What panel should I buy for dry camping flexible or the largest watt panel available

I have a camper van with 4 110ah agm universal batteries.Right now I can charge them by 135amp brushless alternator,Black+Decker smart charger when ac is available or a Honda EU2000.I need to add solar but need hepl.Should
I go for solar film or the most watt per solar panel I can fit?Space is limited and I dry camp in winter in NH .So how effective
are the choices available?I noticed prices are finally dropping is something new coming?Should I wait? I have a Xantrex 2000
watt inverter hooked up with 1/0gauge everywhere.But I still need help recharging them after watching 32"lcd dvd tv,microwave,all the goodies at night and being so far from ac power how can I recharge the house batteries?
Thanks
Mylestone

Comments

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    Welcome, first you need to tally up each load with amount of time used and list it here, before we can proceed with getting to PVs. You may be depleting those 4 batteries. or undercharging. what are the charger specs?

    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    To give you an idea--Here is a Video for a small RV trailer installation in this nice thread from Kevin in Calgary Canada that shows designing and installing solar PV in a small RV trailer. Kevin did post a few weeks ago that the system is still working very well for him.

    More or less, if you can get crystalline solar panels (poly panels are a bit less expensive, mono-crystalline are a bit more efficient and cost more $$$/watt). Typically, campers have limited roof space and "thin film" panels, which are about 1/2 as efficient and need about 2x the square footage for same power". So, unless your power needs are small, you would need mono or poly crystalline panels to pack the most power you can on your roof.

    An option is to remote install the panels (move panels 50' into sun, park camper/trailer in shade) and stake them to the ground (reduce wind damage and theft).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • myles mcswiney
    myles mcswiney Registered Users Posts: 6
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    I have a black+decker smart charger that puts out 40=20=10-amps then shuts down when house batteries are full.I need solar to KEEP them charged,And dry camping allows 135amp alternator or Honda EU2000 gen as chargers.Solar seems to be the answer so should I go for the most watts per panel?Then I need to know all the controllers for charging the batteries safely.
    Thanks Solar Shogun
    Mylestone@comcast.net
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    Not quite sure about your question...

    If you just want to use solar to "float charge" the battery bank during storage, then the size of solar array of around 1% of battery AH rating is "good enough" for most applications:
    • 12 volt battery bank with 220 AH of storage
    • 17.5 volt Vmp of panel * 220 AH storage * 0.01 rate of charge = 38.5 watts of solar panel + inexpensive charge controller
    However, if you want to dry camp and not use a generator very often, then the solar array needs to supply your daily power needs.

    And that means you need to tell us how much power you use per day, where you will be camping, and what season(s) you will be camping.

    For most people, they need to minimize their power usage (conservation) first. Converting to LED lighting, using efficient fans, laptop computer, inverter, loads, etc....

    Solar arrays are usually limited on campers/trailers (maybe 2-4x 135 watt solar panels) that are usually mounted flat too roof (does not capture winter sun as efficient vs tilting mounts). So even running a typical trailer heater + circulating fan can use a significant amount of electricity from "flat" mounted panels with winter sun.
    Using a Kill-a-Watt type meter for AC loads, a Amp*Hour/Watt*Hour meter for DC loads, and/or a Battery Monitor all provide helpful information.

    In the end, most people underestimate their loads and overestimate the output of solar PV panels/battery power systems. Plus power needs are highly personal... What is a lot of power for one person is not near enough for somebody else.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • myles mcswiney
    myles mcswiney Registered Users Posts: 6
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    Hi BB could you direct me to the best(most watts per dollar)solar panel. I don't mind paying for quality as they have to endure snow,ice ,water ect so a GOOD panel is needed.I want to charge 4 110ah house batteries but all the room I have is a van root top.I gather the most watts up there the better.Plus I have to mount them safely so at 70mph they do not become airborne! I then need a solar charger ,controller to charge to my batteries.I want a 12volt system and the controller must be 12 volts also!This is all I know about going solar! Naturally I want everything but realize I have to compromise! I also don't want to advertise to thieves I have a lot of expensive gear on or in the camper van.Can you guide me in the right direction.I know I have to go a bit at a time but thats how I learned how to install 440ah batteries and all the wiring safely and correctly!
    Help my friend
    please feel free to e-mail me at Mylestone@comcast,net
  • myles mcswiney
    myles mcswiney Registered Users Posts: 6
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    Hello I plan on operating a 32' OR i COULD GO SMALLER lcd dvd tv which is operated 12 hours a day when its to cold out! Plus a 1000watt microwave I run off the generator!I have led lighting and propane heating to save power but I assume I will use large amounts of power thus the need for more solar charging.I do cut to the bone with power consumption.I can even switch to a 19"lcd dvd tv that is designed for low power consumption . feel free to e-mail
    Can you help with a solar charging system?
    Mylestone@comcast.net
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    Our host, NAWS, has good products, prices, and service. But, frankly, shipping and local service and support are important too. As always, you will have to research what is the best for you--including shipping/insurance to your front door.

