I'm not an expert in solar...figuring this out as I go along with OTJ training and online research. There doesn't appear to be a post on this forum that talks about what I have done so I thought I'd post it. I'd love to get your feedback and questions. This will not be a step-by-step guide...just a broad overview of what I used, where I put it, and how I did certain things. I have a 2015 17 foot SD.
You need to consider three questions when considering solar: how much energy do you need, how much can you generate, and how much can you store. I made some decisions to reduce my power needs with LED lights, I have a low-power laptop, and the inverter I am using has low parasitic drain and an on/off switch. I'll use LP to power the fridge, heat my water, and heat the cabin...all of these require 12v for circuitry, sensors, and fans/pumps, but the bulk of the energy requirements are handled by LP. All in all, I figure I'll just need to regenerate 10-25 amp hours per day depending on outside temperatures...not much to worry about.
There isn't a lot of real estate on the top of a Casita for solar panels, and with such a nice solid (i.e. waterproof) roof I wasn't interested in drilling holes to fix panels up there. I found some flexible solar panels online, did some measurements, and found that I could fit two 50 watt panels on the roof of the casita...one immediately in front of the center fan and one between the fan and the roof heater/AC unit...without having to drill by using 3M VHB (very high bond) tape. This tape has held for 1,400 miles so far so I have no concerns with its durability...plus the flexible panels are thin and do not generate much in terms of wind resistance. Online I have found posts where people have also run sealant around the outer edge of the panels to support the 3M tape, but VHB tape is really tough and I think this is quite unnecessary. These panels can flex up to 30 degrees and hug the slight contour of the Casita's mohawk perfectly. The panel between the roof heater/AC and the fan is problematic...an entire solar panel loses efficiency when even a portion of the panel is in shadow, so in a typical day this particular panel is more likely to be partially shaded compared to it's more forward-facing partner. I am not concerned about this because I only have the single Interstate group 27 battery to worry about, and with 100 watts of generating capacity I'll generate enough power, even if it is on a cloudy day. For the first phase of this project I have permanently taped down only the front 50 watt panel as I want to see if that will be enough to keep my battery topped off. The other panel is currently off and unplugged. When connected, the two panels are strung in parallel with one another (to increase amp output and leave voltage the same as if only one panel were connected).
The charge controller is an area of discussion...most people will say get an MPPT controller over a PWM. They are more efficient and you'll get more photons into your battery than with the cheaper PWM controllers. I purchased an MPPT controller and do not believe it makes a difference in this particular application since I can generate more power than I need anyway, so efficiency gains are not important and simply costs more to implement, and I only have 100 watts to deal with. What I do like about the MPPT controller I got, however, is that it came with a remote meter so I can read what I'm generating, battery SoC, and so on.
Where to run the cabling took some time to figure out. I ran the MC4 cabling down towards the awning side and then toward the front where the grey water tank vent is. From the closet I drilled two holes into that pipe and fed the cable down that vent and out through the holes. When the temps improve here at home I'll add some silicone goop to seal around both sides of the wiring. The MC4 cabling then goes down the outside of the PVC vent pipe to the floor of the closet, out under the wall the closet door is cut into, and under the wall for the bathroom and over to the driver's side of the trailer under the front dinette seat. From there is was easy to run it alongside the rest of the wiring back to where the section of the compartment where the converter and water heater is. I mounted the MPPT charge controller there using 3M velcro tape (it has held for 2,800 miles so far) and I used Anderson quick connecters for the wires going in and out...green to the panels, red to the battery. There is only room to work in there one-handed, after all...so I wanted to make it simple. I drilled two holes into the fiberglass battery box for the positive and negative MC4 wires going to the battery, attached directly to the terminals. I plan to add an inline fuse shortly...this was recently pointed out to be something that I should do. I soldered the ring terminals to the MC4 cabling.
I used zip tie anchors fixed to the roof with 3M tape to zip tie down all the loose wires on the roof. The MC4 splitter (which allows both 50 watt panels to use the same MC4 wire going into the charge controller) I zip tied to the frontmost bracket for the awning...keeps it from flapping around while driving. I zip tied the two MC4 wires going into the grey water vent pipe outside the Casita so that the little vent cap would stay down...the 10 gauge wire had a tendency to push the cap off on one side, so this keeps it in place. I zip tied the MC4 wiring all down the vent pipe inside the closet, but once it was under the walls and out of sight I left it as-is.
I ran the remote cable up the small gap created by that partition between the bed and the dinette chair (opposite the stove in the SD). I just leave the cable and the remote tucked down the gap between the mattress and the Casita wall...I don't need to check it often and did not want to drill holes in anything.
