Lic wrote: I think I will try to open MCU and look condenser, but I am not sure what exactly to check. Any suggestions?
I would think it's not likely to be the capacitor ("condenser" is an ancient term for capacitor); it would have to have *extra* capacitance to cause this problem. [ Edit: Sigh. I contradict myself below; it could also be that the capacitor has very high leakage, but that seems unlikely. ] I think it's more likely to be one of
- Pre-charge resistor
- Pre-charge or one of the main contactors (positive or negative)
- Something causing extra load on the high voltage side, e.g. blown components in the MCU, or more likely given the history we've seen, the On Board Charrger. In particular, it might be those small capacitors in the OBC that blow so frequently. If the DC-DC and OBC 20 A fuse hasn't blown but those capacitors are shorted, then you won't be able to achieve ready.
- The auxiliary battery, especially since it's had ample time to discharge with all the little loads that cars have, and we know that a weak auxiliary battery can cause all sorts of problems. In particular, it might not be able to pull in three contactors, if it's really weak.
It could be the capacitor in the motor controller having very high leakage, but it would need to be nearly a dead short for that leakage to prevent readiness. That's the only part mentioned above that's in the MCU (apart from the 20 A fuse, and it's accessible via a cover), and inside you will see this:
The capacitor is the large black thing with "MEIDEN" written on it. Unless it's melted or otherwise visibly deformed, I doubt that you'll be able to determine much by looking at it, unfortunately.
Only the auxiliary battery is easy to test/fix. Give it a charge with a 12 V charrger, since the DC-DC can't charge if from the traction battery without achieving ready (battery connected to HV circuits, such as DC-DC input). If it's older than say 3 years, replace it. If none of that helps, you'll need to try and measure the drain on the high voltage bus, without electroplating yourself. How confident are you with this sort of thing? I've heard of people activating contactors manually and measuring the resistance of the pre-charge resistor, but this is far from trivial if you're not set up for that sort of thing, and of course one end of the resistor you'd be measuring is connected to traction battery positive.