Since the site owner created this new battery section we might as well start it off with the known specs of the Roadster pack. Much info from here And here Tesla calls their battery pack the Energy Storage System (ESS) Tesla puts 6831 Li-Ion laptop batteries in the ESS. The batteries are a standard 18650 format The whitepaper says the pack stores 56kWh of energy when fully charged. It runs at a nominal voltage of 375volts (about 410v when full, 300v when "empty") Taking into account the voltage, the pack has a capacity of 152Ah. Expected pack cycle life: > 500 recharges. ESS total weight: ~900lbs. The above are the published facts. The following discusses some related details that are a little more fuzzy: The pack can be charged with a 240v, 70amp circuit in 3.5 hours. That is 16.8kW for 3.5hours or 58.8kW. There is some charger power loss, so it makes some sense to take 58.8kW to charge the 56kW pack. Here it says that the ESS has 11 "sheets" with 621 cells per sheet. There is apparently a separate CPU for each sheet to manage the energy being stored in each sheet. For some reason, many have mentioned that the pack is actually organized into 69 parallel groups of 99 serialized cells. This would make some sense as Tesla has said the cells max voltage is 4.15v per cell which x99 cells=410v which is the max voltage they say the pack gives to their PEM. They also shut down the car if the per cell voltage gets down to 3.00v which is the 297v minimum ESS voltage that has been discussed. There has been much speculation as to the exact brand and type of individual cells they use. Here they says that each cell is 2.2Ah. So, if you take 6831 cells * 3.75v (nominal) * 2.2mAh you get 56.355kWh which seems fairly close to the published pack capacity. It has been stated that the ESS can output about 600amps at 375 volts which gives 225kW For a 56kWh pack to output 225kW of power, the cells need to be able to achieve "4C" discharge. There are lots of 2.2mAh 18650 cells, but many can't handle 4C discharge rates safely or without damaging the cells. Some have said that a battery like the BiPower LR18650 or Tenergy might work in this application, although 4C discharge is pushing it hard past rated specs. (Perhaps Tesla only dips into the 4C discharge rate for short burst of acceleration then backs off to avoid overtaxing the cells?) Tesla may be using slightly more unusual "high power" cells that can handle the higher discharge rates. Quote from an article: "The primary reason that Li-ion rechargeable batteries aren't used in power tools is the electrode material used. Currently anodes use LiCoO2, which increases the energy density to provide longer battery drive times for digital gear. LiCoO2, however, has problems assuring safety because of the high heat generated when drawing high current, and as a result Li-ion rechargeable batteries never found much of a market in power tools. A change in the anode material, however, has allowed Sony to productize Li-ion rechargeable batteries capable of handling high currents. The firm will begin shipping its V and VT series of high-output batteries from January 2005. Safety at elevated temperatures was improved by switching the anode from LiCoO2 to Li(Ni-Mn)O2, with Ni and Mn content. Internal impedance, which presents a problem when drawing high currents, was also reduced to about 50mW (about 40% below prior designs) by adopting thinner electrodes and other measures. The new 26650VT battery, for example, measures 26mm in diameter and 65mm in length, and can continuously output 50A in 20C discharge (discharge in 1/20 hour). It can also output 70A pulse (see Fig). The battery capacity is 2500mAh, and the volumetric energy density 250 Wh/l." Here they say that max motor power is 185kW with 80% efficiency when making max power. To me, 80% efficiency means to me that the ESS needs to provide at least 230kW (because 80% of 230 is 185) The battery whitepaper says the ESS can output 200kW max. That seems a bit low. How can the ESS output "only" 200kW and still get 185kW from the "80% efficient at peak power" motor? Perhaps the eMotor is more efficient? Here they say it varies between 85 and 95% efficiency... Even though their battery whitepaper still says "August 16, 2006", I see that they have updated it since then. For instance, it talks about "more than 200 mile" range now, but originally it said "250 miles on the EPA highway cycle".