Portable Solar Panel Setup

[Trvlngnrs]

Hi everyone.

I have a chance to get a new Xantrex C40 controller for $50: http://www.altestore.com/store/Charg...troller/p2070/

I'm thinking a getting this 130 watt panel: http://sunelec.com/index.php?main_pa...roducts_id=645

I'm thinking of hard wiring the controller in my travel trailer, then attaching the solar panel with approx 30' of gauge wire to make it portable. It will just help to decrease run time of my Honda eu2000i generator charging my two Trojan T105 batteries. I live in southern UT, so I get lots of sun, but tend to park the trailer in the shade.

Currently I have a 15watt Battery Minder solar battery conditioner on my trailer to keep the batteries charged while the trailer is in storage. http://www.batteryminders.com/batter...--p-16140.html

Is there a problem connecting both systems to the batteries?

Thanks for your advice
Trvlngnrs

[Cariboocoot]

The C40 is over-kill, as one 130 Watt panel will never come close to 40 Amps @ 12 Volts. 8 Amps maybe.
But, $50? What's wrong with it? That is a suspiciously low price for C40 - about 1/3.

Are you planning on adding more panels in the future? It would certainly allow.

There's shouldn't be any trouble with the two charging systems hooked together on one battery set, except that while in storage the C40 may drain off some current (won't provide any without sun on the panel of course). Simply disconnect it while the trailer is out of use.

It's a good plan. Make sure whatever mounting rack you build for the panel is adjustable and sturdy. You don't want it knocked over by wind or some such while you're happy camping!

[Trvlngnrs]

Thanks for the advice!

There isn't anything wrong with it. it's new in the box. It came with a kit, but the owner ended up upgrading the controller, so he never used it.

Is there any specific type of wire I should use?

I saw some 6 gauge flexible welding cable for $1.40/foot. Is this overkill for a 30' run between the panel and the controller?

[Cariboocoot]

Thanks for the advice!

There isn't anything wrong with it. it's new in the box. It came with a kit, but the owner ended up upgrading the controller, so he never used it.

Is there any specific type of wire I should use?

I saw some 6 gauge flexible welding cable for $1.40/foot. Is this overkill for a 30' run between the panel and the controller?

The panel is rated for less than 7 Amps output, so you certainly don't need 6 gauge wire. Thirty feet isn't really that far of a run either. A rough guess would be that 14 gauge would probably suffice. Perhaps 12.
For absolute accuracy in determining the wire size, see the Voltage Drop Calculator:
http://www.wind-sun.com/ForumVB/showthread.php?t=29
(And more thanks to Solar Guppy for taking on hosting this valuable tool).
(It doesn't run on my net book so I can't do the calc for you.)

I would recommend a weather-proof cable, such as used for outdoor extension cords. But do not use the standard 120 VAC connectors or sometime somebody is going to do something very wrong and something will go "poof!"

[BB.]

You can also play with this simple on-line voltage drop calculator. 30 feet (one way) and 7 amps will give:

• 14 awg => 1.3 volt drop
• 12 awg => 0.8 volt drop
• 10 awg => 0.5 volt drop
• 8 awg => 0.3 volt drop
• 6 awg => 0.2 volt drop

A 10 awg cord would be great. A 12 awg OK... 14 will probably work OK in cool weather--but I would go heavier.

• V wiring-drop = Vmp - (Vbatt+Vcontroller-drop)
• V wiring-drop = 17.5 volts - (15 volts equalizing + 1 volt controller drop) = 1.5 volt margin

And remembering that hot panels have Vmp dropping with temperature.

Regarding plug ends--I like ones that can pull out (instead of twist locks)--people trip or you pull the RV away from the campsite and the panels are still setup (oops).

Also, secure the panels against wind damage (at least--theft can be another issue).

-Bill

[PhilS]

I use a similar setup on my RV. I have a portable panel (~120w IIRC) on 30' of wire because I too like to park in the shade. I also have another panel the same size hard mounted on the roof. (on hindsight I could/should have made the portable on 50' of wire... sometimes 30' is a little short of the best sun)

Both panels run through a C30 controller (with the optional gauge faceplate so that I can monitor performance). The roof mount uses the factory wires that were terminated under the fridge vent.

The portable unit I have connected using a trailer wiring kit. The short pigtail attaches to the controller and the plug is inside the door that you open to raise/lower the landing legs. So, open the door, pull out the pigtail, close the door over it (flat wire, plastic door, no problem), connect the wire from the panel.

