Successful battery change on Macbook Air 13 mid-2012.
After screwing in the new battery, I couldn't connect it to the motherboard. I was afraid of damaging the connection and the rest of the components.
So it seemed easier to me to unscrew the new battery, then plug it in and finally screw it back in one last time. I think that this step lacks a point of precision in terms of reassembly.
Otherwise, it's a good tutorial, thank you very much!