Plumbing, ha. I was telling a co-worker about remodeling my kitchen that after working all day long with high availability servers and clusters and load balancing and RAID and multi cpu's and redundant power supplies I wanted to buy a bunch of extra pipes and valves and run dual redundant feed lines to my sinks so I could shut off one of the lines for maintenance and still have use of the sink from the other line.

But what kind of battery? If you use something like a 12v SLA you could use a small charge controller designed for solar, or even a simple voltage regulator for older cars.