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Old 07-31-2019, 04:38 PM   #1
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Solar Panel 101 for Dummies

Sorry to flog the proverbial steed, but..... I know nothing about solar panels or electricity, but I’m interested in buying a small panel that I could set up on a sunny day to supplement my battery. I have a 13 foot Scamp and will be “on the road” for a couple of months. As I understand it, having a panel could cut down on the time we need to stay at campsites with hook-ups simply because our battery is getting too low to stay at a BLM, Forest Service, or unserviced site. Is there a good link here or elsewhere that can help get me up to speed? There is SO much information and SO many opinions, I’m dizzy. But I’m really looking for a simple way to somewhat expand our options to wander aimlessly, and still have lights at night. We can put the fridge on propane, so our needs for electricity are very modest, but still necessities. Thanks for any basic guidance.
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Old 07-31-2019, 04:48 PM   #2
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Your needs sound similar to mine. I have two 40 watt Coleman panels. They connect to a hub which connects to a controller, which connects to battery terminals. You could start with one panel ( no hub ) and add, if required. I now leave my generator at home.
Got them on sale at Canadian Tire. Open a Canadian Tire account and set a Sales Alert for the panels. They are on sale every few weeks. I paid half what they are currently listed at.
You could pay more for better panels, but why?
Panels come with everything you will need, and some stuff you won't.
Currently listed at $269 CAD. If I recall, I paid $99 and have seen them at $79.
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Old 07-31-2019, 04:50 PM   #3
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I attached a pigtail to my Casita's battery with a PowerPole PP30 plug, and got a Renogy 100W 'solar suitcase' portable solar panel, and put a PP30 on it instead of the default battery clips. The battery pigtail was just enough to fit through the vent on the battery compartment door, so I could leave that closed and locked even with the solar panel plugged in.


This worked great, I'd aim it at the morning sun before going to bed, and on a sunny day my battery would be fully charged by the time I got up.

I had LED lighting in the Casita, so the primary use of electricity was running the heater fan at night, the ventilation fan during the day, and the water pump.

here's the pigtail...


and here's the solar panel setup (far left)

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Old 07-31-2019, 05:14 PM   #4
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The simplest way to deal with the problem is some variation on what Jon said. And it is what I did too.

Get a Renogy 100 watt solar suitcase. The one that comes complete with the controller. Easily found on Amazon. Make up a cord that is long enough to place the panels where they can point to the sun. My cord is a #12 heavy duty extension cord, easily found at Home Depot, and cut to 20' in my case. The suitcase already has the controller and just needs to be wired to the battery with some sort of plug, there are many to choose from, or even alligator clips.

The charging is all automatic and all you have to do is point the panels at the sun, and keep them out of the shade.

The suitcase stores easily and is a wonderful tool.

If this is the route you want to take, and I highly recommend it, you can get more help on doing the plugs and wiring at the battery, but it is all very simple stuff.

With careful use, this should supply all the power you need.

At some point, you'll have to make sure your battery is big enough and in good enough condition. But that is not the driving issue here and may be perfect as it is.

Jump in, get the suitcase and get it set up.

Once you get going, you'll begin to see how it all works out for you and how much power you have to play with.
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Old 07-31-2019, 05:41 PM   #5
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Thanks for the clear and concrete advice. What does the controller do? Manage the charging of the battery as electricity is produced by the solar panel?
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Old 07-31-2019, 06:01 PM   #6
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Thanks for the clear and concrete advice. What does the controller do? Manage the charging of the battery as electricity is produced by the solar panel?
Exactly.
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Old 07-31-2019, 06:40 PM   #7
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I use the Acopower 105 watt foldable solar panel that weighs less than 1/3 of what the Renogy solar suitcase weighs. And it folds into thirds, not halves, so is much more compact. You do have to prop it up on something and it is sort of flexible. But it is so light that it is super easy to store and deploy.

This version (which I don't own) has legs to prop it up, which is a nice addition.

https://www.amazon.com/ACOPOWER-Port.../dp/B07FB643MH
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Old 07-31-2019, 06:59 PM   #8
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I have the Renogy suitcase model as well. Bought on Amazon Prime Day. Like John, I installed a pigtail on my battery which allows me to connect to the battery without leaving it out in the open.

