- D battery
A D battery (D cell or IEC R20) is a size of dry cell. A D cell is cylindrical with electrical contacts at each end; the positive end having a nub or bump. D cells are typically used in high current drain applications, such as in large flashlights, radio receivers and transmitters, boomboxes, products with Electric motors, safety systems, Geiger counters, megaphones or other applications requiring extended run time. Rechargeable and non rechargeable cells are made in the D cell size, with terminal voltage and capacity varying depending on the cell chemistry.
The National Carbon Company introduced the first D cell in 1898. Before smaller cells became more common, D cells were widely known as flashlight batteries. The U.S. military designation for this battery type since before WW II is BA-30. 
As of 2007, D batteries accounted for 8% of alkaline primary battery sales in the US. In Switzerland as of 2008, D batteries totalled 3.4% of primary battery sales and 1.4% of secondary battery sales.  
Dimensions and capacity
Zinc–carbon Alkaline Li-FeS2 NiCd NiMH IEC name R20 LR20 FR20 KR20 HR20 ANSI/NEDA name 13D 13A 13LF Typical capacity 8000 mAh 12000 mAh 2200–12000 mAh Nominal voltage 1.50 V 1.50 V 1.50 V 1.25 V 1.25 V Rechargeable No Special type only No Yes Yes
Capacity varies depending on cell chemistry. In some cases rechargeable cells are made to fit a D cell holder but with capacity as for a smaller physical size.
D batteries have a nominal diameter of 33.2 ± 1 millimeters and overall length of 61.5 millimeters. 
- ^ "U.S. Army Flashlight". http://www.olive-drab.com/od_soldiers_gear_flashlight.php.
- ^ Life Cycle Impacts of Alkaline Batteries with a Focus on End-of-Life - EPBA-EU
- ^  INOBAT 2008 statistics.
- ^ IEC 60086-2 §7.1.4
- List of battery sizes
- Battery nomenclature
- Brand Neutral Drawing Of Alkaline D Battery Based On ANSI Specifications
- Brand Neutral Drawing Of NiCd D Battery Based On ANSI Specifications
- Brand Neutral Drawing Of NiMH D Battery Based On ANSI Specifications
- Energizer D Size Battery Specification for Alkaline Cell
Portable and button battery sizes Portable cells Portable batteries Button cellsLR44 battery • CR2032 battery
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