Modern high-end flashlights drain a high current; in turbo mode it can reach 10A or even more. This forces these lights to use top-notch high-drain LiIon cells, which are difficult to find of good quality. Maybe this is one of the reasons that are driving makers to use proprietary batteries, as we can see in several recent models.
Another issue that bothers me is the contact resistance between the battery and the light, usually at a spring. I’ve seen posts saying that for maximum performance sometimes a spring bypass is necessary (with the BLF X5). This avoids the spring resistance but not the contact one because the contact area remains quite small. I’ve just made a measurement with 2 wires joined by 2 alligator grips, that have a small contact surface, to have something that resembles a contact between a spring and a flat surface. I found a resistance of 0.03 Ohms, which produces a drop of 0.3V at 10A. Such a drop is important using LiIon cells.
So, shouldn’t lights use a better contact, such as a soldered connection on the cell that joins with the light via pins, like a wall outlet?
I’ve seen that practitioners of helicopter/drones, who have higher current requirements, use LiPo batteries. These cells have a better performance at high drain than LiIon cells, and they have pin connectors. Why not use these cells in flashlights?
It seems cylindrical LiPo cells are difficult to find but they’re flexible, so could be put in rigid cylindrical cases to fit in flashlights, at least in modified ones.
The format may be a significant obstacle for single cell lights but less for 4-cell, big models. These could do well with a battery pack to improve contacts. The recent Acebeam X65 already uses a pack. Maybe this trend has already started?
I’m trying to buy 14500 cells for an Astrolux SC and searched for LiPo cells but it’s too much hacking for me and I gave up… An additional advantage of LiPo is that they’re less dangerous to ship, so it’s better than the mess we’re experiencing with LiIon.