My experience of rechargeable batteries is that they are not that reliable or long lifed. Capacity drops as they get old and they are very costly.
Well, as we said from the beginning, it's all about the batteries.
I have some experience with A123 batteries. They're a completely different kettle of fish from anything else I've used. Mine still hold 90% of their charge after 5 years and 100s of cycles. Other people have gotten 1000s of charges out of them. But at present, the specific energy density just isn't there.
The other question is how much the scrap value of a battery is... If you buy a battery for £5000 and scrap it for £4000 after 200 cycles, the economics change again (plucked those numbers out of thin air...). Whatever the figure, it compares well with the scrap value of avgas.