Solar Help Required - Questions For The Experts - Montana Owners Club

REPO · 05-08-2011, 01:42 PM

I am currently planning my solar install on my 5th wheel. I want to start off with a good sized, single panel, and eventually purchase a second one at some time down the road. I have been checking out many, many sites and have found them to come in all sorts of sizes, wattages, voltates, etc. I have the basic understanding of the controler. My question is if it matters what voltage of panel I purchase? By that I mean, can I buy a panel that puts out 30.8 volts, and the controler will knock it down to the required 12-14 volt range?

I really only have room for a couple panels, so hence why I would like to buy a large enough one, so that when I eventually get the 2nd one, I will have more than enough power.

Have a look at this one;
http://www.wholesalesolar.com/produc...rWorld245.html

If anyone has any panel or controler recomendations that would be great also! (not high end! I have a budget!)

Thanks!

firetrucker · 05-08-2011, 02:27 PM

You want a panel that puts out about 15-16 V max if you're going to have 12 V batteries. Anything more than that is just wasted power in the controller. Basically you'd be throwing away more than half the power generated by the panel.

To get the best efficiency, you will want to invest in an MPPT (maximum power point tracking) controller, which, if you're going to use this on a casual basis, is probably too expensive to be worth it.

You'll never have more than enough power, though, but think about getting several smaller panels that can be easily added to.

Bob

REPO · 05-08-2011, 02:31 PM

Quote:

quote:Originally posted by firetrucker

You'll never have more than enough power, though, but think about getting several smaller panels that can be easily added to.

Bob

I would like to initially purchase around a 200 watt panel to begin with, then add anther of the same size down the road. That will give me at least 400 watts, which should be enough for occasion camping trips I would think.

2 for Him · 05-08-2011, 06:11 PM

Repo,
Tom again. If you go with 30 volt panels you will have to have an MPPT controller. Lots of 17-18 volt panels in that range out there.

REPO · 05-08-2011, 06:15 PM

Ahhh, OK. I will stick with the lower voltage units then. What is the min-max I should shoot for?

Mudchief · 05-09-2011, 05:17 AM

REPO, this is a good link to read.

http://handybobsolar.wordpress.com/t...ging-puzzle-2/

REPO · 05-09-2011, 01:45 PM

http://partsonsale.com/perlight-solar.html

Have a look at the 250 watt panel. Its currently priced at $564.00 each, which seems to be a great deal. Its 250 watts, @ 31.1 volts. With this it looks like I may also go with a Morningstar TriStar MPPT 45 amp controller. As mentioned in one of my earlier posts, I would like to confine myself to just 2 panels on the roof once I finally get finished. Unfortunatly, I will probably only buy 1 panel this time, but can add to it down the road, adding another 250 watt unit. I should then have more than enough to power my items, coupled with my 3000 watt inverter. And going with the above posted link, I will be running the appropriate sized power cables, and fusing where required.

Anything I am missing here?

coyoterick · 05-10-2011, 04:43 AM

Read the section on MPPT controllers at handybob's site that mudchief posted earlier: http://handybobsolar.wordpress.com/t...ging-puzzle-2/ and get a PWM controller instead of an MPPT. The money you'll save is better spent on a second panel...I have the Morningstar Tristar PWM controller, it works great.

firetrucker · 05-10-2011, 01:11 PM

You're going to be wasting a lot of the panel's capacity, with the potential of hurting the batteries and the PWM controller, if you go with the 31 V panel. An MPPT controller will convert the voltage to the right value for the batteries, while the standard PWM does not.

This unit sounds more like a grid tie panel rather than a battery panel.

After reading handybob's essay, I'd take a lot of it with a grain of salt. Go to Wikipedia, read some of their articles, and check out the references they provide. Sometimes a little dry, but lots better information.

Bob

nailbender · 05-10-2011, 04:45 PM

Handybob has finally come around and accepted that MPPT controllers are better than PWM and are good to use.

Jack Mayer's site has a lot of good information about solar and is worth reading.
http://www.jackdanmayer.com/rv_electrical_and_solar.htm

Also MOC's own Joe Brown has a great information on installing solar. His site was a tremendous help when I installed my solar system.
http://jolu-solar-jolublogspotcom.blogspot.com/

7.3Ford · 05-11-2011, 11:59 AM

Repo,

I think you will find the 200 Watt panels size (dimensions) to big for RV use. Most use 80-136 watt range. Go with MPPT controller, it will convert panel voltage to battery voltage.

