[@dgrover]

On the topic of battery interrupters, a flexible circuit board version could potentially reduce or eliminate the problem of wire fatigue at the PCB that seems to plague at least some versions. A 20mm x 120mm flex pcb, qty 100, is $2.25 each delivered. (10″ long for $2.62 each.) One end would be circular, goes in between cells or between a cell and the battery contact, gets thinner (maybe 1/4″), and the other end maybe has a 1/8″ jack soldered to it, and/or holes for wires that go off to a jack.

Are flex PCBs (polyimide) robust enough for this? Seems like. Not sure what plating would be best. They’re 0.1 to .3mm or thicker, so should work with most battery holders in terms of not adding much length.

This is something that would require a central purchase due to the setup charges and quantities to get decent pricing. But might be a big upgrade over the PCB disks we’ve been using forever.