Review on MinChen Rechargeable Waterproof Interface Headlamp by Justin Hollins

I've been using the 18650 battery for several years to power flashlights and charge my phone while cycling. My problem was that the packs were not weatherproof and often failed due to corrosion. Since 18650 batteries are very popular, they can be purchased quite cheaply. So I decided to try these cases and I am very happy with the results. I have two cases. I only use one at a time, but I always like to have a spare (just in case I forgot to charge the night before) and multi-day trips. I was a bit worried that the hard plastics would hold up to a rough ride, especially in extreme cold, but they seem to work well. It would be nice if they made an 8 or 10 pack for really long trips, but keeping the extra 18650 in a sealed bag works.