Where exactly does the pilot signal generate from

[X.l.r.8]

Question for the electronics wizards. IF I change the plug on my pigtail to a 14-50 will the open evse know to charge at 40 amps. What I mean is is the part that alters pilot signal in the pigtail or in the box itself? I’m pretty sure it’s in the box but the fact the input cable has the pilot wire has me doubting myself.

 

[X.l.r.8]

Now I voiced it I know it to be in the box because the pilot signal from the 240v end is not required to be connected. It’s been a long day, sorry.

 

[gregd]

No problem. Interesting project... So, my guess is that you had one of the infamous 240 mobile connectors that failed, and replaced the now-inert lump in the middle with an OpenEVSE? Any challenges in doing so, e.g. the internal wiring?

 

[X.l.r.8]

The earth cable on the inlet is short and needs extending, the rest would have been good except the evse board is DOA. So I am patiently waiting to get it finished, it’s a simple enough kit. I have the advanced one just because of the summer sale made it cheaper.

 

[slcasner]

Now I voiced it I know it to be in the box because the pilot signal from the 240v end is not required to be connected. It’s been a long day, sorry.

The pilot signal is definitely generated by the main circuit board within the EVSE, as shown by the purple wire in the schematic diagram. From what I see in the documentation, the max current setting is changed with the pushbutton/LCD user interface and is not controllable by attachment of a different pigtail.

There is no "pilot signal" in the input cable coming from the wall. There are only two line (hot) wires, neutral and ground. Some plugs don't have neutral and some don't have ground; the 14-50 has both, hence four wires total. Most 240V EVSEs, including OpenEVSE, don't need or use the neutral pin; that's why using a plug without it is OK.

The Roadster Foundry mobile charge cable made by Martin Eberhard did control the max current depending upon which of several pigtails with different plugs was connected. (Tesla's charge cables with multiple pigtails, which came later, also do this.) The way this was indicated was through the neutral pin in the connector where the pigtail hooked to the box. The neutral pin of the 14-50 (or other) plug was left unconnected, so this left the neutral pin going into the box available for signaling. The way Martin did it was by hooking a diode between the neutral and ground with the anode end going to ground to indicate a 14-50 plug and 40A charging. For a 14-30 plug and 24A charging the diode was flipped the other way. And for a 20A plug (either 120V or 240V) and 16A charging the connection between neutral and ground was left open. However, Martin was even smarter than that -- he put a thermal sensor into the plug (such as 14-50) that would connect a short between the neutral and ground wires going towards the box if the temperature got too high, then the pilot signal would be dropped to stop charging.

So perhaps this idea of using the neutral pin to tell the controller how to adjust the pilot signal is what you were referring to?

 

[Stefan T]

If i connect pilot to ground, charge my car with 16A

 

[X.l.r.8]

@slcasner that makes more sense to me as the only charger I have ever looked at was that unusual EV one I used to bring the car home.
@Stefan T I am going to do that with a Tesla plug on an extension lead to have a cheap work charger, unfortunatly its 110v here. my garage is wired with 240 and has UK sockets everywhere for all my tools so I guess I could make an adaptor to be able to have 240v 16 amp emergency in case my 3 other options fail lol.

 

[hcsharp]

The pilot signal is definitely generated by the main circuit board within the EVSE, as shown by the purple wire in the schematic diagram. From what I see in the documentation, the max current setting is changed with the pushbutton/LCD user interface and is not controllable by attachment of a different pigtail.
...
The Roadster Foundry mobile charge cable made by Martin Eberhard did control the max current depending upon which of several pigtails with different plugs was connected. (Tesla's charge cables with multiple pigtails, which came later, also do this.) The way this was indicated was through the neutral pin in the connector where the pigtail hooked to the box.

