footswitch
Posts: 9
Joined: Sat Sep 01, 2018 3:13 pm
Location: Portugal

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

Fri Apr 05, 2019 11:48 am

Hey guys.
My OBC (Case #16 on this thread) had the exact same symptoms as ChristopheFR (Case #18).
I remember reading he swapped the bigger components on the top board, but it still wouldn't work.
Just a heads up, finally I got mine repaired. It's working right now.
More details coming soon.
Cheers

ChristopheFR
Posts: 20
Joined: Sat Aug 11, 2018 1:08 am

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

Sat Apr 13, 2019 9:53 am

Hello footswitch,
Glad to read you again in this post.
As for my Z, I finally bought a used OBC that I repaired, same symptoms as electronpusher : I just changed a blue capacitor in the doghouse.
But I hope now to repair the old one: I just desoldered the waffle plate to test the IBGT one by one.
I also have a doubt about the UC2854 component, which drives the PFC.
And what part did you repair?

danielsl
Posts: 1
Joined: Fri Apr 19, 2019 5:38 am

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

Fri Apr 19, 2019 5:43 am

Same problem burnt charger. However I can't anyhow remove bottom board that has filter relay and burned capacitors. How it's done. I thought about replacing them. But they seems glued to the heat exchanger

coulomb
Posts: 175
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

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

Sat Apr 20, 2019 12:12 am

danielsl wrote: I can't anyhow remove bottom board that has filter relay and burned capacitors. How it's done. I thought about replacing them. But they seems glued to the heat exchanger

This is the post from the index on the first page about the bottom board, it might help some:

viewtopic.php?f=23&t=4079&start=20#p36669

Removing all 72 joints really requires a desoldering station, but you should be able to unbolt the Waffle Plate™ from the case and gain access to the two pieces (bottom board and Waffle Plate combined).

footswitch
Posts: 9
Joined: Sat Sep 01, 2018 3:13 pm
Location: Portugal

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

Tue Apr 30, 2019 10:17 am

ChristopheFR wrote:Hello footswitch,
Glad to read you again in this post.
As for my Z, I finally bought a used OBC that I repaired, same symptoms as electronpusher : I just changed a blue capacitor in the doghouse.
But I hope now to repair the old one: I just desoldered the waffle plate to test the IBGT one by one.
I also have a doubt about the UC2854 component, which drives the PFC.
And what part did you repair?


Sorry for taking this long to reply.
It was a "simple" repair, component wise, just the ceramic resistors, 5V relay, main capacitors and so on.
Also a capacitor or two underneath the top board.
No fiddling with the IGBTs or anything like that.

And in fact it worked well for a couple weeks.
Mind you, the first 4-5 charges were self-stopping before reaching full SoC, and I couldn't tell if the icon in the dashboard flashed on those occasions.
Eventually, after a couple weeks, it reverted to the same symptoms once again (plug it in, ventilation test, flashing indicator, relays clicking, no charge).

Haven't reopened it yet.
We'll look further into it, but at this point I'm skeptical that we can get it working reliably.

[EDIT] I noticed that the 12V line goes up initially (during ventilation test), so the charger actually does some voltage conversion before giving up.

kiev
Posts: 996
Joined: Sun May 03, 2015 7:15 am
Location: The Heart o' Dixie
Contact: Website

now it's got me too...

Sun May 05, 2019 10:03 am

i plugged in to lvl2 chargge this morning and it quit after about 25 minutes, and wouldn't restart. Drove around and had the aux and High Voltage warning lights and wouldn't chargge on lvl1. pulled DTCs and had OBC abnormal stop and DCDC converter fail codes. Tried to reset codes but they came right back.

Aux was new in May 2016, installed in Sept 2016, it measured 12.7 OCV and 12.28 in READY. i pulled the Aux from the car and added 1 oz of distilled water to each cell to bring the level up from the bottom of the slot up to near the top of the slot used to site the level.

Maybe it was too low and caused a hiccup, but doesn't seem likely, all the plates were plenty covered. And the OCV is reading 12.90.

Pulled MCU cover and the 20A fuse is blown. Pulled the OBC cover and top board to inspect the blue snubber caps, and they have popped too.

