Solar wiring

[Tilly]

Hello all
Well, we finally bought our very first solar panel. After much helpful advice on the forum, went with the flexible sort (Go Power, Carmanah), at 100 watts. Will affix with vhb tape and a 3m marine adhesive.

A fellow who has done some trickier wiring for us suggested routing the connectors through the power box, to a fuse. That's definitely not what I've been reading. Any thoughts out there as to the benefits of doing this?

I imagine then we wire back to the battery - but forgot to check with him on that!

Happy Friday

[The Minimalist]

What, no charge controller? Basic wiring would be from the solar panel to the solar charge controller then to the battery.

There is no need to get more fancy than that, unless you want to monitor charge rate and usage.

[John Linck]

I wired my 100 watt panel via the unused Romex AC wiring from the roof thru the charge controller and then to the main electrical panel's 12 volt buses. Works great. While voltage drop is a concern, the #12 conductors keep my battery topped off each day, usually by noon.

I added both an inline fuse and a disconnect switch next to a digital voltage meter adjacent to the furnace thermostat. Not sure either is necessary.

John

[gordon2]

Not sure exactly what your guy is talking about doing, but since the battery is wired to the power distribution box, you might (in effect) be connecting the solar controller straight to the battery anyway, even by wiring it to the box. Perhaps the benefit is having the panel and controller fused at the box without having to buy anything else.

However if you read the instructions for abut any solar controller and you will see where they suggest having the run from the controller to the battery as short as possible, and with wire of sufficient gauge. This is to minimize power loss and maximize the efficiency of the solar charging.

Therefore my controller is in the under-bunk compartment at the front of the trailer, and the run to the battery is only about 1.5 feet. I have added a fuse here also.

Sometimes what works is not the most efficient, but the ease of install or other factors come into play and make adjustments reasonable. I would ask your guy to explain for the details and the rational for what he is suggesting.

[Franswa]

I wouldn't use VHB tape...or any "permanent" adhesive...

it's your first try at solar, your first panel...chances are you might just change your mind on location or size in the future

if you chose a flexi panel it will lie perfectly flat on the roof....any old tape (Gorilla?) will do just fine....you have zero windage to worry about

you just picked up a brand new hobby....have fun....

[Tilly]

Hi folks - always helpful. Yes, a new hobby to bore my spouse about!

Question for Gord2: you added a fuse in the panel, even when running the wire directly from panel - controller - 1.5 ft to battery?

Great idea Franswa re: trying out location w milder tape. Thx!

[gordon2]

Originally Posted by Tilly

...

Question for Gord2: you added a fuse in the panel, even when running the wire directly from panel - controller - 1.5 ft to battery?

Great idea Franswa re: trying out location w milder tape. Thx!

Speaking solely of fusing between the solar panel(s) and the controller input, my understanding (as a non-electrician) is that a fuse is not needed for a single panel, or for two panels of the same rating. However two panels of unequal ratings, or three or more panels, wired in parallel, should be fused because a short can result in the entire output of all the panels combined exceeding the rating of the wiring. Although I only use one panel at present, my original plan was to use two of different sizes so I put the fuse in the first panel to be prepared for expansion.

Don't take my word for it however. This page has some information on the subject

Fusing on the output side is a different matter.

As for the panels and mounting your have in mind. I was going to hold my tongue on this but changed my mind. My research has led me to the decision to not mount my thin flexible panel on the roof. Just a few of the many reasons include:

• A history of failures (and even a major recall by Renogy with their subsequent dropping of the product line)
• The fact that they are most efficient with good air circulation. You can expect a drop of around 10% in output when they get hot because they are flush mounted, probably combined with shorter life for the panel.
• The realization that I don't need solar energy all the time and when I do, its helpful to be able to move my panel to a sunny spot, and move it again when the sunny spot moves.

But if I were to use a non-mechanical mount on the trailer, it would the the variety of VHB that was designed for the surfaces used. Have you ever seen Gorilla tape after a few weeks at temperatures of up to 120 degrees F?

[The Minimalist]

Originally Posted by Franswa

you just picked up a brand new hobby....have fun....

Ain't that the truth.................but we're having fun, right?

[Tilly]

Thanks Gordon - helpful page. It has been a conundrum for me, reading about lack of air circulation when using flexible panels; more to ponder, clearly...

