Our Solar System

Updated Saturday, May 07, 2005

  Our rig gets considerable attention as people pull into any boondocking area. It seems we have entered into the fewer number of people who develop their solar charging systems past the battery maintenance phase. It is understandable that this is so because the investment required is substantial and many RVers are not full timers and choose not to be independent of the electrical grid. There are a number of trade offs to consider aside from the financial considerations. For our purposes this expenditure now is the best way for us to go long term because it enables us to be free of expensive hookups which will save us a lot of money as time goes by. The less we use park electrical hookups, parking fees and such, the faster we recoup the cost of the solar system. I will get into the details of the costs later. This is not for everybody. We understand that. If you are interested in knowing more about how we went about this set up keep reading. Just click on the photos for enlargement of details. This is not a how to so much but rather a how I did it description. I recommend that if attempting to install a similar system and you are not experienced that you have professional help to insure a safe installation.

    When we went to see Quartzite, AZ back in January 2001 we were astounded. There were thousands of RV's most of them with some type of solar charging systems. This is a look at the boondocking area east of Quartzite where we stayed. You can see the thousands of RVs across the valley in Quartzite. None of them have hook-ups. They are all boondocking and on their own when it comes to electricity.

    Here, we really got into long term boondocking as there were very few places to get full hookup RV sites. The whole point of being there was to enjoy the fact that we can, and did, live independently of any electrical hookups, water or sewer facilities. It was an enlightening experience to say the least. The short of it all was that as a family of 3 people, 3 dogs, a cat and a parakeet we wanted more comforts and electrical independence than would be possible with our current system. Our original set up, which was installed in Glendale, AZ last June, was just fine for 3 to 5 days with good sun to recharge. It took a 2 week stay with several days of clouds for us to realize that if we really wanted to be independent we had to expand our system. I had to run the generator several times to recharge our battery bank when we didn't get enough sun. When the generator broke, (which they always do sooner or later), we really found out how much we missed the power we wanted. Of course, a few days of no TV, no computers and no microwave can do us all a little good. But, we knew if we wanted to live this kind of lifestyle, long term dependence on hookups and/or a generator was not the solution for us.

    While we were at Quartzite, we met a couple, Frank and Mary Nulty, owners of Solar Solutions, who became good friends. They were really living the "Boondockers" lifestyle. They have been traveling full time for several years and hardly ever used full hookup RV parks. They have had several rigs and are currently using a truck and trailer combination to live in. As with most everybody who chooses this lifestyle, weight and space are at a premium. Their trailer did not have storage capacity for a large battery bank. Frank has a vast knowledge of electrical engineering and figured out that if their RV didn't have the space then their truck did. He installed a larger battery bank in his Dodge pickup truck bed and connected them via a heavy duty cable arrangement. He also installed extra solar panels on the roof of the truck bed cap to enhance their charging capabilities. I carefully examined this approach and asked many questions. I was convinced this was an acceptable way to approach expanding our system. We already had a bank of 4 six volt deep cycle batteries that served us most of the time under normal conditions. I was concerned about adding additional heavy batteries to the front pin weight which was already too heavy. (In preparation to make the modifications we engaged A-Weigh-We-Go to give us a run down on our weight distribution, etc.) I was correct that the hitch weight was a little too much and did not want to compound the problem any further. The remote location of additional batteries was feasible as the we were within our weight specifications on our tow truck a Ford F550 crew cab XLT.

I had also learned from our stay in foggy Park Sierra, CA that extra battery capacity will be needed to allow for those days of reduced solar charging time and shorter days during the winter months. So, adding the batteries to the truck was the way to go. I arranged to meet with Frank at the North Ranch Escapees Park in Congress, AZ. There, we soon tackled the project.

