The new 2017 BMW i3 will be using four M8994 E2 Samsung modules (8.38 kWh each). These modules, according to Samsung, will be > 60kg (>132 pounds) each. Assuming that BMW's modules will weigh 127 pounds (quite favorable), they would be 15.14 pounds per kWh. http://www.samsungsdi.co.kr/upload/ess_brochure/Samsung%20SDI%20ESS%20brochure.pdf Unfortunately Tesla and Panasonic do not have specs out on how much each module weighs... but you can buy them used on eBay! According to eBay sellers, a 5.3 kWh from an 85D weighs roughly 55 pounds. Assuming that eBay sellers are correct (they are shipping these things), the Tesla modules are 10.37 pounds per kWh. 4 Tesla Model S battery modules, 24V, 21.2kWh, 1776 Panasonic 18650 cells BMW 15.14 lbs/kWh Tesla 10.37 lbs/kWh Tesla uses cylindrical cells (round, but light) while BMW uses prismatic cells (thin, but heavy). BMW batteries weigh 508 pounds while the range extender weighs 265 pounds. Why commit 773 pounds when an almost identical amount of weight could be used towards 75kWh of cylindrical cells/modules? Why does BMW, the people that are in love with carbon fiber and everything light weight, use such a heavy, inferior battery technology in their light weight cars?