To the OP; are you talking about the compression of the spring that is connected to the pill or to the tail switch?
I am talking about the little +B spring. Here are some pics to show what I am talking about...
first with a Sanyo 18650, pressing light but firmly against the cell. Notice the -B end of the cell how its level with the end of the body tube, and I measure 2.8A draw.
Next I press harder against the cell to fully compress the +B spring on the pill, notice how the end of the cell is recessed into the light farther now, and the current draw has increased to 3.55A. A gain of .7A.
Next is with a 26650 in the same light. Pressing lightl but firm so that the -B end of the battery is flush with the end of the tube I measure 4A.
Pressing the cell so that the small +B spring is fully compressed I now measure 5.5A... a gain of 1.5A pulling from the DC-DC circuit.
A 1.5A gain is no small increase, especially in a direct drive light. Unfortunately I have no way to measure the corresponding light output. I am thinking I can gain at least some lumens (& corresponding lux) by stuffing a ball/wad of copper braid in the -B and +B springs.
thanks!!
I read this thead and tried modifying a switch by soldering some copper braid from the back of the switch to the end of the spring.
OOPS!!! The plastic housing for the switch melted slightly... enough that the switch no longer works and is basically garbage. Note to self: Solder braid from top of spring to bottom of spring... not to switch.
After I put in a spare switch, I then ended up just hooking the braid over the top and bottom of the spring.
Try it on a couple of different lights, Kramer. Like I said, I've tried it on 6 of them and adding pressure did not make a difference. If you are really getting 5.5A (that is ungodly high) I'm surprised your switch has held up to the load.
Let's see the pill. Is the probe contact being improved when you press harder, ie at a flatter angle so more area?
Yeah I was conscious of that and tried my best to keep all the pressure points and probe angles the same. Not easy with one hand holding the camera... but I did my best.
Is the jump sudden or gradual? Depends on the pressure or suddenly jumps high at some point?
If it jumps suddenly you might be creating a short circuit somewhere near the pill, I suppose with the big surface of the B+ or by bending the spring awkwardly.
Just a suggestion.
Difference of 0.7A seems huge to be just "bad" spring contact.
Viktor
I agree, I think is something else going on here besides flattening of the spring.
It a gradual thing. The farther down I push on the 18650 the more the current draw increases.
This doesn't in any way reduce the actual spring resistance.
The spring is not copper, it is spring steel and has significantly more resistance than copper.
Perhaps not in the strictest of terms, but it DOES help with SWITCH resistance.
There is more area contacting the cell, and the lip I machined provides more contact with the spring as well.
What he's saying is not at all uncommon. Just about every light I have does it, some more than others. I can vary the reading on my 980L by a half amp or more easily. When it comes to publishing figures on a light that does it particularly bad, I try to approximate what I think tail cap pressure is.
Foy
I have done this for my all half flashlight, almost high drain current.
I've just taken a pic.
I've done this for my TR-J12, DRY, all 7135 driver, UF-T50 etc.... and all my mods. also +B spring in some flashlight.
Finished with sand paper for better contact.
I can confirm what kramer5150 experienced. On many lights pressing down increases current readings. I attribute it to the increased contact between the leads and the battery. The more you press, the more contact area there is.
Thanks for your input, I agree. I was guessing the connection was of higher resistance than the entire spring itself in some cases
I was kind of surprised. I stripped some speaker wire bare and slid one end under the base of the spring and loosely looped it around each coil and laid the end of the wire over the top of the spring.
Tried it with 3 different L2Ps and an L2 and every one measured slightly higher on the Foyometer. For example; before wire mod might read 130 and after would be 145.
interestingFoy
I tried covering an entire spring in (silver based) circuit writer. don't bother.
I regularly add copper braid (solder wick) to tailcap springs.
No need to solder to the top of the spring at all.
desolder the spring. Solder the wick to the board (if it isn't side switch...) bring the wick up inside the spring, go outside just before the top loop, then over the top loop and back inside. solder to itself.
edit: and of course, resolder spring. and...even better w/ those brass contact plates. you could solder the wick to that and to the board then just glue the plate to the top of the spring. the spring does its job, and the copper conducts...
I found some cheap wick that apparently lacks flux. That works better because the solder doesn't migrate up through the braid, making it stiff.
In the tractor supply (side switch) zoomie, I did this, and then soldered a filed penny to the top of the spring. I also added braid to the legs of the switch itself just up to where they go into the switch body (they were fairly long).
Pretty cool that something simple like this actually works.
I thought I knew everything but apparently, I was one thing short. Now, I know everything.
smarterthantheaverageidiotFoy
Anyone know what the cell terminals are? Are they coated copper or a different metal? Bare copper ended cells would be cool