Convoy C8+ New look for an old favorite

The XHP-35 can make around 2500-2600 lumens at 2.5A-2.8A, will burn up somewhere North of 3A usually. Anything over 2.5A or so is typically just making more heat without making noticeably more lumens.

The XP-L HI can do around 6.5-6.7A and make up to 1700-1800 lumens. It’s forward Voltage will limit it on a single cell so that it will not burn up.

So if you look at what the single cell from a boost driver is actually being asked to provide, the current from the cell is upwards of 4.5A or more, the driver itself producing heat to go along with the pushed emitter. You’re really not gaining much going 12V XHP-35 on a single cell. That’s what I find in the lights I’ve looked at. Most boost drivers won’t push the 35 to 2.5A from a single cell, so it’s lumens is down around where the XP-L HI is, begins to look like a lot of work to get back to where we started…

Spec sheets? Do we use those here?

BeamO:
The UT02 putting out a pathetic 900 lumens in real world in stock. But the Emisar D1S putting out about 1500 lumens stock. See my measurement google tables. You will fi d various flashlights with a lot of led type and beamshots.

XHP35 will rock once GXB172 or Shocki’s boost driver are out. Which can happen at any time…either close or far, they are a quarter late already.

Thanks, so if I understand correctly this is current draw at the emitter not current draw from the cell? And when the emitter pulls this current, the boost driver is actually pulling nearly twice that from the cell?

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It was all I could find to see the numbers. :person_facepalming: I guess I need to ignore those cree specs and look at real specs here like ZozzV6’s measurement tables.

Thanks I didn’t know! You’re tables are a great reference I should have been looking at.

It really looks like the SST40 dedomed comes out on top over both XHP35 HI and XP-L HI, so I have to also consider that emitter for my mod.

I don’t. I use the CREE PCT. And what I find is that counting the LED only, the highest bin XHP-35 HI is more efficient than the highest bin XP-L HI along its entire rated range. The needed boost driver would have to be less efficient in order for the flashlight to end up less efficient. I thought it’s been said that a boost circuit is more efficient because it’s using the whole voltage output of the cell instead of burning up the voltage difference from the cell to the emitter like linear drivers do. But, I don’t know. Just going off what’s been said around here. I’m curious how real life differs from these widely held BLF beliefs. You mentioned heat, but I’m just looking at efficiency as power in, light out. Heat just makes up the difference in lost power.

In reference to what Dale wrote (post #43 above) how will this new boost driver make the XHP-35 HI an advantage over a FET driven XP-L HI?

Does the PCT go to 2.5A for the XHP-35?

Does the PCT go to 6.6A for the XP-L HI?

If not, on either one, the efficiency numbers are skewed.

The boost driver is converting the ~4V of a single Li-ion cell to ~13V for the 12V rated emitter, so it’s more like 3x or a little more when the cell is fresh. When the cell is dying the driver is pulling even higher amperage to convert 3A to that same 13ish. So the boost driver will pull 5-6A on a fresh cell and up to 9A or more as it dies, that is of course if it’s a regulated boost.

Our FET Direct Drive drivers are very efficient at Turbo as they are virtually direct off the cell, again though we have to consider how far over rated max the emitter is being pushed to get an idea how much more heat it’s making and what that might be doing to the emitter and it’s output. The FET driver doesn’t make heat on it’s own, whereas the Boost circuit does. So that is added into the equation as well.

In the end, if a FET driver is used with an XP-L emitter (HI or otherwise) the output is close enough to the XHP-35 at reduced current levels (those the single cell boost drivers are capable of achieving) that it’s really a waste of money to go with the more complicated circuit.

The SST-40 from Luminus is another not very efficient driver, although it IS capable of 2600+ lumens and from a single cell with an FET driver, the downside to this one to date is the limited tint availability, only available in a blue-white cool tint so far. It’s capable of hitting the cell for 9.8A or so to make the big lumens, so yeah, there’s a lot of heat going on there as well.

Richard worked very hard to make a 17mm boost driver happen, but it just isn’t feasible at that size as it can’t make the 2.5A optimum current requirement for the XHP-35, get’s hot and acts wonky, ends up failing in the long run if pushed that hard. So it’s expensive, difficult to pull off, and the gain is a mere 500 or so lumens IF you can get it work. The XP-L2 is capable of 2300 lumens on the FET driver/single cell configuration so there go the XHP-35’s advantages…

Now, if you’re going to run 4 18650’s in series and Buck the current down to the XHP-35, then the lumens output makes it worthwhile and the throw stays high while adding in a larger hot spot. A clean de-domed XM-L2 will best the 35 in throw, with a considerable lumens disadvantage. So it’s again about compromise and trade-offs.

The UTorch UT02 lights are a good example, using a 26650 cell they still can’t get the driver to boost decent current to the 35 without overheating. They’re giving around 1300 lumens in stock form these days. I pulled the 35 and piggybacked an FET+1 With Anduril running an XP-L HI and am getting 1700 honest lumens for over 200Kcd throw, much mo bettah! :smiley:

Perhaps those new highly touted boost drivers are over a quarter late already for a reason? :wink:

If we could run with a 22mm or 26mm driver, then larger and better components can be used and it might just work, the driver ends up in the $25 range instead of $5 or 6 but there it is, gotta pay to play.

For the record beam0, I have an XP-L HI V3 3A running 6.4A and making 1538 lumens for 1.05Mcd…. from a single 32650 cell.

Yes, that’s 1,050,000 candela, as measured at 50M.

Much higher output, somewhat higher throw, much higher efficacy (lm/W). And fully regulated boost allowing it to get full output from half-discharged cell.
You pay for that with much lower throw-efficiency (cd/W), higher price, larger drivers and worse driver availability.

