Field Power Supply for LX200

I made this box to provide 12 volt power for my LX200, a laptop, and a Kendrick dew removal system. It is based upon the design for a "Power Box 12volt-18volt-110volt for the LX200" by Jim Lowry, which (along with lots of other goodies) can be found in the MAPUG Topical Archive. Mine is a little different in that I wanted a smaller form factor and I do not need 110 volts (at least for now -- but I still have a little room).

The unit as shown provides three 12v cigarette lighter outlets and an 18v switched outlet providing power from the standard Meade #1812 converter located inside the box. 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. The fan and meter can be operated with the master in the off position, and the #1812 has its own power switch. A 5a fuse protects the outlet system, and the #1812 has its own 2a fuse.

The box bottom and sides are made of 1"x6" pine; the wider faces and top panel are made of 1/8" pressboard (thin enough to mount the switches, etc. through). The edges are reinforced by 3/4" aluminum angle, and rubber feet are applied to the bottom. An aluminum handle is screwed on top. The battery sits in the bottom of the box, a three-outlet 12v lighter plug strip faces out the front, an internal 12v switched plug powers the #1812, and the #1812 itself is held in with a double-faced velcro strap. 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. Wires from the battery posts and the fan to the top panel have quick disconnects to allow the top panel to be removed; the 12v outlets are all hard-wired as they must be removed to pull out the battery.

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. A female plug was installed in the press-on cap for the internal 12v lighter plug for the #1812 (see above), and a two-wire cable was run from the back of this female connector to a male connector that is held in place on the front panel by friction. Note the pine reinforcement strips on the backside of the top panel below; these carry the load when the box is carried by the handle. A small doubler strip is also glued in to provide a snug slip fit for the 18v output jack (the plug is slightly tapered so a good press fit works well).

The entire project cost around $100 including a marine battery from Wal-Mart, wood and hardware from Home Depot, and electrical components from Radio Shack.

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.

Update 2005:

This box was a fun project and it served me well. During use over the years I did note that the corrosiveness of the battery acid was taking somewhat of a toll on the components, including the #1812 converter that was enclosed in the box with the battery. I finally decided I needed more power, so I have retired this box and now use a 12v 105aH Marine/Deep Cycle battery. It is enclosed in a standard plastic battery case; I have mounted a 3-outlet lighter plug assembly and a low-profile 1.5a trickle charger on the outside of the case. The power is switched and fused with an inline fuse, and a meter (the same one shown on the box above) is mounted in the lid of the case. When I have 110v available, I simply plug the trickle charger into an extension cord and run everything I can off of 12v. This allows the battery to serve as an uninterruptible power supply, which has saved me much grief when the power has died on the observing field at a star party.