If you enjoy overlanding and boondocking for extended periods of time in sunny climates, it makes a lot of sense to go solar. It’s probably the easiest and best way to keep your truck camper’s batteries charged and maintained. What makes solar power great? What are the benefits? First and foremost, solar power offers true independence, allowing the owner to camp anywhere he or she wants. It also weighs very little, is easy to use, and doesn’t take up valuable storage space like a generator. Solar power also requires no maintenance as there are no moving parts, adopts well to the 12 volt electrical systems found in truck campers, and is easy to install (you don’t need a degree in electrical engineering to design or even install the system). Perhaps more importantly, solar power is quiet, doesn’t emit deadly fumes like a generator, and utilizes a free and renewable source of energy that’s good for the environment.
What components do you need to build a great solar power system for your truck camper rig? You’ll need two or more 100 watt solar panels to generate a charging current, a charge controller to prevent overcharging your batteries, and two or more deep cycle batteries to store all of that power being generated by your solar panels. You’ll also need a roof-top combiner box to connect multiple solar panels to your system, heavy gauge wire to connect everything together, fuses to protect your system from overloads and shorts, and an optional battery monitoring system like the excellent Xantrex LinkLITE or Victron.
It wasn’t that long ago when a solar power system was a major expense for RV owners. It was pretty common to find small, $2,000 systems in many rigs. Fortunately, prices for solar power products have dropped significantly as technology and manufacturing have improved and competition has increased. Here are a few purchasing tips. Avoid buying from cheap importers and from the ridiculously expensive RV solar power stores. Buy your parts from American manufacturers that specialize in the RV marketplace like Zamp Solar. Solar power starter kits, like those sold by Zamp Solar, are great options that can save you both time and money. If you have the time, shop around and look for the best deals from local stores and online merchants. Some online merchants, like Solar Blvd, even offer slightly used solar panels which can save you big money.
Of course, you can save even more money if you install your solar power system yourself. It’s not that difficult. If you can wire a 12 volt battery, you can install a solar power system. When installing your solar panels, minimize the number of penetrations through your roof. When mounting your solar panels, make sure all screws are waterproofed with Dicor or another quality sealant. In addition, I like to use high-bond tape underneath the mounting brackets. It provides a very sticky cushion between the aluminum bracket and the surface of the roof. When installing your system, try to use existing roof penetrations to pass the wires down into your camper. The refrigerator flue is great for this. For multiple panels, both Zamp Solar and AM Solar make a combiner box that mounts to the side of the refrigerator flue. The Zamp Solar model is especially recommended as it uses SAE plugs which are easy to use and plug into.
When buying multiple solar panels, it’s best to get panels of the same size and from the same manufacturer. However, you can buy mismatched panels—-such as a 100 watt and a 120 watt panel—if they match up well electrically. The key technical spec when connecting mismatched panels to the same charge controller is the “Vmp” rating. As long as the panels are the same type (12 volt or 24 volt) and are within 10 percent Vmp you’ll be okay. Note: it doesn’t matter if you use an MPPT or PWM charge controller when using mismatched solar panels as long as they match up well.
A few words about solar panel efficiency. It’s true that monocrystalline panels are more efficient than polycrystalline panels, but that doesn’t necessary mean that monocrystalline panels are better. A 300 watt monocrystalline system produces the same amount of power as a 300 watt polycrystalline system because the efficiency of the panels were already taken into account when the panels were rated. The only benefit going with a monocrystalline panel is its smaller size—a 100 watt monocrystalline panel is smaller than a 100 watt polycrystalline panel because less surface area is required to produce the rated amount of power. Is the extra cost for a monocrystalline solar panel worth it? That’s up to you to decide. In my opinion, the difference in size isn’t large enough to justify the higher cost, even for truck campers with limited roof space. That may change when 100 watt monocrystalline solar panels with a 25 to 30 percent efficiency are being produced, but until then, the difference isn’t enough to say that one is better than the other.
