coulomb
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Location: Brisbane, Australia

Re: Relay testing

Sat Sep 15, 2018 6:44 pm

kiev wrote:i soldered some tiny wirewrap wires to the AC relay coil pins and measured 9.9R with relay off and 0.2R when closed.

I assume that's neutral in to neutral out.

So it seems the relay in jay's failed box is ok. It doesn't make a very solid sounding clunk or snap, but i guess you can't judge a relay by the cover...

I dunno. I think the lack of a satisfying clunk or snap is somewhat damning; I'd consider it somewhat suspect at this stage. It possibly takes less contact pressure to drive a multimeter to a zero ohms reading, but pushing up to 36 A peak into capacitors might require a little more force. There are mechanical things that can go wrong in a relay, which a multimeter test might not always find.

But I think your finding does weaken the "relay as prime suspect" theory.

jray3
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Sat Sep 15, 2018 10:44 pm

Gorfllub wrote:Is that the case? Those of you with dead chargers..... Do you power your evse on a timer or separate switch?

Good theory, but I plead not guilty. Mr Bean’s charging sessions normally end automatically or via the proximity switch on the J1772 handle. I’ve unplugged 120V from the wall before disconnecting the handle a very few times, but not 240V. I never implemented the previously-discussed 240V contactor for scheduled charging, and EVen if, an input line contactor would only be suspect if used to interrupt charging. If used to start charging, it would work just like a normal EVSE startup.
2012 i-SE "MR BEAN" 94,000 miles
2000 Mazda Miata EV, 78 kW, 17 kWh
1983 Grumman Kurbwatt EV,170 kW, 32 kWh
1983 Mazda RX-7 EV 43 kW 10 kWh
1971 "Karmann Eclectric" EV 240 kW 19 kWh
1965 Karmann Ghia Cabriolet

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

Sun Sep 16, 2018 1:14 am

jray3 wrote: and EVen if, an input line contactor would only be suspect if used to interrupt charging. If used to start charging, it would work just like a normal EVSE startup.

Yes, my worries concerned the ending of the charge, not the beginning.
When someone tries to optimize costs by charging only when the electricity rate is lower, then he may end the charge before the battery is full, and then enter into the destructive theory described above.
But I understand you have had trouble while not having unplugged the main socket, so ok.

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

Sun Sep 16, 2018 6:49 am

jray3 wrote:... I’ve unplugged 120V from the wall before disconnecting the handle a very few times, but not 240V.


That's an interesting clue--It only takes once to cause damage.

i had assumed that nothing like that had occurred, but this raises a possible culprit for your box failure.
kiev = kenny's innovative electric vehicle

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

Mon Sep 17, 2018 3:54 am

Footswitch: When I cut one of the CANBUS lines, I was busy checking that the LED that I added to confirm that the doghouse relay was closing (which it did not do) so I was standing at the back of the car. I was able to hear the contactors and fan go on, so I knew that AC input was detected, but silly me, I failed to take note if the charge light on the dash was on or blinking.
Maybe if I get some time I will run the test again.

KIEV: I am thinking with the micro pitting situation on the relay contacts, when you run the relay test, you might have to open and close the relay 20+ times or more. You might find that out of the 20 relay closures, you measure 0.2 ohms the majority of times, but there might be 1 or 2 times when the relay closes that a high resistive value might come up if the contacts are intermittent or the micro pits line up.

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

Mon Sep 17, 2018 8:22 pm

Good idea, i'll have to run some cycles on it and see how it does.

Since the waffle plate is off there is no path to charge the caps, but i could rig something up to put ac thru the contacts. Too bad there is no way to inspect the contacts without destroying the relay. i was hoping this relay would show bad so we could have a culprit and fix it...
kiev = kenny's innovative electric vehicle

Quixotix
Posts: 46
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Location: Seattle

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

Tue Sep 18, 2018 1:58 pm

I apologize if this if this has been answered, but I"m struggling with the terminology in this thread -- vertical pcb (I don't see one), dog house???

