New Solarforce XM-L dropin, 8,4V model

There you go:

Anyone got this on order yet?

Wondering, will it be driven like those 4,2V ones. They seem to draw 1,60-1,70A quite constantly.

Hmm . . . Wonder if this would be well suited for a mini-Mag mod with 2 14500’s?

Finally a multi-mode 8.4 volt XML driver with modes and no flashies. I have been searching for months to find a driver like this with decent output. The problem is it's highly unlikely we will be able to get the driver without buying the whole drop in. Solarforce has the low voltage XPG drop in that I absolutely love it pulls a battery down to almost zero volts great for a CR123 but the driver is made of unobtainium.

It says more than 3 hours run time at 100% output so it can't be driven that hard. Guessing they used two 2400mah batteries you would get 2 hours of run time at 2.4 amps so to get 3 hours so it would need to be driven at 1.7 amps max on high to get 3 hours of run time on high with two 2400mah batteries. I really hope they over estimated the run time and ran it much harder than 1.7 amps on high.

My first thought exactly. :wink:

Nice, an 8.4V. But the spec isn't too promising. Getting 3 hrs runtime using 2 battery connected in series, this one actually is rather low driven. Probably designed with longer runtime in mind.

Assuming 2400mAh battery was used, and runtime is actually 3hrs, current draw would only be 800mA (remember putting 2 batteries in series only increase the voltage not capacity. Current draw will draw from both batteries simultaneously).

The good thing, on higher 8.4V voltage the LED will be brighter even on 800mA, circuitry will be more efficient, and batteries will take less strain. But on paper, until proven otherwise, this drop-in seem ONLY similarly matched with its single battery drop-in cousins, except wiith double the runtime.


I need it for my new L2 extended and it's Solarforce's last chance with Foy when it comes to drop-ins.


I kinda like them to be readily at 1,7A or so. There is a selection of Full-flavor dropins with direct drive or 2,8A.

Because I like my 1,4A low amp dropin, these are also accepted by me. Great option to build Solarforces for newbies, less heat problems yet bright and better runtime :)

I mean: full power "is already done". We pretty much know how much you can get out from XM-L + P60. With this, you get another option without having to solder.

Good try. Well, actually, I'm just being nice - it wasn't really.

You got one thing kind of correct - putting two cells in series doesn't not increase the Amp-Hours of the system. It does, however, increase the number of Watt-Hours.

Your comment about the LED being brighter on 8.4V than it is on 4.2 (assuming it was getting the same current after regulation) is just plain wrong. 100% wrong. 800mA to an LED from a million volts of input voltage will produce exactly the same number of lumens as 800mA to an LED from four volts of input voltage. That's why we use regulators - so that we can REGULATE the input to match our desired output.

To make the math a little simpler, lets assume that a cell is 4V, and that the forward voltage of the LED in question is also 4V (both reasonable approximations of reality for our purposes). Using a buck-converter, a single cell would require the converter to run at 100% duty cycle to maintain the forward voltage of the LED. If the LED consumes (again, using easy numbers for our sake) 2A of current at it's forward voltage, then again, with a single cell, the driver will remove 2A from the cell 100% of the time. Every hour, 2Ah (2000mAh) will be drained from the cell.

Now, switching and using two cells. All else the same. The buck converter will have to run at 50% duty cycle to maintain the forward voltage of the LED. We can't simply drive 8 volts into the LED and expect it to last for more than about 10 milliseconds. The output of the converter will be smoothed by a cap and an inductor, so the LED will see a (fairly) steady 4V. Again, the LED will consume about 2A at 4V. From the LED's perspective, nothing has changed. The two cells, however, will still need to provide 2A of current, but they'll only have to do it 50% of the time. Every hour, 1Ah (1000mAh) will be drained from each cell.

All things being equal, we've doubled the run time without changing the LED's output at all.

Using the numbers that have been assumed in this thread:
2400mAh cells * 3.7V * 2 Cells = 17.76 Watt Hours

17.76 Watt Hours over 3 Hours = 5.92 Watt Hours per Hour

5.92 Watt Hours / 3.5V (Forward Voltage of LED) = 1.69A to the LED.

I would guess that using two 2400mAh 18650 Cells, Assuming this module really runs for 3 hours, it runs the emitter at about 1.7 Amps.


I might sound a fanboy, so don´t mind but about dropins...

I have now had about half a dozen of them and they have always had flawless SMO reflectors. UF or KD dropins have had sometimes flaws even in OP -ones.

Might be just luck and bad luck?

So the emitter is the same... I see... that changes everything! So only the driver is 8.4V and it regulates voltage down towards emitter.

I thought somehow they manage to get emitter that also runs on 8.4V... probably twin dies or something. My bad.

Anyhow, in that case, PilotPTK's calculations are correct. Bottom line still the same.. same output, double runtime.

Exactly - Now you've got it.

Does anyone have this already?

Any idea of the draw with ONE battery only? :)

Ahh, might just order one with a slight risk, going to use this to a one set to my friend.

Thing is, this comes cheaper combined with L2 2011. 3-mode low volt XM-L is not even available as a combo?!

I just got mine a couple of days ago.

Amps in an extended L2X with 2 unprotected Panasonic 18650/2350s:

.42 - high

.18 - medium

.05 - low

Pulled the same with 2 Xtar 18700s.

Amps with L2X single and one TrustFire flame 2400:

.78 - high

.33 - medium

.07 - low

Same light with one Xtar 18700:

.80 - high

.34 - medium

.07 - low

As usual, Solarforce drives their drop-ins very conservatively. This guy has a slightly off-white center spot and a greenish corona that fades to white/lavender. Despite what the low amps suggest, this is a great drop-in that seems purpose-built for the long-man L2X. I love it.



Not sure . . . . 80 maybe? Don't know how it happened.

Fishin, you're one of the few people here that remembers when I had only about a dozen.


Oh, goodie.

Wow! 80 flashlights in a little over a year from when you joined BLF. That's amazing! I think Don is the only one with more lights that you.


old4570 and Boaz should also have more than that. The Foy has a 4-5 times higher flashlight-acquired/per-time coefficient as myself.

That's a new flashlight every ~5 days!

ObsessivecompulsiveFoy much?

I think I have maybe picked up 10 new flashlights for myself since joining up with the BLF team. I guess I'm a underachiever.