Portable Solar

[John Blair]

Hi,

I have my solar panels and now need to order the cabling. I got the panels first because they were on sale and I had to act fast. I thought I was going to order a new trailer and get the trailer in a few months. I had no idea I was going to run into a perfect used 16' Scamp for sale last weekend and buy it. So now I need to order the cables for the panels so I can put them to use (along with the controller and an inverter). I plan to keep the panels mobile so I can park in the shade and still put the panels in the sun. For those of you who do this, how long are your cables to run the power back to the controller in the trailer? I've seen numbers from about 15 feet to 35 feet. Is anyone using longer ones or have extension cables to increase the length when needed?

Thanks!

John

[Pete Dumbleton]

John, I haven't used solar panels so have no direct experience, but were I using one likely I would be doing the same as you -- Park egg in shade and put panel in sun.

However, at least one person on Yahoo Scampers reports good results with the panel up on the roof, enough so that she intends to anchor it there more or less permanently (she carries it inside or in TV normally) -- Apparently in open shade she still gets sufficient energy for a recharge (but she's in Calif usually and may not use much energy to begin with). I would try that a few times myself and if it worked for me I would be doing that (being fundamentally lazy).

If you do decide to separate egg and panel, err on the side of heavier gauge cabling to reduce DC loss and thereby get a fuller charge (faster, also). I would make up several short cables rather than one long one so as to be able to have the shortest run possible. Also, keep in mind that both conductors in the cable can be 'hot' (battery on one end, panel on the other) so choose connectors that have both sides covered to avoid shorting things out.

[John Blair]

Thanks Pete for the suggestions. I have two solar panels that are fairly good-sized (85 watts), so I think it might be tough to get them on the Scamp (I pick up the trailer on Wednesday so I don't know the exact size of the top space at the moment). I started off with two panels, but may need to add more based on my calculations of energy usage. I wanted to try a season first to see if two will be enough for boondocking a week at a time. I will be getting my cabling and connectors from a solar company (wholesalesolar.com). They were suggesting 35 feet and I was thinking along the same lines as you, so maybe a 15 foot and a 35 and I can use the shorter one or use both. We will be wiring it up as a 24 volt system to reduce line loss and dropping it with the controller at the battery. I was also thinking of mounting two on the trailer and having two portable if we need more. I would only get the portable ones out when necessary. At the moment I want to play with the portable ones first to give me some ideas. Some people have suggested putting heavy duty suction cups on the corners of the panels and then putting them on top when possible or going portable as needed.

Thanks again,

John

[Joy A]

John,

That "she" would be me.

I have a 55 watt panel that I place on the roof of my Scamp behind the large vent. I don't tilt it, just leave it flat. Also, even though I'm in California like you, I spent a lot of time in the PNW under the shade of trees. No matter what the campground or State I'm in I simply look for the best campsite jwith shade and am not concerned about where the sun is. In fact, often times at the coast there is no sun just fog and my panel still keeps the battery up. Now I'm not trying to light Las Vegas with my panel but it works get for me.

Did I read correctly that you have 2 - 85 watt panels???

Or, is it that you have 2 panels that connect for 85 watts.

With 85 watts I wouldn't worry where the panels were placed, sun or no sun.

[Gina D.]

Hi John,

As with any other charging method, you want to keep the length to a minimum to avoid loss, as well as using the heaviest gage practical. As far as the length, with solar, this sort of takes care of itself most of the time. Almost anywhere I have gone, I can find a sun spot within a few feet of the rig.

That said, my pigtail for my 45 watt array is 15 feet of 14 gage stranded wire. I don't think I have ever stretched it that far. 15 feet is 15 feet however, whether you are using it at full length or not.

I do exceptionally well with a group 24 battery and low voltage lighting.

Here is a link to my charging system. I have a bigger trailer now, but I have duplicated the electrical system in the new trailer. I expect to do as well with it.

Solar charging for dumbies (And the lazy... that would be me)

[John Blair]

Hi Joy and Gina,

Thank you for the information. Yes I have 2-85 watt panels for a total of 170 watts. I know some people can get by on much less, but I want to have all the comforts and be able to go when and where I want. Sometimes I will be working so I need to bring those tools along (laptop and satellite internet) + Directv. I estimated all of our usage at close to 1300 watt hours per day. 170 watts of panel x 6 hours per day doesn't produce enough, but I won't know our usage for sure until after we have gone out for awhile. I am just one of those "got-to-be-prepared" kinds of guys.

I have a generator to run a/c if necessary and to recharge batteries, but I hope not to use it much. Once I am comfortable with the solar and where we go, then I can adjust my planning.

I am also planning to replace the 12 volt battery with two 6-volt T-145 (or U-2400). Then I will have about 250 amp hours which will yield about 2500 watt hours (80% maximum usage etc). I used to have an electric car, so I am comfortable working around and maintaining those golf cart batteries.

Thanks for all of your suggestions,

John

[Donna D.]

Aside from solar John, I just looked at your website...beautiful, beautiful pictures! I would imagine you are completely capable of having some FANTASTIC shots while camping. Care to take one or two for the FiberglassRV home page?

[John Blair]

Aside from solar John, I just looked at your website...beautiful, beautiful pictures! I would imagine you are completely capable of having some FANTASTIC shots while camping. Care to take one or two for the FiberglassRV home page?

Hi Donna,

I would be happy to once we go out camping. I just picked up our new baby yesterday and still have to (re)do the paperwork with the DMV (the seller did not put the same name as the DMV had as registered owner, but we will get it straightened out in the next week). In the meantime it sits on our rural gravel driveway all nicely leveled due to some of the things I learned here. (bought the right tools).

Donna, email me directly and we can chat about the kinds of photographs you would like.

John

[Steve L.]

I, too, suggest you pay some attention to the wire size. For the purposes of an estimation: My recollection is that many solar cells put out about 17vDC. A 20 foot wire is a 40 foot circuit length. An 80 watt panel is putting out about 4.7 amps. Put them into the estimator.

Voltage Drop Estimator - DC

You lose amost 3% of your voltage in this example. If you used some of that cheap 18 ga lamp cord, you'd lose 7% and the voltage at the battery would be down to 15.8 volts.

If your solar cell only put out 15 vdc in the second example, the charging voltage would only be 13.8 vDC. It all serves to extend the recharge time.