My New 200 Watt Solar Installation (Now 300 Watts)

OK! Took me longer than I expected (everything seems to take longer now that I'm 74) but I've successfully installed two 100 Watt panels on the roof of my 1707T trailer and completed the wiring.

The installation is complicated by the fact that our trailers "telescope". If they didn't, you could mount the charge controller on any handy vertical surface and run wiring down any suitable path to the "basement". But, since I wanted the controller and charging monitor near eye level, I was limited in my options.

I ultimately decided on mounting the controller on the side of the left side cabinet with the charging monitor on the cabinet's front. The reason I chose this location is because there is already a hole in the roof above it where the TV antenna coax enters. I thought I could bring the panel wires in through the same hole.

This picture shows the silicone I had to remove to gain access to the entry point. I've got it a bit more than half removed in the picture and you can see the hole it was covering.


Here's the entry point with all silicone removed.


I pulled the antenna wire out of the hole and enlarged it slightly so that the two 1/4" PV 10 gauge wires would fit in along with the antenna wire once it was reinstalled.


I added a plastic "grommet" like thing into the hole to keep the metal roof from cutting the wires but I didn't take a picture of that sorry!

The left side of the cabinet had the outlet for the TV antenna and a "cigarette lighter socket" on a plate that I've removed here. You can see the two solar cables inside the cabinet. I'll run them under the floor of the cabinet, which you can see slightly raised. It was stapled in.


I'm limited to four pictures per post, so this will be "continued".

- Jack

Solar Panel Installation - Part 2

This next picture shows the backside of the power monitor meter that I'm going to mount on the right side of the cabinet. It comes with a mounting plate, but it will fit exactly inside the two vertical frames, so I'll mount it there and I had to cut out a hole for the backside of the meter. The electrical cable to the meter will run underneath the cabinet floor too.


The meter fits nicely. You can see the two input wires from the solar panels extending out holes in the bottom right side of the cabinet here too.


Here's the MPPT charge controller mounted on the right side of the cabinet.


It does not interfere with the bunk, and you can see the LEDs and the small status window on its front when you put your head under the bunk. The size of the controller kept it from being mounted on the wall of the upper half. It would not clear the lower half when the top is lowered and it could not be mounted at the ceiling because of needed ventilation clearances. I color-coded the PV wiring with shrink tubing so that I wouldn't hook up anything wrong.

Before attaching the solar panels, I decided on their placement. As you see, they fit between the seams near the front of the trailer, and, there is actually room for two more of them if wanted. I wanted to place them in the front to minimize interference from other things on the roof.


Continued in the next post.

- Jack

Solar Panel Installation - Part 3

Here's what the meter looks like when "powered up". The display you see is the battery voltage and charging current. The current is zero, because the panels are not connected yet. The voltage is above 12.7 because I just disconnected the Battery Minder I keep plugged in at home.


The meter can also be set to show input voltage and current from the solar panels, Current and voltage to a "load" like an inverter if connected and some other things.

The next picture shows the only part of the installation that is less than optimum. I have to run the battery charging wires down from the cabinet to the "basement" and they can't be concealed.


I removed the couch cushions and the plywood under the seat to run the wires down to the floor under the couch.


Then, I ran the wires next to the wall along the floor and under the hot water tank. Having the area exposed made this easy.


One more post and we're done!

- Jack

Solar Panel Installation - Part 4

I drilled two holes in the floor in front of the hot water tank next to the fresh water tank inlet so that I could run the battery charging wires out to the battery box.


I sealed those holes with Lexel, but I didn't take a picture of that.

The wires to the batteries are also color-coded, red for "+" and white for "-". You can see an open fuse holder in the red line over the left hand battery. I installed a 15 Amp fuse there, which should be about right. The max current I should get is about 10 Amps. The controller is rated for 20 Amps.


I secured the panels to the top of the trailer with Eternabond tape. The panels also have six grommet holes each for screw mounting, but I don't think they will be needed. The Eternabond is really sticky stuff! I also anchored the electrical lines down to the roof with the same tape. I sealed the hole in the roof with Lexel, and you can see the "mound" of it at the end of the PV wires, to the right of the air conditioner.


With the couch floor back in place and the cushions back on, the installation looks pretty good to me.


The wire from the cabinet simply flexes down onto the back of the couch when the top is lowered. It works much like the wire bundle from the top to the bottom half of the trailer that's in the bathroom.

So, that's it!. I've got the trailer under a metal shelter, so the panels are shaded. Even so, the meter shows the batteries receiving 0.3 Amps. Since the batteries are already fully charged, it's possible the potential current is even higher. The controller prevents overcharging by going into "float" mode when the batteries are charged.

Hope this has been instructional. Looking forward to seeing how things work during an actual camping trip.

