After nearly 40 years managing money for some of the largest life offices and investment managers in the world, I think I have something to offer. These days I'm retired, and I can't by law give you advice. While I do make mistakes, I try hard to do my analysis thoroughly, and to make sure my data are correct (old habits die hard!) Also, don't ask me why I called it "Volewica". It's too late, now.

BTW, clicking on most charts will produce the original-sized, i.e., bigger version.

Wednesday, August 2, 2017

How long will your Tesla battery last

This video by the folks at Teslanomics suggests that Tesla batteries could take 20 to 25 years to lose 20% of their capacity.

Why do Tesla's lithium-ion batteries last so much longer than those in your phone or laptop?  This fascinating blog post discusses the factors in the life of li-ion batteries.

In summary, the reasons are:
  • The precise chemistry used--EV batteries are designed for long life, whereas phone/laptop batteries are designed for maximum energy output at any time.
  • Whether they are fully charged and discharged with every cycle--usually keeping the battery between 20% and 80% charged extends life considerably.  Tesla discourages you from recharging the battery to 100% except on long trips.
  • Keeping the battery from getting too hot or too cold.  Tesla has temperature controls on its battery chargers.
Tesla must be doing something right because the evidence points to extremely low rates of degradation.


On these data, on average Tesla batteries have 92% remaining after 240,000 miles (380,000 kilometres).  Assuming the decline continues in a linear fashion, that suggests that to get down to 80% capacity would take 780,000 kms (nearly 500,000 miles) of driving.


Tesloop, a Tesla-centric ride-hailing company has already driven its first Model S for more 200,000 miles, and seen only an 6% loss in battery life. A battery lifetime of 1,000,000 miles may even be in reach.   [Read more here]
And here's another article suggesting much lower degradation rates than you would expect extrapolating from your mobile phone/laptop batteries:

Data shows that the Model S’ battery pack generally only loses about 5% of its capacity within the first 50,000 miles and then the degradation significantly slows down with higher mileage. Plug-in America’s data shows several vehicles with over 100,000 miles driven and less than 8% degradation. [Read more here]


Given that EV*s have 100 times fewer moving parts than ICE*s, are 4 or 5 times as efficient converting stored energy to kinetic energy, require negigible maintenance, and have batteries which will last longer than the car itself (and can still be used for stationary storage after the car is scrapped), EV running costs will be much, much lower than ICE running costs.  When EVs have the same "sticker price"as ICEs  (starting now with the new Tesla Model 3), the demand for pure ICEs will plunge.  Demand for long range hybrids will remain until the EV charging network is fully developed, but how long will that take after EV/PHEV* sales dominate total car sales?  How soon before oil sales start to slide and the oil price collapses?


*EV = Electric Vehicle
*PHEV = plug-in hybrid EV
*ICE = internal combustion engine (i.e., running on petrol/diesel/gasoline/natural gas)

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