New to Solar - RV Solar Install

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REPO
REPO Registered Users Posts: 23 ✭
in Solar Beginners Corner #1
First post here!

I am currently reading as much as I can, and checking out many, many websites, trying to make educated decisions. I finally found this forum, and though I should get some opinions from the experts.

I want to install a solar system on our 5th wheel RV to supply power, and recharge the batteries. Where we usually go camping there is no power hookups, hence why we need to generate our own power. I already own a pretty decent 3000 watt inverter. I have limited roof space, so would like to install only 2 panels up there. To get the power I think I would need, I have come up with 2 panels at around the 200 watt range each. As most panels of this size and larger seem to be upwards of 30 volts output, I have decided on a Morningstar TriStar MPPT 45 amp controller.

At first I plan to only purchase one panel, then as funds permit, add a second panel down the road. Can anyone offer suggestions as to if this would be a good setup? We live in northern Canada, and in the early spring and late fall, would need to run the furnace, and that would consume a fair bit of amp hours.

Looking forward to the replies, thanks in advance.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    Re: New to Solar - RV Solar Install

    My first answer--Conservation. Make sure that you have reduced power needs as much as practical (LED lighting, small laptop computer, low power tv or use the laptop, etc.).

    Second, measure your loads (AC, DC, etc.) both "peak loads" and average load * hours of operation (100 watts * 2 hours = 200 Watt*Hours; 5 amps * 5 hours = 25 AH at 12 vdc, etc).

    Third, then we work at planning out your system.

    A 3,000 watt inverter is pretty good sized... It will run my entire 3 bedroom home in suburban SF Bay Area very nicely.

    Most people underestimate their loads and overestimate how much power they can get from solar RE.

    A 3,000 watt inverter may take 30-60 watts just to turn on--then you add your AC loads on top of that.

    For example, a 200 watt panel mounted flat to an RV in Canada during the summer may get 4-5 hours of full sun equivalent per day. An off-grid solar PV system is about 52% efficient from Solar Panel STC rating * hours of sun to available AC power:
    • 200 watt panel * 4 hours of full sun eq. * 0.52 system eff = 416 WH per day
    If you tilt the panel (around 50 degrees from horizontal for Calgary region)--You can collect more power--Perhaps 4-6 hours of sun per day 9 months of the year.

    Now--the question is what do you want to run with that amount of power...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
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    Re: New to Solar - RV Solar Install

    A 3 kw inverter is much bigger than you are going to be able to run, at least anywhere near fully loaded from any small RV battery system.

    T
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #4
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    Re: New to Solar - RV Solar Install

    Agreed that the inverter is way overkill. Its just something I already own, and would like to use it if possible.

    Tripp Lite
    PowerVerter Ultra-Compact Inverter
    3000 watts
    Model PV3000HF

    As for conservation, I am all over that. We don't use TV's or computers when camping. Mostly a coffee pot, water pump, and the furnace when required. I am currently pricing out LED replacement bulbs for the lighting as well.

    The items that concerns me the most at this point, (because I don't understand it) is if it is safe to run a 30 Volt + solar panel, for a 12 volt RV system, using a MPPT controller? Is this even reasonable? Or should I be sticking with several smaller 17 volt panels? (not what I want to do!)

    Thanks!
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #5
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    Re: New to Solar - RV Solar Install

    Get a Coleman stove stop MR Coffee, or use a French press. A single pot of coffee will draw ~300 wh, nearly all your solar output for a day with 200 watt panel.http://www.google.com/products/catalog?q=coleman+coffee+maker&oe=UTF-8&hl=en&client=safari&um=1&ie=UTF-8&cid=15441000232746013296&sa=X&ei=1tLITefPBs3QiAL0kPD6BA&ved=0CDUQ8wIwAg#

    30 volt panel thorugh an MPPT control into a 12 v battery is fine.

    I am not a fan of the Triplit inverter/chargers. They draw over an amp, just doing nothing, and the charging regime is not very good.

    If all you are running is a lights and the pump, you don't need an inverter at all, earthily not a 3 kw one. Sell the one you have, and buy a smaller one.

    T
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #6
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    Re: New to Solar - RV Solar Install

    A forced air furnace is probably something like 8 amps of 12 vdc worth of power... Running something like 4-6 hours a night?:
    • 8 amps * 12 volts * 5 hours =480 WH
    Just a guess... I assume you already have a battery bank for the RV? What size (AH/Volts)?

    How long does the bank last you between recharging? Do you have anyway of measuring the current? A Battery Monitor?