- Jack

nice writeup, I'm thinking about going this direction for the season as well. I don't do a lot of camping at campgrounds with hookups

Thanks, guitarman. I'm hoping it will reduce our reliance on the generator we have.

Just as an aside, I connected the two panels in series. This, of course doubles the voltage to the charge controller but it keeps the Amperage lower over those wires. I used 10 gauge PV wire throughout and there is a total run of about 25 feet from the panels to the batteries. Series connections are also simpler than parallel at the panels themselves.

Additionally, I was concerned that a parallel hookup of the panels might put reverse voltage on one of them if one was in shade and the other was in sunlight. A series hookup keeps the current flow moving in the right direction through them.

The series hookup is possible with an MPPT charge controller, but I don't think it would be with a cheaper PWM controller. The MPPT controller provides more efficient and controlled battery charging too.

The panels, controller, PV wire, connectors and meter are all products that can be bought from Renogy.com, but I found them at considerable savings through Amazon and NewEgg (for the meter).

- Jack

Thanks for the photos and detailed description, Jack- looks nice!!! Please give us a performance report after you've used it a few times!

Thanks, Greg - I WILL be back with user feedback. Just don't expect it any time soon.

RichR asked me a question in a PM that made me aware that I should have told you all exactly what components I used in this project. So, here they are:
All the other small stuff was purchased locally.

The panels are really nice. They are lightweight, easy to work with and apparently very efficient and durable. I found a reference online for a similar product that said you could walk on them and a video showing two people DANCING on ones like these! I don't plan to do any of that.

Anyway, I think that gives you all you need to know about this project and I'll be back in the summer with a report on how it all works.

- Jack

Great write up, Jack. I'm not sure I understand the trade offs between parrelel and series, as I would think the parrelel would provide the additional amps to re-fill the batterey quicker. But, I trust your engineering.

hilltool said:

Great write up, Jack. I'm not sure I understand the trade offs between parrelel and series, as I would think the parrelel would provide the additional amps to re-fill the batterey quicker. But, I trust your engineering.

Click to expand...

Excellent question, sir! Here's how it goes:

The solar panels put out a "given" Wattage, depending on the amount of sunlight they receive. Under optimum conditions, they produce 100 Watts each. Now, Watts is a derived value, computed by multiplying Volts times Amps. The panels can generate 5.7 Amps at 17.7 Volts under optimum conditions which translates to 100.89 Watts.

If you hook the panels in series, the Voltage is doubled while the Amperage stays at 5.7. If you hook them in parallel, the Amperage doubles and the Voltage stays at 17.7 (I'm just using optimum condition figures here, under less than optimum conditions, the Voltage drops, but the Amperage stays relatively constant.)

So, in EITHER case, the same Wattage (about 200 under optimum conditions) gets to the charger controller. But, having the panels in series reduces the electrical loss from resistance in the wires between the panels and the controller since the Amperage is cut in half.

The lower the Voltage, the higher the current has to be to carry a given Wattage and that needs larger wires. Military vehicles are generally 24 Volt systems which allows them to use smaller gauge wiring.

Now the MPPT controller exercises its magic and it reduces the incoming Voltage to a safe level for battery charging - about 13.5-14.5 depending on the state of battery charge. But, it has 200 Watts to "play" with, so, at 14.5 V, it could theoretically send about 13.8 Amps to the battery! It probably never will come close to that level under actual conditions, but the higher Amperage you spoke of into the battery is still there, while reducing line losses over some of the distance between the panels and the battery. In other words, I've made more power (Watts) available to the controller by having the panels in series.

I used this calculator: Wire sizing calculator for Solar Panel Arrays to satisfy myself that the 10 gauge wire I used from the controller to the batteries was adequate. That run is 16-17 feet, and, I assumed a 12V system at 10 Amps there. The run into the controller is 8-9 feet and is calculated using 24V and 5A. I used 10 gauge wire there too. If the Amperage over the entire 25 ft run was 10 A, I would have needed 9 gauge wire at 12 V to keep the losses under 3%.

The only two other considerations were simpler (less) wiring at the panels to connect them in series and I wanted to avoid a potential reverse current/Voltage issue on a shaded panel, which could happen if they were in parallel. I don't really know if the reverse current situation is an actual problem, but it won't happen with them in series.

Finally, I deliberately mounted the panels some distance apart to minimize the possibility of them BOTH being shaded. It could still happen, of course.

These considerations are why you need heavy gauge wire in your tow vehicle from the alternator to the trailer charging tap at the trailer plug too. The Voltage is only about 14V but you're trying to push a high Amperage through to charge the batteries and run the refrigerator. That circuit is normally fused at 30 A.

