Design idea: RV battery system

Tom Cleary
Tom Cleary Solar Expert Posts: 37
Although this will be my first solar rig I have read through a lot of posts and think my system is designed and sized correctly for the application in mind. Just want to say thanks .. hope i am not being repetitive saying that, but the replies to previous queries have been a huge help. Thanks if you have the time to offer suggestions.

My setup is a Eurovan 1993 with which I go dry camping in northern San Diego County. My power budget covers a few lights, a laptop, a swampy evaporative cooler in the summer -- 200 watts or so ought to be enough I figure and still have a little extra for backup. The PV panels will be set up outside the van (about 50 ft away) rather than on the camper roof so the van can be parked in the shade. This is my proposed system:

Kyocera 24 volt 185 W panel with MC4 connectors
Two lengths of 50 foot 8 AWG (100 foot roundtrip) plus a 30 amp fuse to connect panel and controller
Rogue 30 amp controller
Shunt sensor
Bogart Trimetric 2025
Two 12 volt deep cycle flooded cell batteries (Costco)
Morningstar Sure Sine 300 inverter
Ironridge universal ground mount1 panel-UNI-GR/02
1/o welding cable for battery interconnections
1/o cable plus 40 amp fuse for controller-to-battery connection

Best,
Tom

"If it weren't for electricity we'd all be watching television by candlelight.”
George Gobal

Comments

  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: Design idea: RV battery system

    If you are already budgeting 200 watts/hr for swamp cooling, you could go a little higher and get an A/C. You can see my thoughts on this here: http://forum.solar-electric.com/showthread.php?t=9287

    Mounting might be a problem in a Eurovan, but its worth thinking about.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    Re: Design idea: RV battery system

    Is that 200 watts or 200 Watt*Hours per day? Using PV Watts for San Diego, CA (note, I have entered 1.85 kW for panel size and moved decimal point one place to the left--PV Watts only accepts a minimum of 1 kW of solar panels):
    "Station Identification"
    "City:","San_Diego"
    "State:","California"
    "Lat (deg N):", 32.73
    "Long (deg W):", 117.17
    "Elev (m): ", 9
    "PV System Specifications"
    "DC Rating:"," 0.19 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.1 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 32.7"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","12.5 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 4.83, 13.3, 1.662 (i.e., $1.66 of power per month)
    2, 5.35, 13.3, 1.662
    3, 5.91, 16.3, 2.038
    4, 6.52, 17.2, 2.150
    5, 6.05, 16.5, 2.062
    6, 5.98, 15.5, 1.938
    7, 6.26, 16.6, 2.075
    8, 6.62, 17.4, 2.175
    9, 6.02, 15.5, 1.938
    10, 5.88, 15.9, 1.988
    11, 5.16, 13.7, 1.712
    12, 4.67, 12.7, 1.588
    "Year", 5.77, 184.0, $23.00

    Say you you generate ~15.5 kWH per month per 184 watts of panels during the "sunny months"
    • 15.5 kWH * 1/30 days * 1,000 w/kW = 517 Watt*Hours
    So, you will generate around 500 WH per day of "useful" AC power per day... If most everything is DC power, back out the 0.85 efficient AC inverter derating:
    • 517 Watt*Hours / 0.85 = 608 WH of DC power per day
    I would also look at the physical size/weight of a 185 Watt solar panel... You might be better off with a pair of 135 watt panels instead.

    At 185 watts--getting close to needed two people to setup/pack that large of solar panel.

    Also, remember to stake/secure the solar panel--A gust of wind (or theft) could ruin your day (shattered solar panel from a simple fall is useless).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom Cleary
    Tom Cleary Solar Expert Posts: 37
    Re: Design idea: RV battery system

    Hello Bill:

    Thank you for taking the time to respond to my request for feedback. Correct me if I am wrong but it sounds like the calculations show that my proposed rig may be 'underpaneled?' Is that a useful summing up?

    The other feedback about larger panels being more difficult to maneuver and place is something that I have been wondering about... Dimensions of both panels suggest to me that these are objects that are clunky, and difficult to handle. On the other hand, the difference in terms of size isn't that great, the Kyocera 185 is about a foot wider, and about the same length as the Kyocera 135. The difference in weight isn't that great at roughly 8 pounds, but when you have clunky objects to carry, maybe 8 pounds makes a big difference. I haven't personally handled these panels and this is my first pv project, so I don't have a clear idea.

    Am wondering if you might speak to these two points a little more. If you have the time and inclination to do that, that would be great. Thanks very much.

    Tom
  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    Re: Design idea: RV battery system
    Tom Cleary wrote: »
    Hello Bill:

    Thank you for taking the time to respond to my request for feedback. Correct me if I am wrong but it sounds like the calculations show that my proposed rig may be 'underpaneled?' Is that a useful summing up?

    Generically, everyone is under paneled and overloaded when using solar power--It goes with the territory.

    I am not sure I understand your power need though... If you are talking about a 200 Watt steady 120 VAC load:
    • 517 Watt*Hours / 200 Watts = 2.6 hours of run time minimum for 8 months of the year...
    Assuming the panel(s) are setup correctly (tilted around latitude, pointing south, etc.).

    This is where conservation comes in--Perhaps a 20 watt fan instead of a swamp cooler. Net book running at 20 watts, two 9 watt CFL bulbs, and a 2-5 watt LED spot/reading light = ~43 watts:
    • 517 WH / 43 W = 12 hours per day run-time...
    I would suggest going back and measuring your loads (Amps*Hours or Watt*Hours) with a Kill-a-Watt meter for your 120 VAC loads and/or a DC Amp*Hour/Watt*Hour meter like one of these...

