After I assembled the board with beeper, capacitor and the cables it was not working. There was no power at the welding tips. When checking the boards circuit I found this: MCU output -> drives a PNP transistor -> drives the gates of the N-ch FETs. I post a photo of the schematic: It cannot work. The diode is assembled in wrong direction (the PNP transistor will never switch on) and even if it is reversed it cannot work. The PNP transisitor is always on then because the voltage after the diode can never be higher than MCU power supply (5V) plus diode forward voltage. I removed the diode, PNP transistor and the rest and replaced it by a PC817 optocoupler, after that the spot welder works as intended. (The original circuit may work for battery voltages up to maybe 7-8V but not higher). Did the manufactiurer made this change recently? Other users will experience the same issue like me...

After I assembled the board with beeper, capacitor and the cables it was not working. There was no power at the welding tips. When checking the boards circuit I found this: MCU output -> drives a PNP transistor -> drives the gates of the N-ch FETs. I post a photo of the schematic: It cannot work. The diode is assembled in wrong direction (the PNP transistor will never switch on) and even if it is reversed it cannot work. The PNP transisitor is always on then because the voltage after the diode can never be higher than MCU power supply (5V) plus diode forward voltage. I removed the diode, PNP transistor and the rest and replaced it by a PC817 optocoupler, after that the spot welder works as intended. (The original circuit may work for battery voltages up to maybe 7-8V but not higher). Did the manufactiurer made this change recently? Other users will experience the same issue like me...

After I assembled the board with beeper, capacitor and the cables it was not working. There was no power at the welding tips. When checking the boards circuit I found this: MCU output -> drives a PNP transistor -> drives the gates of the N-ch FETs. I post a photo of the schematic: It cannot work. The diode is assembled in wrong direction (the PNP transistor will never switch on) and even if it is reversed it cannot work. The PNP transisitor is always on then because the voltage after the diode can never be higher than MCU power supply (5V) plus diode forward voltage. I removed the diode, PNP transistor and the rest and replaced it by a PC817 optocoupler, after that the spot welder works as intended. (The original circuit may work for battery voltages up to maybe 7-8V but not higher). Did the manufactiurer made this change recently? Other users will experience the same issue like me...

Minor assembly required with soldering iron. The Capacitor and Buzzer need to be soldered on, and leads have to be soldered as well. I put XT-60 on mine so I can power it with a large 5000mah 3S lipo, or use my Lipo charger in "power supply" mode. Very easy to do and board is marked for where the 2 items have to go. Assembled min in Excellent for spot-welding RC battery packs. Works on Nicad and NiMh batteries. Also works well for LiPo's. Make sure you lift the Lipo leads up, touch them together and then spot weld. Fold them back down when done

Minor assembly required with soldering iron. The Capacitor and Buzzer need to be soldered on, and leads have to be soldered as well. I put XT-60 on mine so I can power it with a large 5000mah 3S lipo, or use my Lipo charger in "power supply" mode. Very easy to do and board is marked for where the 2 items have to go. Assembled min in Excellent for spot-welding RC battery packs. Works on Nicad and NiMh batteries. Also works well for LiPo's. Make sure you lift the Lipo leads up, touch them together and then spot weld. Fold them back down when done

Minor assembly required with soldering iron. The Capacitor and Buzzer need to be soldered on, and leads have to be soldered as well. I put XT-60 on mine so I can power it with a large 5000mah 3S lipo, or use my Lipo charger in "power supply" mode. Very easy to do and board is marked for where the 2 items have to go. Assembled min in Excellent for spot-welding RC battery packs. Works on Nicad and NiMh batteries. Also works well for LiPo's. Make sure you lift the Lipo leads up, touch them together and then spot weld. Fold them back down when done