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Thread: Help me oversize my solar panel system for 600w

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    Help me oversize my solar panel system for 600w

    I have probably read every solar thread on the site; so much so, I know stuff but canít find the source for why I know it. Iím installing solar on a Reflection 320MKS 5th wheel that has a 10 degree roof down slope where most of the panels will go. Iím trying to calculate how much I need to oversize my panels for 50 amps into my 12V system (600w). Most of my boon docking trips will not be in un-shaded Nevada summer sunlight. I know I will get different performance pointed north than pointed south. I also have spent way too much time positioning my unit for my direct TV disk to have clear view of the southern sky to know it is hard not to be in some shade.

    That is a lot of preamble for a simple question of how much! This question is to those that have solar installed. What have you experienced? How much panel wattage do you have installed and how many amps are delivered to the batteries? What were the conditions; direct sun, full shade (heavy forest), partially shaded, summer sun, winter sun, RV type and roof slope? I would appreciate it if you could quantify as much as you can and share your experiences.
    Bill & Marsha
    2020 Reflection 320 MKS
    2018 2500HD Silverado 4x4
    Not All Who Wander Are Lost

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    Quote Originally Posted by wjpatter View Post
    I have probably read every solar thread on the site; so much so, I know stuff but can’t find the source for why I know it. I’m installing solar on a Reflection 320MKS 5th wheel that has a 10 degree roof down slope where most of the panels will go. I’m trying to calculate how much I need to oversize my panels for 50 amps into my 12V system (600w). Most of my boon docking trips will not be in un-shaded Nevada summer sunlight. I know I will get different performance pointed north than pointed south. I also have spent way too much time positioning my unit for my direct TV disk to have clear view of the southern sky to know it is hard not to be in some shade.

    That is a lot of preamble for a simple question of how much! This question is to those that have solar installed. What have you experienced? How much panel wattage do you have installed and how many amps are delivered to the batteries? What were the conditions; direct sun, full shade (heavy forest), partially shaded, summer sun, winter sun, RV type and roof slope? I would appreciate it if you could quantify as much as you can and share your experiences.
    Please note, any advice given in this post is purely hypothetical. You will need to do your own research and make sure it is correct.

    There are a number of questions (items) that came up as I read your OP.
    1. What is the TOTAL KWH (Kilowatt hour) or WH (watt hour) of everything you will be using at one time. For example: A/C + Microwave + TV + Satellite + lights + recliners, etc. Each device has a WH rating, Watts is the amount of energy that is used by the device for 1 hour. A Coleman Mach 15 A/C unit has a maximum of 1,900 watts, running, this does not include starting. (I would recommend replacing the capacitor with a Soft Start system). You can calculate the amount of amps based on the following formula: P=IE Or Power (watts) equals I (volts) times E (amps). In the case of the A/C unit, P=1900, I=120VAC. To get the amps (E), you would divide P by I; 1900/120=15.83 amps/hr. This is important because you need this total number of watts and amps to appropriately size your solar system. (This is going to apply to a sticks and bricks house as well.) Then ADD 20% for "wiggle room".
    2. Once you have the total watts and amps you would use at any one point in time, plus 20%, then you can size the battery portion for that number. For us, that number is 400 AHr, 4 BattleBorn 100 AHr batteries.
    3. Once you know that total, NOW you can size the solar panels in watts. So, using the same formula as above, P=100AHr * 12VDC; P=1200 Watts. Plus the 20%, you would need approximately 1400 Watts of Solar to charge 1 100 AHr battery from empty to full in 1 hour. We usually spread this out over 6 hours of total sun exposure so, for 400 AHr, the formula changes a little bit: P=(IE/6) or, to short cut it a little bit, P/6; 1400/6=233.33 Watts. What that means is it will take approximately 233.33 watts of solar, over 6 hours of continuous, direct sunlight to charge a battery from empty to full. You can change the duration of sunlight exposure to anything that you are comfortable with. Maybe change it to 4 hours of direct sunlight, then P becomes 350 watts.
    4. You need to size the wire appropriately for the length that each run will travel to the combiner box, then to the Charge Controller. See https://www.renogy.com/calculators for additional details on that.


