In reply to HeMa:
I'm about 250km North of the Arctic Circle working as a husky sledding guide. I've spent a reasonably significant amount of time North of the Arctic Circle in the winter over the last 16 years or so, so I know what that winter twilight's like
I already have a selection of headtorches with me including a Silva Trail Runner 3, but need to sort a rechargeable option. I've worked out that it may be more expensive to buy a Silva USB battery pack than to buy a complete new USB head torch (so I would end up with 2 battery packs one taking AAA and the other rechargeable).