Bulb Voltage Recommendation!

NtEzyBeingGreen

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Hi, I've been lurking this forum for quite some time now, searching for a good, solid, cheap flashlight for my everyday use (Usually hunting, surveying at night, frog gigging, spotting wildlife, etc.) and after reading many reviews for them, I finally decided to order a Solarforce L2P which I plan to run solely on 1x 18650 battery. I have received the host and I am ecstatic about how sturdy the body is! My problem, now, is I would like to purchase a Cree XP-G R5 drop-in for it, but with all the options available from different companies, which voltage range should I be looking at? 0.8v-4.2v, 4.2v-8.4v, 4v-18v, 3.6v-18v? Or does it make that much of a difference at all? I want a good parallel of brightness and battery life! Thanks!
 

hiuintahs

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I'm not that familiar with these drop-in / host type flashlights but since you are using a 18650 battery, the maximum voltage it will have is 4.20v so I'd pick a module that will utilize the range in which a 18650 battery will operate. You would want something that would go down to around 3v if possible. I see the Malkoff's are 3.4v. Below that you probably loose regulation but at least you'd probably still get some unregulated light. I think that is in the range of most 18650 lights. The upper range won't matter as long as its at least 4.20v minimum.
 

hiuintahs

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One other note. If you use a module that goes from 0.8v to 4.20v, that would work but the 18650 doesn't want to be discharged below 2.50v without damaging the cell so you'd have to use a protected 18650 to prevent that from happening. 0.8v to 4.2v operation is what you typically see in single AA/ 14500 lights. Typically the majority of the power in a 18650 resides above 3.0v and so a lot of the driver circuits just utilize buck (step down) type of circuits for that battery. The forward voltage drop of these LEDs is around 3 to 3.25v.
 

lightfooted

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The answer depends on whether or not you want the option to use a pair of CR123As if for some reason you find yourself in the field with no other option and your battery runs down. Should you decide to use only an 18650 then I would go closer to the max voltage of the cell. Usually that means that you will get the most output for the runtime of the cell. I personally own an L2P and have the XM-L drop-in from Solarforce that was designed for 2.7-4.2 volts. I don't believe they make that version still. I am fairly certain that if you were to drain a Li-Ion down to 0.8 volts it might not come back up again, assuming that the protection circuitry didn't kick in long before that. The only real difference being that some of the drop-ins may not reach the stated output on a single cell. Of course if you try using two cells with a drop-in designed for one, you will blow it out. Though you ~may~ have a second or two before it permanently damages the LED.
 

NtEzyBeingGreen

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The answer depends on whether or not you want the option to use a pair of CR123As if for some reason you find yourself in the field with no other option and your battery runs down. Should you decide to use only an 18650 then I would go closer to the max voltage of the cell. Usually that means that you will get the most output for the runtime of the cell. I personally own an L2P and have the XM-L drop-in from Solarforce that was designed for 2.7-4.2 volts. I don't believe they make that version still. I am fairly certain that if you were to drain a Li-Ion down to 0.8 volts it might not come back up again, assuming that the protection circuitry didn't kick in long before that. The only real difference being that some of the drop-ins may not reach the stated output on a single cell. Of course if you try using two cells with a drop-in designed for one, you will blow it out. Though you ~may~ have a second or two before it permanently damages the LED.

So if I was going to only use a 18650, but in the rare occasion that my battery dies and I'm face-to-face with Big Bear, forcing me to slip two 123's in, I should choose the 3.6v-18v?
 

hiuintahs

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So if I was going to only use a 18650, but in the rare occasion that my battery dies and I'm face-to-face with Big Bear, forcing me to slip two 123's in, I should choose the 3.6v-18v?
Yes, or a Malkoff Devices 3.4v to 9v (a little pricier though).
 

cland72

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Nailbender, a member here, makes custom P60 drop ins. He has a website www.customlites.com if you want to check out available options. I would get a driver that handles 2.8v-6v. This will give you optimal performance using 1x18650, but also allows you to use CR123s in a pinch.
 

NtEzyBeingGreen

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Nailbender, a member here, makes custom P60 drop ins. He has a website www.customlites.com if you want to check out available options. I would get a driver that handles 2.8v-6v. This will give you optimal performance using 1x18650, but also allows you to use CR123s in a pinch.

What would be the difference would I see, using a 2.8v-6v vs a 3.6v-18v, in the case that both would be used in the exact same L2P host using mainly a single 18650 and on the rare occasion, 2x 123a?
 

cland72

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I suppose the only disadvantage of going with a 3.7v-18v driver would be that the single 18650 would hit the voltage cutoff much earlier at 3.6v than it would at 2.8v. Some here might even argue that's a benefit since it would prevent the 18650 from over discharging which would damage the battery.
 

AnAppleSnail

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What would be the difference would I see, using a 2.8v-6v vs a 3.6v-18v, in the case that both would be used in the exact same L2P host using mainly a single 18650 and on the rare occasion, 2x 123a?

You won't like this: It will depend on the circuits.

An LED is best powered by an amp throttle. A "driver" circuit drives the right amount of amps (Current) into the LED, at whatever voltage is needed. This driver circuit will be built for different voltage supplies.

In general, voltages come in three flavors: Multiples of 1.2, multiples of 3, and multiples of 3.6v. These are AA / Alkaline chemistry, CR123A / Lithium Primary chemistry, and 18650 & RCR123 / Li-Ion chemistry. If you had three AAs you have 3.6v or so. If you have 3 CR123As you have 9v, and if you have six (!) you'd get 18v.

Now, how does that driver circuit work? It can either throw away the 'extra' voltage, or trade Volts x Amps for Volts x Amps at a lower voltage. The first kind is cheaper, but it gets hotter in use and doesn't have very good efficiency. That directly leads to lower runtimes. The second is more expensive, but better in every other way.
 
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