200 count of mixed 18650 cells in assorted modem battery packs ($0.20 – Battery Clearing House
Amazon.com: YUWYP 36V Battery 10S3P 10Ah 42V 18650 Lithium ion Battery Pack for ebike Electric car Bicycle Motor Scooter with 20A BMS 500W : Electronics
LG MJ1 18650 3500mAh 10A Battery - IMR Batteries
13S3P Battery Pack with Panasonic B Cells, 10.05Ah, 14.62A, 46.8V, Cuboid Shape, Customizable - 18650 Battery Pack - Lithium Ion Battery Pack - Voltaplex
An Exhaustive Guide To Building 18650 Packs | Hackaday