    It really depends on your needs and your environment. Are some of your loads optional or must be powered (i.e., is computer for play or work).

    And how much you expect your loads to grow (more electronics, charging a camera, Internet hardware, etc.). It is not out of the question to expect your loads to double over the next months/years as you find more things to do with your power.
    The other feedback about larger panels being more difficult to maneuver and place is something that I have been wondering about... Dimensions of both panels suggest to me that these are objects that are clunky, and difficult to handle. On the other hand, the difference in terms of size isn't that great, the Kyocera 185 is about a foot wider, and about the same length as the Kyocera 135. The difference in weight isn't that great at roughly 8 pounds, but when you have clunky objects to carry, maybe 8 pounds makes a big difference. I haven't personally handled these panels and this is my first pv project, so I don't have a clear idea.
    Certainly, your physical size and condition will enter into what you feel comfortable with. As will your storage area for the panel(s) on trips. Also, how often you are going to break camp (5x two week trips a year, or 40x 2 day weekend trips, etc.).

    These guys are single thickness tempered window glass (typically) in aluminum frames. It is, more or less, like moving around an aluminum window of similar size--but 3-5x more expensive if you break it (tempered glass tending to shatter the whole panel instead of snapping a small corner off).

    You can probably manage a 185 watt panel without too much problem (virtually the same size as a 175 watt panel which one guy can handle pretty safely).

    Then you are left with the packing issue--one or two 185 watt panels, or two 135 watt panels (or whatever mix you decide on).

    Also, if you look at getting more panels--Say 2x 185 watt panels and you put them in series for 48+ volt Vmp, then you may have to look at the MorningStar TS 45amp MPPT controller--It has a higher input voltage rating than the Rogue.

    In the end--You probably will need to do two or three paper designs (different panels, controllers, packing space, energy output, costs) and see what the pluses and minuses are for you--Vs the energy output you need.

    I am sorry Tom... It probably looks like a I am waving my hands way too much here--But I cannot make any exact statements based on your needs. Much of this will be just personal choices and your requirements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Design idea: RV battery system

    I see a new "rule-of-thumb" developing: For RV's, put as much panel on the roof as you can fit/afford.

    Since they invariably suffer from poor insolation, quite often high temps, and a certain unpredictability of power consumption. ;)
  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    Re: Design idea: RV battery system

    Seems like a good enough rule, 'Coot. Unless your RV is a camper with a 45 degree roof and you're willing to park in the sun. 8)

    Kamala
  • dgsloan
    dgsloan Registered Users Posts: 22
    Re: Design idea: RV battery system

    I should suggest this to my brother - He was camping in Banff the other day and could have used a good "Tilt toward the Sun" to warm up his camper when it was 10F. He claimed that his battery was too heavy for the front of his Scamper and was looking into some cheap LiFePO4 to reduce the weight. He claims his VW gets 35 MPH = but at what cost?:roll:

    Dave

    Seems like a good enough rule, 'Coot. Unless your RV is a camper with a 45 degree roof and you're willing to park in the sun.

    Kamala
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Design idea: RV battery system
    Kamala wrote: »
    Seems like a good enough rule, 'Coot. Unless your RV is a camper with a 45 degree roof and you're willing to park in the sun. 8)

    Kamala

    Not everyone has your amazing foresight, Big K! :D
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Design idea: RV battery system
    Kamala wrote: »
    Seems like a good enough rule, 'Coot. Unless your RV is a camper with a 45 degree roof and you're willing to park in the sun. 8)

    Kamala

    I'm waiting to see what sort of tracker you're going to mount your camper on. :D
  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    Re: Design idea: RV battery system

    A husky on the tongue of the trailer and a bowl of dog chow? :p

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Design idea: RV battery system
    BB. wrote: »
    A husky on the tongue of the trailer and a bowl of dog chow? :p

    -Bill

    With a Red Rock LED3X in a fruit jar to move the bowl around!
  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    Re: Design idea: RV battery system

    Oh. Right. Now trackers are being recommended/suggested. I see. Hmmm. :roll:;)

    I'm a little distracted right now. Looks the the Twins might go 2 and 13 against the Yankees in post season play. :grr:cry::grr
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Design idea: RV battery system

    forget the new 'rule of thumb' and trackers too. just make them portable and remote mounted so you can put them the way you want to with all of that stuff mounted to the roof. that is unless that's where you will store them for travel.:roll: remote mounting is easier and better in too many ways and would be far cheaper to do. if you must have something on the roof then fine as that could be good to give something while traveling, but park out of the sun where and how you want to and place the pvs remotely.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Design idea: RV battery system

    I had a feeling I worded that badly. Let me try again...

    So, Kamala...I'm waiting to see what sort of tracker you will use to turn your entire camper.

    (The husky idea cracked me up.)
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Design idea: RV battery system

    i know how you meant that dwh, but that often means literally that one has to park a certain way in certain areas. remember that most places have non-level surfaces aka hilly terrain in which to park in. if it slopes favoring the north then the roof mounted pvs won't accomplish much. remote mounted pvs take that headache away and one would then not have to worry if they can fit 10 pvs on their roof or how much they can get with flat laying pvs. the 1 or 2 they may elect to place on the roof can be used in keeping the maintenance charge to the batteries even while going down the road.