Dude, an actual documented voltage drop test, this is great!
So in general, springs take off 0.3V at 6A, that’s a whopping 1.8W power thrown away. I expected some drop but this surprises me a bit. I though it would be way less than 1W.
This sure pushes spring braiding up my mod list. I use silicone wires though, work much better as movements are involved. Pure copper braid normally break after a year.
I think steel springs are the go-to for mechanical strength. Maglite springs are steel. Djozz’s test backs this up, and if you’re braiding/wiring them anyway you don’t have to care about their electrical properties.
Thank you for the test and for documenting the results.
Silicone wire vs. copper braid is going to depend on the length, quality, and size of copper braid used, as well as the length, quality, and size of the wire used. I imagine that the difference between copper braid and 22 AWG wire in the lengths typically seen inside of a flashlight spring is very small; however, if you use tiny wire your results won't be nearly as good.
Thanks you all for the replies, and special thanks to Hank for the elaborate explanation of the testing of the intl-outdoor spring.
I think you are right, I was a bit too negative about them, they sure have their purpose because they are a noticable upgrade for stock steel springs. I really hoped that they would be as good as a copper braided spring, but springs just do not get much better than this. The resistance is not as low as the intl-outdoor spring but much better than steel springs, and the mechanical properties are excellent.
Thinking about these alloys, (I looked it up) phosfor bronze has a conductivity of 10-20% IACS, beryllium-copper is also 10-20%IACS (all depending on the precise alloy). The intl-outdoor beryllium-copper alloy has an exceptional 45%IACS, but at some expense of the mechanical properties. So I think that the elusive beryllium-copper spring that has been the talk of BLF for a while will either be electrically not much better than my phosfor-bronze spring, or mechanically worse to some extend.
Yeah, braiding the Nanjg 105c spring should free up ~0.068v at 6A… now I’ve just got to figure out the best way to braid/wire such a small spring. I think my normal technique involves too much solder wicking up in the copper. The spring is only what, 5mm tall?
And timely too! I just ordered some of those beryllium copper springs from Hank! (I say “just”, ordered em a couple of weeks ago, expecting them any day now)
Your phosphor bronze spring looks like a good one, I wouldn’t mind picking some of those up from you if you are wanting to recoup some of that test budget.
While I don’t mind soldering the 22ga wire inside a spring, I don’t like the steel springs that the solder might not stick to… releasing the bypass without my knowledge or being a “cold joint” that isn’t producing the required result. So the phosphor bronze spring would be an excellent answer, taking solder and already having a low resistance such that it wouldn’t be mandatory to do the bypass.
Nice test, finally able to “see” what’s going on there!
Did the drill a hole through the board mod the other day. So a wire went right to the driver. Anyone have thoughts on the best copper braid to use? This cheap stuff I got probably won’t hold up. Pick up some of those copper springs too- have to order some stuff today.
fell, I use the same 22ga wire that I use for the leads to bypass the springs. Soldering it at the pad first, I try to put a slight coil to it before soldering it on top of the spring, this way it compresses inside the spring and should last indefinitely.
Djozz, very interesting measurements ~0,3V voltage drop for 6A current makes such spring a nice heater :bigsmile: Some time ago I’ve done similar test (for current 3A) and I must tell that Your test doesn’t include one, but very important parameter (surface of electric contact to battery cells terminal). It will be different for every spring (hard to calculate) but also generating voltage losses.