Small Camper Van Solar Setup

Hi,
I am looking for help designing a simple 12volt all DC solar powered system for my camper van.
Hoping to keep the budget under $200.

I am living full time on the road and always boondocking.

I require very little power...I live simply.

Just want to run a propane heater blower fan, dc cooler, and maybe a couple led lights.
All these will not be running at same time all the time.

This is what I figure I'll need...
1 - 50 watt panel
1 - 12volt rv/marine battery
      Charge contoller

 Now will a PMW be sufficient or will a MPPT really be neccessary?

What brand solar panel and charge control do you recommend?

Thank you for the information in advance.


Comments

  • EstragonEstragon Registered Users Posts: 3,576 ✭✭✭✭✭
    What is the amp draw on the heater fan, and the dc cooler?  What is the appoximate duty cycle for each (eg heater runs 24x7 vs an hour in the evening)?  Fridge is typically 1/3 duty cycle (actually running 8hrs out of 24), but my portable DC cooler appears to run constantly by design.

    Based on the above, you can size battery.  A marine "deep cycle" probably isn't the best option.

    A PWM will likely work best.  MPPT generally benefits long pv wire runs and cold ambient temps.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • BB.BB. Super Moderators, Administrators Posts: 28,989 admin
    A propane heater... That can be a big power user... A typical RV heater with fan draws around 8 amps @ 12 volts. Cold night, run 1/2 time,
    • 10 hours * 8 amps * 0.50 duty cycle = 40 Amp*Hours
    -- That is enough to take a typical "car size" battery to 1/2 charge just over night.

    And to recharge that:
    • 40 AH * 14.5 volts charging * 1/4.0 hours of non-winter sun = 145 Watt panel minimum (suggested).
    If your propane heater is (for example) a cat type (catalyst type), and you just need a little electricity to run the auto ignitor--That will be much less energy needed.

    DC Cooler (refrigerator)? That can be all over the map--But any active cooling system is going to consume a fair amount of energy--The wrong one can draw a huge amount of energy.

    Anyway, two ways to design a system... The best is to understand/measure your loads and when/where the system will be used--And design the system to support those loads.

    The other way is to "pick something" (size of battery bank, size of solar panels that will fit, $$$ to spend) and design a system. Then make sure the designed system will support your needs (i.e., a small system, no forced air propane heater)....

    For example, a 50 Watt solar panel for a full time off grid system, I would suggest a 10% rate of charge:
    • 50 Watts * 0.77 panel+controller derating * 1/14.5 volts charging * 1/0.10 rate of charge = 27 AH @ 12 volt battery
    And how much energy can you harvest from a 50 Watt panel mounted to an RV roof...
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Omaha Nebraska
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a horizontal surface:

    JanFebMarAprMayJun
    1.92
     
    2.55
     
    3.64
     
    4.60
     
    5.46
     
    6.26
     
    JulAugSepOctNovDec
    6.18
     
    5.41
     
    4.47
     
    3.17
     
    2.07
     
    1.67
     
    Here we are in Oct/Nov... Something like 2.5 hours of sun:
    • 50 Watt panel * 0.61 DC off grid system eff * 2.5 hours of sun (fall) = 76.25 WH per day rough average
    • 76,25 WH per day / 12 volts = 6.4 Amp*Hours of harvest "average" fall day
    That is a very small system... LED lights, cell phone charger, AM/FM portable radio.

    If you are driving every day--The vehicle charging system would supply most of your energy for charging the battery. If you are parked for days/weeks at a time, and want to use solar only... Then the sizing needs to be much more "exact". Otherwise, you will just keep killing your battery (battery will last weeks/months before needing replacement) and you will be without power much of the time.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 28,989 admin
    A propane heater... That can be a big power user... A typical RV heater with fan draws around 8 amps @ 12 volts. Cold night, run 1/2 time,
    • 10 hours * 8 amps * 0.50 duty cycle = 40 Amp*Hours
    -- That is enough to take a typical "car size" battery to 1/2 charge just over night.

    And to recharge that:
    • 40 AH * 14.5 volts charging * 1/4.0 hours of non-winter sun = 145 Watt panel minimum (suggested).
    If your propane heater is (for example) a cat type (catalyst type), and you just need a little electricity to run the auto ignitor--That will be much less energy needed.

    Anyway, two ways to design a system... The best is to understand/measure your loads and when/where the system will be used--And design the system to support those loads.

    The other way is to "pick something" (size of battery bank, size of solar panels that will fit, $$$ to spend) and design a system. Then make sure the designed system will support your needs (i.e., a small system, no forced air propane heater)....

    For example, a 50 Watt solar panel for a full time off grid system, I would suggest a 10% rate of charge:
    • 50 Watts * 0.77 panel+controller derating * 1/14.5 volts charging * 1/0.10 rate of charge = 27 AH @ 12 volt battery
    That is a very small system... LED lights, cell phone charger, AM/FM portable radio.

    If you are driving every day--The vehicle charging system would supply most of your energy for charging the battery. If you are parked for days/weeks at a time, and want to use solar only... Then the sizing needs to be much more "exact". Otherwise, you will just keep killing your battery (battery will last weeks/months before needing replacement) and you will be without power much of the time.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CrystalCrystal Solar Expert Posts: 111 ✭✭✭
    edited October 2018 #5
    Thanks for the in depth info.

    I looked for specs on both the heater fan and the cooler to no avail.
    According to a search I found the Igloo Powermate 40 dc cooler takes 5 amps.  

    I believe the heater is a catalyst. It ignites by itself.
    The heater fan I can figure no more than 8 amps right maybe less since it a catalyst?


    I will only run the heater for a few hours each night and a bit on chilly mornings.
    The cooler will be ran as needed.  Will use ice if necessary.
    Lights used minimally since I have luci solar lights that work really well at them moment.
    Possibly 100 watt panel would be more accurate for my needs?

    Would this be sufficient with just one 12volt battery?
  • BB.BB. Super Moderators, Administrators Posts: 28,989 admin
    The typical RV heater fan is ~8 amps for everyone I have looked up...

    For the Igloo cooler, that is a thermoelectric type cooler.

    https://en.wikipedia.org/wiki/Thermoelectric_cooling

    There are many good things about TEC, however, temperature drop and electrical efficiency are not good (in a warm climate/car, they do not cool that well--Roughly 35F below ambient; and they take ~4-5x or so more electricity vs a good refrigeration compressor). Not a good candidate for running off a small solar power system.

    Ice for the cooler is one option... Another is some form of compressor based portable cooler, or propane based. Especially if you are going to be dry camping for longer periods of time.

    Here is a link/review of various cooler options... Look for refrigerator compressor based... Do not bother with thermoelectric unless you are driving or setup in a hotel room:

    https://www.fabathome.net/best-electric-cooler/

    If you are going to go with a small solar power system... Then a propane based RV refrigerator is your better option (you should be able to go 1-2+ weeks or so on a 20 lb propane cylinder. Of course, it needs to be vented to the outside for fresh air and fumes.

    RV absorption type refrigerators that run on propane--Many have 12 volt and 120 volt power options. Just beware, propane refrigerators are terribly inefficient when running from electricity (i.e., don't run on 12 volt battery power from a solar power system).

    Sometimes you can find a good one in an RV wrecking yard.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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