I’m wondering if there is a decent affordable cell welder. Purpose is rebuilding tool batteries and that sort of thing on an occasional basis. K-weld has been recommended but is pretty expensive and might be overkill. https://diy500amp.com/ has a bunch closer to my price range but might be underkill. Any thoughts? Thx
A bit delayed, but I also built my own with a starter solenoid and a used car audio capacitor. I use a bench power supply to change the capacitor and made a diy foot switch to trip the starter solenoid.
This approach is pretty cheap, very repeatable, and easy to control.
Changing the bench supply’s voltage lets you dial in the amount of energy delivered per weld. Just keep in mind that energy stored = 1/2CV2 so don’t jump from say 5 volts straight to 10 volts thinking that you’re doubling the power - that’s a 4x increase.
Wow I didn’t know about car audio capacitors. What capacitance did you use? What voltage, typically? They are on the expensive side, but impressive. I bet they could also jump start car engines. I’m not keen on using a lead-acid battery so capacitors seem like an ok alternative.
I made my own out of a motorcycle battery (which I have lying around in abundance), a length of jumper cable, a starter relay off of I think a 50cc scooter with a random salvaged microswitch as the trigger, and two short lengths of sharpened 10 gauge Romex as the probes. It works a treat. I haven’t fried a single 18650 with it yet.
I think my total net bill of materials was about $12, not including the junk I already had lying around, the majority of which was the relay.
Interesting. I don’t have a motorcycle battery around but I do have one of those lithium portable jump starters. I wonder if that could work.
In theory, yes. But those usually have electronics in them in an attempt to save you from yourself. So it’s unlikely that the thing would fire when you wanted it to without being fooled into believing it was hooked up to a 12v battery in some way.
You can get off brand motorcycle batteries online for like $20. The quality is irrelevant for this application, especially since you probably won’t be welding hundreds of battery tabs in a day. The point is that they can reliably deliver enough amperage to weld the tabs while having a low enough terminal voltage to be unlikely to deal either yourself or your cells a mischief.
Fair enough. Jump starters often have an override button so they’ll still operate when the car battery is at 0V, but IDK how it works.
It’s worth a try.
Maybe later I’ll post a picture of my gimcrack contraption.