Hopefully just changing these will get me back on the road, but it is still a puzzle about what is causing this havoc with the OBC...

There is a tiny fuse on the top board before AC enters the bottom board, and a tiny fuse on the output of the DC after the filter on the way over to the MCU. There is also a tiny fuse inside the DCDC for HVDC going into that section. Yet none of those fuses pop, it is the external fuse inside the MCU, and it is the snubber caps on last stage of the FETS before the output filter and the tiny output fuse.

Maybe something is blowing the MCU fuse first and that causes a chain reaction to blow the snubber caps--but what can this thing be...?
kiev = kenny's innovative electric vehicle

coulomb
Posts: 175
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: now it's got me too...

Sun May 05, 2019 11:10 pm

kiev wrote: Maybe something is blowing the MCU fuse first and that causes a chain reaction to blow the snubber caps--but what can this thing be...?

I've had a few false starts answering this question (yet again).

Here's all I can come up with today. Charrger is charging at near full current. MCU fuse is somehow not vibration resistant, and under warming from the charge current, it lets go. All the charge current pours into C115 (220 μF 450 V), and its voltage shoots up very fast; much faster than a battery ever would, and faster than the control circuit is designed for. It notices the over-voltage, and pulls back the current. It overshoots, as control circuits often do, meaning that it cuts the full bridge off completely. Or there is a special circuit to notice a severe overload, and it cuts off the full bridge. Zero percent PWM. But there is still current in the inductors, with the full bridge open circuit one side, and C115 at maybe 400 V on the other side. The only path for the inductors to continue to dump whatever current they have left into C115 is via C121 and C122, our blue or surface mount friends that are not designed for this amount of current. The excess current blows them to smitherines, and the resultant arc finally discharges the flux from the inductors.

Mind you, I don't know how big these inductors that I'm talking about are. There are whoppers in the PFC circuit, sure, but maybe these aren't big enough to blow your nose. If the main output-side inductance is actually the leakage inductance of the transformers, then my theory is toast.

The answer would seem to be to beef up the peak current capability of those capacitors that keep blowing (and probably their voltage rating as well). That might cause something else to blow instead, but I suspect not.

@Kiev, would you consider beefier replacements to see how they go? But I don't know how to prove that you've thereby fixed it "for good".

pbui19
Posts: 165
Joined: Tue Jan 07, 2014 12:17 pm

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

Tue May 07, 2019 6:31 am

So it seems a weak 12v aux may not be a culprit then ?

Also, perhaps we should take preemptive action to deal with the marginal fuse contact integrity ?

kiev
Posts: 996
Joined: Sun May 03, 2015 7:15 am
Location: The Heart o' Dixie
Contact: Website

Re: now it's got me too...

Wed May 08, 2019 4:17 pm

coulomb wrote:...
@Kiev, would you consider beefier replacements to see how they go? But I don't know how to prove that you've thereby fixed it "for good".


yes i would consider this. i had posted some photos of alternative HV ceramics that i had available, 1000pF at 3kV and at 6kV. Both are much larger physically than the little blue caps in the OBC.

Would you reckon these would represent a beefier cap since the voltage rating is higher, or were you thinking that the capacitance value also needs to be increased? Or does it need to be decreased to 500 or 250 pF, but with the higher voltage ratings? i just don't have a feel for the impedance and frequency response needed for a safe level of current flow thru the caps (without blowing them).

ps i found some higher rated fuses (30A and 40A) in the same ISO style holder and frame, with same voltage rating, ~$20 each in quantity.
kiev = kenny's innovative electric vehicle

coulomb
Posts: 175
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: capacitor ratings

Wed May 08, 2019 11:43 pm

kiev wrote:Would you reckon these would represent a beefier cap since the voltage rating is higher, or were you thinking that the capacitance value also needs to be increased?

I say don't change the capacitance value unless you really know what you're doing.

My feel is that they just need to be physically bulkier to absorb the energy pulse(s) in their mass. The higher voltage rating helps too obviously.

ps i found some higher rated fuses (30A and 40A) in the same ISO style holder and frame, with same voltage rating, ~$20 each in quantity.

Please post details. I didn't think that the MCU fuse was any sort of standard, let alone ISO.

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