Lithium coin cell battery to power LED?

[ghost_a*]

i bought a 2AA battery holder and am using that to power my LED that i'm going to use in my crystal chamber.

however, i also have a 3V CR2032 lithium coin style battery.
i held my 5mm 3.7V 20mA 2600mcd blue LED to the coin itself and it lit as brightly as ever.

this is probably a dumb question, but why are these types of batteries not used to power LED setups inside lightsabers rather than 2AA batteries in a battery holder which would be equivalent to 3V anyways.
just at about 10 times the size consumption within the hilt.

this is basically what i'm talkin' about:

http://www.amazon.com/gp/product/B0002ZPHZG/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000EG4I08&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1BBNCVV012QYMRMNH8SS

and here's a pic of mine, with my 5mm LED.


http://img813.imageshack.us/img813/125/img20110109140015.th.jpg (http://img813.imageshack.us/i/img20110109140015.jpg/)

[Novastar]

It's the mAh, not the voltage that would essentially make things impossible.

You have to think of batteries also as a finite source of energy--and also that energy density is still consistent (to a certain extent) with other real-world applications. For example, a glass of water will almost NEVER hold more water than a large jug of water. Even if you were to "highly compact" the water in the glass (pressure?)... it would still be nearly impossible to get the same amount of value from it--so-to-speak.

The same holds for little coin-cell batteries. Sure, they can have 3v or 1.5v or 3.6v or blah-blah-blah... but they will likely NEVER have a comparing overall energy capacity / density vs. an alkaline cell or Li-Ion 18650 (for example). Additionally, you can't draw 1000mA at any given moment from a coin-cell... it's far too weak to output that kind of "punch".

The short of it is... "coin-cell" style cells and "9v" cells (which are just 6 AAAA cells all together) are useless for the LED sabers we design, because they cannot yield the power nor the runtime. :)

[psab keel]

The answer is a simple one. Capacitance. As an example, two AA NiMH Batteries average around 2000 mA which if you were to run a high power LED at 500 mA, your LED would stay lit for about 4 hours. The coin cell batteries, while small, have nowhere near that kind of capacitance and in turn would only give you a moment or two before the battery is drained. LED's are current sensitive devices, not voltage sensitive. You can run an LED over the recommended voltage as long as you are limiting the current into it. Make sense?

[acerocket]

Many reasons. First off, most these batteries are primary type. Meaning they are not rechargeable and will need to be replaced when they die. You will be replacing them often in a saber if you use them. Second, and most importantly, they just don't have the discharge current. A quick Google search yilds a Sanyo spec sheet. These cells are rated for a maximum continuous discharge rate of 4 mA with a pulsed discharge rate of 20mA. Since your LED wants 20mA to run properly, your CR2032 will nto last very long and you might even ruin your LED. It's just easier to run the crystal chamber LED of the main power supply and resist as necessary.

[ghost_a*]

totally answered my question :)
thanks guys

i'll stick with the 2AA battery holder.