August 8, 2012

Final electrical & solar

With the paint finally dry (it took 3 days!) we were finally able to finish up the electrical.  First up was to install the vent fan.  There were two sets of wires that came out of the oak frame, red and white for the fan and black and white for the solar panels.  We first applied a ring of silicone putty at the very edge of the opening (Darrell found this at work and has no idea what it actually called) and then ran a heavy bead of caulk along the underside of the metal fan frame before positioning it on the roof.  We also put a dab of caulk at each screw hole before screwing it down.  Then all that was needed was to tie together the wires and install the white trim. 

After the fan was installed and the caulk mostly dried, we needed to drill a hole into the side of the aluminum so that we could run out the wires for the solar panels.  We then installed a liquid-tight connector to seal the hole.  We found this little guy in the electrical department at Home Depot.  The wires were then ran through the connector and into a black rubber tube that we fed into the connector as well.  This tube would then end underneath the nearest solar panel protecting the wires and giving us a water proof seal into the trailer. 

Next we were finally able to install the solar panels we purchased back in may.  Darrell was able to bend some metal angle clips we had used in other parts of the trailer to create simple brackets to attach the panels to the roof.  The panels had an aluminum frame around them already that he was able to screw the brackets to then, after some careful positioning, screw them directly to the roof, first filling the holes with caulk. After they were installed, he neatly trimmed the solar panel wires to length and connected all three together with a couple of caps and lots of electrical tape.

Back at the front of the trailer, we needed to install the second liquid-tight connector that would be attached to the tongue box.  With that done, the first of the cedar running boards needed to be attached since it would be difficult after the tongue box was installed.  Where the side walls and plywood skin met the metal trailer frame was really unfinished looking, plus the red frame was kind of ugly.  I decided the best way to cover the frame and finish off the trailer was to use cedar stock that could be attached directly to the side walls and skin.  The cedar would complement the darker okoume and wouldn’t need to be stained or treated with anything as it is a naturally weather and rot resistant material.

Next was installing the tongue box.  We decided to get a locking, weather tight box from Harbor Freight Tools, the same store we got the trailer frame from.  It was inexpensive but well built and we knew it would fit on the tongue perfectly.  Darrell first cut a hole in the back of the box where all of the wiring would come through. This eliminated the need for additional openings, thus preventing any leaks from occurring.  Of course this was where the liquid-tight connector fed through.

Within the tongue box we planned on housing the following components:
1)      Fuse panel
2)      Battery
3)      Solar charge controller
4)      Standard battery charger (120V kind)
5)      Spare components (Wheel bearings, chocks, etc.)
6)      Extension cord

The fuse panel was designed by my Dad and it consists of a volt meter, a 10Amp or 20Amp throw switch (depending on how much of a load we are going to be consuming) and a fuse block which has 12 inputs. We are only using 6 so that leaves room for a few for additional electrical items in the future if we want to add anything.  It also include a small has a small volt meter linked in so that when we push the red button under the LCD panel, it shows how much charge we have in the battery.

Each item within the trailer is wired to an individual fuse, this makes diagnosing any problems a breeze. The fuse box also is a terminal block which gives me the opportunity to only have to run one positive and one negative connection back to the battery.

Speaking of the battery, we opted for a larger marine deep cycle wet acid battery. This will give us the required capacity throughout the day that we would need without the worry of depleting the battery too much. The calculation is rather simple, you add together the amperage that you are going to be potentially consuming and multiply by the amount of hours that you will be using these amps.  In the electrical post, Darrell explained what we thought our potential Amps and Watt hours would be – it came to approximately 4.5 Amps.  We figured that we would not be using anything in the cabin during the day and would probably only be using the fan or charger or lights at night so max 15 or so hours.  Rounding up this gives us 70 Amp hour required.  The rule of thumb when selecting your battery is to basically double this capacity, thereby landing us at 140 Amps.  So we ended up buying the DC31 Sportman Marine Deep Cycle battery from our local marine store which has exactly a 140 Amp hour rating.  A bit overkill… maybe.  But we won’t have to worry about running out the battery in a single day.

In the electrical post Darrell also talked a bit about the solar charge controller.  The other thing that should be mentioned is that it also bypasses the fuse panel completely. Since we are dealing with such a small wattage on the solar panels you don’t really need to worry about any fuse needs. You connect the solar panels directly to the controller and then the controller directly to the battery.  We get around 14 volts in the direct sunlight which charges the battery over the course of a few hours quite nicely.  Typically the system will begin charging around 13 volts, and stop charging when it reaches 14.7.

One additional thing we did that is super convenient was to install a second volt meter in the cabin.  This is a smaller version of what is attached to the fuse panel, but works in the same way and is hard wired back to the fuse panel.  In this way, we can check on the battery levels while inside the cabin without having to get out, open the tongue box and all that.

Best of all, when all was said and done and everything was installed, the lights worked!!


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