Solar of the Absurd
I receive questions about the Enterprise’s peculiar solar power system, and peculiar it is. One would like to think that my solar system is being presented here for you because it’s unusual, and might give you something to learn or to think about. True enough. It may inspire you to consider unusual options when suddenly confronted by major obstacles. It may also convince you of the real value of both diligence and thoughtful learning. It will also underscore that haste makes waste, and that ignorance can derail even the best laid plans.
My original goal was to quickly acquire an old, mid-sized travel trailer having a certain floorplan that I needed. Then I would slightly modify the interior space, install solar power for full-time boondocking, and hit the road before cold weather set in. I’d never done anything remotely like this, and am not particularly “handy”. Time was exceedingly short, and I’m not above trading away sophistication and elegance for whatever is workable. When a rain cloud is overhead, a tarp and a stick is often better than a pile of arched steel spans, roofing materials, bricks, and bags of mortar.
The Master Plan
Think of my system as “modular”. One solar panel, one solar charge controller, and one battery pack – nothing unusual about that. Each component is closely matched to the other to maximize performance and minimize cost. The only difference is that, to get much more power than it can produce, you don’t then start upsizing the individual components. Instead, you simply add more of these modular solar assemblies to your project, placing them where you need them. I’ll be the first to admit that upsizing is usually the least expensive way to scale up power. A bigger solar panel usually costs less than two smaller ones. A higher capacity charge controller normally costs less than two smaller ones. Same for batteries.
But, I’d stumbled upon a sweet-spot for my purposes: A 195W solar panel, a 180W solar controller that actually maxed out at 200 watts, and 208Ah of batteries. At least at the prices I was seeing online at the time, two of these systems cost less than swapping in a larger controller to deal with two panels and four batteries. Plus, they desulphate the batteries once charging is done. My devices that need power are spread throughout the trailer, and I had no desire or ability to bury long strings of wire within its existing structure. Having no time to spare, I ordered four panels (780 watts total), four controllers, and some batteries. I know, that’s a lot of watts, but my office is closer to a photography, video and audio editing workstation than it is a perch to check email on a laptop.
Surveying the wreckage
I then found a local 1994 Gulf Stream Innsbruck with the floorplan I needed, and towed it home. Everything in it still worked, and it had a leak-free, one-piece aluminum roof. My hope of roof-mounting my panels evaporated however, when I found that the roof was so badly dented and unsupported that roof-mounting was impossible even if I somehow found space for the panels – which I could not. Lesson one was learned. Time to come up with Plan B.
Desperate men do desperate things
Plan B was to mount the panels removably on the sides of the trailer. Since the trailer’s awning took up most of the passenger side, the only option was to rig up mounts all along the driver’s side. Since four 45-pound panels are quite a load and old trailers aren’t noted for having solid body structure, my son and I looked at the awning mount and decided that the similar header on the other side was our best bet if the wood wasn’t too deteriorated to allow wood screws to bite in. We’d rig up a mount that allowed hanging the panels and swinging them up into position with telescoping painter’s poles. They’d have to be dismounted and stowed inside the trailer for travel, and carrying and lifting them would be a significant nuisance for a physically mature person such as myself. I accepted it as an enduring reminder of Lesson One: bring a ladder tall enough to inspect the roof.
My son cobbled up a system from the local hardware store parts bin, and started installation. It was difficult to blindly align steel hooks into loops, but it worked, and it held securely enough. Whew! Fortunately, this hanger style kept the desired ability for panels to adjust beyond horizontal so that trailer positioning to capture maximum sun would not be critical. MC4 solar wires were then terminated in SAE plugs, which allowed power through specific points in the trailer walls, where the various battery packs and controllers would be.
Attention then turned to the inside of the trailer, where mods to the living space had already been completed. The “master bedroom” in the front was now a full working office. The full-height closet stayed intact and had space near the floor for four 104Ah 12V deep-cycle AGM batteries. Yes, four 6V AGMs would have been a lighter, more powerful choice here, but I was unfamiliar with them and wanted all cells to be interchangeable throughout the system at this point. This 6V superiority at this location was more like Lesson Six anyway, so let’s just skip it here.
The Modular Approach dictated that the four cells be split into two independent systems to power all the office equipment, and this was accomplished with two small controllers mounted inside the closet. One panel, one controller, two batteries – times two. The closet wall next to the desk surface was populated with multiple cigar lighter-type sockets. A 300W inverter would allow everything needed to run. Done.
At the other end of the trailer, I needed a CPAP machine to sleep halfway decently. It had to run no matter how overcast the sky, or however I overused any other device, anywhere. Since it could run directly on 12VDC, I wanted at least five days runtime before having to pray for sun or plumb it into a different battery pack with an extension cord. It used a 5-amp fuse and included a heater for humidification, so it was no toaster, but was no LED light bulb, either. For the sake of weight, I opted for a single 104Ah AGM battery with the hope that a 195W panel would tend to charge it well even in heavy overcast. (This did work out just that way.)
