DIY Arduino Battery Spot Welder
KaeptnBalu @ instructables.com has build a DIY spot welder based on Arduino board. It is powered from a 12V car battery with enough current capability to solder nickel strips on battery packs. The board generates two short pulses with the first one to be 1/8 of the time of the second one. Pulse time of second pulse is adjustable by the potentiometer and displayed on the screen in mS.
DIY Arduino Battery Spot Welder – [Link]