Alkaline chemistry: Panasonic's alkaline cells hold their voltage far longer under load than the zinc-carbon batteries that are still common at the low end of the shelf. In anything that draws real current — a torch, a portable radio, a ride-on toy — that is the difference between a battery you change monthly and one you forget about.

Anti-leak seal: Each cell is built with a seal designed to contain the electrolyte if the battery is run flat and left in place. Leakage is what kills the contacts in an expensive torch or a child's toy, so the protection is aimed squarely at the device rather than the battery.

Tough coating: The cell jacket uses a hard nickel-and-iron alloy coating that resists denting and corrosion in transit and in the battery drawer, keeping the contact surfaces clean so current flows without the intermittent drop-outs a corroded terminal causes.

Ten-year storage: Kept unused in a cool, dry place, these cells still deliver their rated power after a decade. That makes a spare worth keeping for the torch, the emergency radio and anything else you only reach for when the power is out.

What it fits: D cells are the large cylindrical size used in heavy-duty torches, lanterns, portable radios and boomboxes, ride-on and remote-control toys, and some musical instruments and amplifiers.