    A Kill-a-Watt meter for measuring AC power is nice. A DC Amp*Hour/Watt*Hour meter can be handy too (if you don't plan on spending for a Battery Monitor).

    In the end--we can make lots of guesses--but it would be much easier for us, and your wallet, if you can get a good handle on your power needs.

    A good inverter to use (laptop, cell phone charging, etc.) would be a True Sine Wave inverter (TSW). One just large enough for your loads.

    MSW inverters are much less expensive than TSW--but much better for wall transformers, small electronics, and motors (MSW, modified square wave, can cause some devices to overheat/fail).

    A couple of FAQs:

    All About Inverters
    Choosing an inverter for water pumping

    To compare with a nice TSW 12 volt 300 watt inverter--take a look at this one.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #7
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    Re: New to Solar - RV Solar Install

    Thanks for all the info! You are correct in that I need more info, unfortunatly as of yet, I have not purchased any sort of battery monitor, or amp/volt meter to prove what I require. As for batteries, I am currently running a couple of 12volt deep cycle batteries, and they are not high quality. Eventually, I would like to step up to (4) 6 volt units. For now I need to rely on the solar set up.

    Also, understandably, a 200 watt panel would not be sufficient, this is merely my starting point. Maybe I should go with a 250 watt unit, with the plan to add a second 250 watt unit in the future. As it was mentioned that the furnace will require upwards of 480 watts, clearly I need at least 500 watts of panels at a bare minimum.

    Again, I am just starting out, with plans to end up with a decent system in the end. But for now I can only afford certain parts of the system, but don't want to buy them twice, so want to be sure that what I do buy is going to fit my needs down the road and be of a somewhat good quality.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
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    Re: New to Solar - RV Solar Install

    A couple of notes. First, all calculations derive from the loads. Battery size, PV size, inverter size etc all derivative ve from the loads.

    Second, you must realize that these loads have a power draw, in watts or amps, but they also have a time component, and every calc need to relate to both. For example, a light bulb may draw 100 watts. That in an of itself means little. What matters is, how long is that light on for. The same 100 watt bulb, on for one hour. Is one watt hour ( wh)

    So one. You have determined your total load in in WH, then you can determine how you re going to get that into a battery. The general rule of thumb is, take the name plate rating of the PV, divide that by two to accunnt for all cumulative system loses, then multiply that number by 4, to represent the average number of hours of good sun you might likely get on a per day basis, over the course of the year.

    So, a 200 watt panel might produce like the following: 200/2=100*4=400 wh/day.
    You might get more, you, you might get less, this would be a design average.

    So do. An honest assessment of your loading, and then figure out what the hardware needs are. Just as an a FYI, we live off grid, with 400 watts of PV, feeding into 450 ah of batteries. On an average daily basis, we use ~ 500-800 wh/day. This is a well balanced system, that gives us three days reserve, and we can recharge to 100% nerly every day.

    Tony
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #9
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    Re: New to Solar - RV Solar Install

    Thanks again for the reply!

    Yes, I have the watt/hours thing somewhat figured out. But looking at what BB had mentioned, the furnace alone is good for 480 Watt/Hours per day alone. Now if I switch to LED lights, and keep the water pump use to a minimum, I am thinking that maybe 300 watts of panels should be fairly sufficient?

    300/2=150*4=600 WH

    And this is on a GOOD day, got to factor in cloudy days, possibly parking areas with too many trees, etc.

    Is it safe to say, that I can error on the high side, rather than on the not enough panel side?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #10
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    Re: New to Solar - RV Solar Install

    More or less--extra solar panel power is not going to be a problem--other than being expensive.

    Choosing a 135 watt, 200 watt, 235 watt panel, etc... Really depends on what will fit your RV and the $$ per watt pricing.

    Also, roughly, 135 watt panels are about the largest that you can ship using normal shippers (post office, UPS, etc.). 175 watt panels are about the largest a single person man sling around on a roof.

    And, when buying panels over time--There is not a lot of standardization with larger solar panels right now. Depending on the solar controller and how you wire them (series/parallel), you do have to "match" Vmp/Imp of the panels to the controller input for everything to work correctly.

    Remember, the example of the heater load for your RV is just a SWAG on my part to give you an example of how to measure/do the calculations... And a rough idea on what you are looking at for sizing.

    There are catalytic heaters for RV's that use zero electrical power--depending on your RV and personal choices--perhaps you can find a lower power alternative for heat.

