Hi guys, Its been a while and my brain has gne soft, (blows the dust off the chess set).

 

Right,

I've got a LED it is a 2.5V at 11mA

I've got a battery at 1.5V 1800mA

How long would the battery last if the led worked at this low voltage.

worked it out and I got some silly number, something like 43 sec's.

 

Can someone show me the way this would be worked out so I know for the future.

My cals were:

(1.5 * 1.8)/(2.5 * 0.011)

That says my led would only last 108s, my maths has gone!!!

 

Jon.

Batteries are rated in mAh, i.e. milliamps * hours

I work it out to 98.18 hours as an Ideal, however without having the LED specs of current by voltage curve, it`s impossible to be 100% accurate.

Batteries are rated in mAh, i.e. milliamps * hours

 

oops, thats why My cal are off by a long way.

 

Thanks guys!

PS can you show me how this was worked out as I can the numbers close to YT's but I'm out by a factor of 10. (EG 981.81 HR)

the batt is capable of 2.7Watts for 1 hour

the LED draws 0.0275Watts

 

so 2.7 / 0.0275 = 98.18

 

at least that`s how I worked it out