How new can a Leaf be and have vulnerable OBC diode?

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five10man

New member
Joined
Jul 23, 2021
Messages
2
Location
TX Y'all
Hi All,

Short version: How new can a Leaf be, and still have the vulnerable diode D547 inside the OBC? Did the diode problem go away, either with the 6.6kW OBC or with the Gen 2 Leaf?

I have searched all through here (forum search and Google search,) and on teh interwebz and I haven't seen an answer. What I have seen is no anecdotes about newer-than-2013 cars blowing a diode. Please feel free to light me up with your horror stories, repair stories, and tales of how you charmed the dealer into replacing OBCs.

Long version: I manage a fleet in Texas which includes eight 2017 Leaf Ss. My org has ChargePoint CT4020 2-port EVSEs, and since the freeze in February of this year (power went off and on numerous times, numerous brownouts as well) the EVSEs are doing weird stuff when you go to plug in a second Leaf. No symptoms when one Leaf is plugged in (although it sets a "pilot unreachable" error code that can be read online,) but when the second Leaf goes to plug in it says "Charger Unavailable: and sets a different code that doesn't clear until both cars are unplugged.

Point of interest: the EVSE where this is happening the most (a matter of parking schedules, I think) got replaced right after the freeze, so I think I can eliminate EVSE problems as a source of the hassle.

The EVSE people say it is the cars, because the problem goes away when they unplug. :roll: The mechanics - not an EV tech among them, but they can read codes - say it is the "charger" or EVSE because the codes they read tell them so. I was breaking the rules of my job by even using a voltmeter on the cars, so I'm hoping the big pool of knowledge here can help me out.

I have checked the diodes in five of these cars, and instead of megohms one way and K-ohms the other, I read completely open one way and 1-2 M-ohms the other way. This looks to me like a bad diode, but all of the writeups I read and videos I see about diode failures are unclear as to whether or not they are referring to the 3.3kW or 6.6kW OBC, and I don't want to screw up the diagnostic process based on an assumption.

I would like to be on firmer ground when I finally get a Nissan dealer person who actually speaks EV to return my calls/emails. I am not looking forward to sending in one of these cars and having the tech say "It charges just fine on our equipment. Your equipment is faulty!"

Thanks in advance! :beer:
 
Why not just drive each LEAF to a nearby public L2 charger and do a test charge. If the diode is blown, the car won't charge. So, a quick and definitive test...
 
Did you happen to get any pictures of the board and diode? Seems like it is a different board design between the 2012 and 2017, and the reference designators are likely different too.

Most multimeters have a setting for a diode check function which would give better results than measuring resistance. A diode is like a one-way valve, it passes current in one direction but blocks it in the other. So your readings seem like what a diode might be expected to do with opposite polarity measurements, but the diode health is inconclusive.

The odds of 5 cars having the same fault of the same part seems unlikely unless there is some common cause.
 
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