I’m not sure if it will be viable / practical to build. The below probably also implies a custom build. I’d like to build more than 1. A bit more detail about what I have in mind:
Goal: The main idea will probably be a flood light, but some throw might be required. I’m thinking about the farmer / hunting team driving in their trucks, scanning the perimeter from inside (passanger seat) / outside (on the back). There should be a lot of light, for a long time, constantly. The range I have in mind is probably around 150-200m.
Portable: Should not be too heavy to carry, but does not have to be that small. It will obviously be a big light. Should have an attached battery pack which will prabably require in-light charging. Its going to be a mission removing multiple 18650s/26650s for individual charging.
High Output: I’m thinking about 6-8 XHP-70s doing around 4 amps each, possibly each led having its own regulated driver. This should be good for around 18-25k lumens. Heat sinking should obviously be good to do constant runtime. One might think about active cooling, but this might be an issue with robustness, dust, damp weather. Individual reflectors or optics? I believe an optic for each led would be easier, but getting throw from this might be an issue? Not sure how available optics are for these leds? Individual reflectors, not easy to build, better throw, getting a nice beam pattern also not that easy.
Robust: The light should be strong, simple, single mode (my first option) and weather resistant.
Long Constant Runtime: Should be able to run the light constantly for around 60 minutes. If the light pulls 8 leds x 4 amps (32 amps) one will probably require around 14 x 3200mah 18650s, something like 2S7P. Mmm, this might not be that safe? Maybe some of the RC battery packs might be a better option, also for the charging requirement. To make this easier, a 12v system might be better? Then, I think the 12v XHP-70s are not very popular/freely available?
It would be great to just hear some comments / get some advice first. I’ve seen some interesting custom builds on YouTube. As said, this is very early days, not close to sure if I’ll jump into this boat!
You can start by reading this thread by Old-Lumens. He built a Triple XHP-70 lumen monster that you can get some inspiration from. In fact, his build would just about meet all of your requirements.
All XHP-70’s and XHP-50’s are capable of being run in either 6V or 12V configuration. You just need to buy the right MCPCB for the configuration you will be using. I know there are 6V-only MCPCB’s available, but AFAIK, the 12V MCPCB’s are actually dual-config capable (either 6V or 12V, depending on jumpers). But, yes, they are available.
18650’s will give you the most capacity per cubic inch, and also most capacity per dollar. They are also very common, so very easy to find and buy. I’d recommend using them over 26650’s if you have a specific amount of space and want to fill it up. If, however, you want to keep the cell count down, then 2X 26650 can hold more capacity than 3X 18650. Extrapolating that, 14X 18650 would roughly be equivalent to 8X 26650.
I think you meant to say 2S7P configuration for the 18650’s that would give you 8.4V to work with. Yes? Those will fit into a pipe with ~55mm interior diameter, whereas the equivalent 2S4P 26650 build would require ~65mm interior diameter pipe. If you’re into inches, that would be a 2-1/4” ID conduit for the 18650’s and a 2-1/2” ID conduit for the 26650’s for roughly equal capacity. With a thin-wall conduit, the 18650 configuration could be held in your hand without needing another handle. Then again, the head is going to be around 8-9 inches diameter if you go with only a triple build with the same reflectors O-L used. So, you could group all the cells into a larger diameter conduit and make the total body length a few inches shorter, and add a handle for carrying. That would probably end up looking better.
Hi David. Thanks for the feedback. Sorry, I did mean 2S7P - 7 parallel banks of 2 cells in series each. I’ve corrected the OP. You gave me some ideas, I’ll reply shortly…
Why not use 12v vehicle supply? Gonna be far easier than managing all the cells required to give that sort of output for that sort of time! I do a lot of hunting and we use a night force roof mounted lamp and a Vinh modified fatmax (pistol grip awesomeness around 350k lux) for the occasional times we get out the truck.
I’d like to build something myself, thats what makes it fun, for me at least. I’ve been thinking about a 12v supply and it might be a good idea. One might think about an optional battery pack, that can be attached at the bottom of the light, something in the line of 2 or 3 x 7ah lead acid batteries. Will be heavy though, charging will be easy.