1. Roof-Top Mounted Rigid Solar Panels
Rigid panels come with the longest warranty in the industry, typically 25 years, and provide the best value for your rig. Monocrystalline and polycrystalline panels are, by far, the most popular types of rigid panels. For the smaller solar power systems—like those found in truck campers—it’s best to go with 12 volt solar panels wired in parallel. Panel placement on the roof of your camper is critical. The slightest bit of shade can knock a panel’s current output from 6 amps to 1 or 2 amps, so care must be taken to avoid mounting your panels too close to anything that can shade your panels like air conditioners, vent covers, and satellite dishes. Of course, this can be difficult to achieve on a small truck camper roof, but distances from these obstacles should be maximized, if possible. In order to keep the physical size down, I wouldn’t go with anything larger than a 120 watt polycrystalline solar panel for a truck camper because you’ll need to be able to get around on the roof to do maintenance.
When it comes to mounting your rigid panels, you have two several options. You can mount them either directly to your roof using aluminum brackets waterproofed with Dicor sealant, or you can mount them directly to a roof rack system like those shown in the photograph above. The benefit of the latter approach, of course, is that there is less of a chance of water intrusion over time than direct roof mounts. Tilting mounts can also be purchased for your rigid panels, but should only be considered if you plan on camping for extended periods of time in a single spot. For those who are constantly on the move, fixed mounts will serve you better and save you time in setup.
2. Portable Solar Panels
Due to the limited space on truck camper roofs, portable solar panels are a terrific option. Portable solar panels can be purchased with or without a charge controller, meaning it can tie-in with your existing roof-top solar power system or it can operate independently and in parallel with your main system. Portable solar panels have two big advantages over fixed roof-top mounts. One, they can be moved to avoid shading from nearby trees and obstructions. Two, they can be tilted and aimed toward the sun to increase the panel’s power output even more. This is especially useful during the winter months when the sun’s path tracks lower in the southern sky. Yes, it’s true that tilting mounts can be purchased for roof-top installations, but they can’t be aimed at the sun like a portable panel. The only negative with a portable unit, of course, is that it can be stolen if you don’t keep an eye on it. When operating in parallel with the roof-top system, physical access to your batteries or a 12 volt charge port with your batteries will be needed. Two of the better portable solar panel units are Zamp’s 120 watt solar kit and Renogy’s 100 watt moncrystalline solar suitcase.
3. Flexible (Thin-Film) Solar Panels
Rather than using silicon wafers like those found in monocrystalline and polycrystalline solar panels, flexible solar panels are made by depositing a thin layer of amorphous silicon on a substrate of glass, plastic, or metal. Flexible solar panels offer several advantages over standard rigid panels. Perhaps, the biggest benefit for truck camper owners is that they’re lighter and thinner. This makes them ideal for pop-up truck campers that generally have thinner, less robust roofs. Not only that, flexible solar panels are impervious to the effects of shading and high temperatures, conditions that can adversely affect the output of rigid panels. They also produce more power in low light conditions than traditional “mono” and “poly” solar panels. Perhaps the most important benefit is that flexible solar panels can be mounted on curved surfaces or surfaces with a bend. The benefits of being able to do this are obvious. Are there any negatives associated with flexible panels? There are a few. Care must be taken not to bend them too much as they’re prone to cracking. Durability is another problem as they can be damaged and scratched more easily from things like tree branches. Because of these issues, the warranty associated with flexible panels is usually limited to a period of 10 years.
Mounting flexible panels to your roof can be done in one of two ways: by using Butyl tape underneath the panel and by using either Dicor or Eternabond tape to seal the edges on the panel or by using butyl tape and screws in a traditional manner (most panels have four to six grommets for mounting to the roof of your camper).
4. Charge Controller
The charge controller functions as the “brain” for your solar power system. It regulates the voltage from your solar panels to prevent your truck camper’s batteries from being overcharged and permanently damaged. Unlike solar panels, which are sized by watt, charge controllers are sized by amp with higher amperage models generally costing more. The amp rating needed is dependent on how on the total amperage being produced by your solar panels (a 12 volt 300 watt system will produce a maximum of around 18 amps). For most truck campers a 30 amp controller will be more than sufficient and will allow plenty of capacity for future growth. A 100 watt solar panel typically generates 6 amps, so even four 100 watt panels would produce only 24 amps total.
