Store cool and dry
Keep spares in a cool, dry place in their original packaging when possible. Avoid gloveboxes and direct sun — heat accelerates self-discharge and leakage risk.
Low self-discharge (LSD) NiMH
Modern “ready to use” NiMH cells keep charge much longer on the shelf than older NiMH. They are still ~1.2 V cells — check the device allows NiMH before using them as alkaline replacements.
Primary cells
Alkaline and lithium primary cells also self-discharge, just more slowly. Rotate stock: use older packs first. Discard swollen or leaked cells safely.
Installed vs spare
A cell sitting unused in a remote still ages. If a device will sit for months, remove cells when the maker recommends it (especially alkaline in cameras and clocks).