Nissan/AV L2 EVSE not charging

Sorry, I guess I'm still not following. Could you please describe the entire circuit path for the leakage current that will trip the EVSE's GFI? I'm just not seeing it. And what role does the rain play in that circuit path?

Thanks,
Wayne

wwhitney said:

Sorry, I guess I'm still not following. Could you please describe the entire circuit path for the leakage current that will trip the EVSE's GFI? I'm just not seeing it. And what role does the rain play in that circuit path?

Thanks,
Wayne

Click to expand...

Ok, lets assume the worst-case scenario, that your house's ground rod is bad or disconnected and/or it's far away from the car. You car is also dirty, so the rain water wets the car which is grounded through the EVSE and your houses wiring. Let's also assume your neighbor's ground rod is close by and his electrical system has a neutral at a slightly different potential, which could simply be caused by a heavy load on his neutral. Now there is a current path from the neighbor's panel, through his ground rod, the actual earth, through the dirty water, through the car, the EVSE, and back to neutral at your panel. Now if the EVSE is watching for a ground current fault (not all do), it would see current flow on the ground conductor. This could exceed it's trip current. (some as low as a few milliamps)

Now many of the lower-cost/simpler GFCI designs only measure the differential current between the 2 load conductors, and don't bother with ground, as any ground faults would be detected by the differential error. The better designs also monitor the ground conductor for any appreciable current flow, which would cover more fault scenarios. You typically see this kind used in medical equipment for obvious reasons. I would think a comprehensive EVSE design, especially at 240V, use this as well.

The Panasonic L1 EVSE does not monitor ground conductor current, so it would not trip in this scenario, the only way would be to have leakage to/from ground and hot (or neutral if a big enough potential difference exists).

First of all, MrZorg, I am sorry I hijacked your thread! I probably should have started a new topic, but yours was close enough. Sorry.

And thank you, ingineer, for your thoughtful comments. For everyone else, this is your warning... electrical discussion follows!

One of the advantages of doing all my own electrical work is that I know how things are hooked up. My LEAF sits under a steel canopy in front of my workshop. The canopy and my shop sit on a concrete slab with a LOT of re-rod in it. The ground is via the Ufer system... concrete encased re-rod that is tied to the reinforcement in the slab. Fellow named Ufer developed the system during WWII for protecting ordnance in storage bunkers in arid climates. Concrete is a much better conductor than dirt. The grounding electrode conductor junction with Ufer is outside, so I checked it today. Less than 0.1 Ohm between conductor and electrode. About 0.1 milliVolt AC potential between them.

The electrical panel is about seven feet from the EVSE; I pulled three #6 copper wires to the box upon which the EVSE is mounted. Total length maybe twelve or fourteen feet. No neutral wire.

So the car, if grounded through the tires while it was raining, was in contact with the slab containing the grounding electrode.

If I had to guess, the EVSE GFCI probably just compares current on L1 and L2 and does not monitor current in the ground conductor. Gary might have a better idea, and several of us have posted good pictures of the inside of the AV EVSE. Wouldn't be too difficult to test; I could try and run a hundred milliamps or so into the chassis of the LEAF, using the EVSE ground as the return circuit. I haven't taken the time yet to re-read what AV says about how their EVSE handles ground fault trips. I'll do that.

Most of us are not familiar with the concept of earth grounds at differing potentials. My first exposure was when hooking up a new ground rod to my house electrical service. When I touched the new grounding electrode conductor to the existing ground system in the service entrance, small sparks jumped.

I may try spraying the car with a hose while it is charging, just to see if I can trip the GFCI. I'll wear rubber gloves for that experiment! I did try charging for a few minutes today; everything worked fine. And as I said earlier, I examined J1772 plug and socket carefully and found no trace of moisture.

-Karl

Ingineer said:

Ok, lets assume the worst-case scenario, that your house's ground rod is bad or disconnected and/or it's far away from the car.

Click to expand...

Seems like this assumption isn't actually necessary for your scenario.

Ingineer said:

You car is also dirty, so the rain water wets the car which is grounded through the EVSE and your houses wiring.

Click to expand...

OK, so I would think the car chassis would be insulated from the ground via the rubber tires, but let's suppose it isn't. What is the connection between the EVSE and the car chassis? I would think that the EVSE L1 and L2 (and charger inputs L1 and L2) would both be isolated from the car chassis/ground. Where does L1 or L2 get connected to the car chassis/ground?

Ingineer said:

Now many of the lower-cost/simpler GFCI designs only measure the differential current between the 2 load conductors, and don't bother with ground, as any ground faults would be detected by the differential error. The better designs also monitor the ground conductor for any appreciable current flow, which would cover more fault scenarios. You typically see this kind used in medical equipment for obvious reasons.

