First of all let me congratulate with all the members of this forum specially with the active members!
I have a Peugeot iOn of 2012 where I have replaced 2 times the Pre-charging resistors of 4.7 ohm in a period of 9 months.
Now I have changed the resistors again, the AC input relay even if measuring it with a milliohmmeter with 10A test current the contact resistance was less than 10 milliohm, that for me it was OK. Once the relay was on my hand I opened it and the contacts were OK, clean. So I changed it for nothing...
Now I have been monitoring the charging current, the relay coil voltage, and the voltage across the 2x4.7 ohm resistors using a Power Quality Analyzer simultaneously.
I hope you can see the images here:https://we.tl/t-C9pWeZmYKR
I have carried out just a few charge processes fully monitored. And in all of them I have noted that the relay coil voltage is always 5V but it has some instability / anomaly period too.
During that period it drops to 3.6V instead of 4.8 / 4.9V for several seconds also several minutes (in another survey even down to 2.6V!). Of course if the coil voltage drops too much, the relay will open and then the resistors blow....
I have tested another relay but same brand and model by my power supply, if the voltage drops down to 1.5-1.7 V it opens its contact, as its nominal voltage coil is 5V. I think that at 3V the force to close the contact will be lower than the normal and this can cause sparks and soon or later the resistors blow too.
The 5V for the relay and its return of come from the top board, and as I have another OBC, I tried swapping the top board including the flat cable, just to insulate the fault, but without success.
Has someone traced the part of the circuit that supplies the coil ? I guess there will be a transistor and some other basic component around it. But the top board works, so probably the problem is in another part.
Can the problem come from the circuits connected to the connector CN101, so from outside the OBC?
I have tested the voltages (5V, 5V, 12V , 16V) on the capacitors on the top board and looks OK (even no ripple) but I have not monitored them by the PQA over the time....
I think to use hot air and cold air to stress some components, but dangerous for the resistors...
Can someone give me any suggestion? Thanks in advance.