might be a stupid one, but why have something like a nitecore nb10k Gen3 for 50$ when you can have 3 18650 Keeppower P1840TC 4000mah batteries, which double your charging speed in town and are cheaper with 13$ each?

Weight will be a tad bit higher in the 3 batteries( they weigh 50g each vs 150 for the nitecore but you have to have 2 more cables), for the same capacity, but the big positive effects are:

• you can charge all of them at the same time, which should at least double your charging speed vs the 18w of the nitecore
• which means if your charger has multiple ports, you can speed up your charging time, while in town, you only need very short c-c cables or y-cables with multiple c ends and instead of charging with 18w in the nitecore you can now charge at (not 100% sure but i think it is ~15w but x3)
• cheaper, and you can take as many as you need, instead of a 6 or 10k block to increase capacity
• protected so no accidental catching on fire, can easily be made waterproof with a plastic container
• no single point of failure for the powerbank, as you have multiples
• if you change your flashlight to one that supports 18650, you will have swappable batteries for them, without charging your flashlight, with even more inefficient converting.
• 18650 flashlights are not much heavier empty most of them are around 60g, are waterproof(e.g. armytek elf ip68) unlike the nu25 with its meager ip66, and can easily be modded for a lightweight headband, if you don't already have a sports cap

Downsides:

• charges slower, so you will need a multi port charger to benefit from charger all at the same time
• you need multiple cables or y-headed ones that can support the output.
• charging devices is slower, but at night, that does not count that much

Or am i seeing something completely wrong and my math is just off and i am not thinking correctly?

edit: in the 21700 camp with the vapcell 6k with fast charging for 78g it looks even worse for the nitecore it seems