My first solar array had 8 very large and very, very heavy batteries much like the ones shown here. They worked but didn't feed power back into my house. My new array (10KW) has the new generation of lithium-ion batters (LG). Much, much lighter and they retain 30% of their power in case of power outages. They also feed power back into my house at night or when the sun isn't out, thereby vastly reducing my consumption. Anyone thinking of installing solar should definitely use this new generation of battery backup if they can afford it. Not that much more expensive and a tremendous improvement on efficiency.
I tried to attach a photo but it didn't work.