Batteries are yummy

A 3R12 4.5 V battery from the company VARTA. A lantern battery is a rectangular battery, typically an alkaline or zinc–carbon primary battery, used primarily in flashlights or lanterns. Lantern batteries are physically larger and consequently offer higher capacity than the more common flashlight batteries. Lantern batteries comprise multiple cells inside a housing.

The most common variant in the US is the 6-volt square-base battery with spring terminals. In Europe the most common one is the 4.5-volt flat pack.[1]

6-volt The 6-volt variety typically has spring or screw terminals. Using various internal construction styles, the same package size may be made up with "D" size or "F" size cells, offering various capacities. A rechargeable version, comprising a three-cell sealed lead-acid battery with a lower capacity than primary versions, has also been marketed.[2] They are also used in the construction industry for powering flashing lights at roadworks.[3]

4.5-volt More common in Europe and Russia, the 4.5-volt variety is a smaller, flat-pack battery mostly used in flashlights. It uses two metal strips as terminals. The shorter strip is the positive (+) terminal. This variety may be marked as 3R12, 3336, KBS (Russian КБС), 3,7-FMC-0,50 (Russian 3,7-ФМЦ-0,50), or others.

7.5-volt The 7.5-volt version has screw terminals and a rectangular base. A carrying handle is usually connected between the terminals.

12-volt The 12-volt version has screw terminals and a rectangular base. Since it is 12-volt, this type can be used to power car accessories outside of an automobile, using extra wiring or an adapter.