Wonder what you'd get for a 5 yr old Tesla? Since i dont see that anyone would buy a 5yr old used battery car.. would't pay anything for a 5yr old cordless screwdriver..
Well after doing my research I've recently bought a 5 1/2 year old 28k mile Peugeot Ion, and the battery is absolutely fine.
According to Diagbox it has 83% of the raw new battery capacity remaining, and the range that I am getting is meeting or exceeding what they got new. Most of the capacity loss happens in the first year or two then it tends to flatten out. It has probably done about 500 cycles so far and should be good for at least 2000 cycles before there is an obtrusive degradation in capacity.
On the other hand my 2 1/2 year old iPhone 6 battery is almost dead - it's down to 50% of the factory original capacity and intermittently shuts down on me. (I'm about to replace the battery myself) It has also done about 500 full cycles.
The batteries in Electric cars are WAY more robust and long lived than those you'll find in phones, power tools and so on, are designed for much greater cycle lives, and are looking like they will do at least 4x the cycles of consumer grade batteries like those found in phones. There is no incentive for someone like Apple to make a battery that lasts 12 years or even 6 years, 3 years (which is typical) is "enough", and lets them keep the cost down to maximise profit, and maximise the energy density. They would rather you buy a new phone after 3 years anyway.
On the other hand EV car makers are acutely aware that battery longevity is the biggest fear of potential buyers, and have done everything they can to over engineer them and optimise cycle life and longevity even if it means a significantly lower energy density, or not making the full capacity of the battery available. (The battery management system on many cars including mine only really charges the battery up to about 85% of its raw capacity, which more than doubles the lifespan compared to using that remaining 15%)
There were problems with the battery in Gen 1 Leaf's in very hot climates but apart from that I'm not aware of any EV's with unusually poor battery life, if anything nearly all of them are greatly outlasting expectations and some manufacturers have actually increased the length of their battery warranties. (Mitsubishi in the i-Miev in the US market, and Tesla)
Of particular note are Tesla's where a combination of a particular long lasting battery chemistry and active temperature management using water cooling are recording amazing mileages with hardly any battery degradation. At 5 years old and 150k+ miles most still have 95% of their original capacity.
Would I buy a Tesla at 5 years old (if I had the money...) you bet!
5 years old is a good time to buy any EV - most of the depreciation has already gone but you still have a few years left on the battery warranty and the majority of the capacity still available.
Only time and hindsight will tell, but my gut feeling is the fear over battery longevity in EV's will be found to be vastly overblown - the Y2K of this decade....