Troubleshooting and repair for On-board Charger (OBC)

[coulomb]

Ah, perhaps 401, with vestiges of underlines indicating which side is down. So 400 uH. I have no idea if you can get that value in that size.

Edit: though 400 isn't an E12 value, 390 would be closest. And another nearby similarly sized inductor does look like it's marked 104.

I guess 10mH may be possible in a tiny package with enough iron or other material.

[kiev]

Or how about "102" after blinking at them some more? i can look at them and blink, and it changes from a 4 to a 2 to a 7.
The clear coat on the chips could be removed to help make an id.

[318iEV]

A similar looking inductor L603 on the board reads 101 with a slanted 1



Which could explain the possible "/01"

With dull markings and the reflective clear coat it was borderline impossible to see clearly with the naked eye.

[kiev]

That's a great picture, thanks for posting it. 101= 100uH makes more sense for the smaller filter inductors compared to the larger wound "102" power device at L602.

It appears to have a dot before the slanted 1 , such as used to indicate that the part is lead-free. Maybe the mold maker somehow blundered a bit when setting up the mold die and thats how they all look?

[kiev]

Hello everyone, help determine the type of transistors in the photo


Mod. Edit: https://imgur.com/a/ujtCqpf

That's a tough one--they are covered with epoxy and i have never seen those,

[coulomb]

That's a tough one--they are covered with epoxy and i have never seen those.

Indeed. But any general purpose or switching transistor pair should work.

[kiev]

PM from makey
Hello, I had a lot of MIEV chargers in the repair, and this is my opinion about the 4.7R resistors that are burning.
What do you think if you put a relay with a delay of 3 seconds in parallel with the resistors, and power it from 220V.
For example, here is this https://tervix.ua/product/Tervix/sistem ... c_12_230v/
...
Hello, thank you for answering me
I realized my mistake, it won't work because of the delayed relay :(

I had 10-15 OBC in repair, the malfunctions were different
Errors of previous masters, damage to the wafer plate, but most of all - burnt resistors (4.7R)
After replacing the resistors, they burn again (80%), they burn both at the start of charging and in the middle, after a day or a month ((((

I'm looking for a reason

On the forum, you wrote that the problem is with the 12V battery, but the power supply of the relay is 5V, there cannot be such a large drawdown

maybe during the pause for BMS balancing the relay turns off and does not turn on???
is it possible that the problem is in the FPC -plume?

if you replace the resistors, then you should also replace the AC relay because it is suspect as being the culprit or being damaged also.

If the 12V supply gets a glitch due to an old or weak cell, or sulfated plate in the battery, then it puts a glitch on the 5V supply also, which can drop out the relay--then the 4.7 resistors end up carrying all the current and blow the fuse or burn up. If the relay opens while under high current load, then the contact surface of the relay will be damaged. The OBC controls the current and pulls back the load current whenever it wants to shut itself down; but a sudden or unexpected loss of 5V while the relay is at high current is an abnormal shutdown, and the controller is not fast enough to prevent the damage.

A strong and healthy 12V battery is VERY important for operation of an EV. Most people don't pay enough attention to keeping the 12V fully charged all the time, and making capacity and/or specific gravity checks twice a year. Early detection of a battery getting worn out or weak can help prevent electrical damage of ECUs.

[makey]

I disassembled the two relays to find out what the problem was, the relay contacts were in perfect condition (looking under a microscope) there was no carbon deposits


https://imgur.com/a/P6Wte5C

What do you think about installing a 4700uF (10 000uF) capacitor in the OBC on the VCC (12V)? To compensate for surges in battery voltage

[kiev]

That's good data about the AC relay contact surfaces. So maybe they can be ruled out as culprits.

Consider that the resistors are not in the circuit during charging, they only carry AC power for a very brief time during the initial pre-charge at OBC start up. There is a chain of abnormal events (culprit) leading to the resistor failure (symptom). Just replacing the resistors without correcting the root cause does not solve the problem. Unfortunately it is difficult to test an OBC to troubleshoot this circuit.

Maybe the 5V supply circuit has been compromised by a previous failure, or was the root cause of the initial 4.7R resistor failure?

Without knowing the culprit it is difficult to determine what might be a good solution, e.g. adding large capacitor to the 12V supply.

There are external factors to consider in addition to the internal OBC circuits

[vik013]

Recently we discovered that the charger can be carried away by a faulty standard heater when it begins to flash onto the body.