Rechargeable lithium battery type 21700, 3.7V 4000mAh
AA Batteries - USB Rechargeable Double A Lithium Batteries - Li-ion Battery Cell - 1.5V / 1700mAH (4-Pack) - Not NI-MH/NI-CD/Alkaline Batteries - ECO-Friendly and Recyclable - No Memory Effect(Green)
RYOBI USB Lithium 2.0 Ah Lithium-ion Rechargeable Battery FVB01 - The Home Depot