>The above claim is exactly what made me skeptical: the greater availability of something reduces its price, so 50% of the price of a new one just doesn't sound right, unless there's some identified other immense need for them: the number of "used" batteries available to the market would be huge if the number of the buyers of the electric cars would significantly increase.

On the one hand there is something to your intuition: 50% is a near-maximum price that basically assumes people will be buying batteries for the grid/home. This could be for solar, or people could want stationary batteries at home to keep a quick top-up charge for their car. Alternately companies could buy extra batteries to top up their electric fleet, or to supplement solar, or to take advantage of off-peak demand.

On the other hand the actual resale price is basically irrelevant. The scrap price of a car is a few hundred dollars, so a battery would have to fall to like 5% of it's own value to not be worth recycling. At that price you wouldn't be able to sell the things fast enough.

The volume isn't a real problem. There's a 20+ year lag time before enough cars are being recycled to make this an issue. IF used battery supply ever exceeds demand -very unlikely, given the always falling cost of solar- there is pleeeeeenty of time for recycling to start. The short and long term problems are very different. The absorption mechanisms that seem insufficient at high volume are a bridge to the recycling that seems immature.

>That can only pull down the price of the used ones and increase the price of the new ones. The real question is where the ultimate prices would be, considering these effects.

It would pull down the price of used and other secondary batteries. Normally this would increase the price of a new commodity, but batteries are supply-constrained and their price is set by the number we can make. It would also pull down the price of new batteries, since they would have fewer buyers at the higher price point. More likely the lower demand would have no effect at all.

>Also, Tesla claims that their lithium batteries last extremely long, that is so if the battery's not completely discharged, but every lithium battery in every notebook I have had was the first to die or degrade very fast, even if I surely never "deep" discharged it. And it's so small compared to the ones in the car. So there is some significant difference somewhere between what's claimed and what I've personally experienced.

I dearly love this stuff, and explaining it (I'm an electrical engineer). There are a bunch of reasons for the difference! The biggest one is actually heat- your laptop gets super hot in use and uses the batteries as a heat sink, but an electric car very carefully cools its battery (unless it's a Leaf). A battery at 60C can drop to 60% of its original capacity after just 3 months. This kills laptops dead after just a few years even if you keep them plugged in every second you own them.

The second biggest is depth of charge. The average daily drive is around 30 miles, or 10-20% of an electric car's battery. Most trips are just short errands or commutes, not long drives. You may not deep discharge your laptop, but a battery will do 5,000 cycles if you discharge it to 85%, and 1,000 if you discharge it to 50%. The best results are with normal discharges under 20%, which nobody does with a laptop but almost every single electric car does. A <10% DoD will last for tens of thousands of cycles.

I really can't overstate how dramatic the difference is. Batteries as we currently use them are very badly mistreated, and when they are kept in <90 F conditions they last 2-3 times longer. When used lightly they last 3-4x longer. Both situations happen naturally in a car. Even in very hot climates the hot days never get anywhere near to the temperatures in a laptop or phone.

>And what's the market for the used up consumer electronics lithium batteries?

Currently more lithium is used to make ceramic glazes than batteries. Collecting and reselling the hundreds of different kinds of batteries from junked laptops is a healthy, profitable business in Asian countries. There simply aren't enough batteries to warrant real recycling though.