The Troubleshooting and Repair for On-board Charger (OBC) Thread

[DBMandrake]

Here is a simplified functional schematic of the OBC, MCU and Pack, showing details of the HV DC Output section with the snubber caps and MCU fuse that seems to blow.

The snubber caps in my OBC were definitely 2kV not 3kV as shown in your diagram - one was undamaged and easy to read. I fitted 6kV replacements which were approximately 3x as thick as the original discs.

During charging there is about 10 Amps of current from the OBC to the Pack thru the MCU 20A fuse.

The DC/DC converter can draw more than 10 amps though when the car is being driven I presume ? Otherwise why make the fuses more than double the current drawn - which actually peaks at less than 9 amps while charging.

The 20A fuse in the OBC has never been found to blow even though it is in the same current path as the MCU fuse?

Ok that's new to me - are you referring to the fuse on the corner of the main PCB not far from the snubber caps ? I thought that fuse was on the input side of the charger ? If it's directly in series with the other fuse why bother to have both ?

Anyway as to why doesn't it blow instead - it's not that surprising. While they're both nominally 20 amps they're significantly different in design and will have different fusing speeds. If the triggering event is a snubber going shorted (which is still what I favour) then whichever fuse is a faster fusing type is going to blow first and save the other one... it's possible of course that the other fuse has now been "stressed" and could potentially fail in the future.

BTW the snubber caps are not connected to the output of a regular 4 diode bridge as shown as far as I remember - they're connected to the maximum output branch of that large conglomeration of diodes on the waffle plate shown on one of your earlier hand drawn diagrams ? I assume the diagram above is simplified to ignore this ? Too much simplification of the actual circuit may make it impossible for us to analyse possible fault causes.

 

[coulomb]

The DC/DC converter can draw more than 10 amps though when the car is being driven I presume ?

I'd say a max of about 4 A. Say 14 V x 80 A + losses ≅ 1200 W; 1200 W / 360 V = 3.3 A.

Otherwise why make the fuses more than double the current drawn - which actually peaks at less than 9 amps while charging.

Maybe when they started with 10 A fuses, they blew even more often?

Ok that's new to me - are you referring to the fuse on the corner of the main PCB not far from the snubber caps ?

It would be, yes. F102.

I thought that fuse was on the input side of the charger ?

That's F103 in the top board with the processor.

If it's directly in series with the other fuse why bother to have both ?

Because there are two sources of power: the charger, and the battery. A short in the middle potentially needs to be cleared from both sides [ edit: was "from either side". ]

If the triggering event is a snubber going shorted (which is still what I favour)...

I favoured that theory too. But I've just thought of another possibility. The battery voltage will fluctuate significantly and quickly with traction power and heavy regenerative braking. And as the battery ages and its internal resistance increases, the fluctuations grow over time. The high dV/dt will cause current to flow through the two fuses, as capacitor C115 has significant capacitance and will resist the change of voltage. This current might fatigue the two fuses. Perhaps the MCU fuse also sees more of the DC-DC current, and so fatigues faster than the one on the charger output. This fatigue causes the MCU fuse to blow, causing the inductive kick that blows up the under specified snubber capacitors.

The solution would appear to require a relay between the charger output and the MCU, before the take-off to the DC-DC converter, so that the charger output is disconnected from the battery when not actually charging. Alas, this will need pre-charging, so that's another relay. Or some mechanism as in the Elcon/TC chargers where the relay always switches at near zero volts. The DC-DC converter might also need some protection, if it has a large capacitor at its input. I wonder if the later charger models have this feature?

BTW the snubber caps are not connected to the output of a regular 4 diode bridge as shown as far as I remember - they're connected to the maximum output branch of that large conglomeration of diodes on the waffle plate shown on one of your earlier hand drawn diagrams ?

