Hey there,

The 2004 Prius also uses NiMH batteries which are recyclable and according to HybridCars.com Toyota (as well as Honda) have said they would recycle the batteries of their cars.

It is unlikely that individual cells will be replaced in the battery pack. Instead the whole pack will probably be replaced at the same time. This has to do with the fact that as batteries age they will exhibit slightly different performance characteristics and you generally want them all performing alike.

For the degradation over time Toyota claims to have run the cars out to 150,000 miles without performance degradation of the NiMH batteries and they warranty the batteries for 8 years/100,000 miles see Toyota FAQ. I can't vouch for this number with outside info about NiMH. I saw a figure of 10,000 discharge to 60% cycles (which is equivalent to 3.5 discharges every day) for the prius battery before significant performance degradation but I didn't see any data.

So, short answers: 1) The batteries are recyclable and Toyota says it will do so and 2) The batteries may last out to 150,000 miles without significant performance degradation.

Hope this helps
Christian