Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

[kiev]

2 of the 3 big nichicon 420V 680uF capacitors in jay's box have bowed up the top dome of the relief valve/notch. i don't have a reference designator for them, so for now they are 1,2,3 from left to right, where number 3 is closest to the big hot inductor during charging.







Gonna need some help finding these GX(M) with 4 solder terminals--i'm not having any luck so far.



EDIT: Ran a simulation to see how long it might take to charge these caps using 340 pk AC voltage at 60 Hz.

[JoeS]

Kenny, good work! Thanks for posting that related information on the other thread. You're right - these devices don't show up. Still looking...

Not much derating going on here... and if they're really only rated for 5000 hours at full voltage and high temp, some of us are there already.

A few questions:

1. What are the length and diameter in mm of these caps? From your photo I make it to be about 35mm dia.
2. I take it these are part of the output LC filtering and experience full pack voltage?
3. I don't understand their four-terminal configuration. Schematic?

[kiev]

...

A few questions:

1. What are the length and diameter in mm of these caps? From your photo I make it to be about 35mm dia.
2. I take it these are part of the output LC filtering and experience full pack voltage?
3. I don't understand their four-terminal configuration. Schematic?

Howdy Joe,

1. Looks like 35 D x 55 H, for the body of the cap. It is using regular solder pins, not the Snap-in type.

2. i still have to figure out how to trace the waffle plate with the diodes and fets, but it appears that these caps hold up the first DC buss created by a diode bridge across the AC input and before the PFC circuits.

3. if you look at some of the pictures of the bottom of the bottom board you can see the 4 cap solder terminals. A and C are Blank (probably just for structural support, while B is (+), and the last pin is (-). This is likely related to the '(M)' option of the GX electrolytic caps, but is not shown on any datasheets so far.

[coulomb]

1. Looks like 35 D x 55 H, for the body of the cap. It is using regular solder pins, not the Snap-in type.

What's the lead spacing for the active leads? It should be 10, 22.5, or 25 mm.
Edit: It looks like 22.5 mm from the photos, but it might be 25 mm. I calculate 23-23.5, assuming that the dotted circle underneath the PCB is 35 mm. Oh! Some Nichicons come with 22.0 mm spacing. So it could well be 22 mm.

2. i still have to figure out how to trace the waffle plate with the diodes and fets,

Yeah. That might not be easy to replace. If a couple of devices shorts out, it might be necessary to replace them with discrete components on longer leads, bolted separately to the heatsink. Ick.

Then again, the hard epoxy might be the type that melts at a specific temperature, and you might find that those are standard components under there. But I suspect that they might be bare semiconductor dies.

but it appears that these caps hold up the first DC buss created by a diode bridge across the AC input and before the PFC circuits.

Right. So like the 2-3 capacitors in the PFC stage of the Elcon chargers, not like the one near the MOSFETs. Hopefully, they have proper snubber capacitors, perhaps on the Waffle Place™. (I love that name )

[coulomb]

You're right - these devices don't show up. Still looking...

I think that this Rubycon capacitor is a pretty good fit. Better ripple ratings, same voltage, capacitance, diameter, and life, and Rubycon is also a good Japanese manufacturer. But it's 65 mm tall; will the extra 10 mm be a problem?

https://www.digikey.com/product-detail/ ... ND/6050306

[kiev]

Hi Kiev:
On your schematic of the Doghouse, you show the output of the drawing which will either be from the closed relay, or from the bypass resistors. If the pcb is still fitted in the box and heatsink still intact, so you cannot probe the bottom of the board, is there any points on top of the board where you can probe these output points while power is on, so it can be determined if resistors are ok, or relay contacts are ok?

There are two wires (a white and black) with quick connects that run from the top board down to the bottom board next to the dog house. Are these related to this part of the circuit?

