Battery spot welder box

prusaprinters

<p>I got myself a cheap battery powered spot welder (fancy name for a short circuit controller :-) ) from one of the usual suspect sites - the one with the single high discharge LiIon battery, the long strip PCB and three power transistors ("MOS tubes" in chenglish).<br/> The problem I have with this is that it laughs openly in the face of any kind of idea about safety - everything is out in the open and the PCB is intentionally pulled into a curve. Sure, it's only 4 Volts - but the battery can still supply a short circuit current of a few hundred amps, good enough to fuse any screwdriver to the terminals (no, I didn't try this as I still need both the battery and my screwdrivers).<br/> So I printed a simple case for that incendiary device that covers up all the open contacts. The case consists of three parts:</p> <ul> <li>a lower body that basically houses the battery</li> <li>an insert that holds the PCB (and prevents the middle screw from pressing into the battery)</li> <li>a lid that covers up everything on the top<br/> Requires 4 pieces of M3 countersink screws and matching nuts for assembly (I guess you could also wrap it in duct tape). Printed in transparent PETG so I can still see the LED.</li> </ul> <p>Yes, the welder works. Don't press hard and give it a little time (a dozen or so clicks). And yes, a freshly welded test strip is HOT (ask my right index finger...).</p> <h3>Print instructions</h3><p>Printed in transparent PETG. 2 walls and 15% infill are sufficient, this is not an especially mechanically stressed part.</p> <p>About the name: this is my second incarnation of the lid - the first one was lower with an open top until I realized that this would still permit to put a screwdriver across the battery terminals. No, I realized it before I killed a screwdriver.</p>