It hasn't happened for most Totoya Prius drivers, but one day – perhaps 150,000 or so miles down the road – it will. An indicator light will appear on the dash to signal that the battery pack is past its prime and needs to be replaced.
Some critics of hybrids and electric vehicles have pointed to this moment as proof that these vehicles actually have more environmental impact than conventional autos, as battery packs potentially clutter up landfills with toxic materials. Only, that's not what's happening at Toyota.
When a Prius battery pack reaches end of life, Toyota provides a UPS shipping container so the battery can be sent to a recycling center. For U.S. cars, that center is in California. The batteries are shorted out to prevent accidents with any remaining charge, then all of the components are disassembled. The plastic case is shredded and recycled. The electrolyte is decanted and the rare earth elements recovered. The nickel plates are sent to a smelter where they are used in making steel. All the components of the pack are recycled or reused, leaving nothing to go to the landfill. The same recycler is already equipped to deal with the lithium batteries found on the Chevy Volt, Nissan Leaf, and plug-in Prius.
Of course, there is the problem of cost. Toyota has lowered the price over the years, but a new Prius battery pack still rings up at $2,589. And while some Prius batteries are fine up to 300,000 miles, facing a potential bill that large can make Prius owners decide that seeing 150k miles on the odometer makes a good time to trade. It can also make buying a used Prius with mileage in 6-digits unattractive. That's why some dealers have instituted a policy of replacing batteries on high mileage trade-ins before they're put up for sale.
Having a fresh battery on board assures purchasers that they'll drive for years without worrying about that little light, and helps assure dealers that a used Prius won't spend too long on the sales lot.