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Topic: Solar Panels on roof, wondering what size output they are (Read 1803 times) previous topic - next topic
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Re: Solar Panels on roof, wondering what size output they are
Reply #25 –
If your charge controller is the Heliotrope RV30, 30 Amp non-MPPT controller, the output voltage will only tell you the battery voltage. You need to monitor the voltage at the INPUT side of the controller, and multiply that times the current to get the power output of the panel mounted on the roof. Maximize the current drawn by turning on lights and fans until the voltage drops to less than 13 Volts before measuring the current.

There are three types of charge controllers:

1) Shunt controllers simply connect the panels to the batteries and allow the batteries to drop the panel voltage when the panels cannot supply the current the batteries will accept. When the battery voltage rises above about 14.3V, the controller shuts off until the battery voltage falls - which is quickly - and then turns back on - and off - and on.... Not common any more.

2) PWM controllers, pulse-width-modulation, such as the RV30. These switch the output of the panels on and off very rapidly to control the output voltage, once the panels put out more power than the rig and batteries can use. At that point the output voltage remains constant, so no light flickering, etc. More sophisticated than shunts, but maximum current is limited by the spec of the panels.

3) MPPT controllers, maximum-power-point-tracking. These controllers do a power conversion using PWM technology with a transformer to allow the panels to deliver their maximum potential power. The output Amps delivered is actually higher with this type of controller than what is coming from the panels, when the demand is there, charging the batteries faster.

Steve
2004 FL
2013 Honda Fit
Re: Solar Panels on roof, wondering what size output they are
Reply #26 –
Quote from: Steve  - 
The output current you read is NOT the panel output, but the Blue Sky output to the batteries and accessories. Although there is some small conversion inefficiency, it is a pretty close approximation of the current output power of your panels
Thanks all, I think I understand what you guys are saying, I had to read all the posts twice but I'm pretty sure I get the watt/amp/volt relationship now, and how the controller changes things too. Question regarding the above quote from STEVE; on the 3000i you can read the "amps in" and "amps out" on the dial when you scroll through all the display points. I understand how you say the controller changes things because it is feeding the volts necessary to the battery so the amps have to go up, but are you saying the "amps in" reading is already adjusted for the volts necessary to go to the battery? Even though it says "amps in" (meaning amps in from panels right?) it really is just an amps in reading based on the adjusted voltage, not a true amps in reading? If that is the case why does it read that way? If you have a display for amps in and amps out, what would be the reason for not showing true amps in and then adjusted amps out?
Thanks for the education guys, I promise I'm watching videos while talking to you all too; trying to understand all aspects before I start on the project.
John
1999 26.5 Rear Bath
Re: Solar Panels on roof, wondering what size output they are
Reply #27 –
Hi John;  The SB3000i tracks the best power point dynamically. Many times per second.  The 'Amps in' is what it is receiving from the panels. The 'Amps out' is what is going into the batteries. The difference, minus some power to run the controller, and some conversion loss, is to show you what the gain in power is, due to the MPPT feature. A bit of advertising there I think.  One trick is that early dawn, before the panels are even putting out 11 volts, you can have current being put in to the 12 volt batteries. It takes about 12 volts to put current into lead acids at 10 volts.  LiF batteries take higher voltages but because of their low impedance (willingness to accept current) just a little bit of higher voltage allow current to flow into the LiF batteries.  MPPT is a small extra cost that will provide dividends in extra power generated and saved.  RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Solar Panels on roof, wondering what size output they are
Reply #28 –
"what would be the reason for not showing true amps in and then adjusted amps out?"

That's exactly what it does. The "amps in" reading is just that: the amperage from the panel, at whatever voltage it's putting out. And "amps out" is what's going into the battery, at the voltage it wants to see for charging.

Let's say (assuming lots of sunshine) that it's a 100 W panel putting out 5.5 amps at 18 volts. That's a fairly common spec. So the "amps in" reading will be 5.5. The MPPT controller converts that into 7 amps at 14.3 V--higher amperage but lower voltage--in order to bulk-charge your batteries. So the "amps out" reading will be 7.0.

