I have been using the HF 310 Lumen LED Headlamp for over a year. HF Headlamp I really like it for what I use it for (working around the shop, working on my car, etc.) it puts out a lot more light than my previous LED headlamp. I was just using their free AAA batteries in it because it would eat batteries like candy, and several of them leaked and eventually, the headlamp would not work anymore using AAA’s. I ended up buying another to use in the meantime (plus I have a ton of their batteries, I’d buy something to get a pack free whenever I had a coupon), but I figured if the only thing that was wrong with the old one was that the battery contacts were damaged, why throw out a perfectly good light. So I found a 18650 battery holder on Fasttech and temporarily wired it to the headlamp to make sure it still worked. Once I confirmed it did, I permanent attached the wiring and superglued the battery holder to the original battery compartment.
As you can see, I reversed the original battery compartment to superglue the new battery holder on to it, the other side is not flat and would not have provided a good surface to glue the new battery holder to. The side of the original battery compartment with the AAA’s is usually on the inside touching the head with a rubber cover over the battery compartment. I had to stretch the wire since it was coiled, to give some slack because now the wire enters the battery compartment from the opposite side. I routed the headband so that it holds the battery in place. It makes it a little snug fit for my head, so if you have a big head you may need to route the headband so that its under the original battery compartment and use some other kind of strap to keep the battery in place, if you choose to make a similar mod. Its not that the battery is prone to falling out, it stays in the compartment pretty well on its own, but I like having the extra security of the strap. But having the hard plastic against my head, as opposed to the rubber of the battery cover, has been OK. Its not as uncomfortable as I’d feared it would when I first did the mod and realized I’d have to reverse the battery compartment to get it to work with minimal time and invasive changes. The only thing is that since the battery’s exposed, I likely will not use it when I am working on my car, especially when I am under the car and usually rest my head on the ground. Unless I figure out a way to make my own rubber cover for the battery.
Granted, its not a nice, factory looking mod. If anyone knows of an enclosed 18650 battery holder, please let me know. Also, if anyone does a similar mod, I pretty much left the original battery compartment the way it was, I just gutted the interior and used the shell to glue the new battery holder to. If I were to do it again, or re-do this one, I will probably grind off the lip that the battery holder is sitting on. Its not very clear in the first image, but the battery holder is just sitting on two lips that originally kept the rubber battery cover in place. I’d grind that off to give more gluing surface, superglue just barely works to hold these two plastic parts together. Other than those points of refinement, I am very happy with the mod.
I have nothing to measure the light output with but my eyes, and I would have to say that it is slightly brighter with the 18650 and it gets very warm to the touch, which it did not with the freebie HF AAA’s, but even with my old Trustfire Flame in it, it lasts a lot longer than those AAA’s. If HF would take their headlamp and make a re-chargeable version of it with an 18650 as the battery, it’d be very close to perfect for what I use it for, IMHO. Maybe not the brightest out there, but plenty bright for what I need.