    So, it's not really an easy answer to your question, without knowing more specifics.

    As for the Charge Controller, you will definitely want a MPPT Charge Controller, NOT a PWM controller. See https://www.renogy.com/blog/what-is-...e-controllers/ for more details.

    As for directional pointing, you can do that, but now you are adding much more weight to your roof and coach. I just plan on mounting them flat, with enough wattage to cover the discrepancy... I.E.: that 20% overage.

    For 6 BattleBorn batteries, use the same formulas above to come up with your total wattage output from solar. Once you have that, then you have to decide on the type of panels. Monocrystalline is the way to go there, but, now, do you want 28 50W panels, 14 100W panels, 7 195W panels, 5, 280W panels? Each has their own positives and negatives, primarily being the size and weight of each panel. You could also go with an industrial panel that has 1000W, but there is likely nowhere on your roof to mount it.

    Hope this helps, and sorry for getting technical, but there is no way to avoid doing so in order to convey the information properly.
    Mark & Mary. Currently hailing from New Mexico. Hopefully full timing in late 2022.
    Current camper: Purchased a 2021 DG Reflection 320MKS!
    Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel

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    Quote Originally Posted by wjpatter View Post
    I have probably read every solar thread on the site; so much so, I know stuff but can’t find the source for why I know it. I’m installing solar on a Reflection 320MKS 5th wheel that has a 10 degree roof down slope where most of the panels will go. I’m trying to calculate how much I need to oversize my panels for 50 amps into my 12V system (600w). Most of my boon docking trips will not be in un-shaded Nevada summer sunlight. I know I will get different performance pointed north than pointed south. I also have spent way too much time positioning my unit for my direct TV disk to have clear view of the southern sky to know it is hard not to be in some shade.

    That is a lot of preamble for a simple question of how much! This question is to those that have solar installed. What have you experienced? How much panel wattage do you have installed and how many amps are delivered to the batteries? What were the conditions; direct sun, full shade (heavy forest), partially shaded, summer sun, winter sun, RV type and roof slope? I would appreciate it if you could quantify as much as you can and share your experiences.
    I know I can edit my post, I have already done that, but I would like to address your last paragraph.

    So, with any Solar system, it will depend on the amount of direct sunlight each panel receives and the duration of that direct sunlight. The slope of the roof doesn't matter as much as say, 50% of the panels in shade. Here is a good article on shading: http://www.pvresources.com/en/sitean...nganalysis.php.

    It goes into much more depth that I am willing to here in the forum.

    So, it comes down to your total wattage and AHr use, both during the day and after sundown. After sundown, it comes down to your battery bank, during the day, is a combination of your battery bank (how much it needs to be recharged) and how much energy you use.

    Unfortunately, there is no "one-size-fits-all" for solar. It is unique to each installation and use case.
    Mark & Mary. Currently hailing from New Mexico. Hopefully full timing in late 2022.
    Current camper: Purchased a 2021 DG Reflection 320MKS!
    Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel

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    For what it is worth there are other expert sources for information that you need to look at and possibly ask question of. The GD forum (Find on GD web page under technical help) and the GD solar power forum on Facebook. Arizona Wind and Power also has some great information on their web page. Amsolar.com is another source too and has complete kits just like Arizona Wind and Continuous Resources. I have used all in getting information on my system upgrade - even though I did not buy from all of them.

