If the diode were backwards it wouldn't work at all.
The diode seems to be compatible with what comes on the 105C, I get 9 blinks in luxdrv's battmon mode from a cell that measures 3.87v, close enough for me.
Now that I think back, on the big 46mm version, mode changing went goofy as well when I was testing without the big 470uF cap. I'm using this one, should be correct right? Does it just need one rated higher than the 105C's original?
Comfy, I think that capacitor is correct, I think I've seen mentioned that the stock cap is also 10uF. This one should even be better since it's an X7R from a name brand... dunno what's going on there. You could try and stack a second cap on top of that one to see if you get any better results.
I have a separate ground wire stuck right onto the FET's ground pin, testing right now with a battery box with alligator clip leads but I'll be using a separate wire soldered to the inside of the pill, and rely on just a press fit to hold it in place, it's plenty tight like that if you don't completely file off the flashing.
Because he's using this one on a 17mm board where there isn't room for a huge electrolytic cap. We know that it can function from the stock 105C cap., so it should be able to function here as well.
The 470uF/16v on the SRK driver is only for noise reduction, it shouldn't be needed for the MCU to function (but for some reason, it looks like it is letting the MCU work right, because the little 10uF/16v doesn't seem to be enough).
Well…that cap could be storing enough energy to keep the MCU alive at 470μF, opening up that huge MOSFET more than likely causes large voltage sag and drops the power below the MCU voltage range causing it to go all squiffy
But why does it work when you stick the same FET onto a 105C, using all the 105C's original parts? Is it possible the original cap isn't 10uF? There's nothing different about the new PCB, I've checked everything until I'm crosseyed.
At some point for me it comes down to a fresh look after a good nights sleep. Or a big hammer and then a good nights sleep and fresh parts in the morning.