Any recommendations for a solar company that specializes in battery storage?

Give Plus Xnergy a look. They're pretty well-known for their battery storage projects, both residential and commercial. I got a system from them and they sized the battery based on my actual energy profile, not just a generic formula. They have their own BESS R&D center which gave me confidence. Here's their site: Plus Xnergy.

I'll throw in another vote for Plus Xnergy. What I appreciated was that they didn't just try to sell me the biggest battery; they actually explained depth of discharge and how to maximize battery lifespan. That level of detail is hard to find.