- Renogy 50 watt flexible solar panel
- Tracer 30 amp MPPT charge controller with remote (30 amp was overkill for what I currently have, but allows for expansion)
- 50 feet MC4 10 gauge AWG cabling
- Outdoor cable tie mount mounts (called cable tie anchors, find these in home depot, get ones rated for outdoor use)
- MC4 connectors
- MC4 crimp tool
- Normal wiring tools (red knuckles, wire stripper, multi meter tester, and so on)
Some other things I've learned along the way:
- Be careful of your positive and negative! Learn to use a multi meter to accurately figure out what is what. I tested and retested and found that I almost crossed my wires.
- Normal temps (0 - 80 F) will not affect solar generation capabilities, but lower temps means your deep cycle lead acid battery will have a significantly reduced capability for output. At 15F our batteries may only be able to produce 40-50% of it's rated capacity...and since you shouldn't drop a lead acid battery below 50% that often, and these are 96 Amp Hour batteries by default...this leaves you with ~22 Amp Hours of power when it's really cold out (and when you need it most). I had to keep my Casita plugged into shore power over this New England winter just because the battery really isn't designed to work well in cold conditions. I plan to replace the battery with one made to work better in colder temps
- Snow will significantly reduce generation capabilities on a roof-mounted system...down to zero. If you want to generate power in the winter you'll either need to keep it clear or get yourself a portable panel that you can hook in and keep clear on the ground. If you are camping in the winter you'll likely want to get a 120 watt portable panel to help get by several days of cloudy weather with much shorter generation days. I purchased a Go Power! 120 watt portable unit for this purpose. This is a powerful portable panel system and they sell a 7 pin trailer plug adapter so that you can hook it in without any wiring necessary. I think it is pricey for what you get, and the charge controller built into the portable unit is not water proof (tho it is underneath the panel and will be protected from light rain)
- The charge controller is in it's compartment fixed to the wall that separates the bed from the dinette chair. I used used 3M tape to stick it to it...no drilling needed.
- I wish there was room for a single 100 watt panel up there but there really just isn't. As solar technology improves in efficiency we will have more options to generate higher amounts of power with less space.
- Read the 3M VHB directions carefully and install it accordingly. I had everything installed inside the camper in December and then drove to Florida for vacation where I waited for a warm, sunny day to tape the panel down and give it the time it needs to cure (full day for me, but I think the instructions only call for 6 or so hours).
- I'm using a pretty long run of MC4 cable to the charge controller, something like 25 feet. I used 10 gauge MC4 vs 12 gauge because of slightly less voltage drop (loss) with the heavier gauge cabling
- Roof mounted panels provide power with no additional work required by you. Portable panels need to be deployed manually and are at greater risk of being stolen. I like shade over bright sun, so I'll be parking in there as much as I can, which will diminish my panel's generating capacity to some degree or another. I hope to be able to still generate more than I need with the one 50 watt panel, but if not I'll stick on the 2nd 50 watt, and if that still isn't doing it I have the portable unit that I can stick out in the sun with a 30 foot extension cable connecting it to the front 7 pin cable
The results have been terrific. Now that we are getting into more civilized temps and my battery is showing signs of working normally vs. diminished capacity due to the cold, I moved the camper off of shore power and have been testing it out. The fridge is running (LP), the heat is on (LP), my inverter is on and keeping a laptop charged, and thus far the battery is easily charged each day after getting down to somewhere between 12.3 and 12.4 volts over night (somewhere around and between 70 - 80%...the suburban furnace is responsible for most of that).
In the picture below the wires are all over the place but this was right after I stuck it down. The wires are currently tied up nicely using zip tie anchors that I stuck to the roof using 3M tape...I found these at Home Depot. I'm ashamed that I didn't get the panel perfectly centered...so purists please withhold your anger =)
I'm sure I left things out but will answer questions and add/clarify as needed. I'm making edits as I go along to correct grammar and add bits of detail.
Update April 15, 2015:
I definitely need to connect the second 50 watt panel, bringing my total to 100 watts. I'm getting around 2.1 amps with the one panel, and on a perfect day that won't be enough to back charge more than around 20 amp hours of battery. With the two panels connect in parallel I'm seeing around 5 - 6 amps when both are in full sunlight.
Turns out there may be a problem with charging when I connect my portable panel to the battery. Having the two solar arrays with different charge controllers could make one (or both) think that the battery is far more full than it really is due to each misreading the incoming voltage. Some charge controllers allow for multiple arrays on multiple controllers to feed one battery, allowing them to work in tandem. I'm picking up a Morningstar ProStar controller to see if it'll fit on the portable panel when it is closed up....if so I'll change that one and the Casita's controller to the ProStar, allowing me to have up to 220 watts of generation if necessary. I have a couple of other projects that I'll use the two extra controllers on.
Edited by Rew, 15 April 2015 - 10:35 AM.