Using the new Xp-L2 at high current with Linear Driver and 4P cells

Flashlight Modding and DIY Parts
1

Hi everybody, in a nutshell, I want to build a single emitter, high current light from this SRK-like host (except no e-switch) that has 1s4p cells, and I've decided to keep it in this battery configuration, so I'm limited to 1s voltage ranges.

Here's the host from fastech this version is known as the SME-4628 :

https://www.fasttech.com/products/0/10020308/4368900-sme-sme-t628-led-flashlight-gift-set

It's a 46mm driver size and I already have mtn electronics 46mm linear driver, basically a giant Nanjg style 7135 driver. discussed in this thread:

https://budgetlightforum.com/t/-/27369

and found at mtnelectronics here:

http://www.mtnelectronics.com/index.php?route=product/product&product_id=270&search=46mm

The driver shelf and led shelf are not very far apart, so I've ruled out piggy-backing a boost driver for an xhp-50 or something, although that would be better and I plan to do that with a different light in the near future. I just feel keeping the light in 1s configuration without having to mod the reflector etc is much easier and more geared towards my skill level at this point, so let's just assume the light is going to be single cell voltages without a boost.

I plan to run an Xp-L2 at max 5A by removing chips from the normally 12a mtnelectronics driver and Rmm has kindly agreed to flash the driver with firmware to use without an e-switch.

http://www.kaidomain.com/p/S026187.Cree-XP-L2-HD-V6-1C-White-5700K-LED-Emiitter

My question is basically to check my understanding and decide if using a linear driver with plenty of battery overhead (for example, four 25r's in parallel so each cell is only having to give ~1.25ah) is the best choice here. This light will be used as a tool for seeing outdoors, navigating a boat, and 'cause super bright lights you make yourself are cool of course, otherwise I'd just buy something off the shelf. I wish there was a perfect buck driver for this situation, but its a unusual size driver and small driver cavity, so options are limited.

But back to my question, I figured choosing the linear 46mm instead of the Fet direct drive version is the best choice with the low Vf of the Xp-l2 from a practical standpoint, If I'm going to use the light out in the wilderness and not just to make the brightest flamethrower I can. Is this a correct assumption? Or will the lower Vf of the Xp-L2 cause the 7135's to heat up excessively? All of this is assuming I can really improve the thermal path of this light via adding copper around the led and reflector, silicone thermal pads, and whatever else I can come up with or copy from others on here. If you were going to build a high current single emitter light with 4 parallel cells, is linear and the Xp-l2 the way to go?

Or, would a different LED like the Xm-l2 or Xp-l hi serve better from a Vf standpoint? I know the xp-l hi would throw better, but this is going to be an all purpose flood/spotlight so really I'm most concerned with matching the driver and LED correctly for efficiency over throw/beam pattern, and I think the Xp-l2 would be easier for me to get right in the reflector vs the Hi version.

After scanning the forums as much as I could to try and understand the relationship between Vf and battery current in linear driver, I was wondering if anybody would care to give their opinion on this setup and if it could be improved while staying within the parameters of 1s cells and either an Xm-l2 or Xp-l2 size emitter. By the way, the led will be on the 32mm maxtoch dtp board and I'm going to do as much potting of the driver and additional copper as I can manage, and the host has decent mass and cooling fins, so hopefully the 5a will be handled well, even though it won't be used on 5a for longer than maximum ~60seconds at a time. Is 5a a pointless gain in lumens for the heat it will generate?

Thanks for taking the time to read this and add anything you care to. Also, lots of thanks to all those who post their testing results and opinions on here, and spend hours and lots of money to test these things. Too many to list, but it's been extremely helpful and informative.

2

Did your light have the 7135 based driver that some of those lights had? I have the same light, different brand, and I just bypassed the current limiting resistors to go straight DD with some regular low current cells. I used an XM-L2 in mine, just to keep the focus and centering the same as it was work the OEM emitter.

3

I’m going to jump in on this thread unfortunately not to be useful but because I logged on just now to ask this very same question. No joke!

I’ve stumbled through many of the same thoughts but I am now definitely limited to 3p battery config.

I’m wanting the the brightest emitter for this criteria similar to you but maybe willing to be a bit more risky :wink:

Options:
Xml2 u4
Xpl v6
Xpl2 v5
Sst40?

I know the last two will be the brightest in dd but has anyone successfully run xpl2 or sst40 using a dd driver?

Op, if you are going to be limiting current to 5amps the emitter brightness of these four leds will be neck and neck. The battle for the brightest at 5amps will probably be won by the best bin. For example, if you have xpl2 v4 and xpl v6, the first gen xpl will be brighter since Cree does their Brightness binning by amps. However the xpl2 will get higher amps from 4p if current is not restricted. So if you want to get up to 6-7amps from 3v you will need low vf emitter as xml2 will run out of headroom.

