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garygid
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Re: Nissan/AV L2 EVSE not charging

Sat Feb 19, 2011 8:02 pm

I did not open the "glob" on the left, but the MOV (voltage spike reduction) guess is likely correct.
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wwhitney
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Re: Nissan/AV L2 EVSE not charging

Sat Feb 19, 2011 8:56 pm

Ingineer wrote: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.
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

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Ingineer
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Re: Nissan/AV L2 EVSE not charging

Sat Feb 19, 2011 9:12 pm

wwhitney wrote: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.
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!
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kolmstead
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Re: Nissan/AV L2 EVSE not charging

Sat Feb 19, 2011 9:39 pm

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

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Re: Nissan/AV L2 EVSE not charging

Sat Feb 19, 2011 10:08 pm

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?
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 9:22 am

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

http://www.responsivespace.com/mjw/EVSE ... 0Guide.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

wwhitney
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 9:55 am

Ingineer wrote: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.
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

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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 10:47 am

wwhitney wrote: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.
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.
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 10:54 am

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.
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wwhitney
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Re: Nissan/AV L2 EVSE not charging

Sun Feb 20, 2011 11:09 am

Ingineer wrote: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.
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

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