The basic original solar system consisted of the main battery bank, Heart 2500 watt inverter/charger, a 30 amp solar controller and of course the 2 original 120 watt Kyocera solar panels. The Kyocera 120 watt panels gave us the most wattage for the money and are top quality panels warranted for a minimum of 20 years. The existing RV main battery bank consists of 4 Trojan T105 6 volt deep cycle 110 amp/hr batteries wired in a series to make 2 12 volt banks, 220 amp/hrs each, paralleled together to make a total bank of 440 amp/hrs capacity.  

Now if this is clear as mud I will try to detail the methodology of how to correctly add up amp/hr capacity and volts.

Illustrated below is an example of 6 volt batteries wired in a series which add up to 24 volts but the total amp/hrs are only 200. The voltage (current) is additive but the amp/hr capacity is not.

Each Battery Capacity 200 Amp-Hours @ 6 VDC

Total Battery Bank Capacity 200 Amp-Hours @ 24 VDC

Each Battery Capacity 100 Amp- Hours @ 12 VDC

Total Battery Bank Capacity 400 Amp-Hours @ 12 VDC

Here, two 6 volt batteries are connected in a series where the amp/hr capacity is constant but the voltage is combined to equal 12 volts.

  Next, an example of how a a group of 12 volt batteries are wired in parallel. Note that the voltage remains the same but the amp/hr capacity is cumulative.

  Batteries can also be combined to increase voltage. Here the battery group is wired in series to give a total voltage of 24 volts but note the amp/hr capacity remains constant.

  Of course, the batteries can be both wired in series and paralleled together to keep the desired voltage and increase the amp/hr capacity of the system.

Now with this in mind, what I did was create one large battery bank made up of 8 six volt batteries. Each 6 volt T105 battery is wired in series to another 6 volt battery creating a battery set that adds together to make one 12 volt battery bank. Each 12 volt battery bank is then paralleled together to add together their amp/hr capacity to equal the large amp/hr capacity desired.

                          880 amp/hrs total potential capacity

I re-built the box already on the RV batteries. I also lined it with reflective bubble wrap to help keep the batteries at a more stable temperature. (TIP: Put the foil side away from the batteries!) Lead acid batteries are like people when it comes to temperature. If you are comfortable then they are. If you are not then they are not. The temperature range for optimal charging is about the same as it is for people. So, if you want efficient long lasting batteries then make them as comfortable as you can. A good insulated box will help accomplish this.

 I also used hydro caps on all the 6 volt batteries. Hydro caps capture the hydrogen and oxygen gases given off from the water electrolyte and recombines it to form water again. The water drips back into the battery reducing the need to add water to replace lost fluid and prevents potential explosive gas from entering the RV compartment. It is very important to remember that when using lead-acid batteries that they will gas under the normal charging process. This gas is not only explosive but is also corrosive. The lead-acid batteries must be contained in a vented compartment that is air tight from the interior of the RV. You can avoid this problem by using hydro caps or another type of battery such as gel or glass matt batteries. Gel or AGM (glass mat) batteries are excellent batteries for this type of application but can be cost prohibitive when starting up a system. Lead-acid batteries can be more work but can last a long time (years) if set up and taken care of properly.  

When looking for batteries for solar battery banks the amp hour capacity is the important measure of deep cycle performance. This differs from the CCA (cold cranking amps) usually seen in common automotive applications. We discussed adding an extra pair of batteries to the front compartment but decided it was better to keep the weight off the RV and put it on the truck which has the weight capability to handle the extra load as planned. Furthermore, batteries should be matched together when new so as to keep the aging process uniform. It would have involved moving the original RV bank to the truck and putting new ones on the RV. Instead, we put the 4 new T 105's on to the truck, two in each side tool box. Since the 1st set of batteries were still relatively new initially I decided to wait until later to move them out of the primary position in the RV.  I have since rotated the battery sets so the newer ones are in the RV.  Rotating the batteries is a good thing to do especially in this set up because of the different environments the batteries are placed in. When rotating I keep the same groups together based on age. Charging is not always absolutely equal because the truck is sometimes disconnected from the RV when we are gone on errands or for other needs. When reconnecting the batteries together they will equalize their charge over the whole bank. It does make determining the exact charge a little more difficult. I will be adding a separate Link 10 battery monitor to the truck side soon.

