SmarToools RB40 AAA 1.5V 750mWh USB Type-C Rechargeable Li-ion Battery (Sold as a 4-Cell Pack; 2-Cell RB20 Pack Also Available)

The SmarToools RB40 is a rechargeable AAA pencil battery that refills from a USB Type-C cable, so there is no charger cradle to hunt for when the remotes, wall clocks, torches and wireless mice around the house run flat. It is sold here as a 4-cell pack, and the matching 2-cell RB20 pack is available as well. Unlike NiMH rechargeables, each cell uses lithium-ion chemistry with an internal step-down circuit, which holds a constant 1.5V output instead of sagging to a lower working voltage as the charge drains away. Capacity is 750mWh per cell, and the Type-C port built into the cell itself takes a 5V input and brings a flat cell back in about 2 hours. Cycle life is rated at up to 1200 recharges, and every cell carries protection against overcharging, overheating and short circuits. The rated operating range runs from -20°C to 60°C. The constant voltage is what makes these worth having in devices that get fussy as ordinary cells fade — wireless mice and keyboards, digital scales, blood-pressure monitors, LED torches and battery-hungry toys. For a household that keeps a drawer of half-dead pencil cells, a set that charges from the same cable as your phone is far less wasteful, and topping several cells up before an evening of load-shedding takes only a couple of hours.