Brenda Ann wrote:


"joe" wrote in message
...
Brenda Ann wrote:


"Brenda Ann" wrote in message
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"Bob Dobbs" wrote in message
news:4980fa76.3113218@chupacabra...
Even all the flashlights are all LED nowadays.

Not all, but the superior ones are. They now make Luxeon single LED
flashlights up to 10 watts (perhaps even higher) that outshine any
handheld incandescent flashlight (except perhaps the heavy duty halogen
flashlights that will only work for a few minutes on a fully charged
battery) with a very good quality white light. I have one such Luxeon
flashlight with a 3 watt lamp that is about 1/3 the size of a two "D"
cell flashlight that is many times brighter and has a better beam.



P.S. I'm not sure how they measure the wattage. I think it may be
similar to the way CFL's are co-rated (i.e. the wattage listed is the
incandescent
equivalent). Otherwise, the small batteries used would last only a very
few minutes at best.

Consider that a single AA battery has about a 2 watt-hour capacity. A D
cell
is much more.

See:
http://www.zbattery.com/zbattery/batteryinfo.html

Battery life should be much better than your expectation.


2 Wh sounds awfully optomistic for a AA. These flashlights use a couple
of 1000mAh li-ion batteries in series. To extend the life of the lamp, and
the useful battery life, they also use regulator circuits within the
flashlight.
These can't help but use up some battery power. 1A x 6V = 6W at 1000mAh =
6W for 1 hour. For the 3W flashlight, assuming zero power wasted as heat
(which isn't true) would mean 2 hours of use. for the 10W light (uses the
same batteries), it would be about 40 minutes. Obviously, these
flashlights can be used for more than these short periods of time.

You've gone from "a very few minutes at best" to "2 hours of use". Which is
it?

A 2 watt PR3 lamp produces about the same light as a 1 watt Luxeon LED. (
About 20 lumens.)

CR3 Lithium batteries are more like 1300-1500 mAh capacity.

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