Howdy skylogger,

Here is a picture showing the solder pads to which the closed AC relay output gets transferred to the diode bridge down on the waffle plate--it should be mains voltage if the relay and resistors are intact. i would solder some small wires to the pins sticking up and run them toward the left wall and up above the top board where you could easily access them with a voltmeter. i don't think it would be safe to attempt a measurement directly on the pads with voltmeter probes.



The AC gets filtered in the small box screwed to the charger cover, then goes into the charger to the top board and thru a surge supressor and filter, then thru the white and black jumper wires down to the bottom board to the relay doghouse, then thru the relay to the solder pads in the picture above.

In the upper left quadrant of the waffle board are 4 diodes that rectify the AC to create the first DC buss.



The diodes are DF25V60, 600V 25A SMD rectifier diodes made by Shindengen.

[coulomb]

The diodes are DF25V60, 600V 25A SMD rectifier diodes made by Shindengen.

Ok, I'll bite

How the hell do you know that?

Is there a PCB under the potting on the waffle plate™ ? How does the heat get from the components to the plate?

[skylogger]

Hi Kiev:
The charger that I am working on is back in the car, at a friends house, so on my next visit there, I can do like you say and solder a "LINE" and "NEUTRAL" wires out to a point I can connect a volt meter to and fire it up. Just to be clear, Your Arrow pointing to "LINE" is sorta pointing between the two pins, so I guess this means these two pins/pads are connected together? I know once I get there I could scrape the solder mask off, but I figured you already knew and it would save me scratching around inside the box. Also the "Neutral" arrow you drew, is pointing in the middle of a group of 4 pins/pads. Are all 4 of these joined together, or should there be one out of the 4 that is the Neutral point.
I guess if I had a storage oscilloscope, I could see the soft start, with a voltage a bit lower than 240vac (I'm in Australia) and then when the relay closes a second or 2 later, I should see the full 240vac at the test points you pointed out to me if the relay is working?

[kiev]

@coulomb,
i used an xacto knife to scrape the epoxy off the diode. It is a very brittle material, and in a thin layer it can be levered off with a blade. Also i use a hot solder iron on thicker sections--the heat pulverizes the surface to a gray powdery dust. So heat and scrape, rinse and repeat until down to the chip.

The upper right quadrant has 10 chips, 3 of them are DF20L60U fast recovery diodes. i haven't drilled down to a board yet, but surmise there is some sort of pc board under the epoxy to which the parts are soldered. The aluminum bottom plate is 2mm (0.08") thick and measures 5-3/8 x 6".

[edit] uh oh, it appears that the FETs or diodes in the lower half are different size devices, and the tops have been etched to remove the part numbers. Why such security measures deep in the bowels of a charger...?



@skylogger,
yes you are right on all questions--almost all of the pads are connected in pairs with a fat trace below the solder mask. The "neutral" (usa 120vac) cluster of four are all connected together also. It could be labelled "line2" for 240vac such as we use for Level 2 charging. [edit for usa mains power]

[coulomb]

It could be labelled "line2" for 240vac such as you use there.

Actually, we (and nearly every country outside the USA and Canada) have one line and one neutral; the neutral is earthed at the main switchboard by a neutral to earth link. We just don't have center-taps on our 240 V transformers. All our general purpose outlets are 240 V (occasionally 415 V), none are 120 V.

We're supposed to be converted to the international standard of 230 V, but we comply by saying our tolerance is -5% to +10%, or some such. In practice, I've never seen it below 240 V here. I see that the USA has no interest in following the international standard, i.e. 230 V and 115 V.

@kiev, Thanks for the info on the waffle board™. A photo would be great; perhaps when you have more gunk scraped off. Did you consider an oven? A few minutes at around 100-120°C would not hurt the semiconductors, and might save a lot of time crumbling off the coating. I've heard that some of the thicker and/or harder potting has to be melted off; perhaps Kelly controllers are like this?

Any thoughts on what to replace the coating with when it's ready to be fired up (so to speak)?