So, I got four 200ah lead acid batteries
 

As the title suggests, I recently got four 200ah 12v batteries. An uncle of mine works in hospital maintenance and these got swapped out as per their preventative maintenance schedule. He knew I would be interested, so he nabbed me four of them. They are quite large and heavy, but also hold a good amount of power (~9.6kwh total, less usable of course). But, I don't really have any great ideas for them right now, and I'm wondering if you guys had any ideas?

Energy storage for PV/wind?

I doubt they would be good for extending the range of an EV...

Could be back-up power with an inverter. You'll need to use them occasionally which could be as easy as charging phones, power tools any other light usage power needs. You'll get an idea of how long they can go before needing a recharge---most inverters won't let the source go dead.

I've been thinking about setting up a small 12V system in the house. Phone charging, maybe some minimal lighting. Hook up a smallish solar panel to keep it topped off. Its an idea, not the best, but an idea.

Sure, that's what I'm doing. I bought a deep cycle battery and a 2000 watt inverter. At first I used the old battery from my truck to see how it worked out. Its great really, I can do a lot of things for a short while if the power goes out. (not tested how long though)