Electrical Systems, Charging and Solar Electrical components and wiring, batteries, charging systems, generators and solar topics.
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Old 02-05-2015, 04:00 PM   #1
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Default My New 200 Watt Solar Installation

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
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Old 02-05-2015, 04:15 PM   #2
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Default 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
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Old 02-05-2015, 04:27 PM   #3
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Default 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
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Old 02-05-2015, 04:45 PM   #4
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Default 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
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Old 02-06-2015, 08:44 AM   #5
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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
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Old 02-06-2015, 10:48 AM   #6
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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
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Old 02-06-2015, 08:29 PM   #7
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Thanks for the photos and detailed description, Jack- looks nice!!! Please give us a performance report after you've used it a few times!
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Old 02-07-2015, 10:11 AM   #8
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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:
1. The panels are Renogy 100W Bendable Panels: Amazon.com : Renogy® 100W Monocrystalline Bendable Solar Panel : Patio, Lawn & Garden. I paid $197 each for them when I ordered them from Amazon.
2. The charge controller is Renogy's 20W MPPT model: Amazon.com : RENOGY® Tracer 20Amp Negative grounded MPPT Charge Controller 100VDC Input 2210RN : Renewable Energy Charge Controllers : Patio, Lawn & Garden. This was the cheapest source I could find. I also bought the kit of 5 pairs of MC4 connectors you see on this page too.
3. I found the meter at the lowest price here: Remote LCD Meter MT-5 Meter for Tracer MPPT solar charge controller Meter-5 - Newegg.com. But, I see there are even cheaper sources now. It was shipped (free) from China.
4. The PV cable and Eternabond tape were also bought from Amazon: Amazon.com: 50' solar cable Bulk Black #10 AWG 1000 volt PV Wire with XLPE insulation: Industrial & Scientific and Amazon.com: EternaBond RSW-4-50 White Roof Seal: Automotive
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
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Old 02-11-2015, 09:35 PM   #9
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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.
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Old 02-12-2015, 09:57 AM   #10
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Quote:
Originally Posted by hilltool View Post
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.
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
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