This is 4 conductor wire with polarized plugs. I use two wires for each + and each -. The plug on the panel wire is the one with 3 exposed terminals. The pigtail on the RV is the one with only one exposes terminal, and that terminal and the wire next to it are wired to negative so there isn't an exposed terminal on the pigtail that is 12V, to prevent it from contacting any metal on the RV and causing a problem (to say the least).

I do not have any mount for the solar panel. I only drilled a hole in the frame big enough to pass a good bicycle cable lock through. Since we usually park around trees it's easy enough to find a place to lean the panel in the sun and lock it to a tree. Also easy to move as the sun angle changes. The cable both keeps it from blowing over, and "walking off".

One time we had no trees and I just put the portable panel up on the roof.

Phil

[dwh]

I'd go with a standard 50' contractor's 10 gauge twist-lock extension cord. 3 wires, black, white and green - perfect.

There is a connector issue though...as Coot mentioned there is a (slim) possibility of a mixing ac and dc accident.

One thing I don't like about Phil's (sorry Phil) setup is that there are exposed positive and negative pins on the PV panel, which means while it has sun those pins are hot. I think I'd have reversed the connectors so that on the PV panel there would be only one exposed pin so the panel can't be shorted out and the guy handling it can't get bit.

One way to prevent the accidental ac/dc mix problem would be to switch ends - i.e., have the male at the PV end and the female at the RV end (which would mean the opposite for the cord - female at the PV and male at the RV) - but that creates the same problem as Phil's setup - hot exposed pins coming off the PV.

I guess what I'd end up doing would be to cut off the female end of the cord and make the cord male at both ends, so that I could use female at the PV (no exposed energized pins) and female at the RV. That would require that the cord always be plugged in to the RV first and then the PV.

Otherwise, you would be toting around the RV end of the cord with exposed hot pins that are energized by the PV.



EDIT: Left something out...

With the cord male at both ends, it also (seemingly) prevents Coot's accident, since the hot end (female) of a normal 120v twist-lock CAN'T be plugged into either the RV or the PV.

But no...that's no good either, since one male end of the modded cord could be plugged into the PV and the other into 120vac. Or one end into the RV and the other end into 120vac.

Hrmmm...tricky issue.

[nsaspook]

I'd go with a standard 50' contractor's 10 gauge twist-lock extension cord. 3 wires, black, white and green - perfect.

There is a connector issue though...as Coot mentioned there is a (slim) possibility of a mixing ac and dc accident.

One thing I don't like about Phil's (sorry Phil) setup is that there are exposed positive and negative pins on the PV panel, which means while it has sun those pins are hot. I think I'd have reversed the connectors so that on the PV panel there would be only one exposed pin so the panel can't be shorted out and the guy handling it can't get bit.

One way to prevent the accidental ac/dc mix problem would be to switch ends - i.e., have the male at the PV end and the female at the RV end (which would mean the opposite for the cord - female at the PV and male at the RV) - but that creates the same problem as Phil's setup - hot exposed pins coming off the PV.

I guess what I'd end up doing would be to cut off the female end of the cord and make the cord male at both ends, so that I could use female at the PV (no exposed energized pins) and female at the RV. That would require that the cord always be plugged in to the RV first and then the PV.

Otherwise, you would be toting around the RV end of the cord with exposed hot pins that are energized by the PV.



EDIT: Left something out...

With the cord male at both ends, it also (seemingly) prevents Coot's accident, since the hot end (female) of a normal 120v twist-lock CAN'T be plugged into either the RV or the PV.

But no...that's no good either, since one male end of the modded cord could be plugged into the PV and the other into 120vac. Or one end into the RV and the other end into 120vac.

Hrmmm...tricky issue.

Some of the best connectors for DC cables are Anderson types. http://www.amazon.com/Power-Pole-Con...ref=pd_sbs_t_1

[BB.]

They are OK--Our host NAWS also sells them too:

Anderson Power Pole Series

-Bill

[Trvlngnrs]

You guys are great! Thanks for all the advice you've given me!!

Is there a particular panel you would recommend for my situation. I'd like a 90 - 130ish watt panel. Not the most expensive, since it will be more vulnerable to theft, etc.

The Sun 130 watt panel I linked above is $260, but....the company charges $105 for shipping! I'll look thru NWAS to see what they have to offer........