Note that the, xpl2&sst40 will be more effitient than xml2 or xpl at the same current.

I just don’t know how hard these low vf leds can be pushed? Surely someone must be trying this out there somewhere:) I’m really hoping to be able to go dd with xpl2 or sst40!

4

If you are only doing 5A, an XPL V6 might be a better choice with your 7135-based driver. With the low Vf of the XPL2 the 7135s might be fine, but they will generate a lot of heat, quite possibly too much heat.

Regarding running the XPL2 or SST-40 direct drive, I think you are getting into the danger zone if running single emitters especially if you are running multiple cells in parallel. With the SST-40 and a fully charged high drain cell you will be very close to the ~8.5A that djozz found his LED died at. With the XPL2 people have run then direct drive without killing them. Check their respective djozz test threads for user reports.

5

unfortunately mine came with the cheapest version of the drivers seen in these lights, here's some pics of it in this thread,

https://budgetlightforum.com/t/-/43819

but I don't really want to go the unregulated direct drive-route in this setup. It'll probably be run with unprotected high output cells, I'll save the protected ones for lights that really require them. Modding the stock board and repeat testing to see what happens after I may or may not have gotten the mod right was something I figured would be better handled by just buying one of the mtn electronics boards and considering it squared away at that. I wish I had gotten the 7135 version that comes in some of these

6

Thanks for the advice EasyB and Lightrider, I'll take that into consideration, especially since I can de-dome the XP-l at a later date if I chose to, where I won't really be able to with an Xp-L2. Texas Ace's death test of the Xp-l2 is mostly what I was considering when trying to answer this question myself, but I didn't think about the importance of which bin led I'm using.

https://budgetlightforum.com/t/-/43270 - Texas Ace's Xp-l2 info

At the relatively high currents were talking about, does the XM-l2 size package offer better thermal characteristics with it’s larger size base, or will that matter if they’re both on similar dtp copper boards and only running for max 60-90seconds in turbo, often much less?

Is the V6 bin in Xp-l2 I got from Kaidomain believable or do they often inflate/alter the bin claims of their leds? I seem to have pretty good luck with them in limited experience, just wondering

Starting to think you guys are on the right track, xp-l hi or xp-l v6 might be better in this application and save the Xp-l2 for a high efficiency Convoy tube light-type thing maybe with a buck driver or something.

7

Xml2 actually has a bit more thermal resistance than the others. It doesn’t like going above 5.5amps. Atleast the “newer” ones anyway. I think people were pushing the early ones up to 7? EDIT: xml2 2.5 vs XPL 2.2 degC/W.

Kaidomain is very trustworthy and an authorized cree dealer. So they will sometimes have rare higher bins from cree. I’ve not heard of any trickery or outherwise shenanigans like some of the “other” places. :slight_smile:

8

Whatever becomes of this light, here's some pics of the switch board with springs bypassed, jumpered the traces and added a 6A switch. Had to use a smaller green boot from a cheap c8 to accommodate the taller switch, original boot was black.

Unscrew the tail cap to reveal the switch board:

not the cleanest, but I'm getting better.

and the shelf the aluminum circle sits on which has the mcpcb on top. Very little room underneath for a taller driver than stock. There's anodizing under the aluminum board, so I'll probably sand that off for a better thermal path to the aluminum shelf. Has arctic silver on it from previous attempt at modding:

Original probably fake XML with thick aluminum mcpcb:

9

Looks like fun!
I don’t think you need to worry about the anodized shelf. I believe it was discussed somewhere and found to be insignificant. As I’m writing this I’m realizing that I don’t have good memory of this discussion. Maybe it does matter? Are more confident than I? :smiley:

10

not like my case, normally i receive complete order from XP-l ,but yet slight shortage from XP-l . last time i bought from other suppliers recommended by my venders, if you need to buy a relative better price and lower transaction risk, you can go to hongkong inventory. www.hkinventory.com , my batteries and chips orders are all fulfiled compared with major prevailing supplier at a, like say, 60% lower price, those vendors gave me a really good price, and i make it successful by escrow one week. escrow order . though Xp-L2 can deliver on a genuine basis and Xp-L2 sometimes gave me headache for shipment delay, they’re 80% satisfictory on a whole scale. last week i got my 4 order by HKI escrow 2 weeks,( actually 5 days after payment cos they are counting for business day) pardon if any grammer mistakes. :wink:
also one worth mentioning is that I requestecd a full refund based on escrow order cos the China vendro refused to ship out 3 days after my payment since my customer can not wait esceeding 3 days more and cancelled order, i dont know if i can get the same treatment by EasyB and Lightrider.

