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New 400 watt solar projeck
I just removed the original 2- 85 W solar panels placed by LD at the factory and replaced them with 3-100 W panels I bought at Costco(Grape Solar Panels). They are wired in parallel. I think I may add another 100 W panel and wire in the 4 panels in series and replace the PWM controller with a MPPT controller. This I believe will max out the 10 gage wire routed through the roof by LD.
The panels are attached to the roof with 3M VHB tape? and NOT placed over roof framing members.  It seems strong. I can not imagine the panels pulling the roof off. The panels 30 in. x 30 in.
The solar is  routed down the fridge vent and was done by LD at the factory.

What do you think? Matt
2002 MB
Re: New 400 watt solar projeck
Reply #1 –
Series connection means if there is any shadowing on any one panel, it will cut the current to the whole string. Even if it means running a new larger gauge lead down from the roof, I highly recommend parallel connection. Series connections are typical for many off-grid solar installations where the panel array is in an open fixed location without shadowing issues, and the higher voltage is advantageous for a long run back to the controller/battery shed. You can always start using the 10ga, and if you measure a noticeable voltage drop with your parallel array, then upgrade the wiring. Assuming your panels are flat on the roof, you will never see 400W of solar even in the summer. In the winter, maybe half of the summer rate. The resistivity of the 10ga is about 1 Ohm/1000'. If the total down run is about 20', total series resistance will be 40/1000=0.04 Ohms. Say 300W/13V=23A. 23A X 0.04Ohms = 0.9V.

Steve
2004 FL
2013 Honda Fit
Re: New 400 watt solar projeck
Reply #2 –
Thanks Steve. The 10 gage wire length to the controller is less than 10 feet. AM solar led me to think that the series and MPPT was gonna let me add more solar  without having to upgrade the existing 10 gage.  The shading issue was never brought up.  One thing with parallel is there are more wires to manage on the roof and more MC-4 connections to manage that are stiff and bulky.  There is usually some shade wherever we go as we typically camp in the mountains.

Thank you again,

Matt
2002 MB
Re: New 400 watt solar projeck
Reply #3 –
Quote from: Matt Jones  - 
Thanks Steve. The 10 gage wire length to the controller is less than 10 feet. AM solar led me to think that the series and MPPT was gonna let me add more solar  without having to upgrade the existing 10 gage.

Four 100W panels in series will put out a maximum of about 8 amps, so the 10 gauge can carry it safely, and with negligible voltage drop. Of course, the output from the MPPT controller will be over 30 amps, and you'll want more than 10 gauge there.
2005 Jayco 24SS
Re: New 400 watt solar projeck
Reply #4 –
As recommended on this board, when installing solar panels I insisted on 6 gauge wire so I could add panels later.  Never did it... am at 100 % every day by noon,  although I watch videos and download podcasts, use lights every day.  Installers say I might need more someday, but not yet.

Got out of Alaska and shoveling snow, down to Arizona, now am parked in boondocking next to a rig running a dammed generator, and wonder why this has to be?

Sigh.  Kristin
1997 MB
Re: New 400 watt solar projeck
Reply #5 –
"[I am] now... parked in boondocking next to a rig running a dammed generator, and wonder why this has to be?"

I was tooling down the road late one afternoon with no particular place in mind when I spotted a huge rest area totally devoid of other vehicles. Wonderful! Pulled up roughly mid way on the off hwy side and settled in for the night. The sun dropped below the horizon and in those few short minutes of twilight a semi rig pulled in. Yup, you guessed it, he parked directly behind me! And of course, he left his engine and semi-fridge running.  >:(  After I'd been in bed for a bit I said to myself, "Self, this is foolish!" So I got up, lifted the levelers and moved to a spot way behind him and had a quiet night. Guess he was lonely!   ::)
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: New 400 watt solar projeck
Reply #6 –
I'm planning on rebuilding my solar.  I'm thinking 2 300w panels, if I can place them on my 24'.  Definitely going with lithium iron & MPPT.

I'm also considering dropping the generator and making that space into storage.  Is that a pretty common practice here or would folks recommend against it?

thx,

--paul
A 2003 23.5'  'TK
Re: New 400 watt solar projeck
Reply #7 –
Quote from: Kristin Lambert  - 
As recommended on this board, when installing solar panels I insisted on 6 gauge wire so I could add panels later. 