In between, in the living area, resides one original equipment cigar plug-type outlet wired to the house battery, intended to power a TV set. Because it’s part of the trailer’s DC power harness, it lead to a single 104Ah flooded house battery that resided outside on the trailer tongue, in a rack built for two. All that had to be done here was to mount the remaining controller near that battery (in a sheltered location under the trailer) and link it to its dedicated solar panel. A 150W inverter would be mounted right next to the cigar outlet to power the 120VAC TV.
The Titanic leaves the shipyard
All of these small solar systems were hooked up for testing. The controllers immediately came on and indicated that the batteries were already fully charged, which they were. The trailer was now located under heavy tree cover, so not much could really be evaluated. Cold weather was already arriving, so we prepped the many other things to deal with on the trailer, and I set off on the Grand Adventure, and the Enterprise’s maiden voyage. Bon voyage, Pops!
This type of panel installation doesn’t allow deploying it on the road, so I wasn’t able to play with the system until I finally boondocked just outside of the Petrified Forest National Park in Arizona. I hung the panels, plugged everything in, and the controllers again signaled a full charge. This was suspicious, because I knew the batteries weren’t fully up. Equally odd was that the controllers started charging in earnest for just a few minutes during sunset, and again at sunrise. Then they acted like they were done – until sunset. Actual battery voltage wasn’t boosted except during these moments. A digital voltmeter showed that the panels were happy. The controllers weren’t, the batteries weren’t, and I was in trouble.
“All is well!”
I would have felt really stupid about my not knowing what was going on and why, except that in my weeks of phoning the solar controller’s techs and feeding them my panel’s measured voltage outputs, they saw no reason for this odd behavior and assured me of eventual success. Between two of them, they had me waiting for the controllers to acclimate, throwing blankets on the panels to “reboot” the system, measuring exactly when the units turned on and then went into maintenance mode – with panel voltage inputs, and making me think that my recently load-tested house battery might be failing after all. I was getting parasitic losses, so I replaced it. Then they walked me through disemboweling one of the units to try readjusting potentiometers blind. By the two-week point, I was semi-permanently boondocking in the Quartzsite LTVA, and was still without a speck of electrical power except for running the tow vehicle’s engine to charge the house batteries. I was too panicky to be discouraged. It was clearly past time to jump ship on brand loyalty and the glorious cost advantages of the Modular Solar approach.
The solution: mo’ money
I finally had a cellular data signal for the Internet, now that I was in Quartzsite. I called a Alt E Solar sales guy who immediately diagnosed the problem – I had simply purchased 18V panels without realizing it, and the behavior of the Brand X controller clearly showed it was a robust PWM unit that was rated at a nominal 12 volts only. He was upbeat, asked about the rest of the system, and confidently recommended two MPPT Morningstar controller models. What’s more, he conveyed not the slightest suspicion that he might be talking to the village idiot. That was the clincher. I ordered one as a test under a guarantee of functionality. It ran like a refrigerator, and I ordered the remaining two, consolidating the office pack into four cells instead of two pairs. I was so grateful to have all systems up and suddenly flawless that I almost gladly ate the $500 increase in MPPT system cost. I was up to my eyeballs in 12V power in less than half a day. Lesson Two. Know exactly what you’re buying, and why.
The hole in the hull
That cost penalty now makes my system almost nonsensical. Sure, each subsystem is very compact and efficient, avoiding long internal runs of thick cable. But now that I’ve had time to review available space again, to have the truck and trailer weighed at each tire, and to let things in my brain soak, I think I’d only stick with the original plan if I’d intelligently ordered 12V solar panels. That still makes cost sense and keeps things simple. Nice as they are, multiple MPPT controllers make one’s wallet hurt, and point toward at least partial consolidation.
There is one side benefit to keeping this type of system, though. As it is today, I can choose to throw a third solar panel into the office pack if I want to, merely by standing under the panels and rearranging MC4 connections. That throws close to 600 watts at it, for a faster charge. I’ve done that twice just for geeky thrills, but it’s really pointless in Arizona. This capability may come in handy back in the Upper Midwest, where the sun is much more elusive. Stealing a panel doesn’t necessarily mean that either the house or CPAP pack must be abandoned, since it takes seconds to plug the house TV outlet into the CPAP’s battery (using cigar plugs on a cord) so that the house solar system charges both packs, albeit with efficiency losses.