As Ron said, it's not strictly necessary to show amps in from the panels, since all you really care about is what's going into the batteries. But it's always nice to see that the MPPT circuitry is doing its job. MPPT used to be a deluxe, extra-cost feature, but now it's so widespread (I've seen it in $40 controllers) that it's not worth considering anything else. From what I and others have seen, MPPT can get 10%–30% more power from a given solar array than either a shunt or PWM controller.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Solar Panels on roof, wondering what size output they are
Reply #29 –
Awesome, thanks guys, I must have misunderstood what STEVE was saying in his post, but it looks like I had the right idea on the "amps in" and "amps out" reading. Looks like I got a cool job to undertake when we get back from our trip. Heading out to NC for a week with friends, do some sight seeing on the way there and the way back; new brakes, new tires, and gonna do some solar tracking with the cool new battery monitor to figure out just how many watts we really need on the rig. Thanks everybody for all the help, you rock!
1999 26.5 Rear Bath
Re: Solar Panels on roof, wondering what size output they are
Reply #30 –
Solar guidance,
94-TK 22.6 length.
Thinking about adding a solar panel from Rich Solar to my Daze. Panel info- One - 250W panel with a Victron Charge controller - MPPT 100 /30
The Rich panel size is L 62 x W 36
I will attach between the escape hatch & AC unit. I have a few inches of space  bathroom skylight and the placement and panel. 
The 22.6 does not have space on the roof for more panels considering space.
I suppose if there is a 14” x 20’ solar panel that could possible fit on the passenger side of the Daze.

My daze has 2 GC2 Interstate batteries.
 Question, what are the different ways to get the cables to the batteries considering my layout.
Oh, I do not have a generator.  I do have a BLUETTI for the eBike, phones etc..
Thank you for your comments in advance. I do plan on purchasing a new cigarette lighter inverter for the TV.
1994 Twin King
Re: Solar Panels on roof, wondering what size output they are
Reply #31 –

Hi Chris;  I have a '99 TK on the Ford E350 chassis.  Your roof should be pretty close to the same dimensions as mine with just the shorter 'snout' of the GM chassis accounting for the shorter overall length of the rig. Mine is 23.5'.
   I put three  100 watt Renogy panels between the roof vent and A/C unit. As far over to the passenger side edge as possible, and lifted up to minimize shading from the escape hatch and A/C unit. ( and also the whip CB antenna, and radio antenna).  That Renogy panel also comes in a 1/2, 50 watt size, and it is next to the escape hatch on the passenger side. Another 100 w panel is prewired for behind the refrigerator vent along side the A/C unit. 4" stand up there to be at the same level as the railing/ladder. (panel not installed yet).
   I ran the wiring using a 'J' box through the side of the refrigerator vent on the forward inside edge. Down through the refrigerator area, close to the boiler tube. Stay as far from that as possible, it gets hot!  Down through that 'fridge floor and into the battery compartment area. 
   With no generator, is there anything else there? Storage compartment?
   I ran a flex conduit through the floor inboard of the battery box, but inside the vanity cabinet. Behind, inboard of the step, underneath the rig to the forward side of the coach door step well area, and back up into the space aft of the side cab door. That may be Ford specific.  I put my Solar Boost 2000 in the wall at about 4 feet up, which provides good visibility from the kitchen and driver side couch.  The controller was later upgraded to to a SolarBoost 3000i (Thanks Kent!) to handle more current when I went from my original 11% efficient panels (148w 3 panel) to the Renogy 22% efficiency 3 (300w) panel upgrade.  There was enough depth at that location and empty space to accommodate wiring and air cooling. As part of that I recessed the fire extinguisher into the wall, and used that hole (extinguisher insert removed) to work on the conduit/wiring. I used 8AWG at the time 23 years ago.
   Walking on the roof is a tight space around the bathroom vent.  RonB
   Amazon/ Renogy 50W is 23"x20"  Amazon.com : Renogy 50 Watt 12 Volt Monocrystalline Solar Panel (Compact... 

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Solar Panels on roof, wondering what size output they are
Reply #32 –
More panels are better than bigger panels, i.e. a pair of 125W panels is better than one 250W model. Even a small amount of shading on one panel can kill most of its output, and shade on and off is nearly impossible to avoid most places.

