noob wants to go solar on fifth wheel has questions

hosealmond
hosealmond Registered Users Posts: 8


Hey everyone,i currently live in a fifth wheel in florida.lots of sun here year round.I have been reading up on on the solar systems setup and have a basic understanding at this point.I am curious if it would be possible to set up a battery bank in the area that contains the backup battery now?Was thinking this because i thought i could run the panels to those batteries along with a charge controller and fuse and take advantage of the fact that the rvs back up system is already set up to run that way.Is this possible or would I have to design the system around that completly?Thank you kindly

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: noob wants to go solar on fifth wheel has questions

    Welcome to the forum.

    Adding solar to extend the range of your battery supply is about as easy as you think: panel & charge controller connect to existing battery. No problems with having a battery connected to more than one charge source. You don't even need "full panel" capability as you won't be relying on the solar to recharge, right? You will have to know the capacity of the battery to make sure you get enough panel to do something; a 15 Watt panel puts out about 1 Amp which would only maintain a 100 Amp hour battery, not really add anything to it.
  • hosealmond
    hosealmond Registered Users Posts: 8
    Re: noob wants to go solar on fifth wheel has questions

    Currently I am hooked up to electricity but wanting to go off grid completly.was thinking of using 500 or maybe a bit more in panels.would it work the way I have described?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: noob wants to go solar on fifth wheel has questions

    Okay, that is not so easy.

    First of all, if you've got grid why do you want to turn it off? It is highly unlikely you will save any money.

    Second, to evaluate an off-grid potential you need to start by measuring all your loads. You'll be surprised at how much they are and how small that battery suddenly becomes when asked to provide full-time power. I seriously doubt one battery will do it, unless it is a massive forklift battery.

    Taking an RV off-grid is not always wise. For one thing you are practically locked in to a 12 Volt system without a lot of reworking. And that system Voltage has practical limits in terms of maximum power delivered and total Watt hour capacity.

    It isn't a matter of "how many panels" but rather one of Watt hours (Volts * Amps * time).
    Say you use very little electric like I do at the cabin: <3 kW hours per day. Since panels only produce when the sun shines, you have about 5 hours a day to gather that energy and store it. So first you need 3kW hours of battery: on 12 Volts that's 278 Amp hours or a minimum 556 Amp hour battery. Double that would be better to limit the DOD to 25% (extends battery life and gives a day of redundancy). You have one 12 Volt battery which is probably 100 Amp hours or so. In other words 1/10th the capacity. And if you did have that 1112 Amp hour 12 Volt bank you would be looking at two charge controllers to handle the current and pretty big wires. That's why you go up in system Voltage; to reduce the current needs.

    Recharging that much battery in 5 hours takes around 1200 Watts of panel, as they don't produce their full rating throughout that time frame.

    So you see going totally off-grid is much more complex than adding a panel to maintain a battery. Without that Watt hour figure you can't even guess what the system would be like.

    Take a look at your last electric bill. Somewhere there's a number for kW hours used and another for the time period. Divide it out to get a daily Watt hour usage figure. That will be your first clue.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: noob wants to go solar on fifth wheel has questions

    Sorry to sound like a broken record--But we really need to know your loads (AH or WH per day, by season) or at least your battery bank size/capacity to help with an off grid system.

    Can give you some starting points... 4x 6 volt 220 AH golf cart batteries would be a good start (2 in series, then those two in parallel)... That would give you a 440 AH battery bank at 12 volts.

    The starting rule of thumb for charging a battery bank is ~5% to 13% rate of charge (you should not go less than 5% on an operating battery bank, and can go upwards of 25% rate of charge--but that is usually costly and not usually needed for solar power unless you cannot use a genset and need the power, for A/C, etc.). So:
    • 12 volts * 440 AH * 1/0.77 panel+controller derating * 0.05 rate of charge = 343 Watt array minimum
    • 12 volts * 440 AH * 1/0.77 panel+controller derating * 0.10 rate of charge = 686 Watt array nominal
    • 12 volts * 440 AH * 1/0.77 panel+controller derating * 0.13 rate of charge = 891 Watt array "cost effective maximum"

    A 10% array of 686 watts would supply, assuming 52% system efficiency and an AC inverter with a minimum of 4 hours of sun per day (i.e., non-winter time for much of the US):
    • 686 Watts * 0.52 system derating * 4 hours of sun minimum = 1,427 Watt*Hours of 120 VAC per day (average minimum for 9+ months of the year)