    To quote myself and give you some reading:
    BB. wrote: »
    Our general suggestion for getting into solar PV electricity:
    1. Conservation--Reduce your power needs by changing to LED/CFL lighting, Energy Star Appliances (computer, TV, etc.), and just turning things off. For AC devices--get a Kill-A-Watt meter to measure their draw.
    2. Know your loads--You need to measure your loads... Watts*Hours (average power * time) or Amps*Hours (for 12 volt / DC loads). Average usage per day and by season (more sun in summer, less in winter -- same for PV power). This is where you set your expectations for your solar power system. Generating the solar power is expensive (~$1.00 TO $2.00+ per kWhr vs $0.10 per kWhr for utility power).
    3. Design the System--This part is pretty straight forward. Define your location, season(s) of use, mounting of panels (fixed, flat or tilt, how much space, etc.). Generator backup power, battery monitoring equipment, how much you want to spend (range of solar panels, charge controllers, inverter, battery types, battery monitor, etc.).
    Here are some frequently asked questions that will help you with the understanding the basic issues:

    All About Charge Controllers
    Read this page about power tracking controllers
    All About Inverters
    Choosing an inverter for water pumping
    Deep Cycle Battery FAQ
    Solar Radiation Tables for US
    PV Watts--Simple Solar Power Calculator Program (use Derating=0.52 for off-grid systems)
    For 12 Volt & RV Systems - HandyBob's long discussion and rant is about 99% right on how to make RV and similar 12 volt systems work correctly. One of the few "non NAWS" articles that we recommend.

    Here is a nice thread with video from Kevin in Calgary Canada that shows designing and installing solar PV in a small RV trailer.

    Our host is Northern Arizona Wind & Sun (Flagstaff Az) and they have a webstore with a good selection of components to build your own solar system. You do not have to purchase from them--but it is a handy place to find reliable products at reasonable prices to layout your system.

    If you have questions about those products, or others from different vendors--please ask. We are all volunteers here with no connection to NAWS (except for Windsun, the Admin from NAWS) and are happy to help.

    Of course, being north of the boarder, your choices for solar RE components may be different (and custom duties may alter your choices too).

    In the end, we normally recommend that people design their systems based on their loads...

    However, you can also design your system around your battery bank (limited size and weight--so you don't have much flexibility regarding batteries). What is your current/planned Battery bank setup (AH and Volts). We can size the array to give you good support for the batteries. No use designing a huge a array if you are battery bank limited.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #11
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    Re: New to Solar - RV Solar Install

    That is some great info there!

    I am going to stick with the MPPT style controller, as from what I just read, they are well worth the money.

    Now just to figure out my panel requirements...................
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #12
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    Re: New to Solar - RV Solar Install

    I would highly recommend that you read HandyBob's manifesto:

    http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
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  • PhilS
    PhilS Solar Expert Posts: 370 ✭✭✭
    #13
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    Re: New to Solar - RV Solar Install

    I installed one panel permanently on the roof of our fiver. I have a second panel, stored under the bed, that I can either put up on the roof or 30' away from the RV but in the sun. We prefer to camp in shady areas and that's exactly the opposite of what you want with solar.

    Of course, I put a bicycle cable through the panel frame and around a tree to help prevent it from "walking off".

    Phil
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #14
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    Re: New to Solar - RV Solar Install
    PhilS wrote: »
    I installed one panel permanently on the roof of our fiver. I have a second panel, stored under the bed, that I can either put up on the roof or 30' away from the RV but in the sun. We prefer to camp in shady areas and that's exactly the opposite of what you want with solar.

    Of course, I put a bicycle cable through the panel frame and around a tree to help prevent it from "walking off".

    Phil

    Hey Phil, that is exactly what I would like to do! Hence why I would like to stay with 2 larger sized panels, over say 3 or 4 smaller sized panels. I will mount one permanently, and make one moveable as you do, as we also tend to camp in heavily treed areas. (northern BC, Canada)
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  • PhilS
    PhilS Solar Expert Posts: 370 ✭✭✭
    #15
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    Re: New to Solar - RV Solar Install
    REPO wrote: »
    Hey Phil, that is exactly what I would like to do! Hence why I would like to stay with 2 larger sized panels, over say 3 or 4 smaller sized panels. I will mount one permanently, and make one moveable as you do, as we also tend to camp in heavily treed areas. (northern BC, Canada)

    I used an old Xantrex controller (C-35) and just have both panels hooked to it. That means I had to use 12V panels. One panel has a long wire with a polarized plug, the other end of which tucks into the box for the landing leg switch.

