Just a follow up. Eventually it was the middle pin which was the battery presence one. I wired a resistor there and it was able to boot up. But i had some problems supplying enough current to it. It was simply so thirsty :)
Eventually 1A works. Also, i spent some time designing and printing the plastic block to fit in but the first idea was not working. It was killing all the thiny buck converters that i had. So i got some pretty strong DC-DC power supply and converter, set it to 3.8V and now it’s working fine.[br]
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