Hi, guys it’s been a while since I’ve used this site. I am enjoying the 18650 convoy you last recommended for me. Today I’m looking for something different. I want to buy a helmet mounted light which has and external battery for night mountain biking. I’d like it to have atleast 2000 lumens and be able to run for atleast 2 hours. Ideally the light would have a 2 to 3 foot long cable that would run down my back into my Camelbak to get that weight off my head. Something similar to pic related. They have really nice ones for $300 plus but I’m sure you guys can help me get a nice Chinese one for $80. I looked around the forum and I cannot find where you are discussing things like this. If you could please point me to a thread like that or just drop recommendations it would be much appreciated. Thanks!
Good question. I have an old Lupine for this application, but that one’s expensive as hell. I’ve never seen any talk here of this type of light, looking forward to people’s recommendations.
2k lumens for 2hours and 80$ headlamp sounds sci-fi
Yeah, I don’t think 2K lumens for 2 hours can happen with a single cell headlight in 2024.
Maybe with several cells, but that would be quite heavy. 
2 XM-L3 (in series, with a synchronous boost driver) running 1000lm each, and 2 21700 cells in the backpack might just be able to pull that off without costing too much.
Whether or not that can be made for 80$ (even in China) is a different question. Maybe 3x18650 instead, since those are easier and cheaper to source.
Will need some seriously beefy cooling fins on the head (or require the owner to drive the bike real fast :D).
What do you mean that sounds Sci-fi? My 2016 Diablo MK seven could do 1300 lm for one hour and it’s so small and it probably has just one tiny 18 650 battery in it. You’re telling me if I had like a big old battery block inside my camelback they probably has three or 418 650s or maybe some of those large larger 21700 batteries we couldn’t get 2000lm for an hour?
I want something like this, but for a third of the price. You guys mentioned that it getting too hot could be a problem and it would need big fins. That certainly makes sense. I will be riding in 100° temperature here (even at night) in Arizona so it’s gonna be hot to start with. Also, I was reading in this article which I will link that having more than 2000 lm is not desirable because it will temporarily blind you and mess up your night vision. So perhaps I don’t need 2000 since I will already have my convoy on my handlebars. But I would Like something larger than the exposure MK7 that I typically use on my head.
Choosing The Best Mountain Bike Lights for Night Riding | The Pro's Closet
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I guess you have to DIY.
Probably going to get this sci-fi light
Years ago, I was using a wired headlamp set up although it was halogen /nicad not led. I have since moved on to using a single cell self-contained helmet mounted headlamp. I carry spare cells and replace the cells when needed. For me this works really well. I feel less constricted without the wire from my helmet to the backpack. I’m also able to ride without the backpack too.
I understand your riding style and sessions are probably not like what I’m doing.
…for 80$ ?
I am also interested in this “external battery” headlamp design. I know you can run the Convoy H2/H3/H4 headlamps from a power bank, but their USB-C port position in front is not ideal for this use.
Manufacturers often use numbers that can be misleading. All flashlights can maintain their maximum output for only a few minutes (1-5), after which they must step down due to excessive heat. The sustained output level largely depends on the size of the body/heat sinks.
A flashlight advertised as “1300 lm” likely steps down to approximately 300-500 lm within the first five minutes, then maintains this level for the rest of its runtime.
The only reliable method to determine a light’s sustained output is by examining tests that include runtime graphs. Typically, the runtime graphs have this pattern:
Btw human perception of brightness is logarithmic: to perceive a brightness twice that of 1000 lm, one would need to increase the output to 4000 lm. The perceived difference between 1000 lm and 2000 lm is not that substantial.
You can get close to that, but the price increases substantially, into the $500-$800 headlamp class. 1Lumen tested a couple.
Thank you for this suggestion
You could DIY 2 heads from a Convoy M1 or similar onto a helmet mount 