3 X LR44 for Wee?
- Thread starter munchs
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I don't know how much voltage drop you'd get under load, but you're talking about 4.5 volts vs. 3.7 nominal under load for Li ion.
That just might be enough to let the magic smoke escape.
Tim
That just might be enough to let the magic smoke escape.
Tim
Morelite
Flashlight Enthusiast
I know that can be done with the Peak Matterhorn that uses the 10180 cell but the output is much less and the runtime is cutdown by 50% or so. The SR44 cells will provide better runtimes than the LR44's.
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I don't know how much voltage drop you'd get under load, but you're talking about 4.5 volts vs. 3.7 nominal under load for Li ion.
That just might be enough to let the magic smoke escape.
Tim
I'm not so knowledgeable at electronics, but won't the resistor in the LE handle it? I'm not sure though...
SR44 cells are much harder to find than LR44 cells. LR44 I found on the net has 1.5v/150mAh capacity. Won't they last longer than 10181 cells?
Morelite
Flashlight Enthusiast
At 150mAh they should last longer than the 10180 cell. I doubt the ones I had where 150mAh or they where past their expiration date. I guess I'll get some new ones and try this test again.
Sampolainen
Newly Enlightened
- Joined
- Mar 26, 2008
- Messages
- 37
Are those alkaline cells? If so I'm pretty sure that at the wee's consumption their capasity will slump down below 10180. That's how alkaline batteries work. But I think it is a good idea to use them in a pinch, I know that I'll do it if it comes to that.
Illum
Flashaholic
not sure for your wee... but for the Orb Wee NS, it'll draw 200ma from the 10180
We know that wees use resistors rather than a circuit to compensate for the small size.
For 10180
R = V/I
R = (Vin-Vdrop)/I
R = (4.2-3.6)/0.2
R = 3
For the sake of simplicity we'll assume the SMT resistor is 3 ohms [I wouldn't be surprised if they used a 3.3 ohm resistor, as they are more common]
3xLR44 cells assuming they don't sag under load :huh:
3 = (Vin-Vdrop)/I
3 = (4.5-3.6)/I
I = (4.5-3.6)/3
I = 300ma
An XR-E s usually driven above 350ma, so your cree won't be damaged.
Theres not enough umph for the button cells to heat up the resistor nor give enough surge to last that 300ma for any longer than maybe a second.
LR44, assuming alkaline...will sag to nothing under 300ma of load
I don't have a wee...but it doesn't make sense how something could fail.
Note: The capacity has nothing to do with the internal resistance. You could use four LR44s and still have less voltage under load than the 10180. in fact, certain LED keychain lights relies on the internal resistance of LR44 cells to limit fowarding current.
We know that wees use resistors rather than a circuit to compensate for the small size.
For 10180
R = V/I
R = (Vin-Vdrop)/I
R = (4.2-3.6)/0.2
R = 3
For the sake of simplicity we'll assume the SMT resistor is 3 ohms [I wouldn't be surprised if they used a 3.3 ohm resistor, as they are more common]
3xLR44 cells assuming they don't sag under load :huh:
3 = (Vin-Vdrop)/I
3 = (4.5-3.6)/I
I = (4.5-3.6)/3
I = 300ma
An XR-E s usually driven above 350ma, so your cree won't be damaged.
Theres not enough umph for the button cells to heat up the resistor nor give enough surge to last that 300ma for any longer than maybe a second.
LR44, assuming alkaline...will sag to nothing under 300ma of load
I don't have a wee...but it doesn't make sense how something could fail.
Note: The capacity has nothing to do with the internal resistance. You could use four LR44s and still have less voltage under load than the 10180. in fact, certain LED keychain lights relies on the internal resistance of LR44 cells to limit fowarding current.
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Daylight
Newly Enlightened
The LR44 batteries doesn't feet in my new wee ti, they are too thick :thinking:
NOTE: To anyone trying this, you need to put tape around the batteries after holding them in a vertical stack otherwise they will short out when the metal casing of the light touches all the sides of the cells. Sorry if this is obvious but it might not be in a hurry 
Well, 3 X LR44 will not fit.
But, 5 x 394 (SR936SW) does nicely. On a 50L pill, it will not cause problems. It's not very bright as well. Probably 20-30 odd lumens.
It will however require some sort of spacer as it will not contact. Not long enough. Wrap the batteries with tape to avoid accidental activations.
I use 2 x of the little black disk in the tail of my Eagletac T10LC2 to complete the circuit.
Run time is not very long.
But, 5 x 394 (SR936SW) does nicely. On a 50L pill, it will not cause problems. It's not very bright as well. Probably 20-30 odd lumens.
It will however require some sort of spacer as it will not contact. Not long enough. Wrap the batteries with tape to avoid accidental activations.
I use 2 x of the little black disk in the tail of my Eagletac T10LC2 to complete the circuit.
Run time is not very long.