Click to expand...

I wasn't aware that any GFCIs had a separate current transformer for the EGC, but I'm not familiar with the standards for medical equipment. What fault scenarios would this cover that the differential current in the circuit conductors would not cover? Or is it just that the trip threshold on the EGC can be set even lower than the typical 5ma GFCI threshold, because under proper operation there should be no current on the EGC? In any event I don't think that EVSEs typically have a current transformer on the EGC.

Cheers, Wayne

wwhitney said:

OK, so I would think the car chassis would be insulated from the ground via the rubber tires, but let's suppose it isn't. What is the connection between the EVSE and the car chassis? I would think that the EVSE L1 and L2 (and charger inputs L1 and L2) would both be isolated from the car chassis/ground. Where does L1 or L2 get connected to the car chassis/ground?

Click to expand...

It's "relatively" insulated if it's clean and dry. Tire companies normally add a bit of conductive material to the tires to help dissipate static charges. (known to be responsible for a lot of gas station fires)

Once it's dirty and wet, it's a pretty good conductor however, more than enough for a few mA!

There are 5 pins in the J1772 connector: L1, L2, Pilot, Proximity, and GROUND. The ground pin connects the building electrical system to the car.

wwhitney said:

I wasn't aware that any GFCIs had a separate current transformer for the EGC, but I'm not familiar with the standards for medical equipment. What fault scenarios would this cover that the differential current in the circuit conductors would not cover? Or is it just that the trip threshold on the EGC can be set even lower than the typical 5ma GFCI threshold, because under proper operation there should be no current on the EGC? In any event I don't think that EVSEs typically have a current transformer on the EGC.

Click to expand...

Most of the GFCI's I've looked at that have this feature do not use a CT. They simply use a small shunt to detect any current on that conductor. One of the reasons this secondary detection might be useful is if the CT fails open in the GFCI or an external source of power somehow enters your car. (or your body in the case of medical equipment)

This line of thinking has made me realize another possibility; The spec says that the EVSE should perform a ground check. Maybe a high-resistance ground or intermittent connection caused the trip?

In the Panasonic EVSE, they verify they can pass a small current between ground and L1 as their ground verification. In this scenario, a neutral to ground disturbance could cause this test to fail momentarily, such as during a thunderstorm.

Anyway, we are all doing a bunch of speculation. We could make a more accurate assessment if we knew the methods used in the AV EVSE.

kolmstead said:

First of all, MrZorg, I am sorry I hijacked your thread! I probably should have started a new topic, but yours was close enough. Sorry.

Click to expand...

That's quite alright. I like learning new things. The only thing more to really contribute to the original thread is whether the replacement works or not. I'll follow up on that Monday...

MrZorg said:

kolmstead said:

First of all, MrZorg, I am sorry I hijacked your thread! I probably should have started a new topic, but yours was close enough. Sorry.

Click to expand...

That's quite alright. I like learning new things. The only thing more to really contribute to the original thread is whether the replacement works or not. I'll follow up on that Monday...

Click to expand...

If you could get pictures of the inside of the thing during installation, that would be cool! I've seen the back half, but I've not seen any posted showing the front.

ing: sent you some pix in a PM. Most of the good stuff is in the main (rear) housing:



-Karl

kolmstead said:

ing: sent you some pix in a PM. Most of the good stuff is in the main (rear) housing:
-Karl

Click to expand...

Thanks Karl!

Looks like they watch differential current between L1/L2 and L2 current, but nothing on the ground, either shunt or CT. I assume that "black glob" in the upper left is a bundle of MOV's for surge protection?

-Phil

Seems like garygid figured out what the gob was when he examined mwalsh's EVSE at one of the get-togethers. But I couldn't find it just now by searching. I'll ask him.

-Karl

I did not open the "glob" on the left, but the MOV (voltage spike reduction) guess is likely correct.

Ingineer said:

It's "relatively" insulated if it's clean and dry. Tire companies normally add a bit of conductive material to the tires to help dissipate static charges. (known to be responsible for a lot of gas station fires) Once it's dirty and wet, it's a pretty good conductor however, more than enough for a few mA!

There are 5 pins in the J1772 connector: L1, L2, Pilot, Proximity, and GROUND. The ground pin connects the building electrical system to the car.

Click to expand...

OK, so the tires earth the car chassis, and when you connect the EVSE, you have re-earthed the EGC. But since the AV EVSE doesn't seem to monitor the EGC, stray ground current doesn't explain the tripping. If it is the GFCI in the EVSE that is tripping, it would have to be to a line-to-ground fault, either in the car or in the EVSE.

