEMA 14-50. This pin is very tiny, so I suspect it would not be up to code to carry the necessary ground current in the event of a fault. (I think the ground can only be one wire size smaller than the hot wire size, and this is less. I assume that any neutral tap would also have to be larger that what is implied by the size of this pin.) So, the wiring doesn't appear to be inline from front to back of the adapter.

Thanks so much for your post and the others as well. Based on this information I don't think I'll direct wire. I'll just set up a 14-50 R in the bollard and plug the UMC in. There are other advantages to that set up as well, not the least of which is that I can plug in other devices for power.