I was under the impression (might be wrong) that OpenEVSE developed a system very similar to the Tesla UMC that determined allowable amps based on which pigtail you were using. I know they were working on this a few years ago. Without that the system is dangerous because it can draw too much power from a circuit not rated for it. You can't rely on the user to dial down the amps (from VDS or charger) based on the outlet capacity because the user may not know it's necessary, or how high they can safely set it. In fact it's a violation of the NEC to have a mobile charge cable that does not automatically adjust the pilot based on the outlet being used. While the NEC does not require UL marking for a mobile cable, NEC compliance still applies.

 

[X.l.r.8]

That’s exactly the thought that went through my head. But the AC power in has no pilot, it just calls for power to the EVSE board, however the EVSE does a self check but I still don’t have a working board to see if you can override that. I’m only going into a 50a circuit and I have the roadster cable not the Tesla one so I’m pretty confident on its ability to deliver 40A constantly. But I wondered how it stopped people charging at a higher amperage that the circuit was designed for. Waiting patiently right now for the new parts to come.

 

[X.l.r.8]

Also do the rules change for a mobile or Wall connecter? Because it’s marketed as a wall connector that is mobile, much like the Tesla unit with the hardwired plug, I just thought it would be good to use the pigtails from the roadster UMC to be able to use 120 in an emergency. Plus it allowed for more cable to play with, and it was free cable more importantly.

 

[hcsharp]

That’s exactly the thought that went through my head. But the AC power in has no pilot, it just calls for power to the EVSE board, however the EVSE does a self check but I still don’t have a working board to see if you can override that. I’m only going into a 50a circuit and I have the roadster cable not the Tesla one so I’m pretty confident on its ability to deliver 40A constantly. But I wondered how it stopped people charging at a higher amperage that the circuit was designed for. Waiting patiently right now for the new parts to come.

The AC power has no pilot because it's generated on the main board in the OpenEVSE module. It generates the pilot based on which pigtail you have connected.

 

[X.l.r.8]

But the open evse does not call for a pigtail, you can basically put any AC input you like. Or simply hardwire it. Am I missing something?

 

[hcsharp]

Also do the rules change for a mobile or Wall connecter? Because it’s marketed as a wall connector that is mobile, much like the Tesla unit with the hardwired plug, I just thought it would be good to use the pigtails from the roadster UMC to be able to use 120 in an emergency. Plus it allowed for more cable to play with, and it was free cable more importantly.

Yes the NEC rules change for a wall connector that is hard-wired. Those have to be UL marked. Having said that, a lot of "wall chargers" get around this by not being hard wired. They install a short cable with a plug on the end, usually a NEMA 14-50P. The pilot on many of those is fixed at 40A (or something less, often at your choice) because they take the position that you won't be using a pigtail as it comes with a permanently wired plug that's not meant to be used with pigtails.

 

[X.l.r.8]

Ah, it’s sold as a 40A charging system, with the ability to custom your requirements, not as a universal connector.

 

[gregd]

I just thought it would be good to use the pigtails from the roadster UMC to be able to use 120 in an emergency.

Not sure the Open EVSE can run on 120v. I think it's designed for 240v only; at least I recall mine is. (I have the 50a deluxe model from about 3 years ago.) If nothing else, what voltage is your contactor coil spec'd for?

 

[n2mb_racing]

If you have a CAN SR, you can just buy a Model S / 3 / X UMC cable and use it... That's what I've been using every day for 3.5 years. The new UMC has adapters for pretty much every plug.

 

[X.l.r.8]

The open evse is $300, definatly works on 120v, at least the advanced one does. Also the open evse is 40A not 32A. And it’s meant to be reliable but that’s not exactly proving true right now. I’m a fan of recycling the older thicker cable.

 

[X.l.r.8]

 

[X.l.r.8]

So after deliberately trying to repurpose the EVSE I decided that the kit is not reliable, in fact I’m patiently waiting for a response. The first board turned up dead, the second only lights the display. Despite turning the contrast screw either direction it’s simply not working. Unfortunate because I was hoping for great things. So far it’s cost me as much as any juice box that works out of the box. The least exciting thing I have brought for my roadster and it should have been a great addition, thoroughly disappointed with the system.