C8, 2x18650 build question

I want to build a 2x18650, xhp70.2, Convoy c8. I have all of the body parts including a choice between an o.p. and smooth reflector.

Finding a 17mm driver for this build has proved to be an exercise in futility. I wound up finding some 17 to 20mm brass ring adapters on eBay and bought them - I hope the threads match!

Well, I think I may still have the same problem. Am I able to use a 6v emitter with a 3v rated, 2 cell driver? In other words, why would an 8.4v - or more rated driver power a 3v emitter but not a 6v one?

Sorry in advance if this is a challenge to my own common sense, but I’m really trying to grasp the electronics end of building these lights while trying to be safe at the same time.


If you’ve never built a xhp70 light, you will be impressed with a C8.
The reflector is big enough to give you a good hotspot and plenty of spill. With around 5000 lumens it will be fun.
Try the smoke reflector!
You can also do 2 18350s without the extension tube. It’s a great build with a DD driver, which I assume you can get right now? Hence your driver question…. which I can’t answer.
Or you can skip the driver, and run straight power to the led from 2 cells for now and stick a driver in it once you get one.

look up zener modded fet+1 drivers many 17mm options

Thanks for both of your responses.

I was looking at this driver for my c8 2 cell build. It doesn’t mention anywhere that it can or can’t be used with a 6v emitter.


- I have a high power, multi emitter drop-in that I believe is direct drive. It’s power is awesome, but drops way too quickly and steadily - something I want to avoid.

- As far as running 2 18350’s, I actually want the the longer body and longer runtime.

- I never heard of a “smoke” reflector. What’s its effect and where can you buy them?

- I considered FET drivers but I felt the driver I listed here would yield better

many drivers are available all depends on what you can fit in a c8 i’ve used a similar driver 22mm in a blue laser c8 build works great.
thought you were looking speifiall for a 17mm

I built a 2 cell C8 with an extension tube for 2x18650 and a sliced LH351D. I used Mtn’s 17mm MTN-MAXlp 2s buck driver which worked great. Excellent driver with great firmware.

That’s the driver I wanted to use with their 4.5 amp build - their highest recommended for a 6v emitter, but it’s not available right now. It is available in 3.5 amp, though. The driver from AliExpress is rated at 5 amp. How much difference in performance will I see between 3.5 and 5 amps?

Have you seen the C8.2 versions, instead?

Suited for 1, 2 or 3 batteries

Ok, now I’m thoroughly depressed!

I think is what you are looking for. FET Driver - 17mm

You can order it with the Zener mod for 2s input. So if you select “yes” to the Zener mod and 6v lvp. Then you can do two 18650’s in series to power a 6v XHP70.

Thanks, but for this build I’m gonna stick with my original choice provided it works with a 6v emitter. Does anyone know the answer to this $64,000 question?

That’s a buck driver for running a 3v emitter. So it is meant to run off either one 18650 or two and step the voltage down.

I’m using this driver in another build


Other than the size difference of the 2 drivers, one description mentions “6v/xhp70.2” and the other doesn’t. I’m using the same 8.4v battery/6v emitter combo in both lights. How do I find out for certain if the driver I want to use will or won’t work with a 6v emitter?

Same question here, hoping to get some ideas too.

My 2S C8 build is with an SST70 so I’ve also been looking for a suitable driver.

Mine is the older style Convoy C8 (not C8, not sure there is an ext. tube for C8?) Does your C8 have a 17mm or 20mm driver space?

At one point the older Convoy C8’s only had a 17mm driver space, I guess that was upgraded to 20mm at some point? I got mine shortly before the C8+ came out so it’s a later model of the older style. The best I can tell the stock driver space in my C8 measures 20mm but I haven’t been able to get the driver out, the retaining ring is very tight so I need to make a pliers/tool to fit the small holes better.

I looked at the 20mm MTN-MAXlp Driver in 6V output the maximum drive current is 5A, but I’m thinking I’ll want more than that to drive the SST70, so I’m also looking at the MTN 20mm FET/Zener If I go that route I may need to limit current so the led doesn’t fry.

I also was looking at the 20MM Lexel Buck driver 2S into 6v XHP50/70, Adjustable input and output voltages and current up to 8A, looks like $21 (euros) shipped, sounds perfect! however Lexel hasn’t been around for months (it was mentioned he may have been ill)

I would just message them and ask to be sure, but the question was answered in the Q/A: “3v” (Scroll all the way down below the reviews)
By the way “LHT Flashlight store” on aliexpress is actually Kaidomain or “KD”, they always reply to my questions via the aliexpress message center,

Here’s a link to that driver on the KD website: KD 20mm P4000 Driver, you can check out all their drivers here

Auto correct…. SMO reflector.

Unless it says for 6V emitter it is probably for a 3V emitter.

In principle a buck driver should work for both a 6V and 3V emitter, but there is some configuration in the driver which determines the max output voltage. That is pretty much all I know about it, but I wouldn’t count on it working for a 6V emitter unless it says it does.

My C8 has a 17mm driver pocket. How were you able to fit a 22mm driver in there? Did you bore the head and tap new threads? The adapter rings I just ordered are going to be useless. I thought they would adapt a 17mm opening to accept a larger board, but it’s actually the opposite.

As EasyB said the default is 3v but most drivers should list input and output voltage. If you look at the driver you listed it says “Output 6v” so that is what needs to match your LED. It also says “Input 6V-12.6V” that is what needs to match your battery voltage. That driver could run a 6V LED off of 2 or 3 li-ion cells in series. the other driver you linked to is not labeled as clearly. It gives us two important pieces of information (1) it is a buck driver, that means it is meant to step down the voltage and (2) it will take 1 or 2 cells and so it goes from 3V-9V input. So since it does not step up the voltage and it can run on one cell, it is not meant for 6V LEDs (The pictures also show output at roughly 4V). So again EasyB gave a good short answer, if it does not list output voltage you can probably assume 3V. Looking at specs., learning about different driver designs and making a few inferences can aid you too. Hope that helps.

First, I want to thank everyone on this thread for sharing and helping. Nice people - Good help!

Ok, 6v driver it is - or is it? After reading everyone’s comments, I was thinking of just scraping the xhp70.2 all together.

Finding a 17mm, 6v, 2 cell, buck driver is impossible. Mt. Electronics is the only place that offers something that may or may not workout. This is their only 17mm buck driver that will support a 6v LED. The 4.5 amp build is sold out and Richard doesn’t know when he’ll have more. So I need to step down to 3.5 amps. As I posted earlier, I’m new at this so be patient. Ok, here it goes: I don’t know if 4.5 amps is too much current, enough or too little for an xhp70.2 with 2x18650/10 amp batteries. More importantly, what percentage of performance can I expect to lose going from 4.5 to 3.5 amps (best guess)? In lumens maybe?

Thanks again

(1) If you want to simplify things, do FET driver, 3V XHP50, and use one battery. With a good high drain battery (Molicel P26, VTC5, etc.), that would probably make about as much light as as an XHP70 at 4.5A.
(2) It doesn’t have to be a buck driver, the FET driver I linked above from mountain will work too. It will almost certainly pull more than 4.5A though (Like closer to 10A with good high capacities 18650’s that will handle 10A. If you want max output, that’s the ticket. That’s a super hotrod though.
(3) If you can find a zener modified constant current driver that would work too. Those drivers are very common but if you don’t want to do the mod. then that might be a deal breaker. It would be hard to find a modified one ready to buy.
(4) XHP70 has been tested as making 4,110 lumens at 4.5A and 3,380 at 3.5A.