Panasonic NCR 18650 3400mAh 3.7V – Flat Top Battery $5.25

From Battery Junction:
Features:
Unprotected Cell
High Energy Density
Environmentally friendly
Specifications:
Battery size: 18650
Chemistry: Li-ion
Voltage: 3.7V
Capacity: 3400mAh
Max discharging current: 4.87A
Diameter: 0.72" (18.4mm)
Height: 2.7" (68.5mm)
Weight: 1.65 oz (47g)
Batteries sold individually.
https://www.batteryjunction.com/p…gJFpPD_BwE