electronpusher
Posts: 43
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Tue Sep 18, 2018 8:50 pm

skylogger wrote:On the second OBC that I just finished working on, I've been told that the charging failed during a night that there was a storm and heavy rain. This could point towards a blackout, brownout, or power surge as the source of the falult.


Just playing catch up on this thread, haven't had a chance to look at our OBC, and only received the replacement caps on Monday, so I intend to work on it over this weekend. Still waiting on the fuse from Mitsu though.

Interesting @skylogger, this could be the cause. When we had the failure with our iMiEV we had it connected to our charger connected to the off-peak circuit of the house (since moving we no longer have off-peak, we have solar/batteries instead, but I degrees). So in our situation the fault is likely to have occurred when it was charging that night (it was fine the night before obviously), the power would have turned on sometime between 12am and 1am, and then turned off again sometime between 5am and 7am. This may have caused our failure, as it is a dead cut from before the EVSE. It is an interesting theory that is for sure.

As for the fuse, would this work?

https://au.rs-online.com/web/p/products/7686125/?grossPrice=Y&cm_mmc=AU-PLA-DS3A-_-google-_-PLA_AU_EN_Fuses_Sockets_And_Circuit_Breakers-_-Fuses%7CCartridge_Fuses-_-PRODUCT+GROUP&matchtype=&pla-392408123959&gclid=CjwKCAjwxILdBRBqEiwAHL2R83h1tofZAmpYGq3XjzV7kQaFTuUlk5U7LQTOp2rdwHPg-NR5KHvu2hoC0T4QAvD_BwE&gclsrc=aw.ds

Quixotix
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Location: Seattle

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

Tue Sep 18, 2018 9:16 pm

coulomb wrote:They are 1 nF (1000 pF) 3150 V capacitors, as specified in this post: Murata DEHR33F102Kppp .

Whether they should be replaced with something "stronger" is debatable, but you are unlikely to find a higher DC voltage rating.


Does anyone have suggestions on where to buy quality capacitors (I'm in the USA)?

A quick search on eBay shows there are capacitors rated up to at least 40kV. Would a 1000 pF, 15 KV "Cera-Mite" capacitor be a bad idea? Are all capacitors from eBay a bad idea?

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

Tue Sep 18, 2018 11:09 pm


Electrically, yes it would work, and it seems to have very roughly similar "speed" (it's hard to tell, because the original fuse has very wide times for blowing at a particular current).

But you'd want the "bolted contacts" version of that fuse, which unfortunately none of the regular parts suppliers seems to stock. Even if you found that, the bolts are 45 mm apart, and the holes in these would be 50.6 mm apart. So you'd have to enlarge the slots.

The best I came up with is in this post. It's also a photovoltaic 38x10 mm fuse (the original is a non-standard 31x7.2 mm), but with the bolted contacts, and the holes are 51 mm apart. So again, you'd need to enlarge the slots. The Australian version of the Mouser URL for this part is https://au.mouser.com/ProductDetail/Bus ... YZ2445BpOV . It's almost expensive enough to get free shipping; add something inexpensive to the order to qualify for free shipping (AU$45 minimum order). Something I ordered recently from Mouser took 6 calendar days to arrive (to an Eastern capital city address).

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

Tue Sep 18, 2018 11:27 pm

Quixotix wrote: Does anyone have suggestions on where to buy quality capacitors (I'm in the USA)?

I'd try the "usual suspects": Mouser, Digi-Key, Newark.

A quick search on eBay shows there are capacitors rated up to at least 40kV.

I meant to say "in a similar sized package". Though I see that some of the Vishay capacitors go to 7.5 kV. They are a bit thicker than the originals, but there seems to be room in there for somewhat larger capacitors.

Would a 1000 pF, 15 KV "Cera-Mite" capacitor be a bad idea?

There is quite a large range; the name "Cera-Mite" seems to cover all Vishay's ceramic capacitors. Some are rated at only 1000 VDC; I think we'd want at least 3000 VDC rating to be no worse than the originals. The originals and therefore the PCB holes have 7.5 mm spacing. You can of course bend the leads to a certain extent to accommodate other lead spacings. I think that a 15 kV rating is way more than is needed.

From the "R" in the series name, I'm guessing that these use the X7R ceramic formula. These are among the worst for non-linearity and variation of characteristics with temperature. I wonder if we'd be better off with some sort of film capacitor. Of course, film capacitors can have higher inductance.

Are all capacitors from eBay a bad idea?

It's a highly mixed bag. As long as they are genuine branded components, not some knock-off designed to look like branded parts, then I don't see a problem.

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

Tue Sep 18, 2018 11:34 pm

Quixotix wrote: Did anybody notice what the Murata data sheet says about these DEH series capacitors:
...
Do not use these products in any automotive
power train or safety equipment including battery
charrgers for electric vehicles
and plug-in hybrids. ...

(My altered boldness)
I think I did notice that in passing, but it didn't occur to me that perhaps this is the Root Cause (or one of them). Perhaps these are just the wrong capacitor to use in an automotive environment.

