Solar panel is hooked up and working! - Fiberglass RV


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Old 04-20-2013, 05:54 PM   #1
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Solar panel is hooked up and working!

I haven't made the installation pretty and have a bit to do yet, but my hookup is charging the trailer battery so I'm excited! From Solar Blvd I ordered a 75 watt panel by W Solar and a Morningstar Sunguard-4 PWM controller. They arrived in separate boxes on Thursday and Friday. Today I went out and bought a 7 pin RV receptacle (thanks to Gina and others for this idea!), some splices, and a 10' extension cord. Total investment: about $155, including shipping and tax.
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The wiring was super simple. 2 wires from the controller went to the RV receptacle, which I then can plug into with the trailer's pigtail. I cut the extension cord in two, and the short end got attached via butt end splices to the other 2 controller wires (3rd wire in cord is not used). The same wires in the long end got attached to the solar panel's wires.
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So now, when I set up at a campground the solar panel hookup is as easy as 1-2- (and maybe) -3. Plug the controller into the trailer pigtail. Plug the panel into the controller. But if the 10' cord (well, only 9' long now) is too short to get the panel into direct sunlight, I can add a 25' extension cord... or a 50'... or both. I already carry the cords. If I'm hooking to solar, that means I don't have electric hookup... so I don't need the cords for anything else!

This installation reminds me of the insurance commercial they ran on TV not long ago. It was so easy, even a cave man (like me??) can do it (Grunt, scratch, grunt).
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Old 04-20-2013, 06:18 PM   #2
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The "scratch" part is TMI

Good for you, success!
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Old 04-20-2013, 07:52 PM   #3
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Looks good. I can't wait to try such a set-up. As I recall, the longer the cord, the less benefit you will receive though. You might test that out with your cords of different lengths.
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Old 04-20-2013, 08:19 PM   #4
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Solar Solution

What an elegant and inexpensive solution. The panel is 24x38 and appears to have a durable frame, do you see issues in transporting to and storing while camped?

I struggle with charging, iPads and iPhones while camping. With your panel design I could see charging devices off my dual 6 volt batteries during the day using 12 volt adapters. All at the same time the solar is charging the batteries.

How did you settle on 75 watt? Is that a generally accepted size?
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Old 04-20-2013, 09:21 PM   #5
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What's the wire gauge on the 50' tether!

jack
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Old 04-20-2013, 09:41 PM   #6
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Cathy, certainly there can be some losses from long wire runs, and heavier gauge wire would help. But I recall reading somewhere that the most critical area to have short or heavy wires is between the controller and the battery. There I have only a very short run. Once the controller steps down the voltage, current losses from inadequate wiring can be considerable.

Paul, 75W was a relatively convenient size and weight that I roughly estimate should be able to keep my single 12v battery from running dry. My usage consists of occasional Turbo/Maxx vent fan use @ 1.4A on low, a few LED interior lights, brief use of the water pump, and sometimes a 10-15 minute blast of the furnace to remove the morning chill. I've had the battery run down after 3 days without charge input, so if I can get 25-30 amps per day from the panel I think it would keep my battery right up there. Even 10 or 15 amps should prolong my boondock time until I'm ready to hook up and go somewhere else. The panel should yield 15A in about 4 hours of full midday sun, or in a full cloudy day's worth of diffuse light.

The panel came in a cardboard box with a styrene foam sheet on the glass side, so I'm saving it and using it for transport. I'll probably put it behind the back seat, standing up in the footwell area. Although under the bed would work also. It's only 15 lbs.

I think my 12v battery is about 90 amp-hours, something like that. This setup would work the same if I ever upgraded to a larger battery, or to 2 6v batteries.

All the supplies wires on the controller and the solar panel were plenty long. Between my 9' of extension cord and, oh, about 4' of panel wires, I can stretch the panel out about 13' before even needing to add an extra stretch of extension cord.

Since the photos I've covered the splice areas with electrical tape. I foresee no problems doing the connections this way since the setup will not be subjected to high wind forces that could stress the connections or drive rain into them; the setup will be stored inside while driving. I suppose soldered connections would be stronger and perhaps might transmit current somewhat more efficiently, but for my power needs I expect the crimped splices and tape to work fine.
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Old 04-20-2013, 09:44 PM   #7
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What's the wire gauge on the 50' tether!

jack
I think my extension cords are 16 gauge wire.
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Old 04-20-2013, 10:13 PM   #8
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Mike, 16awg is too small a conductor. At 25' you may be able to use # 12 or 10 but fifty feet of #16 will produce a lot of resistance and an appreciable voltage drop.