    Your battery bank, if discharged 25% per day (2 days backup and 50% maximum discharge) would supply (with no sun) around:
    • 12 volts * 440 AH * 0.25 * 0.85 inverter efficiency = 1,122 Watt*Hours per day (no sun, for two days)

    That should be enough power for most people that have propane stove/cooking/etc... One thing to watch for--Many RV's have a 12 volt fan powered space heater--And they can take quite a bit of power to operate (something like 50 WH per hour--Over night for 10 hours 250-500 WH--which would be 1/2 of your available off grid power--which would be less in winter/farther north).

    By the way, if you will be going north, have you thought about being able to tilt your panels for winter sun/shedding of snow?

    The ratings of your inverter for a 440 AH @ 12 volt battery bank would be:
    • 12 volts * 440 AH * 1/8 hour discharge cycle * 0.85 inverter eff = 561 watt maximum continuous recommended (conservative)
    • 12 volts * 440 AH * 1/2.5 max surge current * 0.85 = 1,795 Watt maximum surge (starting pumps, etc.)

    For a 12 volt system, I normally suggest around a 1,200 watt inverter maximum--That is >100 amps of 12 VDC Current--Already a lot of copper wire to support his load.

    If your loads are small, I would suggest starting with a MorningStar 300 watt (600 watt surge for 10 minutes) 12 VDC TSW inverter. Efficient, rugged, and has a "remote on/off" and a low power "search mode" which you do not find any were else for small/inexpensive/12 VDC inverters. You could always get a larger/less expensive inverter if you have to power some larger loads (tools, etc.) from time to time.

    Personally, I am not a fan of parallel battery strings--But for a smaller/beginner system, 2-4 6 volt 220 AH golf cart batteries are a good set of "training batteries". The are not that expensive and if you make a mistake--You are out much less money.

    For backup, look at a Honda eu1000i or eu2000i type inverter generator--They do not use much fuel and can power a 20 amp 12 VDC battery charger (eu1000i) or 40+ amp charger (eu2000i) for heavier loads and during bad weather (1-2 gallons of fuel per day type operation, or even a bit less).

    If we know more about your needs, we can probably help a bit more (and you may not know your needs at this time either).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hosealmond
    hosealmond Registered Users Posts: 8
    Re: noob wants to go solar on fifth wheel has questions

    Thanks for the response.I wish there was a direct chat feature on here as its easier to explain things.Do you have an im address I could reach you by possibly?I could better explain my thinking.thank you very much ;)
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: noob wants to go solar on fifth wheel has questions
    hosealmond wrote: »
    Thanks for the response.I wish there was a direct chat feature on here as its easier to explain things.Do you have an im address I could reach you by possibly?I could better explain my thinking.thank you very much ;)

    Yes, perhaps you could. But that doesn't mean I'd understand it. I sort of need well-written words to comprehend what's going on. And sufficient time to mull them over in order to formulate something that approaches an intelligent response. Even then it doesn't always work. :p
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: noob wants to go solar on fifth wheel has questions

    You may have missed the post I made just a couple minutes before yours...

    Regarding chats/PM/email/etc... Most of the questions you will have are probably similar to those that have been asked before, or again in the future.

    I (we?) like to do most stuff "on the forum" because it saves the discussions for everyone to read in the future (more bang for the buck)--Plus there are a lot of people where with different experiences and views--And while one of writes the "ultimate" post--There are two or three more from different angles that address issues differently/better and sometimes that were not addresses/forgotten in the first replies.

    We are pretty easy going here--Feel free to ask away--We have all been noobies at one time or another here--Who have been helped by those that were here before us.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hosealmond
    hosealmond Registered Users Posts: 8
    Re: noob wants to go solar on fifth wheel has questions

    Okay sorry Let me explain some things so you guys see where I am coming from. :)

    I am living on a friends land,I have the fifth wheel plugged into an outlet outside that he installed which is connected to his house and breaker box.

