Visit our Popular Forums

mtbob · 02-16-2003, 11:19 AM

Brian,yes they are 80w panels. Solar Elect had a special on and provided them at the same cost of the 75's. The batteries are lead acid as they were already purchased and in use when we went the solar route. One is in the battery compartment and the other two are inside under one of the sofas on the street side.

nwclassic · 02-16-2003, 11:10 PM

Thanks to all for replies... a picture is beginning to form!
Maurice -- how about stringing parallel or shorter route 10g and making the connections (fwd galley, refer comp and battery) with two 10g wires instead of the present one?
mtbob -- any problems w/ the under couch lead acid batteries... are they vented outside? If not what means are used to manage the H gas?
John -- I agree and see more benefits in the flat roof mount.
Brian

RoadKingMoe · 02-17-2003, 06:11 AM

Yes, one could run the two wires parallel for the + side and run a new - cable under the trailer. That would support two panels.

The batteries under my couch are in compartments that are only open to the outside. The door to that compartment isn't sealed tightly allowing the hydrogen to escape to the outside. The door is on one battery end, so on five sides the compartment is warmed by interior air.

JaceBeck · 02-17-2003, 07:56 AM

Maurice,
Any thoughts on the Maximum Power Point Tracking controllers (like the RV Power Products Solar Boost 2000E) ? Is there any value to these? I am going to install something this spring for our weekend dry camping trips to the MN Northwoods.
Thanks!
JC

RoadKingMoe · 02-17-2003, 09:56 AM

They use a DC to DC converter to step down the panel voltage a little to get a little more current at the charging voltage. This process is only about 80% or so efficient, so you don't see all of that gain.

The greater the difference between:

panel voltage minus voltage drop of the panel to controller wiring,

and

battery voltage plus voltage drop of the controller to battery wiring,

the more gain they give. And when this difference is small, they can actually lose a little charge current. Minimizing voltage drop of the cabling is critical with an MPPT controller.

The colder the panels, the higher their voltage, and the more gain an MPPT controller gives. They do better in March and Sept than in June, so they tend to help offset the loss of lower sun angle and shorter days a little bit.

The deeper the battery is discharged, the lower its voltage, and the more gain an MPPT controller gives.

Expect a 5-15% gain in the real world, depending on time of year, except when it's hot outside, when you might see a slight loss.

The SB2000 is only a two-stage charger with a bulk mode and 14.0V constant voltage mode to do the last 10%. Odds are you'll run out of daylight before the 14.0V mode gets much above 90%, and the evenings use will take it down well below that, so it won't be the battery-boiling problem that this voltage might lead you to believe it would. That would be a problem with a 24 hour converter though.

MPPT controllers are probably a good idea unless you mainly camp where its really hot.

nwclassic · 02-17-2003, 05:10 PM

Maurice -- I'm in awe... I need to plug one ear so that all of this info doesn't spill while I'm getting more!
The 120W panels that a vendor described to me were said to be 60x28x4". Quick measurements (it's raining again) look like I've got that and a little more between AC and FF roof vent. Could mount two it seems.
So about these MPPTs... if you treat your batteries the way they like to be treated (no deep discharge) by conserving, generator, alternator or large battery bank use, are they a good investment? If so, recomment one or two. If not,recommend a preferable controller. In other words, what's Maurice's ideal setup? Thanks.
Brian

dienst1 · 02-17-2003, 05:58 PM

I purchased 6 120w flat panels based on measurements taken from the roof of my 1981 28' Excella motorhome. Before installation was begun it became apparent that the final result would be Coyote ugly. I went back to the internet and found the following sources for flexible panels. They are less efficient than the flat SCC cell panels but would look much better because they would conform to the Airstream shape. By the way; the flat panels have never been installed and are for sale.

http://www.solaraenergy.com/Solara_E...duct_List.html

http://www.gosolar.u-net.com/flexibl...s_Unisolar.htm

RoadKingMoe · 02-17-2003, 07:18 PM

From measurements I took on the roof, I don't think two 28" panels side by side and flat would look very good on the curved roof. In fact, I think they'd be ugly. I don't want the panels visible. I'd want the center about 2" off the roof for cooling, so they'd be really high off the roof 28" on either side of center. You could mount them in an inverted V, but then one panel would be tilted toward the sun and the other away from it. In that case, I'd want them hinged in the middle so that you could lift the panel on the far from the sun side and tilt it to match the tilt of the other panel.

About the most flat panel width I'd want to have would be 40" and three 13" wide Shell SM55 would fit within that. I'd have room for two banks of three of those, and I'd wire them for 36V and 2.5A in each bank, and feed their 180W/5A to a Solar Boost 6024 that can step down 24, 36, or 48 nominal volts to 12V batteries... maybe get as much as 60-75AH/day out of this.