Anyway, I'm attaching 2 pictures (I hope). I think that's a capacitor that's completely burned up. Am I right? Assuming it is, does someone know what size it is? Maybe it's the same size as the one next to it, but with the potting I can't read that one either.

Image

Image

About that potting, any hints as to how to replace the burnt part? I'm thinking I will: 1) carefully mill out a pocket where the burnt part is (milling is easy), 2) desolder and remove the heat sink assembly (what I pain) so I can get to the pins for the capacitor, 3) solder a new capacitor into the original position, 4) re-solder the heat sink assembly on.

Is their a better way to fix this?

Should I replace the other capacitor next to it (or any other components) while I have the heat sink assembly off?

Are there likely any small components under the potting that are within a mm or so of the burnt capacitor? I'd like to avoid cutting off any components with my mill other than the burnt one.

Should I re-pot the new component?

Thanks for your help.
Last edited by Quixotix on Tue Sep 18, 2018 3:58 pm, edited 2 times in total.

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

Tue Sep 18, 2018 3:44 pm

Quixotix wrote: I"m struggling with the terminology in this thread -- vertical pcb (I don't see one),

Your charrger doesn't have one. Some (roughly half?) of the chargers have a vertical PCB with surface mount capcitors on it instead of the two through-hole capacitors.

dog house???

That's just the potted area walled off with plastic. Your burned capacitor is inside one, but there are others on other PCBs.

Anyway, I'm attaching 2 pictures (I hope).

I can only see the first one, and only on my phone. If it's hosted on something like Google Drive, you need to change the sharing settings so that everyone can see it. [ Edit: I can see them both now, thanks! ]

I think that's a capacitor that's completely burned up. Am I right?

Yes, that's badly burned (based on the first photo only).

Assuming it is, does someone know what size it is? Maybe it's the same size as the one next to it, but with the potting I can't read that one either.

The two are the same. They are 1 nF (1000 pF) 3150 V capacitors, as specified in this post: Murata DEHR33F102Kppp . [ Edit: the "ppp" might actually be three special characters that aren't rendering well, but in my PDF reader, these characters show up as empty boxes but match "ppp" in a search. ]

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

I'm thinking I will: 1) carefully mill out a pocket where the burnt part is (milling is easy), 2) desolder and remove the heat sink assembly (what I pain) so I can get to the pins for the capacitor, 3) solder a new capacitor into the original position, 4) re-solder the heat sink assembly on.

I would be careful with milling. You don't want to touch the PCB tracks. Others don't seem to have had much trouble removing the potting material with simple tools (perhaps a screwdriver or wooden chopstick).

If you're very lucky, you might be able to leave some pigtail exposed, and solder quickly to the pigtail, so you don't have to desolder the many connections to the Waffle Plate™. You really need a proper desoldering station to remove that plate. Be quick, so that you don't melt the solder under the board. However, it might also be possible to completely remove the capacitors from above, and re-solder them all from above as well, again avoiding removing the Waffle Plate.

Should I replace the other capacitor next to it?

I think that would be a good idea. It is in parallel with the other one, so it has seen exactly the same voltage spikes as the burned one.

(or any other components)

We still haven't found the Root Cause. So it's possible that eventually we'll know what else to replace. But unfortunately, we're not there yet. One thing we're suspicious of is a too-small or too-old auxiliary battery. There are also suspicions about the pre-charge relay. But the relay definitely can't be replaced without taking off the Waffle Plate.

Are there likely any small components under the potting that are within a mm or so of the burnt capacitor? I'd like to avoid cutting off any components with my mill other than the burnt one.

I don't believe that there are.

Should I re-pot the new component?

That would be a good idea. Cars are a high vibration environment, so the leaded capacitors could use some mechanical constraining. But it's also good to keep dust and grime away from the high voltage DC elements like those capacitors. It doesn't have to be the exact same material; I'd use neutral cure silicone. Neutral cure is definitely required, as acid-cure silicone will conduct electricity. Silicone has excellent insulating qualities. If you use some other material, make sure it is designed for electrical work (silicone generally is not), or is known to be a good insulator. I find it hard to source suitable potting material.
Last edited by coulomb on Tue Sep 18, 2018 11:38 pm, edited 1 time in total.

