I just did some resistance measurements on my flashlight (502B) and I’m amazed by the parasitic resistance of the springs… 50mOhms per spring. Times two and that’s almost as much as the IR of the 18650 cell. I might solder some braided wire to it to reduce resistance… But I’m scared to make it look bad.
Right now my light is direct driven. the only thing in series with the LED is the switch (measured at less than 20mOhms!), the parasitic resistors (springs, etc. :~ ) and the transistor for PWM.
That being said, I get about 2.6-2.8A to the LED with a fully charged battery. So here comes the question:
How long does a 8*7135 based flashlight like this keeps the LED to full brightness?
Either I have particularly high parasitic resistance or people just accept that after a few minutes the output starts to drop?
Thanks for your opinion on the subject.
I’m not sure what you mean, you say your light is direct drive but you only get around 2.8A and you ask about an 8x7135 diver…
First off if you really are running DD you definitely need to have copper braid on your springs, no question you need that, around here a lot of us even braid our lower drive current light’s springs cause its so simple and quick to do. Also think about your wires, you should be running at least 22AWG silicone wire.
Now if your light is only pulling ~2.7A on direct drive it sounds like more than just high spring resistance, what batteries are you using? Most decent quality cells are capable of >3A even with stock springs so unless I misunderstand and you are running a driver I’d seriously scrutinize your battery choice.
One last point I’ll touch on while we wait for your answers- no direct drive light will be able to maintain full brightness very long, that’s called “staying in regulation”, it takes a driver to do that, how long it can stay in regulation will depend on the diver, the set drive current and the cell capacity.
My question was: If in direct drive I can barely get 2.7A how the hell can a 8*7135 stay in regulation?
But you answered my question: I need copper braid and bigger wires. Maybe that the transistor used for PWM has a high RDSon too… I don’t know.
About my battery, I use Sanyo 2.6Ah protected. The internal resistance of the cell is less than 100mOhms.
I just added braided wires on my springs… The result is… Well, I let you read this.
