Runtime

[jdac1981]

I have a sf 6p with a dx 11836 drop in and 2 surefire cr123 primaries. Aside from turning on the flashlight and timing how long it takes to shut off, what is the best way to determine runtime? Sorry for the noob question.

 

[cland72]

Do you have a multimeter? If so, measure the amp draw at the tailcap. Remove tailcap, put meter on body and negative battery terminal, and let us know the reading.

Posted using Tapatalk on my HTC Evo

 

[jdac1981]

.78 draw at the tailcap.

 

[jdac1981]

.83 at the tailcap

 

[twl]

Okay, so let's say an average of .8a draw on the battery.
A new set of CR123 batteries gives ~1500mah(1.5 amp/hour) capacity, give or take a little.
So, 1.5 amp/hour capacity, divided by .8 amp draw, comes out to 1.875 hours, or 112.5 minutes of runtime, on a theoretical scale with a full set of batteries.
Since things are rarely perfect to the theoretical scale, you might expect up to an hour and forty-five minutes, out of a new set of batteries.
You'd have to do an actual timed run-time test with your particular light and your particular batteries to get the exact figures, and even that will vary if the batteries have any variations.

 

[jdac1981]

Another noobie question. Shouldn't I take a amp reading at the dropin itself? Ex. Ground the lamp to the body and take a reading between the pos terminal of the battery and pos terminal of the lamp. Would that give a more accurate runtime?

 

[yellow]

... when measuring at the tailcap, You do totally the same, but it is much easier
(only one "wire" is the flashlight body)


PS: have the light run for 10 mins and take the current draw then - much more accurate value than when just firing on ...