Quixotix
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Location: Seattle

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

Tue Sep 18, 2018 4:57 pm

Thanks for the information Coulomb.

coulomb wrote: I would be careful with milling. You don't want to touch the PCB tracks. Others don't seem to have had much trouble removing the potting material with simple tools ...

If you're very lucky, you might be able to leave some pigtail exposed, and solder quickly to the pigtail, so you don't have to desolder the many connections to the Waffle Plate


The traces in that area are on the bottom side of the PCB, right? Anyway, I'll try the hand tool method. I had only LOOKED at the potting material and I assumed it was a hard epoxy. Now that know it's a rubbery material (silicone?), I can see that removing the potting with a hand tool would give me the chance of leaving pigtails from the old components.

You really need a proper desoldering station to remove that plate. Be quick, so that you don't melt the solder under the board. However, it might also be possible to completely remove the capacitors from above, and re-solder them all from above as well, again avoiding removing the Waffle Plate.


I noticed others with more skill than I were having trouble removing the waffle plate. I was thinking i might try to do the replacement all from the top side.

QUESTION: If I raise the new capacitor up so I can solder from the top side of the board, the longer leads won't be a problem from an electrical point of view (i.e., change the inductance, capacitance, or whatever)?

One thing we're suspicious of is a too-small or too-old auxiliary battery.


Regarding the auxiliary battery, here is what I know about mine (just in case it's a useful data point):

The failure in my onboard charger presumably occurred while the car was charging at home. After the failure, I drove the car -- with the 12V batter and the ! warning lights on -- for a total of maybe 45 minutes. I drove until the car shut off presumably due to low aux battery voltage. Half of the time I was driving I had the A/C and headlights on. So, the (original) auxiliary battery had a reasonable capacity prior to the charger failure.

I charged the auxiliary battery immediately after towing the car the last couple of miles home. I don't remember exactly, but when I checked the aux battery voltage it was in the mid 11 volt range before charging.

However, after the dealer had the car for about a month, they claimed the auxiliary battery was no good. The tech said it wouldn't last long enough for the car to finish its diagnostics (or something like that). They put in a new battery.

I have the old battery here. I just checked the voltage. It reads 12.7 volts after sitting (not connected to anything) for a week.

I don't have any real battery capacity test equipment. But, if it would be useful, I can hook an old headlight to it (along with an amp meter and volt meter) and I can give you an idea of its capacity.

Quixotix
Posts: 46
Joined: Sun Jan 08, 2012 8:35 pm
Location: Seattle

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

Tue Sep 18, 2018 8:21 pm

coulomb wrote:They are 1 nF (1000 pF) 3150 V capacitors, as specified in this post: Murata DEHR33F102Kppp . [ Edit: the "ppp" might actually be three special characters that aren't rendering well, but in my PDF reader, these characters show up as empty boxes but match "ppp" in a search. ]


Did anybody notice what the Murata data sheet says about these DEH series capacitors:

See pdf page 60 (paper page 58) in this document: https://www.mouser.com/datasheet/2/281/c85e-522724.pdf
I added the bold.

Applications

Ideal for use on high-frequency pulse circuits such as
a horizontal resonance circuit for CTV and snubber
circuits for switching power supplies.

Do not use these products in any automotive
power train or safety equipment including battery
chargers for electric vehicles and plug-in hybrids.
Only Murata products clearly stipulated as
"for Automotive use" on its catalog can be used
for automobile applications such as power train and
safety equipment.


I guess we use them anyway because there isn't a better option? Do you think it was our MIEVs that caused this statement to be included?

Note: The 3 empty boxes (or ppp) at the end of the part number are where the code letters for the lead style (long, short, crimped, etc) and packaging type go. See pdf page 5 (paper page 3) for the code letters.

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