    So in a nut shell the answer to your question is - It Depends

    I am in the process of upgrading my own set up. I am using 8 awg PV cable. Continuous Resources carers it with matching 8 AWG MC4 connectors, You can also find it on TEMCo web site (back in stock soon) and I think Arizona wind and power has it. What controller (s) are you planning. MPPT would be the way to go to max you solar output. Are you going series or parallel, or a combination (recomended)? What type of battery bank are you using? You need a solar controller that can work with the battery's you select. Also be sure you units convertor will work with selected batterys. GD stock WFCO will not work with Lithium. If lithium look at the Progressive Dynamics units. Panels should also be on switch and fused connections so they can be disconnected if needed. Blue Sea has some great circuit breakers and switches that folks use.

    Bottom line - Panels, solar charger, battery's, and your wiring will all effect you solar performance.

    Last - all solar panels are not created equal. Look at the specifications carefully. In some cases 2-100 watt panels will out perform one 200 watt panel (series connection). Buy from a trusted source. Also in choosing your solar controller, DO NOT just consider volt and amp specifications. You also must meet the max PV voltage specification. This is critical or the MPPT controller will trim the PV input to what the unit can handle, or damage the unit and possibly the panels if things fail.

    BTW I am in no way and expert and learned a lot of this the hard way. Ask a lot of questions and read and learn.

    Hope this helps
    Last edited by powerscol; 02-07-2021 at 01:05 PM.
    2018 Reflection 150 Series 220RK 5th wheel. Reese R20 Titan hitch, Steadyfast system, 2004 F350 6.0 Diesel King Ranch dually, Trailer reverse lights, rear spare tire holder, storage tube

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    Quote Originally Posted by powerscol View Post
    For what it is worth there are other expert sources for information that you need to look at and possibly ask question of. The GD forum (Find on GD web page under technical help) and the GD solar power forum on Facebook. Arizona Wind and Power also has some great information on their web page. Amsolar.com is another source too and has complete kits just like Arizona Wind and Continuous Resources. I have used all in getting information on my system upgrade - even though I did not buy from all of them.

    So in a nut shell the answer to your question is - It Depends

    I am in the process of upgrading my own set up. I am using 8 awg PV cable. Continuous Resources carers it with matching 8 AWG MC4 connectors, You can also find it on TEMCo web site (back in stock soon) and I think Arizona wind and power has it. What controller (s) are you planning. MPPT would be the way to go to max you solar output. Are you going series or parallel, or a combination (recomended)? What type of battery bank are you using? You need a solar controller that can work with the battery's you select. Also be sure you units convertor will work with selected batterys. GD stock WFCO will not work with Lithium. If lithium look at the Progressive Dynamics units. Panels should also be on switch and fused connections so they can be disconnected if needed. Blue Sea has some great circuit breakers and switches that folks use.

    Bottom line - Panels, solar charger, battery's, and your wiring will all effect you solar performance.

    Last - all solar panels are not created equal. Look at the specifications carefully. In some cases 2-100 watt panels will out perform one 200 watt panel (series connection). By from a trusted source. Also in choosing your solar controller, DO NOT just consider volt and amp specifications. You also must meet the max PV voltage specification. This is critical or the MPPT controller will trim the PV input to what the unit can handle, or damage the unit and possibly the panels if things fail.

    BTW I am in no way and expert and learned a lot of this the hard way. Ask a lot of questions and read and learn.


    Hope this helps
    This is good advice. Especially the part about not every panel created equally. Some have N technology , some have great efficiency ratings. Some decide on full unit squares while other cuts the square in half and creates twice the amount.

    There’s no cookie cutter answer , just do the research and buy what is best for you and you budget.

    We went with Newpowa

    https://www.newpowa.com/collections/...cy-solar-panel
    Donna and Dave
    Annapolis, Maryland
    2021 Grand Design Imagine 2500RL / Dodge Ram Longhorn 2500 6.4 Hemi
    350 W Newapower Solar: 3000 Victron Inverter/ Charger: Firefly Oasis carbon foam AGM

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    Quote Originally Posted by wjpatter View Post
    I have probably read every solar thread on the site; so much so, I know stuff but canít find the source for why I know it. Iím installing solar on a Reflection 320MKS 5th wheel that has a 10 degree roof down slope where most of the panels will go. Iím trying to calculate how much I need to oversize my panels for 50 amps into my 12V system (600w). Most of my boon docking trips will not be in un-shaded Nevada summer sunlight. I know I will get different performance pointed north than pointed south. I also have spent way too much time positioning my unit for my direct TV disk to have clear view of the southern sky to know it is hard not to be in some shade.

