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

Posted: Sun Oct 07, 2018 2:52 pm
by electronpusher
ChristopheFR wrote:Electronpusher : I forgot in my last message : félicitation pour cette excellente nouvelle! :P


Merci, j'espère que votre solution va bien.

Excuse my translation, I cannot speak French so used google.

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

Posted: Sun Oct 07, 2018 4:55 pm
by coulomb
ChristopheFR wrote: We also see that the rubbery potting has boiled.

Actually, that grey stuff looks rather similar to some goo that oozed from a similar capacitor (also 2.2 μF across the line) in an Elcon/TC charger:

Image

(From https://www.diyelectriccar.com/forums/s ... ost1019597, in case you are interested in all the details. )

With closer inspection, does it appear to have come from the capacitor? It might be the outer epoxy that's for fire extinguishing. It may have gotten too hot from the resistor that overheated.

1) should I change the capacitor as a precaution?

Given the above, and the difficulty of getting to these components, I'd say definitely yes.

I have not found a supplier in Europe for the Okaya capacitor, do you think that one is correct?
https://content.kemet.com/datasheets/KE ... X2_310.pdf

I agree with Kiev, that replacement appears to be suitable, as long as the lead spacing of 27.5 mm is the same as the PCB hole spacing, as it very likely is (these parts are thankfully pretty standardized). However, the Kemet is rated for -40°C to +110°C, whereas the 310 V Okayas seem to be rated for -55°C to +110°C. If your vehicle is likely to see temperatures below -40°C when parked (it will get nice and warm after operating for a few minutes), then you might want to find a wider temperature range replacement.

The Okaya data seems very sparse compared to the Kemet's.

[ Edit: changed Okaya link to the LE-MX PDF file. I initially read LF. ]

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

Posted: Sun Oct 07, 2018 10:33 pm
by skylogger
ChristopheFR:

In this picture, the resistor on the left is the faulty resistor that I removed from the charger that I fixed.
It appears to have a 7 watt rating.
The resistor in the middle is a close equivalent that I found and purchased from DIGIKEY online and shipped from the USA.
The setup on the right is two 2.7 ohm resistors in series, which gives 5.4 ohms and they are rated at 5 watts but these are in series and are also in series with the other 4.7R Resistor in the doghouse. The leads could be formed like shown so it would still fit into the PCB.
I was looking at using this as an alternative until I found the Digikey option.

Image

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

Posted: Mon Oct 08, 2018 4:35 am
by coulomb
I worry that while the TE Connectivity (guessed by the CGS marking) part is rated for 10 times nominal power for 5 seconds, a cheapo 5 W resistor is rated for only 5 times nominal power for 5 seconds. [ Edit: guessing the TE Connectivity SQ series. ]

This is in a part that will see 120 VAC (presuming 240 VAC at the input, after diode drops) for a fraction of one second. That's P = E²/R = 120²/4.7 = 3064 W! That's 438x its nominal power. Granted, that power pulse dies away quickly and exponentially, but I don't think you want to skimp on pre-charge resistor quality.

For any pre-charge application, I usually like to use the HS series of aluminium cased resistor, which can handle 25 times nominal power for a second, but they would be really awkward to mount. It looks like the originals will last just fine as long as nothing else fails, so I don't think we need to bolt one of those to the chassis. Though something to keep in mind if they do start to blow too frequently.

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

Posted: Mon Oct 08, 2018 10:57 am
by ChristopheFR
Thank you for your answers to all.

To repair my PCB, I'll ask a friend to do the work, he has an electronics lab at the university.

I just have to buy all the components, and to remove the rubbery potting.
Are there small components hidden under the rubbery potting?

The P10K resistor is composed of a resistor and a thermal fuse, and I have found no equivalent in Europe.

I found a resistor 5w and 4.7 ohm equivalent at Digi-key, but without thermal fuse.
Is there a fire hazard?

