Originally Posted by loimpact

So in reading all this stuff, including the recently mentioned Divine light (I've got the generic from ebay)....I've got a couple questions.

1.) What difference is there in 18650 cells? (I have UltraFire greys that say 5000mah) I notice candlepower forum folks laugh at ANY UltraFire cells. Yet, the grey ones I have work ok for me. I usually give them about 1 hour before I swap a cell. Would better cells provide more brightness in a Cree emitter, or just longer life?

2.) So is there such a spread in single-cell 18650 XML lights? Even just XML T6's (which are considered dinosaur now, right?) rate anywhere from 160lm up to 910lm. How the HELL is that possible?

And in addition, what's the improvement scale going from T6 to L2 to L2 U2. (Is L2 U2 any newer or just another letter/# suffix?)

Originally Posted by Litespeedlouie

1)

3) Cree XM-L2 LEDS are a family with many subcategories of tint and brightness. Light makers can buy any any tint and brightness bin they want, although sometimes not all are available in desired quantities and prices. Download the Cree XM-L2 spec sheet and look at page 3.
Cree XM-L2 data sheet

XM-L2 is the main family
There are 7 tint/CCT ranges
Each tint range has several available brightness (luminous flux) ranges, such as T2 or U2. "U"s are the brightest. The outputs listed are a range you can expect when driven as stated from a bare emitter. Any other drive and mechanical configuration will result in different numbers.

Originally Posted by a1penguin

I've noticed that some of the recent high output flashlights get the claimed lumens in "turbo mode" and then they tell you that you cannot run turbo mode for more than 5 minutes. Also some batteries are limited in the amount of amps they can deliver. There are two or three models of Panasonic batteries, some that are designed to deliver higher current (3 amps).




I can't stand battery packs and wires icking up my bike frame! I've been commuting at night since 2009 and I've been happy with Flashlights C8 single battery flashlight on the bars and a slightly smaller barrel shaped flashlight on the helmet. Mountain Electronics has modified C8 flashlights if you want higher power in a single battery format. With inexpensive flashlights, I won't feel bad if it gets destroyed. And as I don't ride in the rain (I'm a wimp) I don't have to worry about weatherproof.


My ride is just over an hour and with a Panny 3400 mAh I don't really notice the light getting dimmer. I have two batteries and rotate after each ride.

Originally Posted by dwmckee

The cheap cell I do not think qualifies as 'junk'. It ran nearly as long as the expensive cell but was way less expensive. No doubt the better cell ran a little longer, but not 3x as long to go along with the 3x price.

Originally Posted by Litespeedlouie

AFAIK, a T6 bin of output level is the same whether XM-L or XM-L2,

Originally Posted by znomit

In between Cree changed the binning temperature from 25C to 85C.
The XML is binned at 25C, the XML2 is binned at 85C (more realistic). This gives about a 15% boost for the same bin.

@700mA Minimum Luminous flux(lm) T6:
XML = 280 @ 25C
XML2= 280 @ 85C ... but 318 @ 25C

And the jump from XLM T6 to XML2 U2 is 280 to 341 (@ 25C), over 20%...(that would make it a U4 if binned at 25C).

Originally Posted by colleen c

It's been a while since I posted here but I have some info that may help or confuses you more. There is a lot of factors here that will affect what you have read. A light can drop lumens when the light heats up. This is especially true in cases with the small lights with LED that are driven hard. It is a waste as all those power are wasted to creating heat and also increase the possibility of damaging the light. Some manufactor will overcome this by using auto step down programed into the driver. One company that does this is the well known Zebralight. Lights that does not have this feature will simply have less lumens after several minute from the initial power on. During this period, you will notice some decrease in light intensity. This process will continue until there is an equilibrium of the heat produce from the emitter and the amount the heat will dissipate from the flashlight body.

Another factor that affect the total lumens coming out of your flashlight can be cause by the batteries. A freshly charged 18650 can yield a higher current load, however it will decrease as the battery get run down. The internal resistant of lower quality battery will affect how well the flashlight can hold lumens regulation. This is a less problem with flashlight that are driven in the lower range since the current draw from the battery is less. If you study search for folks who has charted out various battery, you will notice how the better battery can affect overall performance under a heavy load.

One of my biggest gripe about the ultrafire is the inconsistency of the battery. I order many from DX and most are generally ok with light to medium load application. However there are several bad batteries that stand out from the rest of the batch. Generally speaking, that is ok since I can just simply recycle those in the waste bin. The biggest issue is if you are planning to use those in flashlight that are not single cell. Not knowing how if the cell are equal in spec can lead to some serious issue such as injuries. In this case, it is better to just use better know quality cell that are more consistent with the specification.

Last thing worth mentioning here before I stop yapping. Generally most light tested at MTBR forum are multiple battery cell light. This means that the voltage and current the battery pack can hold better regulation throughout the duration of the light. There will be less current sag from the pack and also the voltage will remain above the 6 volt mark. Keep in mind that Led need some minimum FWD voltage to stay bright. It is something like 3.35v for a U2 if driven at a specific current. Multiple cell pack will have no issue holding this spec but a single cell flashlight will drop out of this requirement after a certain amount of runtime. This is even more so if one was using very cheap flashlight battery............Ok hope I did not confuse you much.

Originally Posted by dwmckee

I am most likely going to use my lights on medion (500lm), low (250 lm) or flash mode. Would the draw in these conditions mitigate the problems of some lower cost batteries? I have about 6 - 8 TrustFire cells that have been running pretty reliably. Not as good as my Panasonics, but still pretty satisfactory, but I am not using any of them to drive a single cell 1000+ lumen lamp.

Also does the breeze from riding help cool the light enough to make a difference?

Originally Posted by noglider

It's really nice to see you back, @colleen c. You seem to be the most knowledgeable person here.