    His place is a double wide that has been altered some.He lives on one side of it that was closed off and made into his own area with a fridge,tv,ac window unit etc.The other half of that double wide his stepson and wife live in along with their son kenny.The whole place is extremely bad as far as insulation is concerned!His side you can see the walls it areas and very little insulation at all.On the other side its better but they have a missing window in the back and covered it with tarp...the elctric bill before I even set up on this land was 450 a month average!!!I am expected to pay a quarter of the total electric bill.Often I am paying 125 a month on top of the rent cost.The only reason his bill is so high is he has the worst insulation I have ever seen in my life!All that aside I mentioned to him going off grid and he laughed and said do it if you think you can.This from a person that doesnt realize their bill could be slashed in half if they replaced a window and invested in insulation....I consider us friends so I don't argue but never the less would like to figure a way out of paying that every month.The land here is rather nice otherwise...I have been reading different things on solar and wind.Bought an ebook called Simply solar homesteading which has been very interesting to read.I have a friend that is going to help me build a solar water heater and possibly a heater as well.Does not get that cold here in the winter though in florida.
    I use currently
    An 80 watt 32 inch lcd tv with dvd player

    2 laptops

    propane stove

    propane water heater.

    the lights are all 10 watt,about 6 or 8 of them.

    a small crockpot I use from time to time.

    A small juicer around 400 watts.

    A small steamer for veggies.

    So just how crazy is my idea to attempt all this?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: noob wants to go solar on fifth wheel has questions

    The best investment you can make is a Kill-A-Watt meter: http://www.solar-electric.com/nsearch.html?catalog=wind-sun&x=0&y=0&query=kill-a-watt
    You can probably get one at a local hardware/lumber/electrical supply

    Then measure the real power consumption of everything you plug in to an outlet. You will be amazed, and possibly appalled. You will also have some reliable figures for how much power you really do use, which would at least have bearing on how much of that bill is yours. It will probably start an argument.

    Then you can get closer to a plan for an off-grid system and estimate the cost of it. Compare that to what you're paying now and see how it works out. Given your situation, I strongly suspect you are paying a lot more per kW hour for the power you actually use than what the utility charges. This means off-grid may indeed be viable for you.

    Or moving, for that matter. :roll:
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: noob wants to go solar on fifth wheel has questions

    If you can convince them if you get a used KWH Meter (old utility meters on EBay) and wire it to your trailer... You probably use around 100 kWH per month ($10 worth) vs the 1,000-3,000 kWH per month for their home (especially if they use AC/Electric heat/electric hot water/electric drier/elec. ect.).

    $450 per month is a large bill, and you guys probably pay around $0.10 to $0.15 per kWH.

    If this is permanent setup--You might find out the charges for installing a separate utility meter for your hookup. Although, this may be a can of worms too (utility charges $20 per month meter reading, local city/county regulations regarding second utility hookups/taxes/etc...

    Yes, if they make you pay 1/4 the bill--You have a choice--If you save $100 per month vs moving vs solar PV power vs getting a meter and offering to pay $0.xx per kWH per month (pay ~1 month in advance or give him $100 to "install" a local meter for you, to wet their appetite).

    For off grid power, it can easily cost you ~$1-$2+ per kWH--And that 100 kWH per month (or less) $10-$20 utility bill will look more like $100-$200 per month once you add all the equipment together (plus on going maintenance, battery replacement, etc.)...

    Going solar, by itself, will not save you much (if any) money.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • hosealmond
    hosealmond Registered Users Posts: 8
    Re: noob wants to go solar on fifth wheel has questions

    Thank you for your response!I will get one of those asap.Moving was also my other consideration.My sister with the massive home(cathedral ceilings and all)has 5 acres,I
    attempted to negotiate a deal with her to build a small cabin on her land based on the one in the ebook I mentioned but unfortunately she declined citing she has to many people popping in and out as it is on her...(relative neighbors)It's funny because my landlord/friend is convinced that because I have a juicer and steamer and 32 inch tv that we are using WAY more than we think and thats why the bill is high(mind you it has barely gone up since i came here)He owns the land,his step son pays the bills after collecting the money...You are right though about the argument potential...my landlord/friend is NEVER EVER wrong lol,even if win him over he will agree at that moment and days later act as if he never did agree and come up with some crap like "Rvs arent designed for things like juicers"what hed doesnt seem to ever get
    is I run that for like 5 minutes in the morning....even at 400 watts it's not running all day or anything but he insists in treating it as so lol.