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

Posted: Mon Oct 08, 2018 4:06 pm
by skylogger
ChristophER:

4.7R at 5watts is a probably not good enough, as the original was a 7 watt rating. Try looking for the 7 watt or or 10 watt versions on
Digikey.

When you test the relay, you might want to try opening and closing it 20 or 30 times and see that it goes to zero ohms each time.
with micro pitting on the contacts , you might find that majority of times, the relay closes ok, and 1 or 2 times its intermittent.
If the relay does not close 100% then current will still flow through resistors for too long and cause them to burn out.

I ended up using the 7W resistor that I found on Digikey, which was the closest I could find to the original at the time.
If I work on another charger with this problem, or re-work this one, It probably would be better to improve on the original
part since this seems to be a weak point of the original design. I found several versions of 10 watt resistors on Digikey
some radial (two leads coming out of same end) and some axial. The Axial lead could be bent over and extended to
still fit the pcb layout. Most of the 10 watt resistors I found seemed to be smaller diameter and longer, and the length
became a problem as it would be too tall and probably bump into the controller PCB on top. I was also looking at
maybe using 2x 10 ohm 5 watt resistors in parallel which would be 5 ohms at 10 watts total, but lead forming was a problem.
COULOMB Brought up a good point that in the more detailed specs on the resistors, they give a wattage rating over a period of time.
So finding resistors with a higher peak wattage rating for a short period of time would be beneficial.

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

Posted: Thu Oct 18, 2018 12:29 am
by skylogger
Hi Kiev , Coulomb:
I might get a chance to work on another IMIEV Charger. I got a call last week that another member of the AEVA (Australian EV Association) has a IMIEV that is causing problems when plugging into the Bollards at the University of WA to charge, and so far it has caused two of the Bollards (EVSE Charge stations) to fail. When the car is plugged into other public charging stations, it works ok, and no damage to the charging stations. The person that normally looks after the charging stations at the Uni is away sick at the moment, so I think the two charging stations are still down. The persion with this car, is having the OBC replaced to resolve the issue so they can continue using the Uni's charging stations in the future. The charger is being replaced by a EV servicing place in Perth, and I asked the owner of the car if I could have the bad charger once this is completed (around 4 weeks to get the new charger from Mitsubishi). The owner of the car wanted it done this way so as to have a waranty on the repairs.

My theory of what the problem is: If the relay contacts weld short and are always bypassing the 2x 4.7 ohm resistors, Then when the charger is first connected to the charging station, a big surge of current is presented to the charging station. Inside the charging station, a fuse, circuit breaker, or maybe some circuit damage has occurred due to the surge. The two Uni charging stations are only designed to handle a 20 amp max load. The other charging stations that the owner has plugged into have 32 amp max loads. I think the other public station that is being used happens to be robust enough to cope with the surge current from the damaged pre-charge circuit. The two Uni charging stations are not commercial units but were built by the Uni itself.

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

Posted: Thu Oct 18, 2018 12:39 am
by mikedufty
That's interesting. I had to replace the plug on our stock charging cord (2010 one with no EVSE) shortly before the charger failed as it was melting and falling apart. I wonder if issues with the charger might have contributed to that, or issues with the plug might have contributed to the charger issue - there was some arcing in the plug just before it was replaced.

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

Posted: Thu Oct 18, 2018 5:25 am
by kiev
Howdy skylogger,

At first i wouldn't think this possible, but then you noted that these were home-built evse units that failed--so we don't know what they are doing within with respect to the charging protocol, ground checks, communications, etc., and i think you have a good theory.

i hope you get to take a look at fixing that OBC and can confirm the suspect relay.

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

Posted: Thu Oct 18, 2018 5:37 pm
by skylogger
mikeduffy:
It sounds like you had the charger replaced under warranty, but are are still having issues at the dealership?
I sent you a PM, and I might have spare parts that could be used to trouble shoot EV-ECU issue.
Is it possible for you to get your hand on / keep the original broken charger? I would be interested in having a look at it
and using it for research if you can get your hands on it. (If dealership does not require keeping it under warranty conditions)