11

Any others who have tried xpl2 sst40 dd successful or not? :slight_smile:

Sorry to OP for taking over your thread a bit.

12

I’m using an XP-L2 in my Convoy C8 with Texas Avenger TA17 Fet+1+6 driver. It draws 9.5A at turbo. It drops down to between 8 and 9A. I measured 2034 lumens at start.

13

Lightrider, not at all, I'm hoping to learn more about the Xp-l2 too as more people use it in real world flashlights. Hopefully the lower vf for efficiency and ability to take higher current makes it more useful, if only they would offer it in a Hi version soon. Thinking of using the xp-l2 with this buck driver I snagged before they sold out in a convoy S series host as a bike headlight/keep in the car kind of light:

http://www.kaidomain.com/p/S024285.KD-BD8P-17mm-Single-li-ion-Buck-2_9a-Driver-Board-2_7V-4_2V

Also looks like a useful one for a red xp-e2 triple. Odd that it only takes a max 4.2v though, seems like it was designed for single-cell low vf lights like red Leds. Hopefully the current can be slightly increased via adding a resistor on top of that r100.

I'll update with pics etc... when I finish the original light this thread is about, definitely leaning towards XPL V6 now.

14

I’m thinking about braving it with the xpl2 in my 3p setup. But then again Ild like to try the sst40 also… ahh. Do I sound confident to you? :slight_smile:

My trouble is that I have a big host and it feels like anything under 2000 lumens would be a dissapointment. I’m kind of regretting going for parallel instead of 3s. But there were a number of good reasons I chose what I did. I’ll keep listening for more advice/information.

On a side note, I’ve asked some of our driver people if it would be possible to have the software regulate the output to 80% or so while battery is fresh and then transition to 100% when bat level drops to 3.9/8 or so. This is of course speaking of the turbo mode. This would be a help for these lvf leds. It would allow the use of dd drivers and keep a very high output even toward the end of a charge. However, either I received no response or I just don’t remember. I don’t remember:)

15

I have build TA drivers with 15+1 7135s without a FET installed, with only 2 channel Bistro firmware if you want
as it has a single channel with one 7135 the moonlight is better and more efficient

the price is about the same as from MTN, but the driver can run with a FET later if you want

2S/2P or 2S/4P is also possible

16

Thanks for all the help guys, Looks like I'm going to go with Xp-l V6 de-domed. Hopefully with a spacer that will fit the reflector nicely. The reflector isn't much larger than a C8, really just wider, especially when you compare it to something like the convoy L2. So this light will basically be a 7135 driven C8 in beam profile, with enough battery overhead to remain in regulation around ~5a for a long time (hopefully).

Now I need to devise a way to get the heat away from those 7135's. My current choices are some small copper pieces I could attach to the 7135 with thermal paste/epoxy/solder, those inexpensive grey-ish silicone cubes, or running solid copper wire from the chips to the body of the light. Ive searched the forums but other than Rufusbduck's building a heatsink around each chip and separating them from the board, can't find a consensus on the most efficient way to heatsink the chips. Any ideas? Is potting with thermal epoxy enough? Which pin is the target to drain heat from? I'm guessing the large ground pin in the back and in the center (front) is where the heat is, so will increasing the heatsinking of the ground-wring on the driver itself be sufficient? Any thoughts or links appreciated, will post final build and beam shots when I got em. Thanks!

17

With the XPL at 5A there won’t be too much heat produced by the 7135 chips. The heat is proportional to the voltage they have to “burn off”, and at 5A there won’t be a large voltage difference. So I don’t think you have to worry too much about the chips burning up. As you suspect, I don’t think there is a great way to heat sink them. You might try those conductive silicone cubes. That is probably the easiest and least messy method.

18

With three 30q cells rested at 4.17v or so and I’m getting 7.9amps with XP-L2 and 8.3amps with sst-40. So it’s pushing the limits as expected. I’m using TA driver.

I really like the tint of the sst 40 when pushed hard. It is white and just barely purplish. So I think I’m going to go wth the sst-40. I hope it makes it :smiley:

19

That sounds awesome Zozz, would love to see some beam shots when you’re able. What cell were you using? Though smaller die size, sounds almost like xhp50 lumens from a single cell. Can you give us an idea of how long you would run it on turbo aprox before stepping down and/or burning your hand? Did you pretty much just drop in the driver and new led or add anything else for heat transfer besides a copper pcb? Would love to know you’re impressions