Hello, I have nokia n900 with broken micro USB port. I want to do something like pic related myself. Any protips? Cutting of normal USB ←→ micro USB cable and connecting it to some conductor would work? How to make case if I don't have 3D printer?
Sorry, what's the "do something"? A battery and a charger? You can replace the battery with whatever you want usually, it'll be +, -, and a temp sensor connector which you can usually leave off or short with a resistor. Some modern ones use digital temp sensors or have some sort of 1-Wire interface to the battery which makes it harder to reuse.
Keep an eye on the voltage too, most of them use 1S LiPo cells so take 3.7V - you can use a buck regulator to go down from whatever you want.