    That is a lot of preamble for a simple question of how much! This question is to those that have solar installed. What have you experienced? How much panel wattage do you have installed and how many amps are delivered to the batteries? What were the conditions; direct sun, full shade (heavy forest), partially shaded, summer sun, winter sun, RV type and roof slope? I would appreciate it if you could quantify as much as you can and share your experiences.
    First, what Solar panels are you considering buying?

    My recommendation is to purchase the highest Wattage Residential panels you can fit on your roof. The reason I recommend using Residential Solar panels is they are usually higher Wattage per sq inch and are more efficient (20% +/-) than the more common 12 volt RV Solar panels like Renogy, Furrion, or other panels found on Amazon or at a Dealer. The other reason is they are cheap when you calculate the Dollars per Watt, here is an example: I recently found a 315 Watt, Canadian Solar, panel for $173, that works out to only $0.54 cents per Watt. Often you will find Solar panels for 3 or four times that per Watt price.

    Using the higher Wattage Solar panels also saves you effort because you have to install fewer panels to get the same (usually higher) Wattage on your roof. In my case I installed 1,220 Watts of Solar with only four panels (I used 305 Watt Canadian Solar panels). The Residential panels are usually only slightly larger then the 100/200 Watt Renogy or Furrion panels that are popular in the RV community.

    My other recommendation is to not worry about your "down slope" or the orientation of the camper when parking the camper. Just put as much Wattage on the roof as you can fit and let the Sun fall where it will. I say this not to be flippant, but because Solar panels oriented in an East/West direction generate only slightly less energy than panels oriented due South. This is because the Sun hits the East/West panels earlier in the day and produce energy later in the day than South facing panels.

    As far as your goal of 50 amps being available to charge your batteries, forget about that. You will only get the max out of your panels at high Noon on a clear day, every other time of the day you will get less, sometimes much less. That is what your MPPT Solar Charge Controller is supposed to do, it constantly maximizes the energy going into your batteries based on the available Sunlight.

    Bottom line: get as many higher Wattage Solar panels as your Roof (and wallet) can comfortably fit. Mount the panels wherever they fit best on the roof. Don't worry about which direction you park your rig because half of the day you will be facing the wrong direction.

    PS: this information will self destruct inside your mind once you read this last WORD !!!

    PPS: here is a picture of how I mounted my 305 Watt Canadian Solar panels.
    Attached Thumbnails Attached Thumbnails Solar Panels Installed (1).jpg  
    David and Peggy
    2019 Ford F350 Lariat, 6.7L Diesel, Dually, Long Bed
    Running with 20k Reese Goosebox (Love It) and Ford Factory "Puck" system.
    Stopping with 8,000 lb Disc Brakes and Titan Hydraulic over Electric Brakes system.
    Powering all this fun with 1200 Watts of Solar, two Tesla, Model S, battery modules, 24 volt Victron Inverter.
    2018 Solitude 310 GK

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    I think there is an easier answer to your question. I did all the calculations and determined that I need 300 ah of batteries and 400 watts of solar (I used 4.5 hours of sun for my calculations). I series connected them and use an MPPT controller. After a trip to Montana (partial shading) for 6 weeks and a trip to Arizona (full sun at winter angles) for 6 weeks I would have doubled the solar power. Even staying within my energy budget I am running the generator to supplement the solar output and fully recharge my batteries. Now, they are FLA batteries so I worry about a full recharge more than lithium but the point is the same.

