URGENT...4s lipo arcing or something on connection

Good day, I am currently building a qav400 and using a pixhawk. I soldered all 4 ESCs to the PCB and soldered the xt60 with positive and negative cable. I connected the motors to the ESCs.
To recap, the battery connector, motors and ESCs are soldered to the board.

I wanted to test motor direction using a spare receiver I have. When I connect the battery to the battery plug thats soldered to the board, I hear an audible crackle or pop that sounds like a spark or something is arching off. I did it a few time to ensure I wasn’t imagining things. Upon investigating the pins in the connectors of battery and board connector, they look like they were sparking or something.

Please assist me.

That is normal. The arcing is caused by the current inrush charging the capacitors in your ESCs. I’ve got a 6s hexacopter with some extra capacitors in line and boy do I pucker up ever time I plug the battery in. Check this link out http://scriptasylum.com/rc_speed/nospark.html .