- Jack

Got it. I forgot about the MPPT controller kicking the amperage, which I had read about when I looked up that controller. Otherwise, my way of thinking is if I have a panel that puts out 5.7 amps under optimal conditions then I am able to put 5.7 amps back into my battery (less-actually) per hour of optimal conditions. With two, Wired in parallel, I would get closer to the neighborhood of ten amps going in per hour of optimal sunlight. But, with THAT controller, I can have the best of both worlds, including the higher voltage for optimal charging (as someone once reminded me in a book- it is VOLTAGE that recharges the battery). Thanks- I learned something.

I am still interested in a more portable system that allows me to place the panels out of shade, as many of the places I park have a lot of it. That requires longer cable runs and this approach would certainly help solve the problem of losing voltage because of it. THEFT, is, of course, another issue but there are ways of discouraging that- at least to a degree.

By the way- I just got back from Phoenix area with a side trip to Sedona----a lot of sun out there . I liked it! And Sedona was gorgeous. I'd never been there. 7deg back here in Wisconsin today. Im trying to plan my first ever "just hitch up the trailer and go" trip in Winter and head to Florida at the beginning of March…..but it looks like the campground situation is already filling up down there. I may have to throw my obsessive planning strategies to the wind and make an adventure out of it!

Good camping.

Rick

Just to clarify something - I DID NOT attach the wires from the controller to the batteries to the top half of the trailer in any way. I don't see how that would be possible and it's one of the things that make installation of solar panels on a telescoping trailer more difficult.

I simply extended them from the cabinet down to the lower half and anchored them there. I also wrapped them with spiral wrap to make the installation a bit neater. When the top is lowered, the wires buckle and form a loop that extends out into the trailer space. Here's a picture with the top about halfway down so you can see how it works:


- Jack

Jack,

Thanks for posting a good tutorial. I just picked up an 80 watt panel with controller for keeping the batteries topped up during storage, and to help out a little while camping. I have been looking at 2 to 3 panels for a hard install on the roof. 300 watts could be possible. That would certainly be enough to camp off grid. That is a future project. Now to get camping.

Jack

Does that power meter have a shunt? If you wanted to measure charge and discharge simultaneously would you have to install a second meter??

Rick, you've asked a question that I can't answer with certainty and I don't know if it has a shunt. It did not come with an internal circuit diagram. In fact, the device and its instruction manual are from China, so you can guess how informative the manual is.

I'm pretty sure the "load current and voltage" that the meter can measure is taken from the load taps on the MPPT controller, which are there mostly to connect something like an inverter directly to the controller. I don't ever intend to use an inverter this way, so, I have not hooked it up to see. I know it's the third function in the meter though, so you simply push one of the arrow buttons till it shows up.

I don't see how you could hook a second meter to the controller. It has only one RJ45 meter outlet tap and I don't know if a "splitter device" would work at all.

I really just got the meter so I could monitor the charging voltage and current. Though, I DO know it will also show me battery capacity in AH, battery capacity percentage and discharging accumulation, which would be an indirect measure of discharge. Again, these readings are available by simply pushing an arrow button. I guess, the first time I take it camping, I'll check these out.

- Jack

Thanks, Jack

I've always wanted a meter system set up for monitoring amp hours used/ amp hours put back but most of what is out there is pretty expensive and use complicated shunt set-ups, at least from my limited diy abilities. That little meter I posted about last year was handy for monitoring what I was getting from my panel to the batterey as long as I had it wired between the controller and batterey. However- I would have needed at least three more to monitor what I was getting from my tow vehicle and what I was getting from charging from shore power and, then, what I using in a day. I know larger rigs and boats tend to have all this wired in and incorporated in one or two meters but they usually involved "shunt boards" with a different wiring system for each function. Anyway- you are correct in stating the obvious that its pretty simple to guesstimate useage by monitoring batterey voltage.....so my guess is your meter is functions and is wired much the same as the little after market "Watts up" one I got------ though it likely works better.

hilltool said:

Thanks, Jack

I've always wanted a meter system set up for monitoring amp hours used/ amp hours put back but most of what is out there is pretty expensive and use complicated shunt set-ups, at least from my limited diy abilities. That little meter I posted about last year was handy for monitoring what I was getting from my panel to the batterey as long as I had it wired between the controller and batterey. However- I would have needed at least three more to monitor what I was getting from my tow vehicle and what I was getting from charging from shore power and, then, what I using in a day. I know larger rigs and boats tend to have all this wired in and incorporated in one or two meters but they usually involved "shunt boards" with a different wiring system for each function. Anyway- you are correct in stating the obvious that its pretty simple to guesstimate useage by monitoring batterey voltage.....so my guess is your meter is functions and is wired much the same as the little after market "Watts up" one I got------ though it likely works better.

