Lithium Ion questions

[FredM]

I am checking out the latest in electric cars and am curious

The Tesla car is claiming 50K miles/ 5 years to 70% capacity on their battery packs.

http://en.wikipedia.org/wiki/Tesla_Roadster#Battery_system

I always see Lithium Ions considered "dead" after 80% is reached. I assumed it was because after 80% was reached the decline becomes severly less linear and drops fast.

Is that true or does it still go down slowly?

Is their any danger to running them that long?
Also do lithium Ions really last 5 years with good age?

 

[LuxLuthor]

There are different levels of quality and chemistries in various Li-Ions. There are also optimal charge/discharge/temperature algorhythms that can give better than average performance, charge/discharge cycles, and overall lifespan. If they built in a 130% higher capacity than was normally needed, then even once it was reaching end of life and down to 80% remaining performance....80% x 130% = 104%

As far as the rate of downturn in performance once Li-Ion's hit the 80% level, it is a sloping curve...but you would have to get the specific test results from their exact setup....and I doubt they are making that public.

I don't know what are the actual facts and verification processes used, so their claim may or may not pan out.

One thing is for sure about trying to switch everyone over to Lithium battery powered cars....there is not enough available lithium element to make enough batteries to accomplish this goal. It gets closer if Bolivia decides to give up their entire huge supply, but they are adamantly opposed at the current time.