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Old 04-20-2013, 10:50 PM   #9
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Mike, 16awg is too small a conductor. At 25' you may be able to use # 12 or 10 but fifty feet of #16 will produce a lot of resistance and an appreciable voltage drop.

jack
Yes, at 50' it should lose 1.6v, going from 17v to 15.4v, a power loss of nearly 10%. If it took my battery 6.5 hours to top off instead of 6 hours, I don't think that will ruin my camping trip. Realize that I would only use 50' if it were absolutely the only way to get into a sunny spot, in which case any losses will be more than made up for by higher production from the sunny spot. But most likely I'll try to choose a campsite with open sky anyway, in which case I won't need any extra cords. I just think it's nice to have the option.
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Old 04-20-2013, 11:09 PM   #10
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Quote:
Originally Posted by Mike Magee View Post
Cathy, certainly there can be some losses from long wire runs, and heavier gauge wire would help. But I recall reading somewhere that the most critical area to have short or heavy wires is between the controller and the battery. There I have only a very short run. Once the controller steps down the voltage, current losses from inadequate wiring can be considerable.

Paul, 75W was a relatively convenient size and weight that I roughly estimate should be able to keep my single 12v battery from running dry. My usage consists of occasional Turbo/Maxx vent fan use @ 1.4A on low, a few LED interior lights, brief use of the water pump, and sometimes a 10-15 minute blast of the furnace to remove the morning chill. I've had the battery run down after 3 days without charge input, so if I can get 25-30 amps per day from the panel I think it would keep my battery right up there. Even 10 or 15 amps should prolong my boondock time until I'm ready to hook up and go somewhere else. The panel should yield 15A in about 4 hours of full midday sun, or in a full cloudy day's worth of diffuse light.

The panel came in a cardboard box with a styrene foam sheet on the glass side, so I'm saving it and using it for transport. I'll probably put it behind the back seat, standing up in the footwell area. Although under the bed would work also. It's only 15 lbs.

I think my 12v battery is about 90 amp-hours, something like that. This setup would work the same if I ever upgraded to a larger battery, or to 2 6v batteries.

All the supplies wires on the controller and the solar panel were plenty long. Between my 9' of extension cord and, oh, about 4' of panel wires, I can stretch the panel out about 13' before even needing to add an extra stretch of extension cord.

Since the photos I've covered the splice areas with electrical tape. I foresee no problems doing the connections this way since the setup will not be subjected to high wind forces that could stress the connections or drive rain into them; the setup will be stored inside while driving. I suppose soldered connections would be stronger and perhaps might transmit current somewhat more efficiently, but for my power needs I expect the crimped splices and tape to work fine.
You did the right thing by using crimp connections. Solder is not a good electrical conductor. It's used a lot but if you look around your tow you won't find any solder connections or in your computed (the traces on a printed circuit may look like solder but there's copper and gold below the solder).

I made a simple aluminum stand from hardware store angle aluminum and flat aluminum strips. Pop rivets hold it together and to the aluminum frame around the solar panel.

I can go forever is I get about 4 hours of sun every 3rd day. That's with a 65 Watt.

Congratulations on joining the solar world.
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Old 04-20-2013, 11:19 PM   #11
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Mike, 16awg is too small a conductor. At 25' you may be able to use # 12 or 10 but fifty feet of #16 will produce a lot of resistance and an appreciable voltage drop.

jack

16 Awg is just fine.

1. The wire is between the solar panel and the controller. Solar panel voltage is above 20 volt out put.
2. 16 Awg has a resistance of .004016 Ohms/foot which equals about 0.1 ohms for 25'.
3. His solar panel has a maximum output of 4.35 amps, which equates to a .435 volt drop. The controller has to take 20+ volts and bring it down to 13.9 volts maximum. That .435 drop don't mean anything.

Mr. Ohm and law are king.
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Old 04-21-2013, 09:45 AM   #12
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Thanks Byron. It's nice to hear from someone with a similar size panel.

You know, I think I still had a wrong thought in the back of my mind. I was envisioning that the controller would take the higher voltage and translate it into a current boost as it stepped the voltage down for the battery. But PWM controllers don't do that, do they? Only MPPT controllers do that. So yeah, as long as the long cords from panel to controller deliver at least 14.1V (set point of this controller is 14.1, not 13.9), the voltage loss they cause is pretty much inconsequential.

Reading up on my Interstate group 24 battery, it appears to be rated at 58 amp hours @ a 5A load. My loads are probably half that, so I guesstimate that I may get about 70 amp hours in warm weather. If I have any problems running out of juice with this system, my next change should be a larger battery.
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Old 04-21-2013, 11:05 AM   #13
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Is the location of the controller the prime consideration in determining the conductor size required, Brian?

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Old 04-21-2013, 11:43 AM   #14
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SOLAR Controller should be as close to battery as possible, but NOT, in the battery compartment.
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