====== Battery UM-1 / D cell ======
The **UM-1** battery is also called **D**, **R20** or **Mono cell**.

The round battery with a diameter of 34.2 mm and a height of 61.5 mm is used in many portable radios.

The nominal voltage of **zinc-carbon** batteries or **R20** or of **alkali-manganese** batteries or **LR20** is 1.5 volts.

**Nickel-cadmium** accumulators (NiCd, resp. **KR20**) or **nickel-metal hydride** accumulators (NiMH, **HR20**) have a slightly lower nominal voltage of 1.2 volts. Not in all cases a set can be operated with accumulators instead of batteries, as the lower total voltage might be insufficient for reliable operation.

==== Further information ====
  * Information on [[wp> D battery]] and generally on [[wp>Battery nomenclature|Battery sizes]]