Document Bad Cap Case issue (?)

[nelsonjchen]

commaai/openpilot#36279 ?

Though, it's a bit unclear if @ereish64 fixed their issue by replacing the capacitor or they are just notifying it is bad (edit: they plan to). There was also no measurement taken of the capacitor after it was removed (does it look bad or actually acts bad).

[nelsonjchen]

Would also like to know if/what that bad fuse case applies.

[ereish64]

My Fluke multimeter can't seem to get a reading on the farad values of either of the 1.5F capacitors. When set to Ohms I can see the values changing so it's not shorted. I'll get you exact numbers when I get home.

No fuses were blown in the car from what I can tell. I assume that's what you meant in your second comment.

[nelsonjchen]

No, please see the blown fuse case in this repos docs

[ereish64]

Got it. I'll provide readings on the fuses too when I get back

[ereish64]

Red dot:
starts at one ohm. Drops to 0.3 ohms after a few seconds.

Blue dot:
starts at 0.4 ohms, drops to 0.2 ohms after a few seconds

Green dot:
starts at 0.4 ohms, drops to 0.1 ohms after a few seconds.

[nelsonjchen]

Cool keep me posted with what you do. FWIW, your readings are consistent with the bad fuse case symptoms.

[ereish64]

It appears that changing the capacitors fixed the issue. I used this part from mouser. They're don't quite fit the footprint of the old capacitor, but I was able to squeeze them in. If I were to do it again, I would recommend finding a smaller footprint.

I did break the screen when putting it back together, so I'll need to confirm that the new one works properly when it arrives.

It ain't pretty but it works.

[nelsonjchen]

@ereish64 Do you have a picture of the bad capacitor? We can leave it in here for someone whos better at part hunting to go figure out what was the original. Also, I think I might not have documented that your fuses are still somewhat out of spec though, that is still true right?

[ereish64]

Sure do.

The one fuse did seem to be slightly out of spec based on the datasheet. Although, everything seems to still be functioning as it should after the capacitor replacement. Maybe 0.3 is on the edge?

[nelsonjchen]

maybe, but it's certainly not how it's supposed to perform from the datasheet anymore.

[ereish64]

Your certianly correct there.

I also noticed that the super capacitors have a max temperature of 85C. After checking the fuses datasheet here it's interesting to see that the fuses also have a max rated temperature of 85C. Most other parts are rated for 105C...