Building a separate storage box was necessary to isolate the batteries from the rest of the tools in the storage bays I already had mounted under the truck's flatbed on both sides. Steel boxes are strong and durable but not the best environment for unprotected batteries that you want to last. I fashioned battery boxes from 1/4" plywood and insulated them with heat reflective bubble wrap before putting the batteries in. In retrospect, I recommend heavier plywood to make it more sturdy over time. I am going to replace the 1/4" with 1/2" plywood and use more insulation.  I had to purchase a set of steel cutting hole saw blades to provide holes for the cabling to go through. This made the job much easier. The 4 new 6 volt batteries were placed in series to make 2 -12 volt units. Each battery set was also isolated with a overload breaker relay in case an accidental short occurred. The batteries were also wired to the truck alternator for charging independently while driving. An on/off isolator switch was installed in the cab so truck charging could be turned off when not needed. This effectively more than doubled our battery capacity. (440 + 440 = 880) This is the back of the truck battery bank compartment. There are two posts to handle the cabling from the front isolator, the battery bank from the other side and the cable run over to the RV connection. This is the exit cabling from battery bank on the right that crosses over to the one on the left. I cut some 1" radiator hose to make rubber cable protectors. Also note all cable connections were crimped, soldered and heat shrunk wrapped for maximum conductivity and protection. Using 1.0 battery cable and taking the time to make good connections is vital in making a long term connections with little or no trouble later on.

Connecting the three battery groups wasn't as difficult as I expected. I used 1.0 gauge battery cable wire to make all the connections and the long run to connect to the RV battery bank. The hardest part here was running the cabling through the 5th wheel overhang to exit and make a clean connection point. The connecting point conveniently was placed where it came through an existing access port where the current wiring for the trailer connections were. We tapped into the tubular aluminum frame of the RV to secure the mount and I used a rubber shock cord as a strap to keep the strain off the connection. When the truck is disconnected the cable is rolled up and stored neatly in the corner of the truck bed next to the auxiliary fuel tank. Dust covers are provided on each connection to help keep the contacts clean.

Now, adding more panels was just fine except for one thing. The current 30 amp controller we had would not handle a potential 35 amp load from 5 120 watt panels rated at over 7.1 amps each. So, I had to decide if I wanted to split the controllers and only buy another 30 amp controller or invest in a larger controller that would not only monitor the charging of the battery bank but allow for equalization of all the batteries as well. The choice: a Trace C-60 solar charge controller. This controller allowed room for expansion and automatic equalizing for all the batteries while only on solar power. It seems not much to do is made over the solar controllers in small systems but I found that when stepping up to a healthy sized system like this it required a more sophisticated controller. Equalizing the batteries on a periodic basis is important for battery longevity. Deep cycle lead-acid batteries are heavily lead plated by design. The process of storing energy is electro-chemical. As a by product of the chemical reaction the sulfuric acid reacts to the lead resulting in crystallization of sulphate on the surface of the lead plates. The sulphide crystals reduce the surface area of the lead as time goes by thus reducing the capacity of the battery. The process of equalization forces the sulphide crystals to dissolve back into solution and returning the surface area of the plates back to normal restoring the expected battery capacity. The electrolyte solution in a lead-acid battery also is prone to stratification. That means the chemical concentration of water and sulfuric acid separates into layers when sitting for long periods undisturbed. Equalization stirs up the solution within the battery. Equalization is done by pumping more energy into the battery than it can hold. The solar system has to be powerful enough to supply enough amperage to stir up the electrolyte by causing a rapid bubbling in the cells. This must be done within certain parameters and over a certain time, thus the importance of a charger/controller that is designed to do this.