[ Edit: I don't think that Kiev's simplification is leaving anything important out. There are two diode bridges in series, with back diodes across each full bridge. The diode arrangement is shown in the revised schematic in this post. It's unusual (to me), but I don't believe that it affects the operation in any material way. ]

 

[kiev]

The OBC fuse is smaller and difficult to see when all the wiring is in place, but this post has a picture of a bare board and the fuse is soldered next to the resistor R104.

http://myimiev.com/forum/viewtopic.php?f=23&t=4079&start=190#p37447

 

[coulomb]

this post has a picture of a bare board and the fuse is soldered next to the resistor R104.

This post shows it is F102 (even clearer in the lower photo).

 

[kiev]

The first post by Dionisiy7 on the previous page has a later version of the waffle plate schematic showing how the 10 diodes are arranged.

The hand notes were posted just for the voltage drop info for testing a WP. Those were made early on while i was guess-tracing everything, but much later i was able to see the xray and draw the circuit.

 

[Sandrosan]

Thanks Kiev, Coulomb and DBMndrake for your valuable comments. Thanks also for the simplified diagram that is very clear for me.

So if my understanding is correct, there are 2 theories:

Theory N 1, the more favoured, a voltage spike triggers the snubber capacitors and then the fuse blows.
Do you think this voltage spike come from AC mains?
If so to replace the triggered snubber caps with more robust ones like at 6kV is a good suggestion?


Theory N 2, (given by Coulomb ) new and I think it can exist side by side the theory N 1.
"The battery voltage will fluctuate significantly and quickly with traction power and heavy regenerative braking. And as the battery ages and its internal resistance increases, the fluctuations grow over time. The high dV/dt will cause current to flow through the two fuses, as capacitor C115 has significant capacitance and will resist the change of voltage. This current might fatigue the two fuses. Perhaps the MCU fuse also sees more of the DC-DC current, and so fatigues faster than the one on the charger output. This fatigue causes the MCU fuse to blow, causing the inductive kick that blows up the under specified snubber capacitors".

Again, to replace the triggered snubber caps with more robust ones like at 6kV is a good suggestion?

Please DBMandrke do not intend my words a critic, I just try to understand more on our cars. Thanks to all.
Sandrosan

 

[Virusman]

Hi Guys, few weeks ago I recived another charger with blowed up blue capacitors.
Replaced them and send back charger.
Now I get it back again. It's not charging.

For the firs time I saw that one of the three capcitor is a little bigger.

Voltage on PFC is 316,9V I'm using true rms multimeter.
Is it okay or it's too low? It's because one of the electrolitic capacitor is broken?

Another think is, when I power up pin 12 and 7 on CN101 and connect 230VAC I don't hear Relay? It's ok?

 

[kiev]

Hi Guys, few weeks ago I recived another charger with blowed up blue capacitors.
Replaced them and send back charger.
Now I get it back again. It's not charging.

For the firs time I saw that one of the three capcitor is a little bigger.

Voltage on PFC is 316,9V I'm using true rms multimeter.
Is it okay or it's too low? It's because one of the electrolitic capacitor is broken?

Another think is, when I power up pin 12 and 7 on CN101 and connect 230VAC I don't hear Relay? It's ok?

1. Did they also replace the fuse in the MCU? Usually that also blows when the blue snubber capacitors are blown in the OBC.

2. With 230 VAC input voltage then the PFC voltage seems okay since it will be adjusted thru the boost switching section transformers to match the pack voltage on the output. The electrolytics can swell due to temperature and still function okay. It may be degraded with respect to a new one but is not likely the issue. The car will throw a DTC code for faults within the OBC, can they get a readout of the trouble codes for you?

3. The relay should only come on if the EV-ECU sends the CAN command to start charging. It is looking at the charging plug communication lines for the J1772 protocol signals. Powering up the 12V pins is only useful for troubleshooting the low voltage supplies created on the control board (3.3, 5, 16V).

