It's quite a different model to petrol: the batteries themselves are very expensive, and the stored energy very inexpensive. Futhermore, the batteries degrade,

It's quite a different model to petrol: the batteries themselves are very expensive, and the stored energy very inexpensive. Futhermore, the batteries degrade, losing capacity over time, making them vary in value, and non-fungible. Practically, battery swapping requires a leasing / rental scheme. Batteries can't just be sold for consumption like petrol. Transporting batteries might make sense for some extremely remote locations with no grid access, but people don't commonly drive far away from the grid. As these batteries are very heavy, I would expect the handling involved to make this far more expensive than just charging on-site.