How To Calculate Run Time?

DavidRZ

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Mar 5, 2018
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Sorry, new guy here.

I would like to calculate run time on a proposed light. What is the calculation? What all needs to be considered to get a decent estimate?
 

archimedes

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Sorry, new guy here.

I would like to calculate run time on a proposed light. What is the calculation? What all needs to be considered to get a decent estimate?

Calculate, or measure ?

Rough calculation can be done from knowing capacity and current draw, then solving for time.

Be aware that this provides only an approximation, as most flashlights are not regulated perfectly flat, and actual battery capacity varies (potentially quite significantly) with many factors (not least of which is current draw, incidentally) .

But simple division should get you in the ballpark ....
 
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terryoregon

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Sep 19, 2017
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You will want to look up the ANSI FL-1 spec on runtime.

The amount of continuous runtime (in minutes) until the light output drops to 10% of its original value (measured 30 seconds after turning the light on).

Then you will have to decide exactly HOW you want to test for runtime (there are many roads). On my lights, I use a light-meter-data-logger, using batteries in the light with a known capacity. No "calculations" necessary.

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orionlightlight

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Apr 12, 2018
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Calculate, or measure ?

Rough calculation can be done from knowing capacity and current draw, then solving for time.

Be aware that this provides only an approximation, as most flashlights are not regulated perfectly flat, and actual battery capacity varies (potentially quite significantly) with many factors (not least of which is current draw, incidentally) .

But simple division should get you in the ballpark ....

I'm interested in knowing the calculations as well. What is the formula exactly?
 

archimedes

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Nov 12, 2010
Messages
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CONUS, top left
I'm interested in knowing the calculations as well. What is the formula exactly?

.... Rough calculation can be done from knowing capacity and current draw, then solving for time.

Be aware that this provides only an approximation, as most flashlights are not regulated perfectly flat, and actual battery capacity varies (potentially quite significantly) with many factors (not least of which is current draw, incidentally) .

But simple division should get you in the ballpark ....

Already posted (see above) ....

Amp-hrs / Amps = hours
 
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