 

[kiev]

Hello. I have the same problem I've seen in this forum. The car has stopped charging. As I unscrewed it, I noticed that the R106 resistor is damaged. This is a resistor to limit the charging current of three 680 uF capacitors. After replacement for a working one, nothing has changed. After connecting the car to 230V, the fan cooling battery turns on for a moment, 350V appears on power factor improvement and in a second a yellow exclamation mark appears and immediately turns off Power factor improvement and the voltage begins to drop on 680 uF capacitors. There are no control signals on the T501 T502 transformers. Error P1A12 appears. I checked all the components that are in the big black cube (transistors and bridge rectifier.) I checked the relay. I noticed that there is a circuit that checks the voltage drop across resistors. All components are functional (D312 D311 D315 D316)

Did someone solve a similar problem?

I wonder why the relay turned off during charging (which caused the r106 resistors to burn)? this relay is controlled by a microcontroller located on the top board.
It is possible that power factor improvement creates too low voltage, and for this nothing further works? The capacitors are at 420 V, and it creates 350V. Maybe it should be 370V or 400V for example?
Diagram of the entire layout ( https://drive.google.com/file/d/1tHilCxdM7tmisq-a1U_R6NnYbFyOVV85/view )

thank you for the diagram with notes, that is a nice version.

Did you check the R105 next to R106? It is a resistor with an internal fuse, and if 106 was damaged then i would expect that R105 would be also.

The P1A12 DTC is a code to indicate an abnormal stop of the OBC. There are internal trouble codes for the OBC that can be read with the MUT tool to indicate which area is failed, but only the dealers have access to that tool.

The PFC voltage seems okay or maybe a little bit high, depends upon your input AC voltage.

Did you verify that the AC relay will function when the coil is driven with 5V? Mind the polarity during this check, and have nothing else connected (remove the flat ribbon cable on CN101).

If the relay doesn't come on during charging then the entire AC voltage is carried thru the big ceramic resistors, which can cause them to fail. Maybe the relay was damaged and should be replaced also. Read the posts by skylogger as he had to do this repair.

The EV-ECU sends the CAN commands to begin charging once it negotiates the signals with the EVSE. This will engage the AC relay, but the PFC voltage will be created momentarily thru the path of the ceramic resistor and sensed by the microcontroller. But then the relay must come on quickly to unload the resistors.

What about the fuse on the upper control board, F701, is it okay? picture of it here, http://myimiev.com/forum/viewtopic.php?f=23&t=4079&start=70#p36883

 

[Virusman]

1. Did they also replace the fuse in the MCU? Usually that also blows when the blue snubber capacitors are blown in the OBC.

2. With 230 VAC input voltage then the PFC voltage seems okay since it will be adjusted thru the boost switching section transformers to match the pack voltage on the output. The electrolytics can swell due to temperature and still function okay. It may be degraded with respect to a new one but is not likely the issue. The car will throw a DTC code for faults within the OBC, can they get a readout of the trouble codes for you?

3. The relay should only come on if the EV-ECU sends the CAN command to start charging. It is looking at the charging plug communication lines for the J1772 protocol signals. Powering up the 12V pins is only useful for troubleshooting the low voltage supplies created on the control board (3.3, 5, 16V).

From my information they first install this charger check if it's ok, it's not. After that they install the first one which also was repaired by me and it's works fine.
What do You think, what more I can check ?

 

[kiev]

i know it's long, but how much of this thread have you been able to read? The first 2 posts have an index and links to other failures, there is also some schematics links.

On page 45 is a schematic with the diode voltages that you can use to check if the high power semiconductors are shorted or open. These are measured at the solder joints on the bottom board. Dionisis posted a really nice cleaned up version up a few posts on the previous page.

i don't know how to check a unit without in a car, we just don't know how to command (CAN buss) to make it work on a test bench. i usually start at the beginning, where the AC comes in and just measure and check every component in the path, check the diode drops, and check the output circuit. Look for burnt or damaged parts. e.g. look at the little diode D301 across the AC relay coil circuit--if it is shorted then the relay won't be able to work.

