I made this box to provide 12 volt power for my LX200, a laptop, and a Kendrick dew removal system. A master switch controls outlet power, a meter shows the voltage of the 34 Amp Hour battery, a fan cools and ventilates the box, and a charging switch isolates the charging posts to prevent accidental shorting between the posts. An aluminum handle is screwed on top. There are mesh-covered holes on each side, with a small 12v fan in one of the holes to provide positive venting and cooling, especially during charging.
Most wiring is on the back side of the top panel.
12AWG wire is used for all connections between the charging posts and the battery, and 18AWG is used for the rest. Terminal posts provide a convenient place to route multiple wires together. Barry M. Batts of Corona, CA built a similar box using these plans and provided good feedback. To view an addendum to these plans containing his remarks and my reply, which provide a few good things to think about when building a power box like this, click here .