What type of controller will work best for your truck camper rig? If you can afford one and have the room, we recommend buying a Maximum Point Power Tracking (MPPT) controller because they’re generally more efficient. But honestly, the capabilities of the MPPT controller are way overblown for small 12 volt solar power systems like those found in today’s truck campers. The MPPT controller excels in cold weather and with large solar power systems using 24 volt and 36 volt solar panels. For a 12 volt, 300 watt mobile solar power system, you’re not going to see much of an improvement in performance with a MPPT controller, if at all, especially in warm weather. In my opinion, you’d be better off buying a quality Pulse Width Modulation (PWM) controller—like the Zamp ZS-30A—and applying the money you saved toward buying another 100 watt solar panel.
5. Deep Cycle Batteries
Storing all of the energy being generated by your solar power system is the function of your 12 volt batteries. Get quality AGM or lithium deep cycle batteries for your truck camper rig like those made by Lifeline and Expion360. Avoid buying automotive starting batteries or RV/Marine batteries (a hybrid of the deep cycle and starting battery) as neither type is designed to withstand severe discharges on a repeated basis. Indeed, the great thing about deep cycle batteries is that they’re designed to be discharged up to 90 percent or more numerous times, and still provide amperage at their rated capacity. When it comes to the battery’s ratings, amp hours are the key and you want more of them. That means buying the largest batteries that will fit in your battery compartment. As for the type of battery, you have three types from which to choose: Wet Cell, Absorbed Glass Mat (AGM), or Lithium Iron Phosphate (LiFePO4). Each type has their pros and cons. Just make sure that you properly care for and properly charge them and that your charge controller is programmed for the type of batteries in your system. If your battery compartment is located inside your truck camper, then you’ll need to buy either AGM or lithium batteries since both types are sealed and won’t out-gas during charging.
Which type of battery is best? Lithium Iron Phosphate (LiFePO4) batteries provides the best value for the money. While they cost a lot more than the other types of batteries, they’re also smaller, weigh less, last longer, charge a lot faster, provide a higher output current and voltage, and provide a more usable capacity (90 percent for lithium ion batteries vice 50 percent for the other two types). The only negatives with lithium batteries are their high cost and the need for a battery monitoring system (BMS). Fortunately, many lithium batteries being made today come with a BMS like those made by Expion360.
6. Wiring and Fuses
Choosing the right size wire for your solar power system is critical. Undersized wiring will reduce the efficiency of your system, and with environmental factors already working against your system, you obviously want to avoid this. Many professional installers use 10 AWG wire to connect the solar panels to the combiner box, and 8 AWG wire to connect the combiner box to the charge controller, and the charge controller to the battery. This approach works well for truck campers, too, but honestly, you’ll be fine using 10 AWG wire for the short wiring runs found in today’s truck campers. If you’re in doubt about which gauge of wire to use check out Blue Sea System’s excellent Circuit Wizard. In-line fuses should also be used to protect the wiring and components in your solar power system from shorts and other catastrophic failures. Place one on the positive wire within a foot of your battery and another in between the combiner box and the charge controller. The size of the fuse or breaker depends upon the size of wire used in your system. Place no larger than a 30 amp fuse or circuit breaker for 10 AWG wire and no larger than a 48 amp fuse for 8 AWG wire.
7. Sizing Your Solar Power System
At this point you may be wondering how many solar panels you will need for your rig. In the introductory paragraphs, we alluded to a minimum of 200 watts with a minimum of 200 amp hours of battery power. The size of your solar power system, of course, depends upon your personal needs. Things like your TV, the inverter, your water pump, your DC compressor refrigerator, lights, and fans all need to be factored in. The easiest way to size your system is to use this Solar Sizing Calculator. To use this calculator you’ll need to know four numbers—total wattage for all of your devices, hours (enter 24), the efficiency of the charge controller used in your system, and average sun hours per day. For total watts you’ll need to determine the wattage consumption for all of your electrical and electronic devices in a single day then divide that figure by 24 (for 24 hours in a day). The wattage figures for your devices can be found either on the device itself or in the devices’ literature. Charge controller efficiency is either 80 percent for PWM or 92 percent for MPPT. For average sun hours per day, we recommend entering five hours for most latitudes here in the continental U.S., except for places like Florida and Arizona, which in the summer, would probably get six.