    Picking your appliances for conservation is always important with solar. But, starting with normal rules of thumbs and 4x 110 AH @ 12 volt batteries. First rule of thumb for off grid systems, try for 5% to 13% rate of charge on battery bank with 10% a healthy amount:
    • 4x 110 AH * 14.5 volts charging * 1/0.77 panel+charger deratings * 0.05 rate of charge = 414 watts "minimum"
    • 4x 110 AH * 14.5 volts charging * 1/0.77 panel+charger deratings * 0.10 rate of charge = 828 watts "nominal"
    • 4x 110 AH * 14.5 volts charging * 1/0.77 panel+charger deratings * 0.05 rate of charge = 1,077 watts "maximum cost effective"
    Using PV Watts for Boston MA, 1kW (1,000 wattss) fixed array mounted flat to roof, and 0.52 system end to end efficiency:
    "Station Identification"
    "City:","Boston"
    "State:","Massachusetts"
    "Lat (deg N):", 42.37
    "Long (deg W):", 71.03
    "Elev (m): ", 5
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 0.0"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","11.8 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 1.85, 26, 3.07
    2, 2.79, 39, 4.60
    3, 3.79, 59, 6.96
    4, 4.61, 69, 8.14
    5, 5.58, 83, 9.79
    6, 6.03, 84, 9.91
    7, 6.03, 86, 10.15
    8, 5.43, 78, 9.20
    9, 4.25, 59, 6.96
    10, 3.15, 46, 5.43
    11, 1.89, 25, 2.95
    12, 1.58, 21, 2.48
    "Year", 3.92, 675, 79.65

    Note that for northern locations, tilting the solar array to your latitude (~42.37 degrees), on average, will collect a heck of a lot more energy during winter:
    "Station Identification"
    "City:","Boston"
    "State:","Massachusetts"
    "Lat (deg N):", 42.37
    "Long (deg W):", 71.03
    "Elev (m): ", 5
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 42.4"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","11.8 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 3.36, 55, 6.49
    2, 4.36, 65, 7.67
    3, 4.79, 76, 8.97
    4, 4.92, 74, 8.73
    5, 5.33, 79, 9.32
    6, 5.41, 74, 8.73
    7, 5.60, 79, 9.32
    8, 5.64, 81, 9.56
    9, 5.13, 73, 8.61
    10, 4.65, 71, 8.38
    11, 3.14, 47, 5.55
    12, 2.98, 47, 5.55
    "Year", 4.61, 820, 96.76

    Normally, for a cabin/home, I like to suggest that you design for "no generator use" for 9 months of the year (the last 3 months is normally winter and, for most locations, it is more cost effective to use a small genset during poor weather).

    So, from above, February is the "9th month" and for a 1,000 watt array tilted to latitude (second table), you would collect ~65 kWH per Month (65,000 WH per month), or for the above suggestions:
    • 65,000 WH per Feb / 28 days per Feb = 2,321 Watt*Hours per day in February
    If you choose the minimum solar array of 414 watts, then the amount of power per day per February, here is the math:
    • 2,321 WH per day per Feb * 0.414 kW array = 961 WH per day (Feb)
    • 961 WH per day / 12 volt battery bank = 80 AH @ 12 volts per day (Feb)
    That is not a lot of power, but it is enough to for lights (CFL/LED), small fan (mix heat), and a laptop computer/modem. And if you use a flat mounted array, you will get 1/3rd less power.

    Hope this helps.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • myles mcswiney
    myles mcswiney Registered Users Posts: 6
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    I need a system that will recharge 4 110ah agm batteries drained 50% every day.Is that possible? I always plan for the worse case scenario and go from there.I gather a charge controller should recognize how much power is missing and replenish it as best as it can depending on how many watts I can put on the van roof without advertising "I have a Ton of solar power equipment and more inside just waiting for you to remove it!!)
    Thanks
    Mylestone@comcast.net
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    God (or the devil) is in the details... Where will the system be? Can you tilt the array? Seasons/months of the year? etc...

