OBC Second Failure

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keepitrunning

Member
Joined
Mar 7, 2022
Messages
10
This is a follow up to my previous post where I thought I had fixed my 2012 OBC model 3NA060 (from the sticker)

https://www.mynissanleaf.com/viewtopic.php?t=33140

After a month or so of normal charging it stopped working again. There is still no obvious sign of failure of a component - no leaking, bulging, exploding etc. On the second failure the OBC had burned out the same thermally fused resistor location (which I had replaced with a normal power resistor) shown in my repair in my old thread.

So then I added in an extra high power version of the same resistor and it burned that out immediately.

Since this is the second failure, I'm going for broke before shelling for the new charger. In the process of pulling parts again, I did discover an easier way to remove the back board without removing the OBC from the vehicle was to remove the giant capacitor on the left side first, which then necessitates less bending of the bracket that holds the large diode at the bottom right of the OBC aluminum case.

A different resource had pointed to needing to check the noise suppression capacitors of type LE335 (blue) 3.3microF on the left side and type LE105 (black) 1.0microF near the 3 resistor chain in the AC section.

I probed these capacitors while still attached to the board and they are not shorted, but they also don't climb in resistance like I would expect on my multimeter, in fact the 1.0microF LE105 shows open when I probe it. I don't have a fancier meter available.

I acquired the vacuum solder station I will need in order to remove the waffle plate, and while I've done that to check these capacitors and the relay in the same AC section, I figured I might as well be ready to replace them, or just plan to replace them from the get go.

What other parts should I replace at the same time that also might go bad soon?

I'm having difficulty finding the OKAYA LE355 and OKAYA LE105 from typical US distributors and also struggling to determine what type of equivalent part would work instead. I'm planning to replace the K1AK005W-KW at the same time...naturally it's out of stock at Mouser. That one might be easier to find an equivalent of, but if there's a go to version, please advise.

Has anyone successfully replaced these components with a different brand? Very little turns up in the forum search on the actual replacements used, so maybe they used to be more available and people were using the Okaya?

I'm loving the helpful community here and hoping that my own experiences will one day guide others too.
 
keepitrunning said:
So then I added in an extra high power version of the same resistor and it burned that out immediately.
That sounds like you have a more serious problem.

Since this is the second failure, I'm going for broke before shelling for the new charger.
Attaboy! :)

What other parts should I replace at the same time that also might go bad soon?
Since that resistor is burning out, it could be some sort of short in the AC input, possibly the PFC IGBTs. Unfortunately, those are in the "Waffle plate"(TM) and are very difficult to replace. So it might be worth doing the diode checks indicated here (for the iMiEV version of the OBC, will not be identical to the Leaf's). Sorry for the ugly image; I'm pretty sure that there is a cleaned up one, but I could not quickly find it.

I'm having difficulty finding the OKAYA LE335 and OKAYA LE105 from typical US distributors and also struggling to determine what type of equivalent part would work instead.
They just need to be polypropylene film capacitors, at least 275 VAC rated, same capacitance, and be X2 or X1 rated (or X1Y2 etc, as long as they're "X rated" :)). This rating is because they are across the mains, so they have to fail open circuit and not explode. They should also have the same spacing (i.e. 27.5 mm for the LE335 and 22.5 mm for the LE105), and it's helpful if they have about the same physical dimensions. Datasheets here and here.

Edit: example replacement for the LE335: https://www.mouser.com/ProductDetail/Panasonic/ECQ-UAAF335K?qs=sGAEpiMZZMsh%252B1woXyUXjx7EvhV2CoVeBsyqceIl%2F%252Bk%3D
 
Sorry to hear it.

Did you pull the DTCs to see what codes are showing?

What is the status of your 12V battery?

The power to close the AC relay is created from the 12V input, and if the 12V fluctuates or drops out momentarily, then the relay can open which puts full AC mains across the 3 ceramic resistors until something blows.
 
