Presently the best batteries to use with intermittent local generation are lithium car battery packs. The price is brought down by the volume production and the volumes are lifted further by multiple applications! This is why Tesla in the USA developed the ‘Power Wall’ idea.
There are similar set ups available around the world, the one I’m most familiar with is an Italian package that uses a standard automotive battery pack and a clever box of electronics that will balance inputs from solar, wind, micro hydro and the grid to keep the charge up. Then, at times of high grid cost and / or low generation opportunity (a windless night perhaps) the battery pack takes over to keep things going . . . .
The cost was ‘designed in’ to be acceptable to a small farmer so that the herd size could be increased because there was not total reliance on the grid (which often failed). With the same battery packs as a Toyota Prius or a Nissan Leaf the price for the storage / control unit combined was around seven to eight thousand dollars in US money when I last looked.
The performance of this kind of battery is optimised for a high charge discharge cycle and failing cells can be detected and swapped out easily.
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