Build a Powerful DIY Spot Welder for Lithium-Ion Batteries | NY-D01

Build a powerful DIY spot welding machine for lithium-ion batteries using an old microwave oven transformer (MOT) and an NY-D01 control board. This project shows how to rewind the transformer, wire the AC input, mount the controller, and assemble a safe wooden enclosure. The NY-D01 circuit triggers the transformer at the AC peak for maximum current, giving clean, strong, and repeatable welds on 18650 cells and nickel strips. Perfect for battery pack building and high-current welding applications.

1. Screwdrivers (Phillips & flat)
2. Wire cutters and wire strippers
3. Pliers
4. Soldering iron + solder
5. Hot glue gun
6. Electric drill + drill bits
7. Multimeter
8. Heat gun (for heat-shrink tubing)
9. Utility knife / cutter
10. Measuring tape / ruler

Main Components

1. Microwave Oven Transformer (MOT) — rewound secondary
2. NY-D01 Spot Welder Control Board
3. Auxiliary small transformer (for AC peak sensing)
4. TRIAC (usually BT136/BT139 depending on board)
5. Heatsink for TRIAC
6. Spot welder copper arms + welding tips
7. Wooden enclosure (MDF or plywood)
8. AC circuit breaker or fuse
9. AC power cable with plug

Wiring & Electrical Parts

1. Thick gauge copper cable (10–16 mm²) for MOT output
2. Enamel copper wire (for rewinding secondary)
3. Standard gauge wires (for control board connections)
4. Heat-shrink tubing
5. Cable ties
6. Terminal blocks / screw connectors
7. Insulation tape

Hardware

1. Nuts, bolts, washers
2. Wood screws
3. Metal brackets (optional, for support)

This project demonstrates how to build a high-power spot welding machine for lithium-ion batteries using a rewound Microwave Oven Transformer (MOT) and an NY-D01 intelligent spot welder control board. The goal is to create a reliable, low-cost spot welder capable of producing strong, clean welds on 18650/Li-ion battery terminals and nickel strips—similar to professional welding machines.

The build starts by removing the original high-voltage secondary coil of the MOT and rewinding it using a thick copper wire, which allows the transformer to deliver extremely high current at low voltage. This current is necessary for proper spot welding without damaging the battery.

To control this power safely and precisely, the project uses the NY-D01 timing controller, which detects the AC peak voltage through an auxiliary transformer and optocoupler. By firing the TRIAC exactly at the right moment in the AC cycle, the controller ensures maximum current output and highly repeatable welds. This peak-triggering method provides consistent performance and prevents overheating or weak welds.

All components—including the MOT, control board, heatsink, wiring, and spot welding arms—are mounted inside a custom wooden enclosure, giving the machine a clean, safe, and organized design. A circuit breaker is added for protection, and thick output cables ensure minimal resistance and maximum power delivery.

After assembly, the welder is tested on multiple nickel strips and lithium-ion cells. The machine produces strong, solid welds, verified through pull-tests shown in the video. This makes the welder suitable for building:

1. 18650 battery packs
2. Power banks
3. E-bike and scooter battery modules
4. DIY electronics requiring high-current connections

This project is ideal for hobbyists, makers, and engineers who want to build a professional-grade spot welder from inexpensive and easily available components.