In a hurry after my first post in this thread because I needed to get it running again, I had looked at the original Okaya sheet
https://pdf1.alldatasheet.com/datasheet-pdf/view/319263/OKAYA/LE105.html

And found some possible equivalents from Kemet that mouser had in stock:
Possible Equivalent??
https://content.kemet.com/datasheets/KEM_F3131_R53B_X2_350.pdf

This looked like it might work for the Okaya LE105 which is X2 rated. (I'm a chemical engineer not a EE, so I don't claim to understand all the specifications.) So I purchased the two below based on length, width, and pin spacing. BUT the 3.3uF was a little TOO TALL (read below).
https://www.mouser.com/ProductDetail/80-R533N410050P0K
Similar series has the LE335 sized
https://www.mouser.com/ProductDetail/80-R53BR43305000K

I also replaced the power resistors with a single 15ohm 25w version
https://www.mouser.com/ProductDetail/284-HS25-15F

With the waffle plate off and my new LCR meter, I could see that both the 1.0uF and 3.3uF had failed open and confirmed the same after removing them. After all the replacements were made, the LCR meter actually reads 4.1uF on the board measured from L to N (I used the Faston connectors above the little fenced ac section labeled LB Y and NB L which trace directly to 1.0uF - you can also use L and N pins of the waffle plate header on the left side that trace directly to 3.3uF and both are connected to each other by longer trace). That might be an easier way to trouble shoot both capacitors, but I was testing with the waffle plate off, so I'm not sure what the reading is if it is attached. I was also able to test the relay activity by supplying 5v to the solder points on the back of the board. I couldn't find an easy trace to apply this 5v from the surface in the future, but other sources had told me this relay rarely fails like the capacitors do.

I had previously tested the voltage drops in the last thread and they had all been normal. I should have probably tested them again but didn't have time.

The Kemet 1.0uF above was a great fit. It is not labelled on the top though - the markings are on the side. The 3.3uF Kemet was a little too tall, I had to add a metal spacer and longer screws because the standoffs were not tall enough to mount the upper control board.

72 soldered pins later and lots of loupe inspection for errant solder and I put it in for testing before staking those components with neutral cure silicone.

It has charged successfully again for several cycles. I've monitored temperatures inside the OBC and it seems higher than I would have designed the system for - I feel like it should be pumping more coolant through it. The waffle plate (liquid cooled side) is much lower temperature than the rest of the boards / coils etc.

Because the already 4 year old batter it had sat for a long while, it needed a completely new battery.

All DTCs cleared and have not returned any new errors.
Fingers crossed that I won't be cracking into it again any time soon.

After completion before staking
BNlpZcz.jpg


Backside after removal of waffle plate for reference in case someone wants to see major traces on back side.
0htzDzg.jpg


Closeup of AC section relay
ydQ2NK0.jpg
 
nlspace said:
Sorry to hear it.

Did you pull the DTCs to see what codes are showing?

What is the status of your 12V battery?

The power to close the AC relay is created from the 12V input, and if the 12V fluctuates or drops out momentarily, then the relay can open which puts full AC mains across the 3 ceramic resistors until something blows.

To answer nlspace from this post, I've attached the DTCs pulled from when it blew the power resistor. They are similar or same to the ones from my first repair I think.

Nlspace pointed out the importance of the 12V battery in my previous repair and that has always been checked ever since. The failure mode he mentions might have caused the first failure before 12V power was always verified, but I'm only 80% sure that wasn't to blame because I had been working with some haste and frustration, but I'm wondering if the the 3.3uF or 1.0uF cap failures could have also been to blame. I had not been able to test these during the first repair because I didn't rig long enough probes to get under the waffle plate. This time I was able to test them under the waffle plate and with it removed and discovered they had failed open. For how long they had failed I'm not sure since there were no exterior visible signs of their failure.

Knowing what I know now after the first repair, I wish I had bought the LCR meter then and checked many more capacitors and other test points when making the first repair. Like a 15 point check list of 12V battery, resistors, capacitors, diodes, relay etc.

iD63vgs.png
 
keepitrunning said:
I also replaced the power resistors with a single 15ohm 25w version
https://www.mouser.com/ProductDetail/284-HS25-15F
The replacement is a type that has a high pulse power rating. That should be good for this application. Two or three resistors would have more surface area to dissipate power; maybe that's why there are three. But with a pulse of power, there is no time to radiate heat from the surface. It's more about the bulk of the resistor. So I think you'll be fine there, even though that resistor looks tiny compared to three five watt ceramic resistors. I guess time will tell.

I think that the capacitors that you replaced are more for EMI reduction and absorbing transients than anything "active". But maybe the resistors were damaged by transients on the mains power for that second that they are active. It can't hurt to have them replaced anyway.

Well done with your second repair; I hope it lasts well this time.
 
Looks like a good job on the repairs, thanks for sharing the details and the photo of the bottom layer of the power board, that is helpful for tracing the board.
 
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