Going beyond the limits of the 18650 battery, Tesla's Giga-factory churns out billions of the larger 2170 cells with 2x more energy capacity; essential for the upcoming Model 3!
Volumetrically the 18650 cell contains about 66cc of chemical energy storage space via a cylindrical designs of 18mm diameter x 65mm long, like an oversized AA battery! New 2170 cells are ~21mm in diameter & 70mm long, containing 97cc of battery chemistry!
Tesla Two Chemistries
NMC for stationary energy storage products like the PowerWall, the nickel manganese cobalt chemistry offers a good balance of cost, cycling performance, calendar life, and safety, but fails to achieve the kind of energy density that would make sense for vehicular applications.
NCA for vehicles, the addition of aluminum to nickel and cobalt gives enhanced thermal performance, better energy density, peak pulse discharge enhancement, faster charge absorption, better fade resistance, longer cycle life, and longer calendar life, the only disadvantage being slightly higher costs.
3 Things destroy lithium ion batteries faster
Deep Cycling, Over Charging & Over Discharging, and High Heat! The cabin of a vehicle produces a green house effect by trapping incoming solar heat energy. Parking a car in direct sun results in substantial cabin heating.
Lithium ion cells last longer when they are kept between 30-80% charged. Fully charging to 100% causes damage to the anode & cathode by swelling & cracking. Discharging below 5% also causes mechanical chemical & physical damage to the anode & cathode. Rapid charging damages the anode & cathode, as does rapid discharging.
Storing a lithium ion battery fully charged will cause it to lose its energy storage capacity more quickly. Lithium ion batteries hold up well when stored %30-50 charged @ about 50 deg F.
Temperatures higher than 122 deg F. damage most lithium ion chemistries.
KWH/ mi vs MPG
Our 2013 Nissan Leaf S was averaging about 3.8 to 5.2 mi per kWh, typically around 4.6! 120MPGe
Tesla Model S's seems to average around 2.5-4 mi per kWh. 85MPGe
Our 2005 Prius has a lifetime fuel economy of 46 MPG
Our 2013 Honda PCX gets about 90 MPG
A gallon of gas contains ~33.7 kWh electricity eq, so an EV that uses 29kWh to go 100mi would achieve 115MPGe : The production of gasoline at refineries consumes about 8kWh of electricity per gallon. 8kWh is enough to drive a Nissan Leaf about 10mi.
When you look at the wheel to well lifecycle energy footprint of gasoline vs charging an electric car from the dirtiest coal power plant, the EV comes out on top with substantially lower net emissions, enhanced further by batteries that can be recycled at the end of their life. The tail pipe emissions from a car & the oil refinery emissions are one way chemical externalities that cause toxic pollution that is bad for the earth & all of life in the biosphere.
Parked 22 Hours/ Day
Most privately owned passenger vehicles sit unused for 22 hours per day, vastly underutilized depreciating capital, they are expensive as a result. Even at 5 mi per hour of charge accumulation, an EV can pick up more than 100 miles of single charge range via a normal extension cord plugged into a regular wall outlet for 20 hours.
The key to electric vehicle adoption is power outlets where cars are parked most of the day! For working people, this means picking up their daily commute range in charge between 9pm & 6am. Night time off peak charging like that also helps to balance grid power consumption, a boon for utility operators who struggle to deal with load balancing fluctuations.
Fast charging stations like the Tesla Super Charger enable electric road trips! Charging lithium at such high rates will shorten the batteries lifetime energy storage capacity performance. Tesla estimates that the Model S battery will last 1000 to 1500 cycles over ~15 years. The key to longer battery life is shallow cycling between 30 & 80%, giving a Model S about 150mi of long life battery mode single charge range that holds up well over time!
Battery History Brief
35Wh/kilogram, the 1859 French Gaston Plante Lead Acid battery was not sufficient to compete against gasoline/ diesel in internal combustion engines as a vehicle power source, even though electric motors have always been more efficient than reciprocating piston engines. The electric vehicles of the early 1900's were too slow, with limited range and slow recharging. EV's were popular back then because early gas cars were stinky, dangerous, loud and unreliable. The silent, clean, reliable electric cars were attractive, especially before the days of urban sprawl.