Click to expand...

A battery monitor works from the negative battery cable. It will get the power to operate itself from the positive battery terminal. The shunt is mounted between the negative battery cable and the ground connection bus. It will measure all current flowing into and out of the batteries. They will usually show state of charge in percentage. Any appliance such as a propane detector that is connected directly to the battery will not be reflected in power consumed.

Balmar has just come out with the smart gauge battery monitor that uses no shunt. It is an easier install. It came out after I installed my battery monitors.

http://www.balmar.net/PDF/SMARTGAUGE MANUAL.pdf

hilltool said:

Does that power meter have a shunt? If you wanted to measure charge and discharge simultaneously would you have to install a second meter??

Click to expand...

I have the same meter. There is no shunt. The meter is actually just a remote display. It is connected to the charge controller using an ethernet cable. It will not tell you how much power you are using unless you use the "Load" connection on the controller.

Using that load connection is not feasible since it is limited to 10 amps for my 10 amp controller, maybe 20 amps for Jacks 20 amp charger. So since the trailer's 12V system is connected directly to the battery, the controller has no way of knowing how much power is being drawn from it. You can however infer the power draw by watching the power going into the battery. Once the battery is fully charged the current going into it drops to zero - even though the panels are ready to supply 200W. Turn something on so that power is drawn from the battery and the controller will start putting some energy into the battery. Watching this was my first indication that the 12V setting in my fridge quit working. There was absolutely no change in current when the fridge was on vs off. But turn on the bathroom fan and you can see it pulling almost three amps.

One last comment. I purchased my 10 amp MPPT controller when I had only one panel. Then I decided two panels would be better - which is very true - but in mid-day sun the most energy I can put into the batteries is 10 amps. 14V x 10 amps is only 140W. I'm losing 60W due to the limit of the charge controller*.

The cool thing is that even after the sun went down (behind the mountain) I had just shy of 2 amps going into the battery.

*actually not quite that much. Since my panels are flat, not angled towards the Sun, they are always in a sub optimal position. Considering that I am at 48 degrees latitude, my panels were about 45 degrees from the Sun. That means that they "see" about 70% as much as they would if they were perfectly oriented. 200W x 70% is 140W. Pretty much exactly was I was getting from them. So I guess my 10 amp controller is okay if I never point my panels at the Sun. As we approach the summer solstice the Sun will be getting higher in the sky, if I wanted to get every last bit of power from my setup a larger controller would be required.

Update on My Solar Power Installation

We just got back from the first camping trip we've been able to take this year, and my first test of the 200W solar panel installation on our trailer.

I'm happy to report it has been an unqualified success! We left on a Wednesday and returned on Wednesday the following week, so we were out eight days. We were traveling about five hours each of four days and I used DC power to the refrigerator during our travels. Each travel day included a stop for lunch that lasted maybe 45 minutes.

We traveled through northern Arizona to Moab, Utah, where we visited Arches National Park and Canyonlands. Our midway stops to and from Moab were at Navaho National Monument. Camping was all "dry" (boondock) camping with no hookups, in fact, we had to get our water from the Arches Visitor Center which we passed during each visit there. We used the furnace the first night and the next morning because it was cold. The refrigerator fan was always on and the FanTastic Fan I installed on our trailer was operating automatically anytime we were camped. Many of you know that I've replaced all lighting with LEDs, so our nighttime useage is fairly low. However, we DID watch a DVD movie two nights using the trailer's video player. Other electrical loads included raising the top at each campsite and use of the tongue jack to hookup and unhook.

I did NOT use the generator at all during this trip. When the sun was at a peak, I recorded 8.2 Amps of charging current to the batteries, but there was always SOME input as long as the sky was light. I'd see about 0.1A shortly after the sun came up and it would increase steadily as the sun got higher. To be fair, our camping sites were fairly exposed, and, except for the first travel day, the sky was almost completely clear.

But, the solar panels were delivering power to the batteries while we were on the road, reducing the dependence on my truck's alternator.

The system was completely independent. My only interface was to look at the charging meter now and then (with a big smile on my face).

While 8.2A may seem low for a 200W system, it was almost exactly what I expected. I've learned that solar panels seem to generally deliver about 1/2 their rated output in actual use. And, as W9GFO posted above, the panels are not really oriented optimally with respect to the sun. In addition, the controller actually reduces the charging current as the batteries approach full charge, to prevent overcharging.

To sum up: The installed system costed less than my generator, required no attention on my part, and actually kept the batteries at an overall higher state of charge than a morning and evening generator run did.

I recommend this setup to anyone wanting to be off the grid while camping!

- Jack

Thanks for the follow-up report, Jack, and glad you were finally able to get some camping in!

So if you're interested in selling your generator now . . .