3.7 V lithium batteries
Bright torch, handheld fan or home-built project: 3.7 V Li-ion 18650 cells and their charger. Charge them the right way.
A Li-ion cell gives 3.7 V, more than twice an AA. The 18650 size (18 mm across, 65 mm long) powers bright torches, handheld fans and many electronics projects. It does not charge in an NiMH charger for AA cells: it needs a lithium charger, such as the 4-slot USB charger for 18650, 14500, 16340 and 21700 cells on this page.