Matheos
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Re: Troubleshooting and repair for On-board Charger (OBC)

Mon Apr 19, 2021 5:36 am

Have you ask Kiev.? a member here about your problem! Send him a personal message! he has more experience I think!

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

Mon Apr 19, 2021 12:55 pm

No don't send me any personal messages about the ceramic resistors, there is a 20 message limit and my inbox is full--just post your questions for everyone to see. If i or anyone else can contribute something useful, then we will respond.

There are already plenty of discussions about these resistors in this thread, just do a search, or a google search for ceramic resistors on this thread to find them.

The 5V power supply was traced out but i don't recall if there is a schematic posted. It doesn't seem normal for it to be fluctuating and indeed it could cause the fused resistor to blow if it dropped too low and opened the relay. It might also blow the snubber caps on the output side--definitely don't want any uncontrolled interruption during charrging.
kiev = kenny's innovative electric vehicle

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

Mon Apr 19, 2021 5:30 pm

Sandrosan wrote:I think these resistors blow only if there is something wrong, because I think they work just for few seconds on the precharging process of the 3 big capacitors.

Exactly. These are pre-charge resistors, If all goes well, they dissipate zero power after pre-charge because the relay is shorting them.

Sandrosan
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Re: Troubleshooting and repair for On-board Charger (OBC)

Tue Apr 20, 2021 1:32 pm

kiev wrote:No don't send me any personal messages about the ceramic resistors, there is a 20 message limit and my inbox is full--just post your questions for everyone to see. If i or anyone else can contribute something useful, then we will respond.

There are already plenty of discussions about these resistors in this thread, just do a search, or a google search for ceramic resistors on this thread to find them.

The 5V power supply was traced out but i don't recall if there is a schematic posted. It doesn't seem normal for it to be fluctuating and indeed it could cause the fused resistor to blow if it dropped too low and opened the relay. It might also blow the snubber caps on the output side--definitely don't want any uncontrolled interruption during charrging.


Yes Kiev, I do not want to contact you privately, do not worry :-) . I prefer to show the argument in the forum so everybody can see and hope to be of help for someone in future.
I have carried out 2 full charging sessions, and the voltage instability looks depending on the charge current (large currrent more instability). So I guess there is a component that is sufferring the heat. But as I said, the top board has been swapped and the voltage instability remains.
I used the hot air on the upper side of the middle board, but in vane.

You said that the 5v power supply was traced, Ok good thank you. I will review all the 67 pages once again hoping to see the schematic posted. I remeber the tracing but not the schematic.

Thanks in advance to you and all that can give me any advice.

Sandrosan
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Re: Troubleshooting and repair for On-board Charger (OBC)

Tue Apr 20, 2021 1:34 pm

coulomb wrote:
Sandrosan wrote:I think these resistors blow only if there is something wrong, because I think they work just for few seconds on the precharging process of the 3 big capacitors.

Exactly. These are pre-charge resistors, If all goes well, they dissipate zero power after pre-charge because the relay is shorting them.


Thanks Columb.

kiev
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Low Voltage Supplies link

Tue Apr 20, 2021 7:38 pm

@Sandrosan, i found the discussion section about the low voltage power supplies on the control board,
http://myimiev.com/forum/viewtopic.php?f=23&t=4079&start=70#p36876

i have to review my notes to see if i hand-sketched the schematic, seems like i would.

Can you monitor your 12V output of the DCDC to the aux battery during a charge when the fluctuations are happening? If the 12V is unstable then it could affect the 5V supply.
kiev = kenny's innovative electric vehicle

Sandrosan
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Re: Troubleshooting and repair for On-board Charger (OBC)

Wed Apr 21, 2021 4:43 am

@Kiev Thanks very much for the low voltage power supply section.

The 12V output of the DCDC to the aux battery during a charge when the fluctuations are happening remains stable around 14.2 /14.3V.

Do you know where the AC coil relay 5V supply comes from? Which 5V regulator? Where is the transistor that drives the 5V for the coil? My eyes are not good anymore even if magnifier lents...

