Yes the cost of batteries would make 24/7 solar completely uneconomic but IMO the way you have done it makes perfect sense - it will be interesting to see how much if at all the repeated heating and cooling of circuits shortens the miners lifespan. Surely having them working some of the time is far better than not at all, and using 100% solar means zero cost input. I also see you run your miners at lower than maximum allowed speeds so that may compensate for the switching off and on as surely thermal damage is greater near the limits of hashrate capacity.