Springs: magnetic=bad?

The best springs are made of copper and its alloys like brass, right? These aren’t magnetic. Yet all the springs in commercial flashlights I’ve paid attention to are magnetic. That means they’re some form of steel.

Should we be checking the magnetism of springs to gauge their quality?

1. The best springs are made from copper alloys, from phosphor bronze and beryllium copper of different types and grades. Copper is actually NEVER used in any kind of compression spring, like in battery springs, because its yield strength is extremely low, meaning any kind of meaningful deformation will results in a big plastic deformation, rendering it almost useless after one compression.

2. Using phosphor bronze and beryllium copper of 15-45% IACS means you can have a spring which can handle much higher power levels. In exchange for higher and higher conductivity though, you get worse mechanical properties, along with cost. Phosphor bronze C54400 19% IACS is a good compromise between high conducitivity and yield strength, and costing the less. While BeCu C17500 45% IACS is the absolute best in terms of current handling, it has quite poor mechanical properties, as seen in djozz’s spring test with the Intl Outdoor spring.

Currently, the best compromise between conductivity and mechanical performance are springs made of BeCu C17530. They have 2x the conductivity of phosphor bronze C54400, and have way better mechanical properties than C17500 BeCu.

So yes, check the magnetism of the springs before testing a high power light to gauge if it needs to be bypassed or replaced.