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-   -   battery capacity (http://www.bikeforums.net/electronics-lighting-gadgets/587306-battery-capacity.html)

ajcurl 09-22-09 05:14 AM

battery capacity
 
mAh is basically the capacity of a battery? The higher the nuber the better? Just playing around with the idea of an old Li ion cell phone battery powering a flashlight. The battery is 1000 mAh....this wouldnt give a very long run time would it? The flashlight is going to be the lowes task force (havnt picked one up yet).

ModoVincere 09-22-09 06:01 AM

Quote:

Originally Posted by ajcurl (Post 9720210)
mAh is basically the capacity of a battery? The higher the nuber the better? Just playing around with the idea of an old Li ion cell phone battery powering a flashlight. The battery is 1000 mAh....this wouldnt give a very long run time would it? The flashlight is going to be the lowes task force (havnt picked one up yet).

depends on the devices current draw. If the battery produces 1000 mah at 1vt, its basically good for 1 watt for an hour. Of course, you don't really want to drain the battery to exhaustion, so half that or 2/3 of it is a reasonable expectation. Now...if your flashlight uses 3 watts, that 1000 mah battery would last only 20 minutes to exhaustion. Again, you would really only go about 1/2 that time or 10 minutes. A 2800 mah battery would last 2.8 times as long as that 1000 mah battery.

ItsJustMe 09-22-09 08:31 AM

Amps is current flow. A milliamp is a thousandth of an amp. An amp hour is the ability to deliver an amp for one hour, and is a measure of the capacity of a battery.

If you have a light that draws half an amp (500 mA) then a 1000 mAH battery should run it for 2 hours. If the light draws 2 amps (2000 mA) then a 1000 mAH light should run it for 30 minutes.

Keep in mind also that all LiIon battery packs contain internal circuitry to limit the amount of current they'll deliver, because LiIons have very low internal resistance, meaning that if you ask a 1000 mAH pack to deliver 20 amps, it'll do it....then it'll likely overheat, boil, and catch fire or explode. Thus the protective circuitry.

ajcurl 09-22-09 06:10 PM

Wow...thanks for the very informative responses, both of you. That cleared a lot of stuff up for me...again thanks!

sjthursday 09-25-09 05:19 AM

why do you want to run Li-ion? For quic recharge?


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