Installing a powerful solar system provides freedom from the utility grid and the opportunity to stay in primitive locations without giving up conveniences
The sun is a gigantic mass in the solar system that everyone expects to come up in the morning and to go down in the evening. It’s the Earth’s temperature regulator, and it is worshipped by many who enjoy basking in its warm glow for recreation. For most, the sun’s power is generally accepted as just part of daily life, but for RVers who relish getting off the grid, the sun is also nature’s power generator.
Solar systems that harness the sun’s rays and turn its energy into electrical power have been around for a long time, and RVers who appreciate the seclusion and economics of primitive campgrounds have embraced this silent power for many years. New, and continuing, technology has leapfrogged solar power to new levels, and RVers can now build systems that make living off the grid more practical than ever. We assembled and installed a robust system using the latest equipment available at the time (this technology changes rapidly) with the help of the experts from AM Solar in Springfield, Oregon, that transformed the fifth-wheel trailer into a mini power station.
While the attributes of a solar system, including electrical independence, are well-established, a primary benefit is to properly condition batteries. Solar power, through a suitably designed system (which includes a good charge controller) offsets continual deep discharges because the batteries are constantly being conditioned in response to actual usage. In the end, lead-acid batteries, for example, can last twice as long. At today’s prices for batteries, that’s a big savings.
Preplanning is crucial to building a good solar system; you just can’t slap a bunch of components together and expect positive results. The first step is to figure out your needs based on how you use the RV. In our case we determined that we wanted enough power to run the microwave, induction cooktop, hair dryer, fireplace flame (for visual ambience), entertainment systems and all the other 12-volt DC accessories in the rig and, of course, condition the batteries properly.
Our goal was to build a system big enough to allow complete independence from the grid, unless we wanted to run the air conditioning. It’s not practical to set up a solar system to continuously power the air conditioner(s), and in our case we rely on LP-gas to run the refrigerator. Systems can be designed to handle a residential refrigerator, but the battery bank and number of panels must be increased.
Our original calculations had us settling on three 160-watt solar panels, two AGM batteries (300 amp-hours), a 2,000-watt inverter/charger and a controller with a boost feature. After discussing our needs with AM Solar owner Greg Holder, we made a number of changes and upgrades. It kind of reminded me of remodeling a stationary home; changes are inevitable.
In the end we upgraded to four 160-watt panels after learning that the extra wattage eliminated the need to tilt the panels to follow the sun. That was a big selling point, since we would rather not spend too much time on the roof. The biggest upgrade was to lithium batteries, which upped the price tag considerably. Then to condition the lithium batteries properly, we upgraded to a Magnum Energy MagnaSine Hybrid inverter/charger.
When all was said and done, we had assembled a very powerful system with all the bells and whistles, banking on optimum performance and long-term reliability. It also satisfied our secret desire to have the ultimate system for our needs.
Lithium batteries are no longer science fiction; use in electric cars has made lithium batteries very popular, and for good reason. They last a really long time and can handle many more discharging/charging cycles than their lead-acid/AGM counterparts. These batteries maintain rated performance when taken down to the maximum depth of discharge, which is an amazing 80 percent. Lead-acid and AGM batteries should not be discharged beyond the 50 percent threshold.
To put the performance numbers in perspective, the lithium batteries used in the test system will provide 240 amp-hours before recharging versus 150 for lead-acid or AGM batteries. An even bigger consideration is voltage. As the charge level in lead-acid and AGM batteries decreases, so does voltage, which impacts appliances and accessories. Lithium batteries maintain full voltage until fully discharged, and then voltage drops precipitously.
Because the performance characteristics of lithium batteries are so much different, a battery management system (BMS) is critical to prevent damage from over-discharging or excessive voltage. Mini BMS circuit boards are wired between cells, and these boards are tied into a master BMS control box. Red lights on each BMS cell-level board flash when everything is OK. Four mini BMS boards were used on the battery bank built for this system.
When the BMS recognizes that the high- or low-voltage threshold has been breached, it automatically shuts down the battery bank, well before any damage can occur. When that happens, the light around the reset button mounted inside the RV illuminates to inform the user there’s an issue with voltage. If any of the mini boards discovers a change in the
threshold voltage — high or low — in any cell, the entire bank is shut down.
Building a battery bank from lithium cells is not designed for the do-it-yourselfer. There’s a lot of science behind assembling the bank, and that should be left to the professionals. The batteries are assembled using individual super cells that are rated at 3.2 volts and 100 amp-hours. These super cells can be configured to offer greater flexibility when looking for space to house the battery bank, unlike conventional deep-cycle batteries that have established dimensions.
For our system we paralleled three smaller cells into a super cell and then put four super cells into series using copper plates to make a 12.8-volt, 300-amp-hour battery bank. Once the batteries were configured and banded, they were initially electrically balanced so the voltage is consistent and at a full charge. This step requires the use of a sophisticated charger that can be controlled accurately.
Normally, lithium batteries are rated for around 2,000 charge/discharge cycles, which in itself is much better than the 500 to 1,000 cycles expected of a lead-acid or AGM battery. AM Solar tunes its proprietary BMS so that it operates in a narrower window than the maximum and minimum voltages established by the battery manufacturer, which increases the expected charge/discharge cycles to 3,000 to 5,000. If the user discharges the lithium batteries 80 percent 365 days a year (which almost no one will do), the batteries should last eight to 13 years. Given a more practical use of the batteries in normal living circumstances, the batteries should last at least 15 years, which makes the $2,599 price tag a lot easier to amortize.
