I recently came across this site that talks about a group in the Netherlands who combined a Nickel-Iron battery with an alkali electrolyser. For the cost of a membrane and a couple of fittings, you get an electrolyser. I think this makes a lot of sense. Nickel-Iron batteries will last a long time before having to be refurbished, and the hydrogen can be used for seasonal energy storage (my preference is methane, others want straight hydrogen or ammonia).