Come on, don’t compare XHP35 HI to XP-L2.
Lumens may be similar, but the latter has terrible tint and doesn’t throw.

BTW, I wouldn’t drive XHP35 to 2.5A in any of the hosts discussed in this topic. I’d rather do 2.1-2.3.

XHP35 is Pareto optimal in throw vs. output. And by a large margin. You can best it in either, but by sacrificing disproportionally lot of the latter. It is also quite efficient from medium currents up, has good tints and doesn’t require dedoming. They only drawback is that it’s 12V.
And I can’t stop thinking that with a larger package and better thermal path it would be even more awesome…

Maybe. I don’t know. Lone Oceans has shown his driver to output more power than XHP35 can take, so maybe not.
Anyway, I stopped holding my breath. :weary:

I didn’t think such currents were possible with XP-L HI and FET.
According to Texas Ace that’s over 4.08 Vf.
Did you win the Vf lottery or did Texas Ace lose it?

Anyway, that “higher throw” of XHP35 HI that I wrote above doesn’t seem right now. In a low resistance host, with a powerful cell XP-L HI might offer a bit better throw.

Wow over one million candela! I assume it has a jumbo size reflector?

Thanks for all the info and explanation, it was going to be considerable hassle and extra cost involved in trying to use the XHP35 HI, so I’m going to take your advice and keep it simple with an XP-L HI and FET driver.

Since you mentioned it, I remember now it was the larger hot spot (not more spill) that had my interest in the XHP35 HI, which would be nice. But even though I do have a 20mm driver space, after reading all this I see it’s still isn’t worth chasing after the 12V emitter. I’m happy this got sorted out before I ordered any parts.

I guess because there’s so many newer production lights using XHP35’s that had me thinking it was the better way to go. The XHP35 C8’s from Kai reportedly get hot quite fast compared to their XHP50.2 version C8’s, now I understand why.

My lights that use XHP35 HI put out about the same lumens as a FET-driven XP-L HI, but they can do it fully-regulated. My XP-L FET lights suck when the battery gets about 50% drained, whereas my boost-driver XHP35 lights still have their full output.

For example, my Zebralight that uses XHP35 HI will provide full maximum output until the battery voltage drops to about 2.9v, which is almost its entire capacity. Also, since I don’t think Zebralight overdrive’s it, it’s more efficient.

So, I think there are advantages to using an XHP35 HI with a boost driver, even if it’s not any brighter than a XP-L HI with a FET driver.

That’s what I was thinking would be the case. I don’t have either in a light right now, so I can’t compare. But, I can’t imagine the XHP-35 HI would ever switch over from being more efficient than the XP-L HI to being less efficient than the XP-L HI just because you go past the CREE max current rating. Both of them will lose efficiency, but the XHP-35 HI should still always be the more efficient of the two.

The emitter will be more efficient. But the emitter-driver combo?
At high current GXB172 is 90% efficient.
At high current FET driver is nearly 100% efficient.
Now, if we’re talking driving lights with a fresh powerful batteries (and that’s what most of this topic is about), XP-L HI V3 driven to mere 5A does 1500 lm with 80 lm/W.
XHP35 HI E2 is doing the same 1500 lm has 120 lm/W. Drop it by 10%, it’s still much better.
With higher currents the difference will be larger.
So with a weak or not-fully-charged cell XP-L HI may be more efficient. Or maybe not….
At high current….not really.

beam0, you can use an XP-L HD (dome on) and get a larger hot spot if throw isn’t everything, which it really can’t be in a light the size of the C8 anyway.

I didn’t like the ringy beam profile in my ArmyTek Barracuda Pro with XHP-35 HI, for example. So I put an HD variant in it and it’s got a very nice beam profile now.

Zebralights are so cheap, think I’ll pick up a few of em and try em out…. (NOT!) :stuck_out_tongue: So yeah, regulated gives the full output level til the cell dies, but what does that do in the long run to the cell? And you get so little warning before it shuts down, at any rate, compromise rears it’s ugly head…

Put an XM-L2 U4 in the C8+, the lower forward Voltage will keep the FET from allowing too much current draw while it still gives out a lot of light, run time is longer, output is similar, large hot spot for a great general purpose light. :wink:

(Edit, 114 lumens per watt vs 109 lumens per watt, are those few lumens difference really worth worrying about? You can’t see 50 lumens difference on the top end anyway.)
(Edit II, what makes the difference for me isn’t efficiency or sheer lumens, it’s the available UI. I can use the FET+1 and TK’s firmware and have a UI that can back up, not go through all the modes but reverse back down to lower modes and conserve the cell when Turbo isn’t needed. That ability, start on moon and long press for Turbo, that is the game changer as far as I am concerned and it’s why I don’t use a boost circuit… even why I use TK’s FET set-up in lights that came with a boost/35 to begin with.)

Dale, the single cell light I’m modding isn’t a C8, but it is an old favorite, an original UltraFire HD2010, which already has pretty amazing throw for having an outdated emitter (XML T6) with east-092 driver (DD but crappy mode arrangement)

I have one of these copper pills:

Takes up to a 26mm MCPCB, and a 22mm linear/FET driver.
I plan to use a Maxtoch XP 26mm Copper MCPCB to keep the wires away from shorting on the reflector.

And yes throw isn’t everything in my plans for it, I want good throw, but with some useful spill / larger hot spot / extra output.

It’s one of my favorite lights and one of my first purchases when I got into this, and I’d like to make it into something special and useful, so I thought it would be a good candidate for an XHP35 HI, don’t want to derail too much here but I’d love to hear any other suggestions.

I’m also considering an XP-L2 HD (dome on) I have a few (stock) lights equipped with it and the tint looks fine to me.