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Thread: Solar?

  1. #1

    Default Solar?

    So I currently have a couple solar panels in my emergency kit. Two Coleman 6w panels and an el-cheapo 1.5w harbor freight special. I used to use them to trickle charge my motorcycle at different times but I would like to build a set up to maintain a full size car or deep cycle SLA battery as well as a separate setup to run NiMH and/or li-ion charger off of. What is required for this? Is it cost effective?

  2. #2

    Default Re: Solar?

    Quote Originally Posted by Buck91 View Post
    So I currently have a couple solar panels in my emergency kit. Two Coleman 6w panels and an el-cheapo 1.5w harbor freight special. I used to use them to trickle charge my motorcycle at different times but I would like to build a set up to maintain a full size car or deep cycle SLA battery as well as a separate setup to run NiMH and/or li-ion charger off of. What is required for this? Is it cost effective?
    There are many threads dealing with this. Typically you have to decide how much current you need to charge things and at what voltage mostly 12v or 5vdc setups.
    I'm not sure what you mean by "cost effective". Unless you really need solar, the upfront cost of panels and associated hardware won't pay itself off in electricity savings very quickly as electricity is dirt cheap something like 10-15 cents per KWH so 1A at 12v to charge a battery from solar would take you 80 hours to get back your KWH (probably closer to 100 hours with losses). If the solar setup cost $25 you could be running it for a long time something like 25000 hours to recoup that cost or 10 hours a day for 2500 days or about 7 years of constant use daily without rain if you have bad weather then could be 1-2 more years added on.
    Perhaps the easiest setup would be a 12v battery and 12v setup and 12v USB adapters with 12V chargers also that way you can charge most things from a SLA battery that you recharge from a panel. IMO if you forsee having access to automobiles then you could invest in $5 worth of gas for the vehicle to run the engine once in awhile to recharge the battery for use charging devices/batteries.
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  3. #3
    Flashaholic* Timothybil's Avatar
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    Default Re: Solar?

    I'm assuming your motorcycle battery is 12v. If so, the same setup you use to trickle charge your motorcycle should also work to trickle charge your car's 12v battery. Just make sure there is a diode somewhere in the circuit to keep the battery from back feeding the panel when the sun is not out. As far as charging USB devices I use a power back to accumulate the solar output, then charge my other devices from there. Granted, there are some losses associated with this method, but it frees me to take the extra power along with me while a second power bank is charging from the solar panel(s).
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    Flashaholic* hiuintahs's Avatar
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    Default Re: Solar?

    Quote Originally Posted by Buck91 View Post
    ...............I would like to build a set up to maintain a full size car or deep cycle SLA battery as well as a separate setup to run NiMH and/or li-ion charger off of. What is required for this? Is it cost effective?
    I wouldn't worry about whether its cost effective if its something you want and/or will be used as an emergency setup. I'll mention what I've done as an example.

    In a disaster situation or grid down for awhile, I plan to use the batteries in my vehicles. That will require a lot more solar power than you currently have. Also when going camping and parking in one location for days.........rather than to have to charge the battery via running the engine or a generator, I will just set out some solar panels. I have an electric 12v refrigerator that I take with me that is the primary consumption of my battery. The battery is good for about a 24hrs. without charging and still able to start the car. The # and size of solar panels is dependent on the amount of current that is being drawn from your 12v battery. For me it's an average of 1 amp or 24Ahrs in a day. Car batteries are typically around 50 to 60 amp hours. There is also the consumption of opening and closing doors and interior lights too.

    So what is needed is a solar charge controller to keep the panels from over charging your battery and one or more decent sized solar panels. Preferable a charge controller that is not mounted on the back of a solar panel but a stand alone unit where you can add additional panels to it as needed. I typically do pretty good camping with 200 watts of solar panel. That is more than I need but you have the night where no power is being generated, cloud cover and the sun moving across the sky causing tree shading before I notice and readjust the location of the panel(s). So you need a lot more than your actual load draws.

    My first solar panel was a 80 watt foldable panel. My next ones were two 50 watt panels. (Those went bad and won't touch that brand anymore). I then picked up a couple of 100 watt panels but that is getting into the max size for easy of portability. I now have six 100 watt panels but mostly for home base. I came across a couple of flexible foldable 80 watt Lensun panels that only weigh 6 pounds each and makes for a nice light weight portable setup for camping. My first charge controller was an Xantrex C35 PWM unit but I have since upgraded to MPPT Blue Sky controllers that I came across cheap on ebay. I mounted them in my own Harbor Freight or Pelican case. I use Anderson PowerPole connectors and can connect up multiple solar panels as long as I don't exceed the 20 amp rating. I made some 30 foot extension cables using 12/2 landscape wire. I'm out of town otherwise I'd take a picture.

    I mention all this not to boast but to just give an idea on what it takes. Like Lynx mentioned, the size or number of solar panels is determined on what appliances or stuff you plan to run from your 12v battery. If just using lithium ion or nimh chargers, the solar panels don't need to be very big. And you can get by with a fairly cheap charge controller.
    Last edited by hiuintahs; 04-15-2019 at 08:07 PM.

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    Default Re: Solar?

    Quote Originally Posted by hiuintahs View Post
    In a disaster situation or grid down for awhile, I plan to use the batteries in my vehicles. That will require a lot more solar power than you currently have. Also when going camping and parking in one location for days.........rather than to have to charge the battery via running the engine or a generator, I will just set out some solar panels. I have an electric 12v refrigerator that I take with me that is the primary consumption of my battery. The battery is good for about a 24hrs. without charging and still able to start the car. The # and size of solar panels is dependent on the amount of current that is being drawn from your 12v battery. For me it's an average of 1 amp or 24Ahrs in a day. Car batteries are typically around 50 to 60 amp hours. There is also the consumption of opening and closing doors and interior lights too.
    Unless you have a deep-cycle battery for your car (which is unlikely), then using it as a power source is probably not a good idea. Anything more than very shallow discharging will really hurt car batteries. You'd be better off to buy a deep-cycle marine battery, and use it as your power source between recharges. And you can always use it to jump-start your car if you ever need to.

    Of course, if it's an emergency, I suppose you should use whatever you have. But if someone is buying a solar setup, they may as well also buy an appropriate battery for it.

  6. #6
    Flashaholic* hiuintahs's Avatar
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    Default Re: Solar?

    Quote Originally Posted by WalkIntoTheLight View Post
    Unless you have a deep-cycle battery for your car (which is unlikely), then using it as a power source is probably not a good idea. Anything more than very shallow discharging will really hurt car batteries...............
    Yes good point but I watch things pretty close. Truck has a Dekka Intimidator AGM battery. Subaru has a Dekka regular starting battery though bigger capacity than stock. Mostly the batteries would just provide the stable 12v power while the solar panels keep up with the load. Both of my portable solar charge controllers have meters for both current and voltage which comes in very handy to monitor things.

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