mikedufty
Posts: 25
Joined: Tue Apr 05, 2016 1:04 am
Location: Western Australia

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

Thu Oct 18, 2018 5:52 pm

I'll give you a call. I did ask about keeping the old charger and they said I couldn't but I might try again once it is fixed.

coulomb
Posts: 106
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

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

Thu Oct 18, 2018 7:02 pm

I happened across this today, from the DiyElectricCar.com forum, DIY Tesla Controller topic:

"Root cause of the drive unit inverter failures discovered and fixed.
NOT caused by overcurrent through the igbts but rather the combination of using 8.8kHz switching frequency through a very low inductance stator and the sudden release of the main contactor on an overcurrent detection. The small drive unit inverter works perfectly at 17.6khz switching frequency and setting tripmode to prechon ensures the pre charge resistor can provide a path back to the battery during release of the main contactor. This was tested to the Nth degree on my recent trip to Romania :) "


Jack is talking about a motor controller here, but it's still a power conversion circuit. It looks like he's saying that as long as the pre-charge resistor exists across the main contactor, then there is a path back to the battery for the energy in the switching inductor (in this case, the stator of the induction motor).

  • In the case of the On Board Charrger, we have the pre-charge resistor across the relay all the time, so if the relay opens, there is still a path back to the battery. [ Edit: duh, it's back to the mains. This is probably not relevant. ]
  • Of course, if the pre-charge resistor has failed, then this is not the case.
  • If the fuse located in the motor controller opens for any reason, then there is no path back to the battery. So something inside the charrger has to "take the hit", and it looks like these capacitors are it. It might be worth installing much larger replacements, possibly with a high pulse power series resistor, which could absorb that energy. The Elcon/TC charrgers have several such RC networks, and I've wondered what their purpose is. They have often failed too, suggesting that they are also under-specified.
  • We know that the fuse blowing is a not uncommon event. Also not uncommon is for those blue capacitors, which are physically but not electrically near the pre-charge resistors and relay, to blow in spectacular fashion.
  • I think that the lesson is that if [ either of ] the fuse [ or the pre-charge resistors ] goes open circuit, then we can expect the capacitors to have to absorb the energy of the inductors, and it seems that they are not large enough to cope with this amount of energy. [ Edit: and of course, capacitors are not normally dissipative elements. Hence the suggestion of a high pulse-power resistor in series. ]
  • It's unclear to me at this point whether suddenly taking away the AC input is a similar event; I'll ponder more.
  • Suddenly losing altogether or having weak 12 VDC power to the charrger may trigger a similar event. It's just not known whether the processor has the ability to detect low 12 V power, or the 5 or 3.3 V that the processor works from. Perhaps it does and shuts down the charge current cleanly, but the manufacturer quite possibly didn't bother.
  • It remains my belief that they pre-charge resistors in the charrger are a little weak for the peak load that they are expected to withstand every time the power to the charrger is turned on. We've seen several but by no means all pre-charge resistors burned, and I don't think we can establish cause and effect as yet. [ Edit: as per the first point, this seems irrelevant to the sudden interruption theory. ]

[ Edit: incorrect smiley strength in quotation :D ]
Last edited by coulomb on Fri Oct 19, 2018 9:07 pm, edited 1 time in total.

pbui19
Posts: 143
Joined: Tue Jan 07, 2014 12:17 pm

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

Fri Oct 19, 2018 1:46 pm

hello - am I understanding this correctly that these cap and resistor are there to protect the relay contact, mainly upon disconnect ? if so, would it more prudent to turn off charging externally by turning off the EVSE AC power rather relying on the relay contact ? am just looking for some preemptive action to protect the inverter/charger. Then what's up trying to keep the inverter/charger cool ?

thanks

Phximiev
Posts: 1187
Joined: Thu Jan 15, 2015 7:25 pm
Location: Phoenix

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

Fri Oct 19, 2018 3:09 pm

Phximiev wrote:Great job! Now is that the same board that controls the charging rate? And if so, how can the charging rate be increased?

:idea:


Just a follow-up and out of curiosity, but has anyone thought about this question in terms of modifying or repairing the board?
2012 iMIEV ES
2014 Chevy Volt

coulomb
Posts: 106
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

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

Fri Oct 19, 2018 6:46 pm

pbui19 wrote: am I understanding this correctly that these cap and resistor are there to protect the relay contact, mainly upon disconnect ?

No. The relay merely shorts the pre-charge resistors, so that full power is available for charging. Certainly, it's best to stop charging by the switch on the J1772 connector. My theory is that the problem is due to some abnormal stopping of charging, and we don't know the reason(s) for this(these) as yet.

But as I try to explain this, I realise I'm very rusty on the fundamentals, and need to think about this a bit more. Sorry if I've caused confusion.

ChristopheFR
Posts: 13
Joined: Sat Aug 11, 2018 1:08 am

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

Sun Oct 21, 2018 8:58 am

Hello tout le monde

I have a question about the resistor P10K

Here is the technical sheet: https://imgur.com/6vaxWtx

first page is 10 watts:
second page is 5 watts
Image
Image

Is the power 5 Watt or 10 Watt?

