Safer to run an LED flashlight with a single cell?

I have an ExtremeBeam M4 Scirrako LED flashlight that I'd like to run with a single protected 18650, rather than the two 18350 batteries that came with it. I'm new to this forum and I'm trying to come up to speed on the ins and outs of Lithium Ion technology. And in the short time I've spent, thus far, reading threads on candlepowerforums it's clear that safety issues and proper use are to be taken seriously. I've read through the very useful Using Li-ion cells in LED flashlights safely thread,
but I guess that fully grasping Lion technology will just take some time and lots more reading.

So my initial questions are:

• Will running the M4 Scirrako with a single protected 18650 be safer than using two 18350s? The two ExtremeBeam branded 18350 batteries it came with don't have much tech specs, so i assume they're not protected. I've read that lights working off of multiple cells are more trouble prone.
• I see that protected cells could be slightly longer in size, so I'm wondering how to ensure that I choose an 18650 that fits.
• Any advice on 18650 cells that are known to work well in the M4 Scirrako would be welcomed.

I've emailed ExtremeBeam about this, but also wanted to get the opinions of the folks in the know.

Thanks in advance

Nothing to be worried about,stick a battery in or batteries do not over complicate the hobby.What did the instruction sheet say?

18350 cells are usually IMR chemistry, which is "safer" than ICR chemistry. Make sure the cells are balanced - have the same voltage +/- 0.1 v. 2 x 18350 is 7.4 nominal voltage. 1 x 18650 will only be 3.7 nominal voltage and this could be too low for the light. Sorry, but I don't know the light. In addition to ensuring the 2 cells are balanced, don't over charge or over discharge. A simple voltage meter is a useful piece of kit. While you don't have to be paranoid - li-ions are used in cell phones and laptops - you should be prudent.

mcnair55 said:

Nothing to be worried about,stick a battery in or batteries do not over complicate the hobby.What did the instruction sheet say?

Click to expand...

The tech specs listed here say only the following wrt batteries:

• Battery Type: Two 3.0 to 3.6 volt CR123 batteries or one 3.6 volt 18650 battery

I'm in the process of trying to read up on chargers (like maybe the Nitecore D4 or the Xtar VP2) and also thought it would be a better/easier/safer idea to run the light off of a single protected 18650 lion cell.

Burlington186 said:

The tech specs listed here say only the following wrt batteries:

• Battery Type: Two 3.0 to 3.6 volt CR123 batteries or one 3.6 volt 18650 battery

I'm in the process of trying to read up on chargers (like maybe the Nitecore D4 or the Xtar VP2) and also thought it would be a better/easier/safer idea to run the light off of a single protected 18650 lion cell.

Click to expand...

If you use two 3.6 v cells (18350s for example) you get 7.2 v.

If you use two 3.0 v (CR123, etc) you get 6 v.

So, it sounds like the light's driver can handle 3.6 v to 7.2 v ranges.


Many lights use boost/buck circuitry to take what the cells output and convert it to what the LED is driven by, etc...but many 'dual fuel' lights are brighter on two IMR 18350 than they would be on two CR123 or RCR123 (16340), or one 18650, etc....due to the higher voltage of a two cell configuration allowing higher lumen output, combined with the higher amp draws the IMR allow, and so forth.