 

[Virusman]

i know it's long, but how much of this thread have you been able to read?

belive me... maybe not all but a lot of from this thread.
neverminde

I found something, this one diode is shorted. Is it DF20L60U?
My plan is to desolder waffle plate, cut leads and solder in that place new diode, I think I should put diode as close as possible bottom plate (heat sink) what is your opinion about that?

 

[kiev]

i had a really hard time trying to cut thru the black epoxy, but if you could remove it then it should be possible to replace the diode(s).

Did you happen to see the picture on page 6
http://myimiev.com/forum/viewtopic.php?f=23&t=4079&start=50#p36810

it shows the layout of the diodes. That schematic you are using was made before i had access to see the actual arrangement--there are 10 diodes in the upper right quadrant of the waffle plate.

 

[Virusman]

Hi, I checked once again the diodes with this new schematic (10 diodes). I disconect all connection I check once again and figured out thtat diodes are ok but connection betweend diodes and trafo's is not. I have to wait for my phone, I got there some pictures from previous repair and I will able to check thtat connection with photos. Before me France guys try to repair it, maybe they make a mistake with connection.

 

[Virusman]

Hi again guys, could some one check connection on board for two trafos?
See photo beloow:

 

[kiev]

Looking at your picture--do you have the BLUE and GREEN on the wrong Tabs? They appear to be reversed, but it is hard to see from that picture.

i think you have the secondary sides of the transformers correct. T5 and T6 are the secondary outputs of transformer 1; and T7 and T8 are outputs for trans 2.

The primary side is the T1A and T1B, which should have BLUE wires coming off the Faston tabs of the board and right next to the Y1 tab (yellow wire to T5).

The other primary wire is the T4A and T4B, which have GREEN wires in the Faston tab covers.

When i put them back together, i start at the bottom of the tabs with the GREENs, then the BLUEs, then Yellow1 and Black1, followed by Black 2 and Yellow 2.

The Output filter coils N and P, are the Gray and Red wires; those appear okay.

 

[Virusman]

THX. Looks ok, green and blue are in the same order as on your schematic.

 

[bigpete]

Hello Kiev,
I changed all this components :

Both 4.7ohm resistor were fused
2.2µF capacitor was inflated
One of three 680µF capacitors was inflated, (I changed three)

To prevent other failures, I changed both 1000pF capacitors, and the relay

I just tested the 12VDC on the 12th pin
With the charrger cable not connected, I get 0VDC
With the charrger cable connected, I get 12VDC for 2 or 3 seconds, and it stops

If I connect my Icarsoft I970, I get this message :
What do you think?

Hi, I have also a problem like yours and plan to replace the same parts in a attempt to fix it. Do you have a copy of your parts order? Need to know which parts and where I can buy them? I live in Norway and here we got 220V, what do you have (in order to get the correct parts)?

 

[bigpete]

Those are great looking snubber caps and a super find to get 6kV rating. Awesome solder job too.

Thanks.

These are the caps I ordered, however I notice that the picture shown is NOT accurate as the ones I received were orange, not yellow, and a lot thicker:

https://uk.rs-online.com/web/p/ceramic-single-layer-capacitors/8313240/

I suspect the picture is from a lower rated capacitor in the same series.

This isn't very pretty but has the measured diode drop voltages on a good waffle plate, with no caps or inductors connected with the fastons.

When you say with no capacitors connected do you mean the electrolytics were removed ?

Thanks for the post, very helpful. I have ordered the capacitors from RS but they are out of stock so I have to wait until april 30. Does anyone knows other places to order these capacitors from?

 

[misterbleepy]

Thanks for the post, very helpful. I have ordered the capacitors from RS but they are out of stock so I have to wait until april 30. Does anyone knows other places to order these capacitors from?

This looks like a similar one to that:

https://uk.farnell.com/vishay/s102m59z5uu83l0r/cap-disc-z5u-1000pf-6kv-radial/dp/2944275?st=1nF%206kV#