I found a resistor 7 watt, and its height is 39 mm, so I just have raise the first pcb 5 mm and it's ok.
https://imgur.com/MUjXuPC

What do you think? I replace both resistors 4R7 by two resistors 7 watt?

DBMandrake
Posts: 77
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

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

Sun Oct 21, 2018 9:57 am

coulomb wrote:
pbui19 wrote: am I understanding this correctly that these cap and resistor are there to protect the relay contact, mainly upon disconnect ?

No. The relay merely shorts the pre-charge resistors, so that full power is available for charging. Certainly, it's best to stop charging by the switch on the J1772 connector. My theory is that the problem is due to some abnormal stopping of charging, and we don't know the reason(s) for this(these) as yet.

Not all J1772 plugs have switches fitted to the trigger, it's an optional part of the spec. My Rolec charger charger for example does not have a switch on the trigger, and I don't think the OEM granny charger does either.

So unplugging this type of charger relies on the pilot signal breaking before the Phase and Neutral.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

JoeS
Site Moderator
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Location: Los Altos Hills, California

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

Sun Oct 21, 2018 2:32 pm

DBMandrake wrote:Not all J1772 plugs have switches fitted to the trigger, it's an optional part of the spec...
Interesting, as in North America I've never seen a J1772 plug without a disconnect switch. Checking out Wikipedia, the schematic shows a switch in the handle. https://en.wikipedia.org/wiki/SAE_J1772 Perhaps an older version of J1772 allowed that?

Worried about the abrupt current interruption using my 240vac mechanical timer, I was actually looking at this schematic with the idea of opening up the handle and have my mechanical charging timer simply replace the handle switch in order to gracefully cut off power to the car... :roll: :geek:
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

skylogger
Posts: 70
Joined: Sun Dec 14, 2014 3:54 am

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

Sun Oct 21, 2018 5:09 pm

ChristophER:
Interesting find on the data sheet for the resistor. I read this a couple of times, and it sounds like they take the "pellet" of a 10 watt rated resistor and add the thermal link, and the addition of the link causes the overall rating of the device to be de-rated to down to 5 watts.
It is interesting that based on this, it looks like between the two resistors, they are putting a 5 watt (with thermal link) in series with a 7 watt.
I'm thinking at the end of the day, it's going to come down to picking what resistors you can actually get your hands on. using 2x 7 watt resistors would be better than the original 5 watt and 7 watt combination in one way, but does the version you found have a thermal link? I guess when you look at the case I had, The 7 watt resistor that did not have the thermal link was the one that blew open, so the thermal link did not actually protect that one.

JoeS: using the timer in the circuit of the gun trigger sounds like a good idea. That would definately allow the charger to go through its natural shut down proceedure in a safe way before the mains voltage is disconnected.

DBMandrake:
On all the 2010 IMIEVs here in Australia with the original charger cord (no EVSE), The connector "Guns" have the trigger that connects the proximity pin to ground when the trigger is released. All of the EVSE and charging stations I've come across here in Australia also have the Trigger/latch. I once came across trying to use a LEAF EVSE on my IMIEV, and thought I had a faulty EVSE, but when I jiggled the gun it started working. I found the trigger assembly had a latch across the top of the connector that was a tiny bit wide and did not smoothly easily drop into the grove on the car connector. This was keeping the trigger from fully releasing and making the ground connection to the proximity pin. I filed down the plastic on the latch and coud then use the EVSE without issue.

DBMandrake
Posts: 77
Joined: Mon Mar 20, 2017 4:57 am
Location: Scotland

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

Sun Oct 21, 2018 10:02 pm

skylogger wrote:DBMandrake:
On all the 2010 IMIEVs here in Australia with the original charger cord (no EVSE), The connector "Guns" have the trigger that connects the proximity pin to ground when the trigger is released. All of the EVSE and charging stations I've come across here in Australia also have the Trigger/latch. I once came across trying to use a LEAF EVSE on my IMIEV, and thought I had a faulty EVSE, but when I jiggled the gun it started working. I found the trigger assembly had a latch across the top of the connector that was a tiny bit wide and did not smoothly easily drop into the grove on the car connector. This was keeping the trigger from fully releasing and making the ground connection to the proximity pin. I filed down the plastic on the latch and coud then use the EVSE without issue.

They all have the trigger as it is also part of the mechanical latch that holds the plug in.

But try pressing the trigger while the car is charging to see if it stops the charging - with my Rolec charger it definitely continues to charge while the trigger is pressed and does not stop until the plug is physically removed.

I'd have to test it again to be 100% sure, but I think my OEM Yazaki charger that came with the car is the same.

Circuit diagrams typically show the trigger as having a switch connected but I don't think it was ever a mandatory part of the spec, and the pilot line uses a shorter pin that is designed to disconnect first when the plug is withdrawn, this causes the charging to stop cleanly before the AC lines are disconnected to prevent arcing etc.
- Simon

EV: 2011 Peugeot Ion
ICE: 1997 Citroen Xantia V6

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