Forum Discussion

bcarroll's avatar
bcarroll
Explorer
Jun 02, 2014

Solar Panels...

I am very interested in Solar panels for my trailer but not sure about how much is needed. Seems like different sources state different amounts of wattage is needed.
My trailer has the usual constant battery drains.. couple of alarms, fridge control panel, radio light, and the normal discharge of a battery. It also has electric jacks(both stabilizer and tongue), and electric awning. I have need of running a CPAP at nights.
While dry camping I would not be using the Microwave or AC, spending most of the time outside. My lights are about 1/3 LED(in the process of converting them all). I would rarely, if ever, use the heater.

I have 2 grp 24 12 volt batteries that won't make it a week. I am looking for something to allow me to last a week and still have enough juice to put the trailer on the hitch.

I am leaning towards a portable panel set up as I could not do any installation myself.
I was told that an 80 watt panel would be sufficient, but... not sure about anything on this subject. I don't want overkill on this, but as I said, need enough juice to hook it up for the trip home.
Any real world advice?
Seeking Advice
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jun 03, 2014
    Hi,

    Then go get Apache Open Office (its free):https://www.openoffice.org/

    And read the golden rules of solar link, then you may understand MPPT and PWM.


    bcarroll wrote:

    I don't have MS office on my laptop and for some reason when I select a free trial for office it says it's only $9.99/mo...lol

    PWM? MPPT? Adjustable set points? a temperature probe? I plead ignorance to all. Man, I really wish I could open those files!

    I will read up on what I can...thanks!
  • time2roll's avatar
    time2roll
    Nomad
    Jun 03, 2014
    Two batteries.... maybe about 200 watts. More in winter less in summer.

    PWM = Controller using Pulse Width Modulation method of voltage control basically clips the 17 to 22 volts present on a nominal 12v panel down to proper charging voltage. Use with 12v panels only. Low cost option.

    MPPT = Controller using Maximum Power Point Tracking is a sophisticated method to extract every watt from the panel by converting voltage into more amps vs just clipping voltage. These can be used with 12 volt, 24 volt and higher panel ratings. More money at about $200 minimum.

    Batteries actually prefer the voltage to be adjusted with change in temperature. The better controllers provide this function.

    Better controllers also have adjustable charging voltage to better match your charging specs.

    Don't go too crazy with all this. Just get some 12v panels and controller and mount them up. It will work well.

    Forum Members Solar Installations With Pics
  • bcarroll's avatar
    bcarroll
    Explorer
    Jun 02, 2014
    pianotuna wrote:
    Consider moving to led lights.

    Here is a simple flow chart.

    Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

    One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

    Solar Spread Sheet N8GS

    For a nice explanation of solar, try this link:

    Golden rules of solar

    I don't have MS office on my laptop and for some reason when I select a free trial for office it says it's only $9.99/mo...lol

    PWM? MPPT? Adjustable set points? a temperature probe? I plead ignorance to all. Man, I really wish I could open those files!

    I will read up on what I can...thanks!
  • bcarroll's avatar
    bcarroll
    Explorer
    Jun 02, 2014
    camper19709 wrote:
    Hi!
    I suggest a 120watt panel permanently attached to the roof. That is what I have. Attachment to the roof is very safe as long as lots of sealant is used on the screws. Clean it once in a while and forget it's there doing it's job. The 120 does a good job of keeping my two 6volt batteries charged. I can drain them with lots of use during the night and once the sun comes up they get charged and ready for another night.
    Hope this helps
    Chip
    Thanks for the input! Eventually I would like to permanently attach panels but want to try it first without the major investment of purchasing and installation.
    That and I'm not sure the trailer I have now will be my long term trailer...
  • bcarroll's avatar
    bcarroll
    Explorer
    Jun 02, 2014
    mwool wrote:
    Solar is cool but you might want a small portable gen instead. I use a small Yamaha converted to propane so I do not have to carry gas.

    If you still go solar it is better to have a 24 V panel as it will maintain charging in lower light. But not sure any of the portables are 24 V. But there are others here with experiance with portable ones.

    I assume you already have an inverter for your A/C items?
    I am leaning away from a generator because of the noise...just came back from Memorial day camping and people around me had a generator, which was not pleasant for me...though I would have loved to had one myself...

    Since I do not claim any knowledge of the ins and outs of electricity, a 24 V panel on a 12 V system just doesn't seem right...won't that damage the system?

    The only A/C item I would need an inverter for would be the CPAP machine...easily gotten.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jun 02, 2014
    Consider moving to led lights.

    Here is a simple flow chart.

    Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

    One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

    Solar Spread Sheet N8GS

    For a nice explanation of solar, try this link:

    Golden rules of solar
  • camper19709's avatar
    camper19709
    Explorer
    Jun 02, 2014
    Hi!
    I suggest a 120watt panel permanently attached to the roof. That is what I have. Attachment to the roof is very safe as long as lots of sealant is used on the screws. Clean it once in a while and forget it's there doing it's job. The 120 does a good job of keeping my two 6volt batteries charged. I can drain them with lots of use during the night and once the sun comes up they get charged and ready for another night.
    Hope this helps
    Chip
  • mwool's avatar
    mwool
    Explorer
    Jun 02, 2014
    Solar is cool but you might want a small portable gen instead. I use a small Yamaha converted to propane so I do not have to carry gas.

    If you still go solar it is better to have a 24 V panel as it will maintain charging in lower light. But not sure any of the portables are 24 V. But there are others here with experiance with portable ones.

    I assume you already have an inverter for your A/C items?

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