Custom Solar Powered Trailer

Our Custom Solar Powered Trailer. Enough power to run our ice-cream freezer, drink cooler, lights, sound system and more.
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Solar Powered Ice Cream
For those who are interested in solar power. Here is a layout of our electrical system

So let me start out by saying that I am not a professional electrician. I have a elemental knowledge of electricity and wiring. I did plenty of home work and lots of studying the latest in photovoltic systems to put this system together. On this web page I hope to explain the components of the system and how they work to power up our freezer, cooler and other electrical needs. Please email me if you have questions or comments on my system skywardkites@gmail.com  Dan Ward.

First I will start with the 
photovoltaic panels (solar panels) 
I choose because of their price point, long life and durability 4 Krocera 130watt 12volt soar panels. These panels produce up to 9amps each. I picked these up and most of my solar equipment at sun electric here in Miami. The price per panel was $ 569.40 (8/12/2008) As most solar equipment, the initial cost is high, but considering never having to pay an electric bill it's worth it. In our case I love alternative energy and installing FPL electric to our concession was not possible.
Next in line is the combiner box
The job of the combiner box is to be able to fuse each panel separately then combine the electricity into one wire to go into the charge controller. I made my own combiner box using a shut off switch box and installing a multiple 12volt fuse panel inside. It's set up so I can pull one panel fuse at at time. This serves two purposes. First it allows me to test each panel separately. By simply pulling three of the four fuses out, the remainder panel power will read on the charge controller. I can rotate through the fuses to see if any one panel is not working properly. Secondly if any one panel should short out (blow a fuse), I will still have enough power to run the freezer and not lose a freezer full of Ice-cream. There is also a main pull on the combiner box. Pull it to disconnect all the solar panels at once.  

Breakers, Charge Controller & Combiner Box



From the combiner box the electricity from the panels is fed into the Charge controller. Now the charge controller is really one of the most important parts of our system. It is the heart and brains of the entire system. The main job of the charge controller is to keep the battery bank fully charged and maintained at charge level that will maximize the use of power we get from the solar panels.
I choose the $ 156.00 (8/12/2008) Morning Star TriStar 45 MPPT  This unit will take up to 45amps. Sense I have 4, 9amp panels my current max amperage (amp.) is 4 X 9 = 36amps. This unit works fine and it gives me ability to add more panels if I need to in the future. 
There are several things I enjoy about this charge controller. It has a easy to understand LED screen that tells me exactly how much power is being used from the solar panels and how fully charged the batteries are. This unit also will maximize the use of the panels and more or less baby sits the battery bank. It also has a number of safety features like protection against things like overloading, short circuits, high voltage, reverse polarity and powers surges. Of course there are many choices for charge controllers. For me this one suits my needs nicely .



Charge controller.

From the controller the power goes through the 12volt breaker box. Here the 12volt electricity is sent to the breakers ( for the freezer, refrigerator, LED lights and 12volt power outlets). It is also sent through the lightning arrester to the battery bank.

12volt breaker box


From the breaker box the line goes to the Battery Bank. Before connecting to the bank of batteries the line connects to a 50amp inline breaker fuse. This is needed not only for extra protection but it also makes a easy quick disconnect. A battery disconnect is a essential part of the system to be able to disconnect the batteries from the rest of the system during maintenance.
I choose 6volt golf cart batteries because of their price, $ 85 each(8/12/2008) , and I have found them to have the longest life. I get around 3 to 4 years out of these batteries. To be able to have enough battery power to keep the system going through periods without sunlight ( nights & cloudy days ) I figured I need 8  225amp hour batteries. On paper I figure I can go up to 3 days without sunlight before the ice-cream turns into mush. So far so good, more than 6 months and the system has had plenty of power.
Above the battery bank I placed my DC to AC power inverter. Sense we use very little 115ac current, a 1000 watt inverter works fine. It is more than enough to power up our sound system, a few lights when needed and any miscellaneous smaller appliances needed day to day.
Acid filled batteries produce gasses that must be ventilated. I custom build our battery bank cabinet with vent holes for air passages 

Battery Bank & inverter 

This so far explains how the solar power is derived and stored. Equally important is how the electrical power is  sparingly used. 

My biggest energy sucking appliances would normally be the refrigerator and freezer. Fortunately a company named SunDanzer now makes very high efficient refrigerators and freezers. These are absolutely the key to being able to keep  cold drinks and frozen Ice-cream without an enormous Solar electric system. They operate on 12 volt brushless DC motor compressors. This means that not only are they efficient, it also means that I don’t have to invert the 12 volt direct current that the solar panels produce into 115 alternating current that most freezers need to operate. Yes I have an inverter for other needs, however it is more efficient to run 12 volt appliances directly because even the best inverters use up some power to invert the DC current to AC current.
Sundanzer 12 volt Freezer


Lighting would normally require a lot of electrical power. I had 3 skylights installed on the roof of the trailer to light up the showcase displays. These have worked great. Without them I would have to draw all day from the electrical system to keep the show case light.

Roof top view of bubble skylights installed on trailer

In my case we are seldom open past sunset and for when we are I have installed LED lighting. I have found that yes they are very efficient, but you need a ton of them to replace the light of a couple of fluorescent lights. They are also very expensive, but are supposed to last for years. I will find out.
a series of LED light bars installed

Update 5/12/2010

So after more than a year and half the system has worked perfectly. We've just had to add water to the batteries. We average about a gallon every 4 months between all the batteries together. Our trailer can get very hot inside so the evaporation is expected. Our system has kept at least 12. volts of charge throughout. Fully charge is 15 volts system, cut off is 10 volts. The only problem we found is that when we have a kite festival and the freezer is constantly being opened to get the ice cream, the freezer won't keep up and the ice cream will melt. So to compensate I throw in a block of dry ice to assist the freezer on festival days. That worked out fine.
Update 1/19/2011

Well we had a very hot and sticky summer with more cloudy days than normal. We ran a 3 foot box fan a lot on cloudy hot days and did put some wear on our battery bank. Although we are still in good condition (12.5vt plus ). We will see how much longer our batteries hold up. They are still working fine. We haven't dropped less than 12 volts, it's just that they don't stay at full charge as long.
I did add another solar panel to help hold up on the cloudy days. I picked up a 200watt no-name 12 volt panel from sun electric. It was on sale for just $ 300.00 It was easy to add to the system because I had over sized the system for this. So in total I have four 150 watt and one 200 watt panels. On any normal sunny day I have way more power than I use. 


Update 12/12/2011

This last weekend my batteries seemed to finally give up. The voltage was dropping below 11 volts. The system shuts down when it hits 10 volts. These batteries lasted 3 years 3 months. I am told that is average for this type of system. I decided to add 4 more batteries to make now 12 X 6volt   225amp hour batteries for my bank. My thinking is that a larger battery bank will  not  have to work as hard and therefor will last longer. Of course the price of the batteries has gone up. I had to pay $ 95.00 each this time from Battery Sales here in Miami. They are good folks who are very helpful and know solar tech talk well. As a matter of fact there store is solar powered, cool.

**** I am working on this page, more to come. Let me know what you think*****
Dan Ward
Skyward Kites




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