[Davie B]

Make sure your panel has a voltage blocking diode in the circuit to prevent the system from running "backwards" and discharging the battery in the dark.


Sent from my iPhone using Fiberglass RV

[JasonCM]

If you have a controller with sufficient amperage, would that eliminate the need for a fuse between the panels and the controller? I.e. if I have a 100w panel that can produce a max of 6 amps, and I have a 20amp controller?

[John Linck]

There seems to be a lot of concern to achieve the most efficiency in solar installations. This makes some sense in 5000 watt home installs. But, at the risk of heresy, I think this is over-rated on our small trailers. Conductor size over such short distances makes very little difference at these low amperages. Just use #12 wire and you will be fine. Line losses pale in comparison to poor orientation, shading losses or lack of LED lights. Panel prices are so cheap these days I just doubled my calculated panel needs and quit worrying. I bought a 100 watt panel and our group 27 battery is topped off by noon on sunny days even with the low sun angles during our off season camping.

Deep forest shade is another matter. Last year at Yosemite we had to tow our Scamp 3 miles to a valley meadow after 5 days in deep shade (darn those pesky trees). After an afternoon of picnicking and reading in the full sun we were good for another 5 days when we returned to our shady camp. The same could be achieved by 2 - 3 hours of towing.

Cheers, john

[Gilles]

Welcome Tilly with your new toy.

I installed this spring, solar panel kit Renogy 100 watts.

They delivered me the 100 watt panel, the length of wire # 10 required the panel to the controller (30 watts) and the required length of wire from the controller to the battery.
In their instructions they suggested intall one fuse 30 watts, between battery and controller, near the battery, which I did.

This way I can add two other panels 100 watts if necessary in the future.

I installed a mini meter reading for monitoring the battery voltage does not fall below 11.9 volts. (I read that lower than that, damage the battery cells.)

4 roof supports for the panel are retained with VHB tape, protected against dirt, water and UV silicone with which I have no name in memory.
(For unbelievers VHB tape, my solar-panel is still in place and solid.)

I spent the wire by the vent of the bathroom, so no holes in the shell.

I used this spring until today and I am completely satisfied.

The trailer was removed the electric kettle, electric toaster, electric coffee maker ...
Everything is on a small propane stove outside with necessary appliances.
All the lights are replaced by LED.
With all these changes, it takes more time to live, taking the time to make our coffee, watch the cooking of roasted, etc ...

Have fun Tilly, adjust your system to your needs.

[Franswa]

when one reads about this subject (12V in general, and solar in particular) the amount of information is overwhelming...at times it is not clear if someone is talking about it in the context of a 2500 square foot house off the grid or a solar panel on the dash of your car to charge your cell phone....

and there is never any hard numbers provided in statements like "locate the controller as close to the batteries as possible"....Is the speaker talking about a forty foot motorhome ?? we don't know and no "leakage" amount is provided

same goes with battery discharge from panels in the dark....I read that "most" solar panels have the "diode" incorporated in the panel...that would make sense but it's hard/impossible to determine....

the good news is that fuses and switches are real cheap compared to all other components....it's easier to include a fuse than to wonder/worry if you need one or not....and sometime in the future that fuse might make it quicker to isolate/find a problem....switches will make it possible to run different scenarios on your system... and find out what works for you and how well in the real world...

STILL having lots of fun.....F

[John Linck]

Originally Posted by John Linck

Conductor size over such short distances makes very little difference at these low amperages. Just use #12 wire and you will be fine. Line losses pale in comparison to poor orientation, shading losses or lack of LED lights.

Got to thinking about my statements above. They apply to most 12 volt circuits in your trailer, but not to a large inverter if you have one. These 1000-3000 watt beasts can really suck the battery amps. Most Scamp circuits do well with 10 amp (or less) fuses. Some large inverters need 100 amps or more. Now we are talking large heavy copper wires and very short runs. Follow the manufacturer's instruction and be careful with online forum arm chair advice.

OTOH if you have a small inverter (<100 watts) for your phone/laptop charging a 10 amp fused circuit is probably enough. Remember, Volts X Amps = Watts so a 100 watt 12 volt inverter will draw as much as 8.5 amps, usually less.

Good camping, john

[Franswa]

and FWIW....my little 150W portable inverter has a built-in fuse inside the plug.... and it specs an 8A.....YMMV