    So you live in a Cabin Cariboocoot or just use it occasionally?
  • hosealmond
    hosealmond Registered Users Posts: 8
    Re: noob wants to go solar on fifth wheel has questions

    All great ideas guys thankyou!I found a meter,I think I could plug it into the outlet outside by the Rv and then plug the rv adaptor into it,Think it would work?

    http://www.aliexpress.com/item/USA-energy-meter-in-plug-kwh-power-monitor-electricity-meter-with-power-factor/587463251.html
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: noob wants to go solar on fifth wheel has questions

    Power is not just a matter of Watts, but Watt hours. Here's my favourite example:
    My refrigerator (at the cabin) uses 120 Watts. My satellite modem set-up uses 40 Watts. They both use the same amount of power. How? The satellite uses 40 Watts all the time it is on, and runs constantly: 40 Watt hours in any given hour. The refrigerator cycles and only runs 1/3 of the time: 40 Watt hours in any given hour. (Yes, it varies for both; this is just an example based on how it works out on average.)

    Your TV may use 120 Watts or 175 Watts depending on how the display is set. Turn down the brightness and you turn down the Watts. The juicer even at 400 Watts if run for 5 minutes a day consumes only 34 Watt hours. You can run a 13 Watt CFL for 3 hours and it will use 39 Watt hours. Watt hours is what you get billed for. I know; preaching to the choir and you'll never make them understand.

    As for RV's not being designed for the juicer ... 120 VAC 15 Amp outlet can handle 1800 Watts and does not care what is plugged in to it. If the load was too great it would trip a breaker or blow a fuse. That's all there is to that argument.

    I spend half the year at the cabin and half "in town" (still fairly rural but on grid). The off-grid power is very expensive ($4+ per kW hour) and the on-grid power is very cheap ($0.10 per kW hour). As soon as I get rid of the electric water heater in town my massive $40 per month bill is bound to go down! :p
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: noob wants to go solar on fifth wheel has questions
    hosealmond wrote: »
    All great ideas guys thankyou!I found a meter,I think I could plug it into the outlet outside by the Rv and then plug the rv adaptor into it,Think it would work?

    http://www.aliexpress.com/item/USA-energy-meter-in-plug-kwh-power-monitor-electricity-meter-with-power-factor/587463251.html

    This is similar to a K-A-W. Is the plug compatible with your hook-up? Sometimes RV feeds are 30 Amp, not 15, and have twist-lock connectors and/or 240 VAC connections. It all depends. As long as the connection meets the standard for Voltage and maximum potential current it is okay. Otherwise the meter will probably fry.
  • hosealmond
    hosealmond Registered Users Posts: 8
    Re: noob wants to go solar on fifth wheel has questions

    I know it would phsyically plug in fine,I need to find out if it is a 15 or 30 amp gonna check,Ok yeah it is 30 amp gonna have to keep looking.Thanks!
  • hosealmond
    hosealmond Registered Users Posts: 8
    Re: noob wants to go solar on fifth wheel has questions

    Okay the connector from the rv is 30 amp but its hooked into a cnnector that is a female 30amp to 15amp male which then plugs into the receptacle,The meter I linked to below is 15amp
    I wonder If that would work then as the adaptor plugged into the receptacle is also only 15 amp?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: noob wants to go solar on fifth wheel has questions
    hosealmond wrote: »
    Okay the connector from the rv is 30 amp but its hooked into a cnnector that is a female 30amp to 15amp male which then plugs into the receptacle,The meter I linked to below is 15amp
    I wonder If that would work then as the adaptor plugged into the receptacle is also only 15 amp?

    It's not so much a matter of "can you physically connect it?" as "will there be more current flowing than the meter can handle?"
    If you can install a 15 Amp 120 VAC fuse on the "load" side of the meter that should prevent it being burned up in case your RV draws more than that. Keep in mind that some 3-prong outlets that look just like that are actually rated for 20 Amps, and even 5 Amps over on the meter could fry it.
  • Volvo Farmer
    Volvo Farmer Solar Expert Posts: 209 ✭✭✭✭✭
    Re: noob wants to go solar on fifth wheel has questions
    hosealmond wrote: »

    An 80 watt 32 inch lcd tv with dvd player

    2 laptops

    propane stove

    propane water heater.

    the lights are all 10 watt,about 6 or 8 of them.

    a small crockpot I use from time to time.

    A small juicer around 400 watts.

    A small steamer for veggies.

    So just how crazy is my idea to attempt all this?

    No refrigerator?