    I could do this 'on the cheap' because I had a couple of panels and the controller, leftover from previous incarnations of our home power system. I found some special rubber grommets for the roof mount that expand when you screw into them. The wire for the portable panel is just a long trailer wiring kit. It is 4 conductor with the polarized plug. I run two conductors for each leg to the panel.

    It was more of an experiment that succeeded and I haven't changed anything since the original install.

    You can PM me if you have more detailed questions.

    Phil
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #16
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    Re: New to Solar - RV Solar Install

    OK, i think I am still trying to decide the best route to go for my initial setup.

    Option 1 - Morningstar Tristar 45 MPPT controller, 2 larger 180-250 watt panels, and stick with my current low end 12 volt deep cycle NAPA battery. (with future plans to add (4) 6 volt batteries down the road)

    Option 2 - Morningstar Tristar 45 MPPT controller, a smaller 100-130 watt panel, and 4 new Exide deep cycle 6 volt batteries. (with plans to add another panel or 2 in the future)

    I found these locally. Only place that stocks 6 volt batteries in my area!

    http://www.canadiantire.ca/AST/browse/4/Auto/SolarPortablePower/RenewableEnergySystemComponents/PRD~0102010P/6V%252BRenewable%252BEnergy%252BDeep%252BCycle%252BBattery/CROSSSELL~0111879%2012V%2BEliminator%2BRenewable%2BEnergy%2BDeep%2BCycle%2BBattery.jsp?locale=en

    I think Canadian Tire has some of the specs mixed up, but I did find this link to Exide specs as well.

    http://www.exide.com/portal/server.pt/gateway/PTARGS_0_0_390_221_16512_43/http%3B/WINAPAQLOG1.Inside.Exide.ad%3B7089/publishedcontent/publish/exide_corporation__public_/transportation/north_america/images/specs_golf.pdf

    Appears to be the GC2 GC-110 (6 volt)

    Thoughts?
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  • soleil
    soleil Solar Expert Posts: 45 ✭
    #17
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    Re: New to Solar - RV Solar Install

    Not long ago, I installed a couple PV panels on my 5th wheel (see post: http://forum.solar-electric.com/showthread.php?t=9915). I have a total of 360W of solar panels (2 X 180W, 24V nominal) charging through a Rogue MPT-3024 MPPT charge controller. With low usage days and good sun, this setup will top off the batteries (4 X 6V Trojans). On mod to high usage days I have to augment charging with the generator. I'm pleased with my setup.

    Bottom line, for my situation, at least, I wouldn't install anything less than the 360W that I have (another panel would be ideal). I agree with Tony with regards to recommendation for higher voltage panel and MPPT controller.

    I didn't see mention of whether you have a generator or not. This will make a big difference in how many panels you require.
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #18
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    Re: New to Solar - RV Solar Install

    Thanks for the reply. I don't plan to use a generator. I would prefer to install the required amount of panels that I would need to maintaine my setup. But that is going to take some time, as I cannot afford it all at once. I have already ordered the MPPT controller, but am not sure if I should invest in good batteries up front, with minimal solar, or invest in the required amount of panels first with minimal battery.
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  • soleil
    soleil Solar Expert Posts: 45 ✭
    #19
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    Re: New to Solar - RV Solar Install

    It doesn't matter how nice or big batteries you have, if you don't have an adequate charging source, they're not going to do you much good ;). Did you say you have two 12V deep cycle batteries? If so, then I'd consider first trying your current batteries with (at least) a couple decent sized 24V solar panels.
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #20
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    Re: New to Solar - RV Solar Install

    Currently I have a single 12 volt deep cycle battery. I really only go camping for uwards of 3 days at a time, so in all reality, I only need the batteries to get me through that time frame, then they can sit and charge until the next outing.

    Just not sure what to buy first!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #21
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    Re: New to Solar - RV Solar Install

    I would start with pairs of 6v golf cart batteries. Cheap, forgiving, and cheap to replace if you make a mistake.

    For rv/vacation spots, you probably will not cycle batteries to death but age/charge/store them to death.

    Even though we talk about 50% maximum discharge for long life, many batteries will have a 500 cycle life at 80% cycling. If you cycle them 50 times a year, they will last 10 year cycle life. Much longer than the expected 3-5 year life one normally expects from inexpensive deep cycle batteries.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #22
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    Re: New to Solar - RV Solar Install

    I would start with pairs of 6v golf cart batteries. Cheap, forgiving, and cheap to replace if you make a mistake.

