My L1 ESVE findings.....

[jwallace3]

Absolutely. Thanks for the tip. I may give it a good lookover if/when I get to that point. Right now I'm still brainstorming of why mod isn't working at 240. Just discussed it with a few fellow engineers here at work and had a few ideas to try before completely de-potting.

I have read some of it and remember seeing it a while back. It's all just for the heck of it. I know this thread got out of control quick, but I did mention early on I'm mentoring 2 EE seniors in their senior project, which is to design a portable L1/L2 ESVE so I will probably do it even if I get the mod to work, just so I am forced to go over the standard with a fine tooth comb and be able to help the students define their specifications and solidify their design.

Right - I was only pointing it out in case you hadn't seen it and knew that he already has a DIY EVSE control module in case you wanted to use that as a starting point for your own design or depending on the level of the students give them something to build from if going down the build from scratch route.

[lincomatic]

Trying to make sure I understand what you did:

Using a Form C relay I wired the common contact to the J1772 connector, the normally closed contact to the neutral lug that originally went to the J1772 connector (this is after the relays on the board and GFI CT) and then I wired the normally open contact to the second 120 leg looping it through the GFI CT. The coil I wired from the input neutral lug to the second 120 leg, so if no second 120 leg is present for 240 charging, the common is connected to the normally closed contact which is neutral and the L1 charging happens. If the second 120 leg is present the relay closes and common is now connected to the normally open contact which connects the second 120 leg to the J1772 cable while looping through the CT.

So here, you have 3 wires going through the CT ... the original hot, neutral, and hot2 for 240V. So when you test 240V, only the two hots have current going through the CT, but the neutral has no current going through the CT, because the relay is connected to neutral before the CT. Even though the only current going through the CT is the two hots, which sum to 0, you get a solid red fault?

Then using the output of the relays and bypassing the CT I tried using that route and L1 threw a fault as well as L2.

So when there are no wires at all going through the CT, it throws a fault in L1?

Am I understanding you correctly?

[jwallace3]

yes, it didn't make much sense to me. My method using the third external relay should have worked just fine. I de-potted my board last night and plan to do some reverse engineering this week to see if there is something I'm missing that the charger is doing.

Trying to make sure I understand what you did:

Using a Form C relay I wired the common contact to the J1772 connector, the normally closed contact to the neutral lug that originally went to the J1772 connector (this is after the relays on the board and GFI CT) and then I wired the normally open contact to the second 120 leg looping it through the GFI CT. The coil I wired from the input neutral lug to the second 120 leg, so if no second 120 leg is present for 240 charging, the common is connected to the normally closed contact which is neutral and the L1 charging happens. If the second 120 leg is present the relay closes and common is now connected to the normally open contact which connects the second 120 leg to the J1772 cable while looping through the CT.

So here, you have 3 wires going through the CT ... the original hot, neutral, and hot2 for 240V. So when you test 240V, only the two hots have current going through the CT, but the neutral has no current going through the CT, because the relay is connected to neutral before the CT. Even though the only current going through the CT is the two hots, which sum to 0, you get a solid red fault?

Then using the output of the relays and bypassing the CT I tried using that route and L1 threw a fault as well as L2.

So when there are no wires at all going through the CT, it throws a fault in L1?

Am I understanding you correctly?

[lincomatic]

Yes, it seems like it's used for more than just 0 net current for the GFI. I guess chris1howell is probably right that it's also being used to measure current for a ground integrity test.

BTW, how did you de-pot it?

[chris1howell]

Since you have your board de-potted, can you activate the third small relay with a 12v source and measure resistance form hot/ground hot/neutral and neutral/ground on the input side? That could answer the question of exactly how the ground check is working...

[lincomatic]

Since you have your board de-potted, can you activate the third small relay with a 12v source and measure resistance form hot/ground hot/neutral and neutral/ground on the input side? That could answer the question of exactly how the ground check is working...

I just powered my Nissan EVSE w/o the ground pin connected, and it blinks the green ready light, refusing to charge. I had my ear against the case, and repeatedly connected/disconnected it from the wall socket ... there isn't any sound of a relay clicking inside.. just the hum of the transformer. So I don't think the 3rd relay is involved in the ground check, at least at power up.

[chris1howell]

Interesting, another theory I heard about the third relay is that it is used to power up the coil of the larger relays. I am not sure why they would do that as it would switch faster and be much less expensive to use a NPN to power the coil.

[jwallace3]

The old fashioned way we used to do it in the Navy. Very small tools and a lot of time. I have most of it cleaned up now, I'm hoping to have time tonight to do some testing/reverse engineering.

Yes, it seems like it's used for more than just 0 net current for the GFI. I guess chris1howell is probably right that it's also being used to measure current for a ground integrity test.

BTW, how did you de-pot it?

[jwallace3]

Alright guys, so the 2 main relays are controlled by transistors and the third smaller relay places a 4.26~ k ohm resistance between hot and neutral on the output of the 2 main relays. So it closes the mains and checks the current path or it would be looking for a voltage source (lack there of really) before closing the mains. What's interesting is the it takes the hot leg prior to the gfi CT and the neutral leg after the CT. So it's using the CT to check for a current path. 120vac and 4.27 k the CT should read around 28 mA.

[jwallace3]

Also the main current path appears to have some transient voltage suppression components which may only be rated at 120 ac so if not upgraded they might blow if you were to ever place the second 120 leg where the neutral originally was.