Tesla uses a mechanically modified version of the commodity Panasonic 18650 battery, similar to an AA, ganged together in large quantities in a thermal and safe

Tesla uses a mechanically modified version of the commodity Panasonic 18650 battery, similar to an AA, ganged together in large quantities in a thermal and safety optimized enclosure. They are in fact very similar to cell phone batteries, chemically. Nissan, on the other hand, built a new battery manufacturing plant in the US, and makes their own from scratch. Once Tesla has the funds they would be wise to make battery manufacturing a core competency and vertically integrate manufacture to keep costs low.