Next step is a longer extension cord, as the best location sun wise is often not right next to the camper.

I like to camp at National Parks that rarely have hook ups. So its a generator or solar panel.

Side advantage for me with the portable unit is I use it on my Escape and my Trillium. And by not being permanently attached to the trailer, I can place it where the sun is, instead of being locked in on top of the trailer.
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Old 07-31-2019, 07:10 PM   #9
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I didn't have to buy wire or connectors for my cheap Coleman.
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Old 07-31-2019, 07:14 PM   #10
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Here are a couple of pictures of my solar plug and the wiring to the battery.
The plug is a simple twist lock, water proof unit with weather cap.
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Old 08-01-2019, 08:50 AM   #11
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Thanks for more helpful info. If I use an electrical wire around 20 feet long to allow me to place the panels in the sun, what gauge wire would I need? I know that too thin a gauge does NOT work well bringing electrical power to the Scamp if the length is too long. So I’d want to buy the proper thickness for the solar panel, but not more than is required for the application.
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Old 08-01-2019, 09:45 AM   #12
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Richard,
I suggested a #12 heavy duty outside extension cord from Home Depot, or equivalent. Then cut it to 15-20'. These are durable, have fine stranded wire and are relatively cheap.

#12 is the wire size and is rated for 20 amps. You will be running about 8 amps during peak sun.

You are right that a small gauge wire does not work well with low voltage, but this size is fine, easy to get, is resistant to damage when stepped on, will lay flat on the ground, is a bright color, and is easily coiled up over and over for storage. It can easily be stored inside the suitcase.
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Old 08-01-2019, 10:22 AM   #13
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If you are thinking about different wire lengths, this site from West Marine tells you what gauge wire to use in two different scenarios, 3% voltage drop and 10% voltage drop. You can see on it how Raspy's advice is good for 3% voltage drop for 20 feet of 12 gauge wire (falls between 5A and 10A on the chart).
https://www.westmarine.com/WestAdvis...e-And-Ampacity

Note that Renogy recommends no more than an additional 10 feet of 10 gauge wire extension to their suitcase . Check to see if the Renogy comes with only MC4 connectors; if so you will have to either buy the tool to install them on the extension cord or buy a cord with them already installed.

I got a cable with MC4 connectors already installed and cut it in two. The MC4 ends of the two cables plug into the solar panel. I installed Anderson power pole connectors on the other end to hook into my solar controller.

By the way, the Acopower panel cable comes with SAE and battery clip ends. The controller can be removed using the MC4 connectors so you can join it to another panel. Renogy does not recommend removing their controller.
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Old 08-01-2019, 10:31 AM   #14
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Originally Posted by Raspy View Post
Richard,
I suggested a #12 heavy duty outside extension cord from Home Depot, or equivalent. Then cut it to 15-20'. These are durable, have fine stranded wire and are relatively cheap.

#12 is the wire size and is rated for 20 amps. You will be running about 8 amps during peak sun.

You are right that a small gauge wire does not work well with low voltage, but this size is fine, easy to get, is resistant to damage when stepped on, will lay flat on the ground, is a bright color, and is easily coiled up over and over for storage. It can easily be stored inside the suitcase.

Can I jump in with a question? I have a controller and a 25W suitcase panel. If I purchase a second panel and connect them (in series), will I be able to charge my Group 27 deep cell battery (Scamp 13')? Do I need a full 100W - that is, purchase a 75W panel - or will a 50W do okay?
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Old 08-01-2019, 10:44 AM   #15
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Quote:
Originally Posted by Air Doug View Post
If you are thinking about different wire lengths, this site from West Marine tells you what gauge wire to use in two different scenarios, 3% voltage drop and 10% voltage drop. You can see on it how Raspy's advice is good for 3% voltage drop for 20 feet of 12 gauge wire (falls between 5A and 10A on the chart).
https://www.westmarine.com/WestAdvis...e-And-Ampacity

Note that Renogy recommends no more than an additional 10 feet of 10 gauge wire extension to their suitcase . Check to see if the Renogy comes with only MC4 connectors; if so you will have to either buy the tool to install them on the extension cord or buy a cord with them already installed.
lead acid battery charging voltages are quite critical. 3% of 13.8V is 0.4, which means the battery would only see 13.4V which isn't enough to fully charge.