For your info, at the moment I put an external power supply at 5V that supplies the coil and it is driven by a transistor which base is driven by the original 5V for the coil. In this way I do not charge of the 70 mA necessary to the coil from the original circuit.
Monitoring the original 5V over time the fluctuations are much less in amplitude (the drop of voltage was down to 4.6V instead of 2.6V).
In the second charging session (on the way just while writing) such original 5V looks even more stable (not less than 5.06V).

Of course this is not a cool solution and generally I want to go to the origin of the problem.
But I want to avoid to remove the lower board (which would be great for deep checking specially where the IC702 and IC317 are located and relative components around them).
Also because the car has almost 120K km and the pack has many cells very weak, limiting the Range at 70 km only , in this season.

Another (not so cool, I agree :-) ) solution that I already prepared (but not tested yet) was to I put an external power supply at 5V that supplies the coil and it is driven by a transistor which base is driven by an RC circuit with 2-3 seconds of delay. In this way the AC input relay closes its contacts (and keep them closed) when there is power via EVSE, apart 2-3 seconds at starting point necessary for the precharging the big 3 caps.
Do you or sameone else know if that AC input relay works just for the precharging circuit?
Thanks again!
Sandrosan

Sandrosan
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Location: Milan, Italy

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

Wed Apr 21, 2021 4:44 am

Sandrosan wrote:
coulomb wrote:
Sandrosan wrote:I think these resistors blow only if there is something wrong, because I think they work just for few seconds on the precharging process of the 3 big capacitors.

Exactly. These are pre-charge resistors, If all goes well, they dissipate zero power after pre-charge because the relay is shorting them.


Thanks Columb.


Sorry Coulomb, no Columb :oops:

kiev
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5V buss on the control board

Wed Apr 21, 2021 5:58 am

That 5V relay is held closed constantly during a charging session; the ceramic resistors provide an inrush by-pass circuit to precharge the 3 caps, then when they meet the full condition, the controller commands the 5V to close the relay contacts.

The microcontroller chip, IC701, pin 38 drives the base/gate of transistor TR301, marked "CGRZ" possibly a 2SC5053, thru R302. This transistor pulls the coil return side on pin 25 of the flat ribbon cable to ground.

The 5V relay supply is on pins 26-29 of the flat ribbon cable and is created from the "switched" 12V supply to the OBC (versus the Hot All the Time 12V line). This 12V is supplied from the OBC relay onto the top board connector, CN101 pin 12, and is held up by C701 and C702. If these caps were leaky then the switched 12V might fluctuate.

Also the OBC relay is supplied thru fuse 11 in the fuse box, so the integrity of both the relay and the fuse should be checked. The EV-ECU controls the coil drive for the OBC relay.

The 5V buss that supplies the AC relay on the bottom board is held up by C703, C705, C706 and C840. There is a circuit on the lower side of the control board that measures this 5V thru a unity gain buffer and sends it to the IC701 microcontroller pin 80 for monitoring.

The 5V buss is created using a PWM DCDC converter chip, IC707, NJM2374A, transistor TR702 and diode D717, from the 12V Switched (and fused F701) supply on pin 12 of the CN101 connector. In addition this 5V is used to create the ~16V supply held on C704 and C707 and sent to the bottom board for the gate drive voltage of the waffle plate.

Since you swapped the board and are getting the same behavior, then it is likely some issue with the 12V supply circuit external to the OBC (EV-ECU, fuse, OBC relay, loose terminal in some connector?...)
Last edited by kiev on Wed Apr 21, 2021 2:49 pm, edited 3 times in total.
kiev = kenny's innovative electric vehicle

Sandrosan
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Re: Troubleshooting and repair for On-board Charger (OBC)

Wed Apr 21, 2021 11:06 am

Thanks veeery much Kiev!!
Tomorrow I am going to check all the part of the circuit deeply, which you so gently describe.
But today charging session did not give any fluctuation, just to help me on the troubleshooting.... :)
As I already have swapped the top board few days ago, and the voltage fluctuation remains, the fault should not in it, but we never know.
I will let you know

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