# item.guide
Side-by-Side Comparison Cylindrical Cells

21700 vs. D Battery

Comparing 2 standards across 4 specifications. 4 key differences identified.

Comparing:
21700
D Battery
21700 →

A 21700 Li-ion cell measures 21.1mm in diameter and 70.4mm in length. Offering 4000 to 5000 mAh capacity at 3.6V nominal, it provides up to 50% more energy density than an 18650 cell.

View full 21700 spec sheet →
D Battery →

A D battery (IEC designation LR20, ANSI 13A) measures 34.2mm in diameter and 61.5mm in length -- the largest common cylindrical primary cell. Alkaline D cells output 1.5V nominal, with typical capacity in the range of roughly 12,000 to 20,000 mAh depending on discharge rate.

View full D Battery spec sheet →

Specification Comparison Table

4 Parameters
Parameter / Spec
21700
D Battery
Diameter
21.10 mm 34.20 mm
Overall Length
70.40 mm 61.50 mm
Nominal Capacity
4000–5000 mAh —
Alkaline Voltage
— 1.50 V

Other Alternatives to Compare

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