Adding the new panels was relatively a simple job. The Kyocera panels are already set up to connect multiple panels so running the wiring was a straight forward process. When trying to size your wiring to the panel load it is real important to use adequate size wire to make the runs which decrease power loss and resistance. The larger the gauge of the wire and the shorter the run the better when using a 12 volt system. I used 10 gauge wire to connect only 3 panels at a time. That means I would have only a maximum potential 21 + amps on a single wire run. To connect them all I would have to have replaced the existing wiring with larger gauge wire. Instead, I ran an extra 10 gauge wire run to handle the extra 2 panels. This made the wire runs easier to manage and gave adequate room for additional panels in the future. I plan on adding a larger gauge main wire down into the RV and shortening the 10 gauge wire as much as possible to connect to the larger main. This will improve the amount of out put available from the panels even more. Be sure to use UV stabilized wiring to prevent deterioration to exposure to the sun over time to the wires that are constantly exposed all the time. The black tank vent stack had adequate room next to it to run the extra wiring I needed. The original installation included a 300 amp catastrophe fuse on the whole system. If a short occurs in the line(s) anywhere there's a chance for a fire to start. I'm dealing with a lot of electricity here so it is prudent not to take safety for granted. Breakers on the battery banks and fuses where they should be go a long way in insuring that the system stays safe.

Post script: Since I wrote this the fuse has saved my bacon! A jack motor worked its way loose and pinched the main power cable coming in from the truck battery banks. It fried all the small gauge wire before it blew but prevented a catastrophic fire! Be sure to fuse all your power points!

We monitor the whole system in several ways. We had a Link 1000 remote control panel and monitor installed with the original system and it is adequate to give us a complete system status at a glance any time. In addition, the Trace C60 solar controller also allows for monitoring by reading the status LEDs on the front panel. I could have ordered a remote panel for it but choose to use the Link for the time being. When you become your own power company learning to read the meters is much more important. You don't have to have an expensive meter to keep track of your system but the more information you can get the better! We sure enjoy having the independence from the electrical grid!

The solar panels and batteries are not the only solar products we use. As you can see, the sun provides us with cooking power, water heating and good old laundry drying. (What a novel idea! Drying our clothes with the sun!)

The North Ranch had a solar day during the Fiesta Days weekend and there were a number of meals cooked with solar ovens. We love ours! We also experimented with solar water heating. We found that with the reflectors the plastic jars of water climbed to over 120º F! That is plenty hot enough for our needs. It can save on propane from heating water with the gas water heater.

We also enjoy the benefits of true sine wave power. The Heart Interface 2500 watt inverter/charger is great for everyday power requirements but we had a problem with some electrical appliances when trying to run on modified sine wave power. To clarify what the difference is, a brief explanation of how electrical power is distributed over the grid is in order. Grid power has to be transmitted over long distances. This is the reason for alternating current (AC) vs. direct current (DC) as far a transmission is concerned. The electrical energy produced is rectified from DC to AC and in this process the movement of electrons is regulated into waves of energy, (60 mhz). These waves are normally smooth in nature and electrical appliances are designed to receive that smooth energy in the expected sine wave form. When using a battery bank the electrical energy is stored using direct current (DC). An inverter creates AC power by alternating the current into the expected sine wave configuration. This takes 12 volts and turns it into 115 volts that is usable by most appliances. Not all inverters does this the same way. Many RVers are disappointed when they purchase an inexpensive cigarette plug in inverter an find that it doesn't power their appliances very well or maybe not at all. This is because most appliances that are designed for AC power expect a smooth flow of electrons in a true sine wave form. Less expensive inverters do not create true sine wave power but rather try to imitate it. Some do a better job than others. Thus, if you see an inverter for sale a bargain price be sure to check to see what kind of power it produces first. An old axiom says that you get what you pay for. True sine wave inverters are much more costly to build thus more expensive to buy. A happy medium can be reached in most cases by using a good quality modified sign wave inverter such as the Heart Interface unit. Cheaper inverters produce a square wave * that many appliances do not like. Better inverters produce a modified sine wave.*   This approximates the shape and flow of a true sine wave form. It works for most appliances but some appliances, such as our sewing machine, require true sine wave power because of complex power requirements of the variable speed motor.. Most of this gets into electrical theory and I'm trying to keep it simple. You electrical engineers can get more into the details if you want. We added a true sine wave * inverter to our system to allow us to run those special appliances that require a true sine wave form. This is an option everyone has depending on the costs involved. It was less expensive to get the larger modified sine wave inverter for the whole RV and then add a smaller true sine wave inverter for special applications. If money is not an object you can get a true sine wave inverter to power the whole system to begin with and be done with it. We choose a Prosine 1000 true sine wave inverter that can act as a back up in case the main inverter goes down for any reason. Applications are as individual as you and your budget are so your case will be different. But, I hope I've given some basis for thought in designing a system for yourself.

