Tail Cap Testing

Regarding tail cap testing: is the object of this test to see what the driver pulls in current? is so could u use a regulated dc supply and get more accurate results?

Just curious!

I just don't see the point... why would that be more accurate?

Won't you think "most accurate result" should be using closest actual setting as normally used, e.g actual batteries? The only difference would be the addition of the ammeter. Even that necessary addition can change your result slightly, ammeter+probe don't exactly have 0 ohm.

Using a dc supply just adds another variable to mess up your result IMO.

if the driver is a constant current driver (e.g. 350mA draw no matter what the cell's voltage is!) then brightness will decline with time because voltage drops with time


How good is your DC supply, does it contain any ripple/noise from the rectifier? If so how does this react with the driver, particularly at lower settings where the driver is chopping the DC itself?

That depends on the forward voltage the LED, at 350mA constant it will take a lot on a 18650 for the brightness to decline, it will be about 2.7v for the LED and Protected Sanyo will cut by that time too. And if the circuit it's made so that it reads the voltage and it actually cuts of at one point then you will see no brightness degradation in time, especially with 2x 18650.

Yes, you could. But it is not that easy, you have to measure voltage at the light, not at the power supply (There can be a significant voltage drop in cables).

I do that test in my review and makes a curve from the result:

As can be seen I do also include a lux meter in the setup.