Alternatively, the Kyocera KC80 are 38" long by 25.7" so two would mount sideways in about 52" of length. I could get four in series for 48V at 4A (192W), but the reality is that peak voltage could be as much as 68V, exceeding the 50V rating of the prewire. Or in series parallel for 24V at 8A but that's more than I'd want to run through my long prewire... one could get maybe 65-80AH/day out of four of these. And four of these at $1342 plus shipping are a lot cheaper than 6 of the SM55 at probably $1650.

If I redid the solar wiring with shorter, heavier cable, I'd probably go for a Solar Boost 2000 if money was a factor.

But for this much money, I'll buy two Honda EU2000s and have air-conditioning.

nwclassic · 02-18-2003, 02:11 PM

dienst1 -- Where are you in your solar project? Have you installed/tested/camped with your flexible panels? And if so, what's your assessment? What kind of numbers are you seeing when that SOCAL sun beats down on your panels?
Maurice-- Since I probably won't see a rapid solution to the battery problem, I expect to keep my Grp27s for now, install one large (120W) panel on the longitudinal axis flat mount now with expansion plans to mount another alongside (roadside) perhaps on a tilt mount (it will show, but form follows function). Buy the Honda gen now and go camping. Some time spent learning the vagaries of solar power may help me arrive at a battery bank answer that satisfies me. Thanks to all for the input...much appreciated.
Brian

RoadKingMoe · 02-18-2003, 02:48 PM

Hey Brian, I guess I got lost and posted it on the wrong thread, but do you have room for 3 KC80 panels up there... 2 will go where a 120 will go, and maybe you'd have room for another on a shorter spot?

That would keep the panel visibility down and get you 240 watts.

nwclassic · 02-18-2003, 09:05 PM

Yeah Maurice, that might work. I'm a little concerned about extra mounting holes,etc. I had the notion that I'd be ltd to three panels and so planned on high watts for each. I've read some on the forum about matching panel size to support locations thus lmting in that manner. I talked w/ a salesman at a solar shop in Bend, OR on the phone today. He was familiar with the components I learned about from you and others. A couple of concerns arose for me; said cable >10g won't fit on controller terminals and loses its V drop protection if stepped down to fit. Also, the panel mounting strategy left me a little cold... basically drill a hole pour some 'siliconesque' goop down it and around. Mount it, screw it and slather it again. The concept offends me...didn't I read somewhere about some pop rivet like objects (Olympics, I think they were called) that made a clean, strong, sealed anchor?
On another note, re space alone, I think I found enough room between my battery compartments below the couch to consider gel batteries. Haven't looked beneath the floor yet to see if adequate support exists. And four gel batteries would likely cost me the arm or the leg. I'm partial to both so will wait and use up my G27s first. Brian

RoadKingMoe · 02-19-2003, 08:37 AM

Sounds like the guy giving you advice doesn't know much about electricity and wiring.

Cabling has resistance along its length. The longer it is, the higher the resistance. The maximum current cable can carry is limited to that which will not overheat it, based on the resistance per foot. However, when you get into longer runs of cable, the amount of voltage dropped across the entire cable may be larger than acceptable, even though the current is well below that which would cause the cable to overheat.

Putting 10 gauge pigtails on the end of larger gauge wire does NOT wipe out your reduction of voltage drop. You have a long run of very low resistance per foot cable and a very very short run of higher resistance per foot cable at the controller end. As long as the pigtail is large enough to prevent overheating at the maximum current, it's fine. Its length is so short that its higher resistance per foot contributes very little to the overall cable resistance.

Using pigtails on larger gauge wire is specifically what Solar Boost recommends. See page 11 of the Solar Boost 2000 Manual.

You don't have to match the panel holes to the trailer ribs. Keep in mind you're going to use supports. Make the supports so that they have good attachment to both the ribs and the panels.

The Olympics may be a good thing, but so is "slathering" when it comes to trailer roofs. Make sure you do it to properly route water both when it's draining off the trailer when parked, as well as when it's being blown back by the wind of the trailer underway. When you use silicone or other sealant, make sure the area it will be applied to is roughed up, and very clean.

nwclassic · 02-19-2003, 09:17 AM

Thanks, Maurice... and thanks for the next six pieces of good info you keep providing. Any doubt that knowledge is power? I think not!
Life is tapping me on the shoulder and I'll be away more than here but will check in on the forum as I can. Stay healthy... I need you!!
Brian

smr95032 · 04-08-2016, 11:59 PM

Try AMsolar, I haven't noticed that suggestion. They do have 160w panels, I put two on my AS. Great customer service and are happy to answer any and all questions.