    So my advice is to take whatever your solar panel calculation says and double it with at least 2 strings of higher voltage on a MPPT controller.

    Just my experience...

    Brian
    Last edited by Scramjet; 02-09-2021 at 01:07 AM.

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    Thanks guys for your input and advice. I still donít fully understand the performance degradation of a panel in the shade. Iíve been spending time on the roof, mapping the shadow from the air conditioners and find that it is much greater than I had expected. I think my next step will be to buy a couple of 100w panels and use them in a portable configuration. Much of my system exists; 4 6v AGM batteries, a 2000w inverter and a Renogy DC-DC 50 amp charger that has a MPPT solar charge controller built in to it. I think with two panels and a 50í cable that I can move in and out of shade and tilt them will give me a feel for how well they perform. All that done and said, I'm thinking after calculating what I need, doubling it is the best advice I've gotten. Still, I like the science project. BTW, the Renogy DC-DC 50 charger running off the truck alternator works like a ding-dong and will be the primary charge source moving from dry camp to dry camp.
    Last edited by wjpatter; 02-18-2021 at 03:35 PM.
    Bill & Marsha
    2020 Reflection 320 MKS
    2018 2500HD Silverado 4x4
    Not All Who Wander Are Lost

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    Quote Originally Posted by wjpatter View Post
    Thanks guys for your input and advice. I still donít fully understand the performance degradation of a panel in the shade. Iíve been spending time on the roof, mapping the shadow from the air conditioners and find that it is much greater than I had expected. I think my next step will be to buy a couple of 100w panels and use them in a portable configuration. Much of my system exists; 4 6v AGM batteries, a 2000w inverter and a Renogy DC-DC 50 amp charger that has a MPPT solar charge controller built in to it. I think with two panels and a 50í cable that I can move in and out of shade and tilt them will give me a feel for how well they perform. All that done and said, I'm thinking after calculating what I need, doubling it is the best advice I've gotten. Still, I like the science project. BTW, the Renogy DC-DC 50 charger running off the truck alternator works like a ding-dong and will be the primary charge source moving from dry camp to dry camp.
    Here are a couple of websites that address shading.

    http://www.pvresources.com/en/sitean...%20vegetation.

    https://blog.aurorasolar.com/shading...ially%20seems.

    https://www.8msolar.com/solar-shading-analysis

    So, on a very high level, I would compare it to getting a tan by lying in the sun. In direct sunlight, you would tan (or burn) faster than if in shade.

    Sent from my phone using Tapatalk
    Mark & Mary. Currently hailing from New Mexico. Hopefully full timing in late 2022.
    Current camper: Purchased a 2021 DG Reflection 320MKS!
    Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel

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    Quote Originally Posted by MoonShadow_1911 View Post
    Here are a couple of websites that address shading.

    http://www.pvresources.com/en/sitean...%20vegetation.

    https://blog.aurorasolar.com/shading...ially%20seems.

    https://www.8msolar.com/solar-shading-analysis

    So, on a very high level, I would compare it to getting a tan by lying in the sun. In direct sunlight, you would tan (or burn) faster than if in shade.

    Sent from my phone using Tapatalk
    These links are useful information but doesn't have enough detail to quantify the design. The shade calculators that I've looked at are for static configurations like a house but not a moving RV, plus I have a 10 degree down slope where I have the most shade free area to mount the panels. Facing North helps and facing South hurts. The tan/sunburn analogy is what I had expected but from the demonstrations from the below link, it looks more black and white. The output of a single cell dictates the performance of the string of cells. That violates my sensibility. I think the science project with portable panels is the only way I'm going to get data that I need for something on the roof. Thanks.

    https://www.youtube.com/watch?v=ofo1HQyGG8s
    Bill & Marsha
    2020 Reflection 320 MKS
    2018 2500HD Silverado 4x4
    Not All Who Wander Are Lost

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