Steve
2004 FL
2013 Honda Fit
Re: Solar Panels on roof, wondering what size output they are
Reply #33 –
Quote from: ChrisB  - 
The 22.6 does not have space on the roof for more panels considering space. 

First, your T/K is a 22', assuming it is on a Chevy chassis. The Ford T/Ks are 23.5’ long.

Dave Kettlemamn’s T/K has, I believe, 800 watts of solar,  it’s all about the layout.
Our short 23.5' Front Lounge has 560 watts of solar plus kayak racks. If the roof was reconfigured, at least 700 watts of panels could be installed.
As Ron pointed out, panels come in a wide range of sizes.They can be mixed to maximize the available power as long as all the panels have the same output voltage.
Steve pointed out that having several panels distributed across the roof reduces the influence of shading.

If your LD came from the Factory with a panel, the original solar controller box can accommodate a Blue Sky 30001, it’s good for about 500 watts of panels. The stock 10 gauge solar wiring should be upgraded if exceeding 200 watts to reduce voltage drop.

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: Solar Panels on roof, wondering what size output they are
Reply #34 –
Quote from: Larry W  - 
First, your T/K is a 22', assuming it is on a Chevy chassis. The Ford T/Ks are 23.5’ long.

Dave Katleman’s 2017 T/K has, I believe, 800 watts of solar,  it’s all about the layout.
Our short 23.5' Front Lounge has 560 watts of solar plus kayak racks. If the roof was reconfigured, at least 700 watts of panels could be installed.
As Ron pointed out, panels come in a wide range of sizes.They can be mixed to maximize the available power as long as all the panels have the same output voltage.
Steve pointed out that having several panels distributed across the roof reduces the influence of shading.

If your LD came from the Factory with a panel, the original solar controller box can accommodate a Blue Sky 30001, it’s good for about 500 watts of panels. The stock 10 gauge solar wiring should be upgraded if exceeding 200 watts to reduce voltage drop.
I have 850 watts (5 170Watt panels)

Had the TV antenna removed, along with the original Lazy Daze panels to maximize what I could put up there.   You do want more panels than a couple big ones, as any shading of a panel turns the whole panel off.

The Victron inverter, MPPT, and four Lithium batteries were tucked in under the passenger side couch, losing roughly half that bay, but freeing up the default battery bay.

I have considered removing the generator and placing another bank of batteries there, freeing up a bit of weight and eliminating the monthly running of the generator.  Haven’t needed it in either trip to Alaska or Newfoundland. But I’m too lazy to do it.
Dave

2017 TK
Re: Solar Panels on roof, wondering what size output they are
Reply #35 –
That's a sweet setup, Dave!
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Solar Panels on roof, wondering what size output they are
Reply #36 –

