Solar for camping - Will this work?

Steven LakeSteven Lake Solar Expert Posts: 402 ✭✭

I've seen these advertised (or at the very least recommended) on a couple of the sites I've found during my wind/solar research as good alternatives to anyone wanting to go off grid while camping. I'm looking into these as a possible way to provide power to a remote camp site. Mostly we'll just need the power for laptops while we're there, and we're only looking to use a 40ah car battery to power the inverter, so the needs won't be THAT much, but they will be enough that I want to do some CYOA before I bother doing the KOA in the middle of nowhere. ;)


  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: Solar for camping - Will this work?

    Short answer is the panels are not very good and a few people here have found that the panels do not output near their rated current.

    You can get two poly-crystalline panels that are about 1/2 the size of the 4 panels that will output more energy into your battery/system.

    Some other issues... A car battery is a terrible deep cycle battery. Take them down more than 15% cycling and you will probably end up killing the battery fairly quickly (may last a camping season).

    Next, powering the laptops... You should measure the power (AC or DC) that they will need to use per day based on typical usage. It may range from 18 watts to 60 watts per laptop depending on size/speed/power save settings.

    A Kill-a-Watt meter is great for AC measurements. A DC Amp*Hour/Watt*Hour meter for the DC side.

    Next, selecting the way to power your laptops... You can use DC power adapters or an AC inverter... Both have their advantages and disadvantages.

    DC laptop adapters are not usually very rugged and may not work well with the 10.5-15.5 volts that a deep cycle battery system may present to a laptop computer adapter... There have been a few reports of failed DC adapters on solar RE systems (probably from high voltage during recharging/equalization). In theory, a DC adapter may be more efficient than using an AC Inverter + AC power brick--but you should measure the actual DC current/wattage to confirm.

    For the AC inverter--Choosing the correct size (smaller inverters waste less energy with smaller AC devices) is important. Also, there are TSW (True Sine Wave) type inverters (good and expensive) and MSW (Modified Square Wave--cheap and may cause issues with some AC loads). Small AC wall wart transformers, some electronic power supplies, and some AC motors do not like MSW inverters very well (the devices can overheat). It is difficult to predict which will work OK with MSW and which will not--The old 80/20 rule--80% will probably work OK, 20% may not--but which is which is difficult to guess... If the remote project is critical--you should pony up the money for a good True Sine Wave inverter.

    Here are a couple articles that talk about your inverter options:

    All About Inverters
    Choosing an inverter for water pumping

    Here is a really nice 300 12 volt TSW inverter--May be overkill for your application.

    Morningstar SureSine, 300 Watt Sine Wave Inverter 115VAC

    Lastly, there is a good chance that the 40 AH 12 volt battery is a bit small / wrong type for your application. We really need you estimated loads (watts and hours of operation per day) to recommend the right size battery bank. Too small of battery and you can use all its power within an hour or so--and kill it in days/weeks.

    And too small of solar array can mean a week or longer to recharge your battery bank.

    In general, first choose the smallest/most power efficient laptops you can find that will meet your needs. And run them only long enough to do the job.

    Next, size the battery bank, inverter, and solar array to meet your needs over time based on the location and season. You can run from 2 hours of sun to 6+ hours of sun per day--A huge difference in output from your solar panels. Also, figure that your solar/battery system will be about 50% efficient. For example a reasonably sunny region and not winter time:
    • 45 watts * 4 hours of sun per day * 0.50 eff = 90 Watt*Hours per day
    A typical laptop/net book will run on around 20-60 watts average power:
    • 90 WH / 20 Watts = 4.5 hours per day
    • 90 WH / 60 Watts = 1.5 hours per day
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Steven LakeSteven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar for camping - Will this work?

    Wow, that's a lot of information. But what I've ready so far is excellent! Thanks for the feedback! I'll chew this over and if I have any questions, I'll post back. :D
  • Steven LakeSteven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar for camping - Will this work?

    Ok, I did a bit more research on this, and here's what I came up with. Now note that the solar cells will likely be setup on a rack outside the trailer and not inside. The batteries and misc extras however will be setup inside a pony trailer in the back. The fridge and freezer are only here as an added extra to go with a cabin design I'm using elsewhere. So I figure that if this setup will run the cabin solar design, it should run the camping design minus the two appliances. Anyways, here's the parts I came up with for the system.

    DC Refrigerator – DCR-165
    DC Freezer – DCR-165
    Kyocera Solar KD-135GX 135 Watt 12 Volt Solar Panel (x4)
    Trojan T105-RE 6 Volt 225 AH Deep Cycle Battery (x4)
    Solar Boost SB50DL Solar Charge Controller – 60amp
    Solar Rack (x4)
    Sunlight Resistant Wiring – 60ft
    Xantrex TCB-10 combiner box
    Xantrex BC1.5 4/0 battery interconnects

    I'm assuming I got everything. Again, the fridge and freezer are only for the cabin version of this setup, but are here to give a general idea of the load we need to support for the camping setup. Note, 3000w inverter not listed, as I haven't settled on the best one yet. Anyhow, will this work, am I missing anything, and do I need to change anything on my plans, or can I run with this as it is?
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Solar for camping - Will this work?

    3000 watt inverter??? Seems way way bigger than needed and will like consume 30 watts 24/7 just to run it. 700watt hours / day just to run the inverter, if it's left on.
    Will you actually have loads that large? And at full 3000 watt load, it will be sucking over 250 amps out of the batteries. Won't take long to kill them.
  • SolaRevolutionSolaRevolution Solar Expert Posts: 407 ✭✭✭✭✭✭
    Re: Solar for camping - Will this work?
    I'm looking into these as a possible way to provide power to a remote camp site. Mostly we'll just need the power for laptops while we're there...

    Check out the thread:

    This is very portable and can be scaled up or down depending on your needs. I've found that if it was just for a couple of days with a few hours of lights and laptops I didn't even need to bring the PV panels.
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