Panasonic NCR18650B_X4 Li-Ion battery (3.7V, 3400mAh, 4-pack) incl. Battery box (accessory)
I use all 4 batteries in a power bank. Bin after 5 months of use, completely satisfied with the low self-discharge and the capacity of the batteries. I have the batteries for the first time with an external charger repeatedly charged and discharged.