I contacted a local battery builder to make me that 10s4p battery. So far to me it looks Allright. It uses second hand e bike batteries (Sanyo NCR18650ga). He showed me a picture that displays the total batteries capacity using his imax b6. I have no idea how those things work.
He only used a normal welder, not a spot welder. What do you have to look out for when buying a battery like this?
By the way the Bms balance cables still need to be soldered on, he is doing that right now, we have had a small miscommunication Here are some pictures