Hi Chris;  So I'm going to reconsider my message to you. You asked how I ran things, wiring and panel. I came up with what I did. But what you should do may be a lot different!
   The panel is good.  The Rich Solar 'Mega 250' is essentially two panels in the same package. They are 33 cells in series each, and internally connected in parallel. Monocrystalline is good. 21% efficiency is good. Rich lists it at 60.6" x 30". It is just about a perfect fit.  I spaced mine up at about 3.5" high to clear shadows and get air circulation underneath.
   The Victron is a little overkill, but that's usually a good thing. MPPT is a very good thing to maximize your solar. Victron is a good brand.
   Essentially you asked how to run the wiring. This a "J" (junction box):  https://www.homedepot.com/pep/1-2-in-Rigid-Type-LR-Threaded-Conduit-Body-with-Cover-and-Gasket-58905/100173062?source=shoppingads&locale=en-US&pla&mtc=SHOPPING-CM-CML-GGL-D27E-027_006_CONDUIT_FIT-NA-NA-NA-PMAX-NA-NA-NA-NA-NBR-NA-NA-NEW-NA_2024_WHU24&cm_mmc=SHOPPING-CM-CML-GGL-D27E-027_006_CONDUIT_FIT-NA-NA-NA-PMAX-NA-NA-NA-NA-NBR-NA-NA-NEW-NA_2024_WHU24-71700000118279170--&gad_source=1&gclid=Cj0KCQjwzva1BhD3ARIsADQuPnWFe1zBNWvR3gBJ913xyGvLZE18Cmu_wWqMaATuKy_6SOIFuOjLn48aAtSMEALw_wcB&gclsrc=aw.ds  and two nipples. One to go through the side of the refrigerator roof vent, and another to go into a bell box to connect the wiring from the one panel. The Bell box and 'J' box have removable waterproof covers. They can be just glued onto the roof with sealant. I put a screw into the roof inside the box, and sealant. Nipple (a coupling): https://www.gordonelectricsupply.com/p/Garvin-Bb-1-2-1-Box-Spacer-Connector/6255254?gad_source=4&gclid=Cj0KCQjwzva1BhD3ARIsADQuPnVKRsQlsnFhb-r5xa0bkkoUrEFwlz77fSzxMbVYS5X4LMLNcVqPkl4aAlv2EALw_wcB  . Use aluminum J box and Bell Box. They hold up to sunlight. I use the J box to fit under the plastic refrigerator vent. It is lower than the Bell Box, about 2" high.  Run the wires from the panel into the side of a single box. I'd cut the solar connectors off, run the wires all the way into the refrigerator space. Splice them there, to run down to behind the drawer. Split wire loom taped solid and screwed onto the wood using a few clamps.  LOKMAN 20 Pack 1/2 Inch Stainless Steel Cable Clamp, Rubber Cushioned.... Use this for the wiring. BEWARE of Copper Clad, cheap and worthless in my opinion. Amazon.com: GS Power Flexible 10 AWG (American Wire Gauge) 50 Feet Stranded... This is solid copper, fine stranded for flexibility. It will run down on the outside of the back of the refrigerator, just inside the outside door, and under into the drawer area (drawer out.) No holes in the refrigerator!  Caulk the holes so carbon monoxide from the refrigerator flame can't get into the motorhome. You should be able to mount the Victron controller under there some where, (see picture) and a circuit breaker about 25 Amp for the Victron connection to your battery terminals on your power distribution box.  Amazon.com: GLOSO Circuit Breaker 30 A E69 for Marine Truck Boat RV Automotiv...     (Lazy Daze used a ten amp fuse  holder, but you need more. Label the wires "solar controller".
   I highly recommend upgrading your Magnetek old fashioned converter to a Progressive Dynamics 4 stage battery charger/ converter.  I get my split wire loom at Harbor Freight.   RonB

As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Solar Panels on roof, wondering what size output they are
Reply #37 –
Quote from: Larry W  - 
If your LD came from the Factory with a panel, the original solar controller box can accommodate a Blue Sky 30001, it’s good for about 500 watts of panels. The stock 10 gauge solar wiring should be upgraded if exceeding 200 watts to reduce voltage drop.

Larry

Larry,
My LD came from the factory with BS3000i and 230w of solar.  I have since added 200w more to make 430w. Do you think LD upgraded the solar wiring in my model?  Should I upgrade it? And if so, are you talking about the 3ft or so of wire that goes from the roof junction box to the Blue Sky controller?  On a RB, that is a relatively easy change.  If you're talking about from the controller to the wiring center, that is nearly impossible as it is run underneath the floor.
Linda
Linda B
Green 2021 RB
2022 Ford Maverick toad
Re: Solar Panels on roof, wondering what size output they are
Reply #38 –
Linda, upgrading the feed may not offer much improvement, but if you decide to, then there is always an option to re-route to a more accessible path.

Steve
2004 FL
2013 Honda Fit
Re: Solar Panels on roof, wondering what size output they are
Reply #39 –
That's an interesting question. Here's my take:

1. For a given wire gauge, the higher the voltage, the lower the voltage drop. Power coming down from the panels to the charging controller is at about 18 volts; power going from the controller to the batteries is at about 13 volts. So upgrading the wire from the controller to the batteries should give more benefit, at least in theory.

2. The longer the wiring run, the more of an effect voltage drop will have.

3. If there's voltage drop in the wire from the panels to the controller, that's a waste, but the controller will still send out the appropriate charging voltages to the batteries. However, if there's voltage drop between the controller and the batteries, the batteries may not receive the necessary voltage for a full charge... unless there's a voltage sensing wire running back to the controller. Such a wire can let the controller know when the batteries aren't getting what they're supposed to be getting, so it can boost its output voltage to compensate. But not all installations have such a wire, and lacking one, voltage drop in the run from the controller to the batteries is much more serious.