I guess we use them anyway because there isn't a better option?

I think we could find a better option, designed for automotive applications.

Do you think it was our MIEVs that caused this statement to be included?

I think that's a bit of a stretch. Possible, I suppose. It's not a good look for Murata that their parts turn up exploded in vehicle charrgers.

The 3 empty boxes (or ppp) at the end of the part number are where the code letters for the lead style...

Thanks.

coulomb
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Location: Brisbane, Australia

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

Wed Sep 19, 2018 1:19 am

coulomb wrote: From the "R" in the series name, I'm guessing that these use the X7R ceramic formula. These are among the worst for non-linearity and variation of characteristics with temperature.

Hmmm. I take it back. From the Murata Capacitor Data Book, the R series (among two others) has a quite moderate and at least linear change of capacitance with temperature. There are plenty series that look a lot worse.

Also. the only series that seems to be rated for automotive use is only rated at 300 VAC. Not much use for putting across essentially a 360 VDC battery rail.

So maybe the original isn't so bad, but I still think we could find a better replacement.

kiev
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HR R Safety Caps, MuRata DEH series

Wed Sep 19, 2018 5:05 am

The safety caps in my box, HR R 102K 2KV, are 9mm in diameter and only rated 2kV.

The MuRata catalog datasheet (C85E.pdf) i found from Newark doesn't have the restriction about EV charrgers, but it has a date code of 06.6.1, whereas the restricted version datasheet was dated March 28, 2018.

So i think that yes the experience of the Miev chargger may have caused them to add this statement.

But still what is causing the massive overvoltage to blow these caps?

p.s. Quixotix, your 220uF output filter Cap looks like it has gotten hot and caused the sleeve to shrink and uncover the top--may want to check/replace if high ESR.
Last edited by kiev on Wed Sep 19, 2018 3:52 pm, edited 1 time in total.
kiev = kenny's innovative electric vehicle

Quixotix
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Re: HR R Safety Caps, MuRata DEH series

Wed Sep 19, 2018 8:34 am

Thanks Coulomb and Kiev.

kiev wrote:p.s. Quixotix, your 220uF output filter Cap looks like it has gotten hot and caused the sleeve to shrink and uncover the top--may want to check/replace if high ESR.


Can I do this with a multimeter? I have a decent multimeter, but not much more for testing electronics.

That capacitor seems to have 3 terminals. If a multimeter will work, what resistance values would be good or bad? Between which of the 3 terminals? I assume I'd need to remove the capacitor from the circuit board?

Note: It's possible the sleeve on the 220uF capacitor was short originally. The sleeve slides up and down freely and I know I moved it before I took the picture. The sleeves on the 680uF capacitors cover the crimp area of the can, and have wrinkles in this area. The sleeve on the 220uF capacitor has no wrinkles and doesn't appear to have covered the crimp area originally.

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

Wed Sep 19, 2018 3:20 pm

Electronpusher: When I ran into problems getting the original 20 amp fuse, I bought the 10x38 fuse type that you showed in your last post.
To be able to use it, I also bought a DIN fuse holder, and ran wires from the fuse holder with small ring terminals that would screw down to the original two screw terminals that the tabs on the original fuse mounted to. You posted link to RS. you might check if RS sell 10x38 fuse holders like this:
https://au.rs-online.com/web/p/rail-mou ... s/7686134/


QUIXOTEX: From your description of your 12v AUX battery, it sounds like during the last run, the 12v battery was also not getting charged.
You will probably also need to check the 20 amp fuse that is located in the top of the MCU (Motor Control Unit)
You will see a small hatch/lid on top of the main cover on the MCU which is the other big box just to the right of the charger.
If you open that compartment you will see the 20 amp fuse inside . If you check that, you might find that blown, which has been quite common
with these charger faults. Once you clear away the rubbery potting around the blown cap, you will probably find remaining leads still coming up from the PCB holes. If like coulomb said, you are quick with soldering, you can attach the leads of a new cap to these remaining leads of the old cap, so you do not have to do rework from bottom of PCB and remove the waffle. I bent the leads into hook shapes, and joined. If you want to replace the other cap that did not get vaporised, just crush it with pliers so it crumbles except leaving its leads coming up from the PCB. then join a new cap to the old leads. After getting these caps replaced and checking the 20 amp fuse, I would run through the process of checking the 2x 4.7 R resistors and the relay by going through the test procedure I listed earlier in this thread.

Quixotix
Posts: 46
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Location: Seattle

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

Wed Sep 19, 2018 4:30 pm

skylogger wrote:it sounds like during the last run, the 12v battery was also not getting charged.


You are right. It was not getting charged.

You will probably also need to check the 20 amp fuse that is located in the top of the MCU (Motor Control Unit).


The dealer replaced a "high voltage fuse" (a $100 part). Is this likely the fuse you are talking about? Is it likely that it the new fuse blue again when the dealer was testing the car?

just crush {the capacitor} with pliers so it crumbles


Thanks for the tip.

I would run through the process of checking the 2x 4.7 R resistors and the relay


I'll look that up. Thanks

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