Okay. Thanks for the tip.

By the way, for those browsing who've thought about building but are still compiling their mental list of do and don't...here's a don't, in materials: I used zinc for electrical connectors.

See the bolt in the foreground, first photo from the inner side of the battery-box lid? Nice and shiny.

The nuts behind it, connected to the wire, had the same sheen 24 hours ago, before their first exposure to a water leak. Blecch!