Electric vehicles today face tough competition from gasoline powered modern vehicles. A Toyota Prius for example achieves about %40 thermodynamic efficiency, translating into 460 mile of range from 10 gallons of gas. With 12,000 Wh/Kg, gasolines energy density is remarkable when compared to the batteries of a Tesla Model S or Nissan Leaf. EV's gain their advantage because electric motors convert about 90% of the incoming electricity into mechanical energy to move vehicles.
When electric vehicle batteries achieve 6,000Wh/kg, the net system energy performance will eclipse anything possible with gasoline in a piston engine. Even with limited early lithium Ion batteries the Tesla Model S already blows the doors off many conventional vehicles in the same price/ luxury size segment of vehicle markets.
Electromotive platforms like the Model S have more energy available for vehicle computing platforms that will become essential for self-driving & autopilot features in almost all future vehicles. By the middle 2020 most vehicles will be offered with electric drivetrain & autopilot features. By 2030 many new cars will come with self-driving features. All the automakers & many information technology companies like Uber are feverishly developing the early generations of autonomous vehicle control technologies.
Vehicle technology, except autopilot, actually peaked in the Williams F1 car of 1993. Computers were subsequently banned from F1 racing because they were though to take away from the competitive aspect of drivers competing and making the race more about which team had the best technology. Adaptive suspension tech was able to maximize ground effect downforce vacuum without a drag penalty by holding the vehicle exactly 6cm above the track under all conditions.
Passenger car designers have started using aerodynamic tweaking in efforts to drive fuel economy towards the 54MPG by 2025 target set by the EPA & DOE. Engines energy efficiency also a target of engineering for friction reduction, direct injection, turbo-charging, hybridization, variable valve control, homogenous charge injection, and ignition timing intelligence. Many of the things developed by engineers for F1 cars over the years are finally making their way into passenger vehicles, though mostly to improve fuel economy & safety.
Aero tweaking a vehicle design gives it better performance since drag effectively pulls on a moving vehicle, any reduction in drag will improve fuel economy while reducing tail emissions. Aerodynamically efficient vehicle have greater acceleration, improved corning dynamics, enhance grip performance, improve safety & better energy efficiency.
When computers drive a car, the maximum possible efficiency will be achieved. Human are incapable of performing the kinds of vast parallel calculations needed to optimize vehicle dynamics in real time. Many fighter jets make use of fly by wire technology because the pilot could never control the aero surfaces fast enough for stabile flight. Commercial aircraft now use neural net pilot safety systems that let a pilot safely land a plane even if the tail section has been ripped of by a mid air collision. The computers neural net takes the pilots input and converts said commands into complex control schemes to make use of rapid active wing element control to regain control of the aircraft, a task far too complex for the pilot to execute without machine intelligence.
Human intelligence varies significantly between people by many orders of magnitude. The safe piloting of a vehicle is a complex issue with age related mental & physical decline. Traffic safety studies indicated that a high skill level driver using a cell phone can pilot a vehicle with greater skill than a limited skill driver in the 40th percentile who is only focused on driving. New drivers & elderly drivers are often lacking good driving skills. Accidents of all kinds are caused by human errors in almost all cases. Equipment failure rarely causes an accident. The most important thing in a vehicle for safety is an intelligent skilled driver paying attention to driving. The people make all the difference! Its the humanity of our roads, the human minds, ideologies & what people are thinking about that affect accident rates. If everyone was focused on driving safely, fewer car accidents would be the result. Clearly drivers are thinking about things other than safely piloting the vehicle.
In the future cars will drive themselves. Car sharing fleets will become the new normal for car ownership as new drivers abandon buying cars, opting instead to sign up for a car access by subscription. They will use their smartphones to request a vehicle, the self driving car will drive itself to come pick them up. They will make use of the vehicle, then the vehicle will drive itself to the next reservation placed by someone else. Instead of being parked for 22 hours per day like most cars today, self driving cars in car sharing fleets will have much higher utilization.