Has anyone successfully ask the mothership to use 6 gauge wire when they install the solar?  I’d happily supply them with a spool of the heavier stuff.
Dave

2017 TK
Re: New 400 watt solar projeck
Reply #8 –
I completely agree with Steve. Suggest you use 10 gage wires to route each panel to the fridge chimney before it goes down. At that point, use a 4 to 1 harness to combine the wires into one pair of gauge 5 wires to the MPPT charge controller. Maybe you are already planning this.
2004 Mid Bath,
2007 Jeep Liberty Towed
Re: New 400 watt solar projeck
Reply #9 –
Quote from: Dave Katleman  - 
Has anyone successfully ask the mothership to use 6 gauge wire when they install the solar?  I’d happily supply them with a spool of the heavier stuff.

Not for the solar drop-line but when I ordered my MB, Todd agreed to run a 4 gauge zip cord from the battery compartment to the upper cabinet next to the tv.  I supplied the 4 gauge zip cord (purchased at Powerwerx) and he charged me $150 to install it.  As you would expect from LD, it was fastened down with plenty of cable tie downs.  The extra heavy duty cable will be used to deliver power to my “yet to be built” ham radio shack on the drivers side of the back lounge.

Dave - Bottom line is, Todd was open to installing the heavy duty wire for me, although it was the only off-menu item I requested.  I would think that if you supplied the wire, he would be open to installing a heavy duty solar drop-line.

- John
Fulltimer with a 2021 MId-Bath “Babe”, 1996 Cherokee “Scout” and “Bandit” the wonder dog 🐶
Re: New 400 watt solar projeck
Reply #10 –
Quote from: Matt Jones  - 
Thanks Steve. The 10 gage wire length to the controller is less than 10 feet. AM solar led me to think that the series and MPPT was gonna let me add more solar  without having to upgrade the existing 10 gage.  The shading issue was never brought up.  One thing with parallel is there are more wires to manage on the roof and more MC-4 connections to manage that are stiff and bulky.  There is usually some shade wherever we go as we typically camp in the mountains.

Thank you again,

Matt
The problem here is not only voltage drop in the wires but also the shadow effects on any single panel which would create a bottleneck for the current flow for the series configuration. Whenever there is a shadow on a single panel, the total in series current flow is controlled by that panel under shadow. The voltage of that panel could also be much lower. If you wire your panels in parallel, each panel's current flow is independent to the other panel. I have 6 100W panel on my 2004 MB, one panel could be under the shadow of the batwing tv antenna but it does not affect the output of other panels. In addition to the merge harness, your MPPT current handling capacity will need to be larger.

I also mount the 2nd row 3 panels at higher elevation when tilt than the first 3 panels to avoid shadows in the early morning of the evening hours. Shadows are big enemy to solar power generation.
2004 Mid Bath,
2007 Jeep Liberty Towed
Re: New 400 watt solar projeck
Reply #11 –
Interesting, AM Solar never mentioned that (shading) and encouraged me to go with a 50A MPPT and the 4 panels in series. Right now I have the 3- 100 W in parallel and 6.7 A is as high a current I have seen.  I am in Torrance CA.  I also added a Victron BMU, Battery Monitor, blue toothed. That has been a nice add. I wrestled the BMV into the battery compartment. Because of potential corrosion you cannot have the BMV in the compartment with flooded batts. They need to be lithium or AGM. I bought Lifeline AGM's, $840.00, ouch. They were hard to find.

Thank you,

Matt
2002 MB
Re: New 400 watt solar projeck
Reply #13 –
Quote from: Matt Jones  - 
Right now I have the 3- 100 W in parallel and 6.7 A is as high a current I have seen.  I am in Torrance CA.  I also added a Victron BMU, Battery Monitor, blue toothed. I bought Lifeline AGM's, $840.00, ouch. They were hard to find.
Are you seeing that current with you charge controller readout or the battery monitor? If the former, keep turning on lights and 12V appliances until the current no longer goes up - that is your solar capacity of the moment. If the battery monitor, with AGMs, see if the voltage is less than 14V. If so, and little else is drawing power, then this is about your solar capacity. If 14V or more, your charge controller will enter voltage limited absorption mode, and the batteries are limiting charge current. If you had lithiums, they would continue to accept a higher current until fully charged or the controller shuts off.

With lithiums and 300W of solar in the SFV, I am seeing a maximum of about 10A this time of year.

Steve
2004 FL
2013 Honda Fit
Re: New 400 watt solar projeck
Reply #14 –
Quote from: Matt Jones  - 
Right now I have the 3- 100 W in parallel and 6.7 A is as high a current I have seen.

Three 100W panels in parallel can produce as much as 21 amps; 3 panels in series will only produce 7 amps max. Perhaps you meant to say your panels are in series?
2005 Jayco 24SS
Re: New 400 watt solar projeck
Reply #15 –
Quote from: pbgiese  - 
I'm planning on rebuilding my solar.  I'm thinking 2 300w panels, if I can place them on my 24'.  Definitely going with lithium iron & MPPT.
I'm also considering dropping the generator and making that space into storage.  Is that a pretty common practice here or would folks recommend against it?