The renogy cable with the MC4 connectors is attached to the solar controller with screws, easily replaced with whatever you like.

I used 25 feet of 12/2 (12 gauge 2 wire marine cable), but I also ran 25 feet of 20/2 signal wire in parallel connected to the voltage 'sense' pins on the solar controller, these allows the controller to compensate for the voltage loss in the wires. there's still a *power* loss in the 12/2, but the batteries get the proper charge voltage, which is critical for lead acid. I used 'spiral loom' to wrap the bundle of the 12/2 and 20/2 so its one 'cable'.

I always try and park my trailer with the tongue pointing north, so the sun rises on the curb side, and sets on the street side, the casita battery is in the rear of the street side, so 25 feet of wire gave me plenty of flexibility in panel positioning.
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Old 08-01-2019, 10:50 AM   #16
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Renogy sells the new foldable, lightweight suitcase solar panels. You pay a little more, but you've got Renogy's warranty. This one comes with a 20 amp controller.

https://www.renogy.com/renogy-100-wa...-with-voyager/

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Old 08-01-2019, 11:34 AM   #17
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lead acid battery charging voltages are quite critical. 3% of 13.8V is 0.4, which means the battery would only see 13.4V which isn't enough to fully charge.
I think, at worst, the line losses would only slightly delay a full charge. As the lead acid battery comes up to full charge, it goes from the bulk stage, to the absorption stage. The amperage is gradually reduced to hold the maximum voltage of about 14.1-14.4 volts. This reduction of amps, at near full charge, would also reduce the line losses in a given wire size. So, as the battery reaches full charge and is about to go into float, the amps will be so low, that line losses will not matter with a #12 fine stranded wire.

The line losses shown in the chart are for amperages much higher that what will be delivered near the end of absorption. So, they mean little with a #12 wire.

Then, in float, at about 13.2 volts, the voltage is still being held above a fully charged state of 12.7. So some charging will still occur. just not enough to heat it or make it use water.

Bottom line: 15-20' of fine stranded #12 with a 100 watt suitcase should produce excellent results with no measurable reduction in charge times or full charge voltage. Much bigger variables would be orientation and shading.

John, I like your marine grade romex. That stuff is very high quality and tinned. I've used a lot of it around boats and it is great. Only downsides are it is expensive, harder to get and may not lay on the ground as nice as a #12 extension cord.

I also like your voltage sensing system to verify what is happening at the battery.
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Old 08-01-2019, 11:41 AM   #18
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Etrailer sent out a basics and how to as to determining needs email two three weeks back. If I didnt delete it will put a link or I am sure one could find it on their website.
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Old 08-01-2019, 11:55 AM   #19
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Can I jump in with a question? I have a controller and a 25W suitcase panel. If I purchase a second panel and connect them (in series), will I be able to charge my Group 27 deep cell battery (Scamp 13')? Do I need a full 100W - that is, purchase a 75W panel - or will a 50W do okay?
Hard to answer this.

1. You'll have to look at the specs on the controller to make sure it can handle the added input amps from a second panel.
2. You'll probably be connecting the panels in parallel, not in series.
3. Any size panel will charge your group 27 as long as your usage doesn't exceed the charging capacity, over a 24 hour period. Somehow, you will need to get more charging amps to the battery than your total amp/hour usage, and as long as that is the case, the battery will charge up.
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Old 08-01-2019, 11:58 AM   #20
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As often happens, when you ask for simple, answers become more and more complicated.

Buy a 100 Watt Renogy Solar Suitcase, which contains everything needed to supply and regulate power.

Buy, and learn to use, a voltmeter.

Look up and print a battery condition/voltage chart to help monitor your usage/needs.
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