Cheers, Wayne

wwhitney said:

OK, so the tires earth the car chassis, and when you connect the EVSE, you have re-earthed the EGC. But since the AV EVSE doesn't seem to monitor the EGC, stray ground current doesn't explain the tripping. If it is the GFCI in the EVSE that is tripping, it would have to be to a line-to-ground fault, either in the car or in the EVSE.

Click to expand...

Correct, now that we know the AV EVSE doesn't monitor ground current this would not cause a trip. But keep in mind you are still not "re-earthing", and you could still get shocked if your car and the "local" earth were at different potentials.

As for the trip, without more information, we are unable to do anything but guess. My best guess is a power line disturbance caused a nuisance trip. There is capacitive coupling of L1/L2 to ground, so any fast transients between ground and either of the lines could trip the GFCI if it's fast enough.

There is also what looks to be current detection on L2, so a voltage surge could cause a rise over some internal amperage threshold too, I suppose.

I still wonder why AV made it not auto-reset. Big flaw!

Hmm.. an earlier post of mine seems to have been lost. If it shows up, I regret the repetition. From the AV EVSE manual, which mwalsh posted back in December, P. 30, AUTO-RESTART:

The EVSE will attempt to clear error codes and restart the charge. Trouble indicator will remain illuminated until the error code is cleared, or time-out has expired.

Ground Fault is a little different. If it occurs as the J1772 connector is being plugged in, everything stops until the unit is reset by turning power off, then back on. If a GF occurs during charging, the EVSE will attempt to restart charging after 15 minutes. It will attempt four restarts before it gives up and leaves the trouble light illuminated. No beeps, but it sounds like a reasonable approach to the problem.

-Karl

Good to know! So the AV engineers aren't bone-heads after all! =)

So what can cause a "fault" light and stop charging without a restart?

Here's the link to Mike's scanned copy of the user/installer manual:

http://www.responsivespace.com/mjw/EVSE-RS User Guide.pdf

Lengthy description of problems that can be decoded by watching how rapidly the trouble light blinks, but nothing about constantly on light, except to turn off circuit breaker and try again. I didn't even do that; just unplugged/replugged the J1772 connector, and then things were back to normal.

Looks like the car went through a normal 'already charged so I don't need to do more' last night. Got one charge stopped email, and Carwings says that the car is still plugged in this morning.

-Karl

Ingineer said:

But keep in mind you are still not "re-earthing", and you could still get shocked if your car and the "local" earth were at different potentials.

Click to expand...

By this you just mean that the earth-car connection through the wet tires will still be fairly high impedance, and so the car and local earth may be at different potentials, and if a person gets in parallel with the car-tire-earth connection, then some current may flow through the person? I expect, though, that it would be hard to get enough potential difference to cause more than 1 ma to flow through the person.

Cheers, Wayne

wwhitney said:

By this you just mean that the earth-car connection through the wet tires will still be fairly high impedance, and so the car and local earth may be at different potentials, and if a person gets in parallel with the car-tire-earth connection, then some current may flow through the person? I expect, though, that it would be hard to get enough potential difference to cause more than 1 ma to flow through the person.

Click to expand...

I know it's silly, but let's say your neighbor opens his panel and "accidentally" connects a hot to his ground rod. Now there is a potential difference of 120V between your "properly" grounded car and the dirt. Then you set out to wash your car... I bet you can get well over 1ma!

This is why local grounding would be desirable.

Generally, I believe that the electrical codes only allow a Residence to have ONE single ground (usually 8 feet deep), and all the house grounds must be tied back to that one point.

Ingineer said:

I know it's silly, but let's say your neighbor opens his panel and "accidentally" connects a hot to his ground rod. Now there is a potential difference of 120V between your "properly" grounded car and the dirt. Then you set out to wash your car... I bet you can get well over 1ma!

This is why local grounding would be desirable.

Click to expand...

OK, I agree that if you or your neighbor's panel has a direct L1-G fault, and its N-G bond is missing so no breakers trip, then you could get local earth at your car elevated above remote earth by on the order of 60V. Then if you are walking barefoot in a puddle and touch some unpainted metal on the car chassis, you could get a lethal shock.

I would count that as a hard to achieve scenario. Moreover, the resistance of the tires doesn't enter into this scenario, and local grounding isn't really going to help. The resistance to ground of a local ground rod will still be sufficiently large to cause a step potential in the vicinity of the ground rod that could shock you. Earthing is pretty useless for shock prevention at 120V.

Cheers, Wayne