Panels in the 100-200 watt range are available in a variety of sizes that will fit in places where 300-watt panels are too large.
Make of measured diagram of your LD' roof, including vents, A/C, antennas, and any other protrusions.
Use it to see what commonly available panels will fit before ordering anything. Our 24' FL has 545 watts of solar and with better planning, 600-watts would be doable. The largest panel is a 160-watt.

I know of few that have removed operational generators. Solar cannot run the roof A/C, a consideration in the summer and it also fuctions as a backup generator at home.
With lithium batteries getting cheaper, engine-alternator charging systems may become more common, with generator bays filled with lithium batteries. Someday.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: New 400 watt solar projeck
Reply #16 –
Quote from: Eric Greenwell  - 
Three 100W panels in parallel can produce as much as 21 amps; 3 panels in series will only produce 7 amps max. Perhaps you meant to say your panels are in series?
I believe as Matt has JUST installed them, his figures reflect winter conditions. The sun is striking at a pretty shallow angle and will not produce nearly as much as in summer.

Steve
2004 FL
2013 Honda Fit
Re: New 400 watt solar projeck
Reply #17 –
Are the two panels installed by the factory wired in series or parallel?

Is there a data sheet for the panels available?
2013 27’ Mid-Bath
2005 Honda CR-V
Re: New 400 watt solar projeck
Reply #19 –
Quote from: Keith Sweitzer  - 
Are the two panels installed by the factory wired in series or parallel?

Is there a data sheet for the panels available?

Quote from: Keith Sweitzer  - 
Are the two panels installed by the factory wired in series or parallel?

Is there a data sheet for the panels available?

Quote from: StevenJill  - 
I wanted to read up on the parallel/series thing with Solar panels. I found this to be good.
What’s The Difference Between Wiring Solar Panels in Series or Parallel? |...
One problem with the article is that it did not point out that using an MPPT controller will give the same early morning - late day performance from parallel connection as you have with serial connection. It will maximize available power even if panel voltage is low. Another advantage of serial connections not touched on - but primarily for off-grid systems - is being able to mount the array far from the controller, such as in the middle of an open, unshaded field. A large serial array could have an output of a thousand volts or more, which would have low losses sending power to the inverter for the same reason high tension overhead wires are used in the power grid. The solar array on our house roof uses a combined system - their outputs are all wired in parallel, but each of those outputs includes a 'microinverter' producing 240VAC split phase. So, all the roof wiring all the way to the house load center is at 240VAC.

Another important point for off-grid and RV solar is that if all the batteries are charged up and you are not using anything in the RV, all that potential solar power is idle - and you can't save it for later... The solar on our house roof is grid-tied - it is always producing the full power the sun is providing, and sending to the grid whatever energy we don't use. This accumulates as excess watt-hours credited that we can tap into on cloudy days in the winter, for instance. It is like a huge storage battery...

Steve
2004 FL
2013 Honda Fit
Re: New 400 watt solar projeck
Reply #20 –
Thanks to all. I have three 100 W panel (nearly square 30"x30") and nearly above booth the batteries and the PWM controller.  i purchased the Grape solar panels at costco(easy return if necessary). The panel are fairly light and I do not believe rated for hale. The sun is really low now at my house. Shade seems to be the more significant condition. A little shade and 4 amps will will drop off immediately. I'm reading the amps at the controller. The BMV will typically indicate lower amperage.

Matt
2002 MB
Re: New 400 watt solar projeck
Reply #21 –
Solar panels are rated artificially at 1 sun (~1000W/sq m), about noon at the equator, and about 72F. In real life conditions, a quality panel has an anti-reflection coating allowing it to collect nearly 100% of incident solar energy and an efficiency ~20%. This means 80% of the absorbed energy is converted to heat - which degrades the performance substantially. Additionally, if panels are mounted horizontally and the sun at apogee is at 45 degrees from the vertical, the panel will only receive a 71% of the energy it would receive were it tilted 45 degrees to the south. So, the power rating of these panels is only useful for comparing panels. There are ensolation sites on the internet that can help when determining real-world performance you can expect. And, this is assuming using an MPPT controller.

Steve
2004 FL
2013 Honda Fit
Re: New 400 watt solar projeck
Reply #22 –
Another point to emphasize is do not mix solar panels with different voltage or current ratings or different ages. When upgrade solar system, the best practice to keep new panels and old panels on separate charge controllers. The older or lower rated panels will reduce the whole system performance if wired together through a single charger controller.
2004 Mid Bath,
2007 Jeep Liberty Towed