    For rv/vacation spots, you probably will not cycle batteries to death but age/charge/store them to death.

    Even though we talk about 50% maximum discharge for long life, many batteries will have a 500 cycle life at 80% cycling. If you cycle them 50 times a year, they will last a 10 year cycle life. Much longer than the expected 3-5 year life one normally expects from inexpensive deep cycle batteries falling for other causes.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #23
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    Re: New to Solar - RV Solar Install

    I tend to agree. I think I am better off buying (4) 6 volt batteries, and a single 120 watt panel to begin with. I will then work towards adding more panels down the road. Thinking about it last night, it doesn't matter how much panel I have, if there isn't enough battery to run the camper in the first place.
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  • soleil
    soleil Solar Expert Posts: 45 ✭
    #24
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    Re: New to Solar - RV Solar Install

    Have you been able to camp for 3 days with your current battery (and no solar)? It sounds like your usage is relatively low. One decent sized panel would do pretty well charging a single average sized 12V battery. It would just depend on whether your single 12V battery would have enough capacity to meet your needs. Run the numbers like others have said.
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #25
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    Re: New to Solar - RV Solar Install

    That is unknown at this point. We just bought the 5th wheel.
    But I can almost be certain to say that if we had to run the furnace at all over the weekend, that it would pretty much kill the battery on the first night.

    To be honest, the furnace usage is my main worry. Fridge runs on propane, lights are used minimaly, (with plans for LED). Not to say that I won't make use of a TV and other appliances down the road, once I have purchased all required items, and have plenty of panel and battery available. (but that won't be until next summer)
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  • PhilS
    PhilS Solar Expert Posts: 370 ✭✭✭
    #26
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    Re: New to Solar - RV Solar Install
    REPO wrote: »
    That is unknown at this point. We just bought the 5th wheel.
    But I can almost be certain to say that if we had to run the furnace at all over the weekend, that it would pretty much kill the battery on the first night.

    To be honest, the furnace usage is my main worry. Fridge runs on propane, lights are used minimaly, (with plans for LED). Not to say that I won't make use of a TV and other appliances down the road, once I have purchased all required items, and have plenty of panel and battery available. (but that won't be until next summer)

    I seriously doubt one battery will be enough. The killer will be the heater. Also, don't forget that the fridge uses 12V even tho it is operating on propane. If the battery gets low, the fridge will shut down.

    Let me reword that: if your heater is running, late into the night the battery could get low. Then the heater kicks on, the surge draws the battery voltage down enough so that the fridge shuts off. You wake up to cold interior and warm fridge. And you have no way to get a charge going until the sunlight hits your panel (IF you aren't parked in a shady spot).

    One panel won't be enough solar either. I DID have the one fixed panel as our only solar source for a year or two, but it wasn't enough so I added the portable one. We have three 12V batteries but also use a Honda eu1000i generator.

    My "yardstick" (both for our home and our RV) has always been the amount I need to operate a generator to keep the batteries healthy. When I don't have to run a gen at all, or only on the second or third rainy day, then I call it "good".

    More gen time in good weather means not enough panels. It's taken me decades to reach the proper balance on our home system.

    Phil
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  • PhilS
    PhilS Solar Expert Posts: 370 ✭✭✭
    #27
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    Re: New to Solar - RV Solar Install
    PhilS wrote: »
    IMore gen time in good weather means not enough panels. It's taken me decades to reach the proper balance on our home system. Phil

    I certainly should add that the PROPER way to figure the right amount of panels, batteries, etc., is how Bill and Coot and Tony and the rest keep repeating: figure loads and build the system to match.

    My way takes longer.

    Phil
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #28
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    Re: New to Solar - RV Solar Install

    And is more likey more expensive,

    Tony
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  • Ronvada
    Ronvada Registered Users Posts: 5 ✭
    #29
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    Re: New to Solar - RV Solar Install

    I have a 5th wheel with one 110 watt panel 4 t-125 trojan batt. and it will hold me up for three days with the heater being used
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #30
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    Re: New to Solar - RV Solar Install

    How many amp hours are those batteries rated for?
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  • REPO
    REPO Registered Users Posts: 23 ✭
    #31
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    Re: New to Solar - RV Solar Install

    I found a place fairly close to me that is seeling the US2200 batteries for a reasonable price. They are 232 amp/hours, and go for around $158.00 each (CAD) I think I am going to pick up 4 of these, I already have a 100 watt panel on order, as well as the Morningstar MPPT 45 controller on its way. Looks like I will just add 100 watt panels as money allows.
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