All of the above points to the conclusion that if you're going to upgrade wiring, doing it to the wiring run from the controller to the batteries will be more beneficial. It's unfortunate that that's a more difficult job, but perhaps as Steve said, you can find an easier (and hopefully shorter) route for that cable.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Solar Panels on roof, wondering what size output they are
Reply #40 –
Hi Andy; if the solar controller is mounted under the refrigerator, the wires to the power distribution panel is about two feet. Directly to the batteries can also be about a foot or two. The space beside the drawer might be the best locarion for access. The down wire at 10 ga. Is what the panel(s) come with and again are pretty short from the refrigerator vent to below the fridge support shelf.  RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Solar Panels on roof, wondering what size output they are
Reply #41 –
"if the solar controller is mounted under the refrigerator, the wires to the power distribution panel is about two feet. Directly to the batteries can also be about a foot or two."

True, and that's what I did in my midbath. But from what Linda said, it sounded as if in her rig, the factory used three feet of wire from the roof to the wall-mounted Blue Sky controller, and then a presumably much longer run from there under the floor to the wiring center. To mount the solar controller under the fridge as you suggested would be a better solution electrically, but it would require a different solar controller--one with either a wired remote panel (e.g., Morningstar) or wireless control via Bluetooth (e.g., Victron Smart Solar). Either one would likely cost a couple hundred dollars.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Solar Panels on roof, wondering what size output they are
Reply #42 –
Sorry Andy; My reply was about ChrisB's '94 T/K (reply #30) and a simple addition of a 250W panel and controller with no other  mods.  Linda of course with a RB floorplan would be a better choice for an all-out install with LiF batteries. etc.    RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Solar Panels on roof, wondering what size output they are
Reply #43 –
"My reply was about ChrisB's '94 T/K (reply #30) and a simple addition of a 250W panel and controller with no other  mods."

Oh, I get it. Well, for what it's worth, here's what I did when mounting a solar controller under my midbath's fridge. I hope the general ideas here will translate to a twin/king layout.

First I build a "breadboard" and mounted all components to it, then wired them together. It's much easier to do it this way than to try to do all the wiring while lying on the floor. With that done, I mounted the breadboard to the "ceiling" of the space under the fridge and completed the wiring.

The attached photos show the breadboard setup, and then the same thing with labels. You'll notice a couple of things. At lower left and lower right there are terminal blocks (Blue Sea PowerPosts). I used them because the Victron controller can only accept a maximum wire size of #6, but I used #2 wire coming down from the panels (600 watts in this case) and going out to the batteries, in order to minimize voltage drop. The PowerPosts let me make the transition from those long #2 runs to a few inches of #6 cable going into the controller.

In other installations I've handled this issue by clipping strands on the last new inches of a larger gauge cable to get it down to a size that will fit in the Victron controller's small terminals, instead of using PowerPosts, but that's frankly a pain. Also, I needed a terminal block on the input side anyway, because I had to be able to combine wiring from the roof panels with wiring from portable panels. I know I've banged this drum before, but I find portable panels to be indispensable in situations like mine right now: camping in a forest, where my roof is mostly shaded but I have a 200 watt solar suitcase set out in a clearing, where it catches the full sun.

You'll note that the positive line from the roof panels is switched on the breadboard. The portable panels are switched elsewhere, where that line ends in MC4 pigtails that allow connecting the portable panels when needed.

Hope this is helpful!

X
X
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
Re: Solar Panels on roof, wondering what size output they are
Reply #44 –
P.S.--I'm sorry about the lack of sharpness in those photos. I had to apply extreme JPEG compression (19/100) to get the files below the stated 49K maximum size. Can that be changed? I'd say 150K per image would be more realistic.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
 
Re: Solar Panels on roof, wondering what size output they are
Reply #45 –
One more note: you can't see it in the photos, but I mounted the Victron solar controller using 3/4" standoffs, so that there's a good air gap behind it. No sense letting it get any hotter than it has to, especially when mounting it in a confined space.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"