Need a battery but only have a smaller one? For low-power devices, this foil trick can help in an emergency.
If the smaller battery has the same voltage as the required battery, use a small piece of crumpled aluminium foil to fill the empty gap so the battery can touch the metal contact properly.
This works because the foil acts as a temporary conductor and spacer. But it does not upgrade the battery or make it last longer. Use it only for short-term, low-power devices, and never let the foil touch both ends of the battery.
