fix the electrodes and tighten,make sure the electrodes is perpendicular to the work pieces.

Battery tabs welding machine http://www.espot-welder.com/cr20321865026650-battery-pack-welder-lithiumnimh-battery-welding-battery-welder-p-2.html

Using the file repair the surface of electrodes and make sure it smoothing,using the sand paper packing the file,grinding the surface of the welding 

electrodes and then using the duplicating paper to check the planeness of the electrodes