Hardware costs for the upgrade:

120 watt Kyocera solar panels                                                                $1,650.00    3 @ $550.00 each

Roof mounts with tilting hardware                                                                $75.00     3 @ $25.00 each

Wiring Harnesses                                                                                        $75.00     3 @ $15.00 each

Trojan T 105 6 volt batteries                                                                     $223.40     4 @ $55.85 each

Trace C-60 Solar Controller                                                                     $209.00

Trace battery temperature sensor                                                                $21.00

Wrangler 200 amp solenoid                                                                        $45.00

1.0 battery cable, lugs & 6 gauge wire                                                       $367.00

Hardware & circuit breakers                                                                     $142.00

Hydro caps                                                                                                 $90.00     12 @ $7.50 each

Prosine 1000 watt inverter, cables & hardware                                          $790.00

                                                                                                              $3,687.40    upgrade total

Original equipment costs:

Heart Interface 2500 watt Inverter/Charger                                            $1,145.00

Link 1000 Monitor/Remote                                                                      $314.00

Original Kyocera 120 watt panels                                                          $1,379.00 2 @ $689.50 each (2000 prices)

Trojan T 105 volt batteries                                                                       $224.00

Hydro caps                                                                                              $102.00     12 @ $8.50 each

10-4 wire                                                                                                  $27.30       14' @ 1.95/ft

2-0 battery cable                                                                                       $27.68         8' @ 3.46/ft

Cable ends (1-109)                                                                                   $21.70         14 @ 1.55 each

                                                                                                            $3,240.68  original solar equipment

                                                                                               $6,928.08 total equipment expenses                

Original installation labor and consulting expenses                                      $   625.00 for 12.5 hours @ $50.00/hr

Upgrade installation labor and consulting expenses                                     $   230.00 for 11.5 hours @ $20.00/hr

There is no Arizona sale tax on RV solar expenses

Grand total for entire solar system                                             $7,783.08

To regain our expenses, in estimating the costs for camping fees using an average of $22.00 per night, one year would equal $8,030.00. Of course, this assumes that we never use full hookups for the entire year. Chances are that we will still occasionally use full service campgrounds on occasion which would increase the time to regain the expenses proportionally. Another plus to our system is that it is portable. Meaning that we can move it to another RV if and when we choose to do so and or we can use it on a fixed permanent structure in the future if we so desire. The savings there will allow us to be self sustaining for our electrical needs far into the future. (And when the energy shortage blacks out the rest of the country, we can still operate as normal independent from the electrical grid.)

Feel free to ask questions if you can catch me. I'm on the way to California to sell power!

Post Script: We've been boondocking now for the last year. The system works! There have been times where we still wish we had more power so I guess we are going to continue to expand the system. We will be adding more panels as the budget allows and I have been studying the wind generator as a back up charging source.  As these items are acquired and installed I will post those updates. 

Remember to equalize your lead acid battery banks on a regular basis! Also, rotate the batteries in each bank and rotate the banks. This ensures that they will age together and be charged equally and should help them to last longer. It will force you  to keep the contacts clean as well.