Build a 1000W Battery Spot Welder Using a Microwave Transformer | Step-by-Step Guide

Published at : 23 Dec 2025

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Hey! Want to make some kind of large battery pack for a project and don't want to have to purchase one of those expensive Spot welders? Well, you're at the right place! Make a DIY Spot Welding Machine for dirt cheap - next to nothing! Just grab your tools, some scrap parts, a broken microwave oven and let's build!
This 1000-Watt Spot Welding Machine produces an open-circuit voltage as low as 2.2V at 450 Amps, when welding (in short-circuit) the voltage drops to about half of that or even less with a current as high as 900-1200A.

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Circuit diagram - Spot Welding Machine: https://drive.google.com/file/d/1ql00_u0Mn5TzKNr5tplSysop932iM270/view?usp=sharing

Materials/parts needed for this project:
Microwave Oven Transformer (MOT)
Microwave Oven (AC powered) Cooling fan
15A Momentary Push switch - https://amzn.to/3eaq8IO
15A On/off toggle switch - https://amzn.to/3T4iApy
10-15A Fuse - https://amzn.to/3rBIsNX
1M of 4AWG Enameled copper welding wire (a.k.a battery wire) - https://amzn.to/3CEQhc7
Electrical wire (12-16AWG) - https://amzn.to/3Ma3L2F
120V 3-wire cable - https://amzn.to/3MecGzV
3mm exposed solid copper wire (spot welder tips) - https://amzn.to/3eaCnFd
UPS Inverter Metal cover/case (A plastic or wooden enlosure can do fine)
1x1" Square stick of wood
Retraction spring - https://amzn.to/3MecUHh
Mini door hinge - https://amzn.to/3ecwffv
(x2) Shortened bolts - https://amzn.to/3edoB4A
Zip ties - https://amzn.to/3EnWs5C
PVC-foam gripped handle
Wooden "Cement Float" Handle
Spray paint - https://amzn.to/3ynQQEC
Nickel strips for spot welding 18650-type Li-Ion batteries together - https://amzn.to/3RXgZBf

18650 cells - https://amzn.to/3QKafro

🪛🔧🔨 Tools and extra supplies I use:
➡️ Soldering Iron Kit - https://amzn.to/3X6L5Wq
➡️ Hot Glue Gun - https://amzn.to/3E6trJG
➡️ Drill Machine - https://amzn.to/3EDe0u8
➡️ Box cutter/Utility knife - https://amzn.to/3hP9MGI
➡️ X-Acto Hobby Knife - https://amzn.to/3XbL7ML
➡️ Cutting Matt (Green) - https://amzn.to/3gil71A
➡️ Needle-nose Pliers - https://amzn.to/3ECTKc3
➡️ Wire Cutters for Electronics - https://amzn.to/3ECut1B
➡️ Wire-stripping tool (Automatic) - https://amzn.to/3hQsMVD
➡️ Screwdriver kit - https://amzn.to/3V6vgNX
➡️ Heat-shrink Tube Kit - https://amzn.to/3AksTPE
➡️ Jumper Wire Kit - https://amzn.to/3UGhMZq
➡️ Breadboard for Prototyping - https://amzn.to/3GlF4ze
➡️ Perf Boards, Pin headers, and Connectors Kit - https://amzn.to/3AkySUw
➡️ Superglue - https://amzn.to/3EE6uis
➡️ Duct Tape - https://amzn.to/3g5mTU0
➡️ Double-sided Tape - https://amzn.to/3Edta82
➡️ Kapton Tape (for battery leads) - https://amzn.to/3X58bNl

Music credits:
CHRIS HAYES MUSIC - CHILL TRAP BEAT | No Copyright Trap
Free Download Link
http://bit.ly/36SP39M

#spotwelder #diyspotwelder #batteryspotwelder