    So, just to make some basic assumptions. 220 AH @ 12 volts per day, assume a minimum 3 hours of sun 8 months of the year for Boston area (~ 8 months of the year), AGM bank with 90% efficient batteries, and 77% derating for solar panels + charge controller, mounted flat to roof.
    • 220 AH * 14.5 volts charging * 1/0.90 eff battery * 1/0.77 system derating * 1/3 hours of sun per day = 1,534 watt solar array
    From our host NAWS (does not include shipping/insurance costs--which can be substantial):



    Kyocera 235GX-LPB


    $395.00 per panel

    $1.68 per watt



    • 1,534 watt array / 235 watt solar panel = 6.5 = 7 solar panels (235 watts per panel (~66" by ~39" rectangular panels)
    For various reasons, you may end up making a choice of 6 or 8 panels to give you a higher Vmp array (smaller wiring).

    You will need a fairly large charge controller:
    • 8 panels * 235 watts * 0.77 system derating * 14.5 volts charging = 99 amps "nominal" into a 12 volt battery bank.
    So, you would need a pair of 60 amp (or larger) solar charge controllers (around $500 to $600+ per controller).

    Does this look like the system you need?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    A friend of mine did a complete set up for his Teardrop trailer, I believe he is a member here as well http://home.comcast.net/~bdosborn/Boxcar/BoxcarSolar.html
  • myles mcswiney
    myles mcswiney Registered Users Posts: 6
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    This panel looks like it meets all my needs its 235watt output but I can fit just one on the roof should I go for a more watt panel,250+watt?! Now what charge controller do you recommend?
    And what do you recomend after that?I have heard of devices that multiply the output of the solar panel charging.Then the Xantrex 2000 inverter has a readout for power left in the house batteries but they (Xantrex)have a digital unit for $280 of so is that an accurate unit to tell me whats left in the house batteries?As for tilting the panel I worry about loosing it at 70mph any Ideas?
    Thanks BB
    Mylestone@comcast.net
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    "I have heard of devices that multiply the output of the solar panel charging."

    you must be thinking of an mppt controller, but i have to clarify that nothing multiplies a pv's output. an mppt controller only recoups some of the lost power and on average may be a 10% improvement from what you'd see with a standard pwm controller. you could go with a cheaper pwm controller or go with something like the rogue mppt controller, but they do cost more than pwm controllers. this will be your decision on the worth of getting as much from your pv as possible. there will be other small mppt controllers coming out some time down the road too if you can wait.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    In the simplest of terms, an MPPT charge controller can match a 12 volt battery to a 100 volt solar array. It is, sort of, like a computer controlled version of a DC Variable Transformer.

    So, either you pick solar panels with Vmp~17.5 volts or so with a PWM type controller, or if you choose panels with a much higher Vmp, and install a MPPT type charge controller.

    You are not going to be able to setup 7-8 big solar panels on your trailer--Only one or two(?). You need to evaluate your loads/needs, or figure out how you will use a genset / shore power to meet your needs.

    One way, use a smaller battery bank for a few lights, radio, cell phone charger, laptop computer, etc At night/during quiet times, and use the genset when your loads are heavier and shore power when you have it (and to recharge the battery bank, if needed).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    So far all of the discussion has been about input and not much about conservation. When I spect and modified our trailer conservation was uppermost. All LED lights, computer case fans in place of a Fantastic Fan, Eberspacher diesel heater, Waeco refrigerator, gas/electric water heater all of which draw little power. I have a high power 185W panel on the roof and now have a 144W flexible that can be taken along and put out on an extension cord. Our trailer is small but conservation is the first step.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: What panel should I buy for dry camping flexible or the largest watt panel avail

    i totally agree the first thing one must do is conserve, but when in a camper/trailer there is automatically a realization by those in it that there is a limit to what they can do power wise and that conservation is somewhat forced upon them so it goes without saying sometimes.

    make no mistake about it that one can use pvs that have a 17.5vmp with an mppt controller. only time a problem could arise is when the pvs are very hot and the vmp drops too low for good mppt operation. this is a rare circumstance for most of us for such a thing to happen with a 17.5vmp rated pv at 25 degree c. if such a case would be then even a pwm controller could have difficulties dealing with it so for the most part 17.5vmp is fine to use unless you will be expecting very high ambient temps to accompany the normal solar heating effects on a pv. places like las vegas or phoenix in the hot summer months can possibly experience problems.