Lithium batteries will not discharge much when in storage, and after testing for five months with no external charging support, the voltage barely changed. Another welcome feature is that lithium batteries do not have to be fully charged each time. That means you can charge them to a certain point (if there’s little sun or electrical power is not available) without negatively affecting conditioning. Lithium batteries can be charged very quickly.
When compared to batteries of equal capacity, the lithium counterparts are smaller and lighter. Each cell weighs only 7 pounds, which means the entire battery bank for this system weighed only 84 pounds, less than the weight of one 6-volt AGM battery.
Undoubtedly, bad press that surfaced a while back created some discomfort when considering mounting these batteries inside an RV storage compartment. Fires, created by battery overheating, were once a problem. The batteries under scrutiny were lithium cobalt oxide formulations and were subject to thermal runaway hazards that led to fires. The newer crop of batteries is lithium iron phosphate, which is basically noncombustible. Combine the latest-generation lithium batteries with a solid BMS, and the system becomes very safe.
Panels and Charge Controller
Solar-panel technology has moved very fast in the past few years. AM Solar specializes in the most up-to-date products and for this installation used its SF160, 36-cell mono-crystalline panels. All the panels are custom-built for AM Solar, and Greg Holder specifies at least 36 cells, so they are large enough to capture the most energy. The panels operate at 18 volts and are rated to have an 8.8-amp output. They measure 263/4 by 581/4 by 13/8 inches, which is very compact, considering the output.
Higher voltage boosts the charging amperage, especially when routed through a Blue Sky Energy Solar Boost 3024iL controller, which is designed to lift the charging amperage to the highest possible level. The controller is a critical component in any solar system. Its main function is to regulate the charging current and prevent overcharging the batteries. The unit used here is rated at 40 amps, so there’s a little room for expansion on the system, which will likely not be needed.
This is a very sophisticated controller, and it features a relatively new feature called maximum power point tracking (MPPT). This gives the controller the ability to boost the charging current (amperage) by converting some of the excess voltage coming from the panels — thus, the reason for panels that operate at a higher voltage. The biggest boost can be realized when the panels are cold and the battery voltage is low.
The controller was tied into a Blue Sky Energy IPN-ProRemote panel that has a tremendous programming capability. Five levels of information, deciphered by the various algorithms in the controller, can be read on the remote screen. The information is extensive, including the ability to equalize the batteries, which is not needed for the lithium batteries. It’s important to allow the installers to set the controller and provide users with the do’s and don’ts to keep from getting in trouble with lithium batteries.
Beyond voltage, the information shows how long since the batteries were fully charged, amperage from the solar array, usage in amp-hours and much more. If you’re a power watcher, you’ll be in heaven here.
An integral part of any complete solar system is the power inverter/charger. This component provides the power from the batteries to run the targeted 120-volt AC appliances and accessories, and charge the batteries when hooked up to RV park power. We chose the aforementioned MagnaSine for its established reliability in the industry to provide pure sine-wave power for all of our sensitive electronics and, most importantly, its compatibility for use with lithium batteries.
Model MSH3012 is the only inverter in the Magnum Energy line that has the hybrid feature, which provides a relatively new twist on inverting power by working in concert with 120-volt AC power when connected to some type of shorepower. Without getting too deep into the electronic wizardry, the MagnaSine inverter provides load support when there’s not enough current to operate the desired systems. For example, if you find yourself visiting relatives and can plug into only 15- or 20-amp household power, it’s not possible to run the microwave and hair dryer at the same time (depending on the demand from other appliances). The hybrid feature will provide the extra called-for current to operate the other appliances, up to the rating of the inverter, which in this case is 3,000 watts. This will prevent breaker tripping and an abrupt loss of power.
Normally, other inverters operate on only one source of power to run the appliances and accessories, and use a transfer switch, which isolates the inverter when plugged into an external source of 120-volt AC power. The hybrid inverter uses energy from the battery bank and an external 120-volt AC source to power the loads; any surplus power can be used to charge the batteries or handle higher loads than the AC input alone can provide.
Controlling the inverter is done through a remote with an LED display that we installed next to the IPN-ProRemote for the solar panels. The panel is loaded with features, and again, takes some initiation and practice to run through the steps. It really allows the user to fine-tune the system to take full advantage of the lithium batteries and other power sources like a portable generator while boondocking.
The output of the generator can be dialed in using the remote panel, which adds greater flexibility when charging batteries and running appliances. Since the MSH3012 inverter can add up to 25 amps to the output of the portable generator for a period of time, it’s possible to run the air conditioner while using a 2,000-watt generator long enough to cool down the interior and remove excess humidity. Once the heavy load is eliminated, the generator will recharge the batteries through the inverter.
Installing a system of this caliber is not for the faint of heart. I highly recommend leaving it to the experts, like AM Solar, because of the many intricate pieces that need to be assembled. For example, it took the better part of a day just to locate a suitable runway for the 4-gauge cables used to connect the panels to the charge controller. It took four and a half days to complete the installation to satisfy all the required codes, ensure that all the components were secured properly and that the wiring was meticulously routed and wrapped.
As one might expect, such a robust solar system is not inexpensive. The complete package described above with all the ancillary pieces like the circuit breaker, fuse, BMS and cables was just shy of $12,000.
Obviously, the results from any solar array will be subject to the time of year and personal usage. On an average day, we consume about 100 amp-hours, which is less than half the capacity of the lithium-battery bank, and we usually have the batteries fully charged by noon when in good sun. The fact that the lithium batteries do not require a finish charge provides great versatility on days when the sun is not as strong.
Except to run the air conditioning, there’s really no reason to hook up, which gives us exceptional freedom to travel at will. We jokingly tell our neighbors that we can sell energy back to the grid, which always initiates a conversation and tour of our system.