Jant the way I see it is you may have to wait a few years for said battery. It's going to be a by-product of ev introduction. Not only will mass production bring prices down but there will also be a second hand market for not just ev's but also batteries pulled from right off's etc. Even a battery with only half capacity left in it, say 35-40kwh will go a long way toward being self sufficient. Having 2 or 3 of them paralleled up being trickle charged by a bunch of solar cells and you'd be seriously trialing the set up toward snipping the service. I still see a communal set up being the long term solution though, ie a group of homes with their batteries interconnected and monitored so a supply can be managed and maintained. That scenario would obviously mean that charging an ev would be done at a station or elsewhere by 10 minute supercharger.