High voltage panels will allow you to use smaller wire. My setup I have two sets of two panels in series (68 Watt + 136 Watt) and the sets are in parallel. Open circuit voltage is 68 Volts, and max output is around 48 Volts. Total cost for my 408 Watt system was $2150 (panels, MPPT Controller, wires, etc). I did the design and installation myself.

My panels don't have any glass, stick right on the roof. You can walk on them, and hail doesn't damage them.

REPO · 05-11-2011, 12:10 PM

Quote:

quote:Originally posted by 7.3Ford

My panels don't have any glass, stick right on the roof. You can walk on them, and hail doesn't damage them.

What brand are they? Where did you get them and what are they called?
Are they as efficient as regular glass ones?

7.3Ford · 05-11-2011, 02:42 PM

Quote:

quote:Originally posted by REPO
What brand are they? Where did you get them and what are they called?
Are they as efficient as regular glass ones?

I think glass panels will have better performance, because they can be tilted for same square inches. The Uni-Solar panels are more shade tolerant because they have a bypass diode on every cell, where glass panels only have 3-5 (string of cell). Any one cell is shaded, it stops the output of that series cells.

I got everything at affordable.solar.com but there are many other sites as well. Prices have come down a little since I did my system, but also got $647 tax credit in 2010, net cost was around 1,500.

MorningStar TriStar MPPT-60 Solar controller and SunForce Inverter

List of materials

I used two Uni-Solar PVL-136 and two Uni-Solar PVL-68. I went with Moringstar TriStar MPPT-60 control, (MPPT-45 would have been fine), because I wanted the Ethernet Port. I use my smart phone or laptop to status, program, get history, etc. via router connected to controller. We travel with the inverter on to run the fridge, and sometimes the ice machine on AC, so don't have to worry about open flame. I can monitor panel output, battery conditions, etc while driving down the road with smart phone.

REPO · 05-11-2011, 04:04 PM

Nice! Do you have any more pictures of your install? Where are your batteries mounted in relation to the picture above? Also, how and where did you run your wires down from the roof?

7.3Ford · 05-11-2011, 05:37 PM

Quote:

quote:Originally posted by REPO

Nice! Do you have any more pictures of your install? Where are your batteries mounted in relation to the picture above? Also, how and where did you run your wires down from the roof?

I ran wires down the drain vent pipe. Someone else at MOC said that was what they did. I cut the vent pipe, put a tee in to get the wire out down in the basement area (behind the back wall). If I find a picture where I came out I will post later.

The 50' MC3 cable was cut in half to give me a male and female connection on the panel side (+ and -), and the other ends go to the controller.

I made this battery box. I lined it with shower pan liner, on the off chance the battery boil over (never happen yet). The MorningStar Controller has its own battery sense voltage and battery temperature sensor.

I used car Audio circuit breakers (30 AMP on panel side left of controller, and 80 AMP on battery side right of controller), which also are used as the disconnects. They are light weight, and work very well. I use this guy, because he ships from USA, not China. http://electronics.shop.ebay.com/Cir...-/32813/i.html

REPO · 05-12-2011, 10:50 AM

What is the bundle of wires coming out of the left side of the Morningstar? Also, how did you tie your inverter into the trailer AC wiring?

7.3Ford · 05-12-2011, 04:33 PM

Quote:

quote:Originally posted by REPO

What is the bundle of wires coming out of the left side of the Morningstar? Also, how did you tie your inverter into the trailer AC wiring?

Wires on the left side are panels wires (+ and -), Battery Voltage Sense, Battery Temperature, and Ethernet.

Inverter (DC to AC) goes to 50AM transfer Switch, and feeds entire AC Bus. I installed a switch to turn Converter (AC to DC) on and off. Normally I just leave the converter off, and solar panels charge the batteries and supplies the DC loads. Only time I turn on the converter is I can not get any sun.

Converter Switch (bottom right) and EMS Display (top right).

Transfer Switch foreground, and EMS-HW50C Electrical Management System in Background.

7.3Ford · 05-14-2011, 08:43 AM

Couldn't find picture with wires coming out the bottom end, but the vent tube is the one on the left running on the 45 degree. That is where I brought the wires out.

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