The band plays on
Lesson Three came a little easier – within a shorter time, anyway. With the entire solar system now up, having AC power would be nice. I unpacked and installed my new 300W AIMS inverter in the office, and a 180W AIMS inverter by the TV plug in the living area. Booting up the computer was alarming – literally. The inverter beeped regularly, and the computer continually crashed and rebooted itself in a kind of dance of death. The inverter’s troubleshooting chart pointed toward the cigar lighter plug. I knew that the computer itself pulled a max of 115 watts, and that the Marinco marine plugs were rated to 180 watts, but I also hardwired the inverter directly to the battery anyway. No change.
The 180W AIMS inverter did the same thing to the TV, and alarmed constantly. As a test, I replaced it with the 300W inverter and it ran okay, so it wasn’t the trailer’s wiring harness. A call to the vendor to inquire produced an immediate offer of an RMA, with the explanation that, “yeah, they do that with some equipment.” Chhyeah! Well, thanks a pantload, Chet! I returned them and ordered two similarly-sized Samlex inverters from a different supplier.
The Samlex pure sine units were plug & play. I did end up hardwiring the bigger unit to the office pack, later. It worked fine through a cigar outlet, but the plug got warm to the touch when everything was turned on. No need to waste precious amperage to create heat instead of to power equipment.
The executive summary
How does this system perform now? In Arizona, it’s overkill, but the upside is that none of the battery packs ever dips below a 75% state of charge even with heavy use. That’s extremely good for battery longevity, especially considering the cost to replace AGMs. In the Upper Midwest? The jury is still out. I’ll be returning there in the summer for three months. I expect to be humbled.
Cheap is relative
It’s valid to ask two questions here. The first is: Why AGMs, if you’re such an alleged cheapskate? Many knowledgable folks don’t bother with them, staying with standard flooded cells like what’s on my trailer tongue. However, I’d had quite a bit of experience with them in the past, and had seen what their constant bath of acid vapor does to plywood and painted metal over the course of several years. I didn’t want them inside a semi-sealed compartment with clothing or equipment, near me, or most particularly near anything involving flame or propane igniters. I have enough problems. I’m hoping to milk 10 more years from this 19-year-old trailer – full-timing, no less. I antied-up.
The second question is: Why pure sine inverters? Two reasons. I got spooked by a little utility Xantrex unit I’d had for years. It is modified sine and warns in its manual to never plug anything into it that resembles a device battery charger, or it will damage the charger. That made me think. Was it going to be truly safe for me to operate all of my electronics and chargers on anything less than what they were designed for? I’ve invested thousands of dollars in my office equipment electronics, and some of it is now difficult to replace at any price. The replacement cost of any single component dwarfed the inverter upcharge. I antied-up.
The Big Question
Despite my self-created trials, I still feel that the most important question to ask about solar is not about what component is compatible with another, but simply about what you want to be able to do each day as you live, sleep, and travel in your home on wheels. What – and for how long? That drives the entire process. The end game is the highest priority, not the equipment. All I did was to screw up the the implementation. Now that it’s fixed, this system meets my needs well, if a little less conveniently than I’d first envisioned. Those panels are heavy.
One more thing. A major factor that I left out in aiming toward a multi-system is me. See, whenever I’m doing something I enjoy, time stops existing. I’m into it, in the zone. I forget the time, forget to eat, forget the coffee percolator, forget to turn off the hose filling the freshwater tank, you name it. Not a multitasker, no. Hard to imagine that I’m available, eh, ladies? Your birthday was when? Fortunately, you probably don’t have this issue, so it’s not a factor for normal humans. Because of this, I knew it’d be easy for me to mindlessly burn through one central pack and then have no lights, DVD, water pump or CPAP. All the alarms I’ve seen go off way too late. Separate packs and independent charging seemed like a good idea to protect me from myself, as would an ability to easily patch in power from another pack to run something normally unrelated to it. That’s just me.
Weight issues abound. Travel trailers don’t have much of a margin of safety once they’re loaded with the usual let’s-go-camping crap. The tires and bearings normally run close to their limits, full-time. I knew early on that loading boxes of books and 500 pounds of solar and batteries would become an issue, so I placed as much as possible forward, to put the extra weight on the tongue. It worked, and that’s both good and bad. The F-250 I use as a tow vehicle can handle the tongue load but, in the long run, that weight has to come off or move to known safe places. Thanks to Smartweigh, I now know where those places are. The fix will involve going back to a single house battery, which is feasible now since all light bulbs have been swapped for LEDs. It will also involve chucking more reference books, and the 248-pound office pack will have to move rearward 6 feet to reside under the couch, toward one side. The 180 pounds of solar panels have nowhere else to stow inside the trailer, so the solution to that will need to be more interesting.
That’s probably Lesson Four: It isn’t really over until you’ve changed predictable problems into unpredictable ones. (Don’t knowingly do something that invites an unfortunate incident, because an accident isn’t really an accident if it’s predictable and inevitable.)