MikeD
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 11:53 am

Ingineer: Care to comment on advisability/effectiveness of AFCI detection especially if you are correct that worn-out plugs/inlets are inevitable? Or do you think the best approach is that worn-out/damaged plugs/inlets are able to be routinely repaired/replaced? I am concerned about the possibility that a worn-out/damaged public charger plug could spread damage to car inlets (and vice versa)...

MikeD
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 12:01 pm

Tony: If you are conceding that the Blink may not have been at fault, to be fair and not to mislead people who aren't able to read all this threads' posts: shouldn't you change the title of your post?

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Ingineer
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 12:14 pm

MikeD wrote:Ingineer: Care to comment on advisability/effectiveness of AFCI detection especially if you are correct that worn-out plugs/inlets are inevitable? Or do you think the best approach is that worn-out/damaged plugs/inlets are able to be routinely repaired/replaced? I am concerned about the possibility that a worn-out/damaged public charger plug could spread damage to car inlets (and vice versa)...
I have not tested AFCI's for this application. On a standard Leaf charging at only 16A, I just don't see this happening, but when we start getting up to around double that, the chances of problems go up markedly.

The right thing to to is for the software in the on-board charger (OBC) to be modified to detect things like this and issue a warning. On the CHAdeMO port, they have a thermistor to detect problems like this, but this is because there can be well over 100 amps of high-voltage DC flowing (Arcing would be disastrous!). Obviously the addition of a thermistor to the J1772 port would also go a long way toward detecting these kinds of failures.

I would design the algorithm to reduce charging power and alert the owner in the event of a high resistance (sagging voltage) or arcing event.

Keep in mind, if a public charger gets a failed contact like Tony's, I seriously doubt it will "spread". It will kill one hungry EV, then be damaged too badly to be used again.

It's obviously prudent to at least take a glance at the condition of J1772 handle connectors before blindly inserting them into your EV. Report any apparent damage to the station owner so they can fix it.

It's too bad the J1772 pins were designed so thinly. They are about the same cross-section as a #12 AWG wire (3.6mm), which nobody would not consider sending 70 Amps though, let alone 30, but someone decided it was ok.

-Phil
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Nubo
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 12:19 pm

Are there different standards for the connector based on the current delivered? For example, these three Leviton J1772 cables: would the difference be only in the conductors, or also the plug? If the latter, would that be standards-based or at the discretion of the manufacturer?

http://store.leviton.com/b/5742800011" onclick="window.open(this.href);return false;

hmmm... actually looking at the details, they all report to have 10 gauge wires. :?
I noticed you're still working with polymers.

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Ingineer
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 12:46 pm

Nubo wrote:Are there different standards for the connector based on the current delivered? For example, these three Leviton J1772 cables: would the difference be only in the conductors, or also the plug? If the latter, would that be standards-based or at the discretion of the manufacturer?

http://store.leviton.com/b/5742800011" onclick="window.open(this.href);return false;

hmmm... actually looking at the details, they all report to have 10 gauge wires. :?
There is no compliance testing for J1772 (That I am aware of), so interpretation of the specifications is up to the manufacturer.

To answer you question, yes, on the higher current capacity handles they always use different contacts, though the contact pin diameter is always 3.6mm.

I guarantee the Levition (ITT) cables are not all 10AWG. That must be a typo.

-Phil
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DaveEV
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 12:52 pm

J1772 was originally designed with 32A in mind (J1772-2001), but was later updated to support a maximum of 80A (J1772-2009).

It does seem that some sort of thermistor would be prudent - along with the onboard charging monitoring voltage drop as it ramps up, though it would have a hard time distinguishing voltage drop caused by a single hot-spot compared to a long service run.

I wonder if a some sort of dielectric grease or switch grease on the pins might help or make things worse?

J1772 power pins are 3.6mm in diameter or about the same as 7 AWG - it does appear that the pins should provide plenty of surface area which should result in any hot spots being focused on the base of the pin provided that good contact is being made.

Looking at Tony's pics, though, make it clear that the heat was focused on the inside half of the pin.

The pins on the inlet appear to be some sort of bi-metal construction - maybe a combo stainless/copper pin perhaps to reduce the electrical resistance of the pin as stainless has a much higher electrical resistance than copper.

It would be interesting to do a proper failure analysis on Tony's connector and inlet.

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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 12:54 pm

Nubo wrote:Are there different standards for the connector based on the current delivered? For example, these three Leviton J1772 cables: would the difference be only in the conductors, or also the plug? If the latter, would that be standards-based or at the discretion of the manufacturer?

http://store.leviton.com/b/5742800011" onclick="window.open(this.href);return false;

hmmm... actually looking at the details, they all report to have 10 gauge wires. :?
That is strange. I always assumed that the pins were all rated at 75 amps, but that the inlets and plugs were just de-rated based on the wiring that was connected to them. Now I see that they all have the 10ga wiring, so that is confusing. 10 seems a little light for anything over 30 amps. Not sure how they can do this for 70 amps.
Michael

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Ingineer
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 12:59 pm

drees wrote:I wonder if a some sort of dielectric grease or switch grease on the pins might help or make things worse?
You would want conductive grease, not dielectric! I would advise against any grease though, as it will attract dirt which will make it worse. The J1772 contact design is self-cleaning.

-Phil
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DoxyLover
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Re: Blink / Rav4 Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 2:16 pm

Personally, I doubt that arcing was involved, at least at the beginning of the problem. I would be much more suspect of just poor contact on the pin. All of the current went through a small part of the surface of the pin, causing the heating.

As other have stated, using voltage sag to detect a problem could be problematic: a long service run could cause the same sag which, distributed over a must larger area, would be harmless. A thermistor to detect heating would be much better.

We'll have to wait to see how many other RAV4/Tesla/other high charging current EVs see similar problems.
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TomT
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Re: Blink Blows Out a Contactor Pin (with gory pics)

Tue Nov 27, 2012 2:20 pm

I rather doubt that the Blink had anything directly to do with this per se since this is obviously a connector issue and many EVSEs use pretty much the same connector. Thus, it could also have happened to any of a number of 30 amp EVSEs.... For all we know at this point, it might have been the car's fault, in fact, and had nothing to do with the EVSE.
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Last edited by TomT on Tue Nov 27, 2012 2:54 pm, edited 1 time in total.
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