Need a panel for Building site.

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tmyc
tmyc Registered Users Posts: 3 ✭
in Solar Beginners Corner #1
I'll be building a home in Hawaii Soon. I would like to install a 100w Mono Solar panel with MPPT Charge Controller to my SUV Battery. During the day I would like the car battery to stay charged so I can make sure I have power the next day if I need to charge my laptop, or have my radio running while working. I think I should have Electric within a month or so. It will be grid tied solar. I just want to be able to ensure I can charge something (MY Car) if the gel battery goes dead on me for some unforeseen reason (Like listening to the radio). I want to be able to use this later if I need to after the build is done. So... 100w Crystalline, MPPT Charge Controller (20,40,Etc AMP Why?), something to keep my car battery (Later additional Batteries) from discharging too. It can be a temporary so I can put it in the shipping container when I'm not on the property. I was looking at this, but is there better out there?  Thanks in advance... This is my first Post, but I understand how things work, just need a start somewhere.
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  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    #2
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    If it was me, I'd find out what panels will be going on the house in the future, then purchase one of those to build your temporary system.
    It is easier (IMHO) to make a big panel feed a small temp system than it is to reuse a 12VDC 100W panel on grid tied sstem.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
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  • tmyc
    tmyc Registered Users Posts: 3 ✭
    #3
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    I won't know that till way into my build. Probably 6 months at least. I need something the first month just to keep my car from running out of power.  I have no way to charge anything when its out. 
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,046 ✭✭✭✭✭
    #4
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    If you are going to charge a 12 volt battery with a 12 volt 100 watt panel you wont gain much, if anything from a MPPT controller. Either buy a larger, cheaper panel and use an MPPT controller or a small 12 volt,(read expensive) panel and an inexpensive PWM controller.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    #5
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    Well, then why not buy a kit, this website lists a Samlex MSK-90 90 Watt Portable Solar Charging Kit for 12 Volts DC.
    Looks like it should suit your needs.
    Other companies make similar units.
    I have bought the Harbor Freight small systems before, but the controllers do not hold up well.  The panels are still functioning, but now with inexpensive PWM controllers.

    Depending on your power drain at night, a single battery in the SUV  may not be sufficient.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
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  • tmyc
    tmyc Registered Users Posts: 3 ✭
    #6
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    Its not like I'm going to be using my battery all the time. I just want a safeguard. I just don't want to wake up 2 weeks from now, and have a car that won't start, and NO ELECTRICITY for a mile. I'm not going to push my car! I also don't like to buy cheap stuff... been there done that many times. 
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #7
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    Using a ~100w 12v kit type charging system makes sense in your application. Grid tied panels tend to be large, and not the sort of thing you'll want to haul in and out of a container regularly.

    A 100w 12v panel is relatively portable. I recently bought a couple of 150w 12v panels which are about 3x3'. You would have to have a way of mounting it facing the sun, maybe a simple frame of 2x4s and a couple of clamps?

    The panel will put out ~5a charging. There isn't much point getting a charge controller much bigger than the panel will produce, but it does need to be able to properly charge your battery. You mentioned "gel", but maybe AGM? The controller has to be able to charge at a voltage appropriate for your battery. Also, be aware that automotive batteries are not designed to be deeply discharged.

    If your loads are just a laptop charging and a radio, mainly during the day, the panel may cover the load without discharging the battery at all. This would be the ideal. OTOH, if you deeply discharge the battery overnight, it will be hard on the battery, and the panel may take much or all of the next day to charge.

    Another possibility is to get a lithium auto booster thingy for around $100 so if you draw the battery down too far you have a backup to get the engine started.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #8
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    Get a gekko. You will need one for all the insects there. ;)
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  • just starting
    just starting Registered Users Posts: 235 ✭✭✭
    edited June 2017 #9
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    I would get a 80w panel about 100$ or less on ebay and a sunguard controller made by morning star 30$ from naws our sponser and buy some pre made 20' 12 awg with mc4 conections and two mc4 connectors and a blade fuse holder and bolt it to the battery with conections not clips.I use this as a back up it will work on gel-agm well or a fla with plenty of distilled water to add and a load every day. The panel size is about2'x3'
    200ah LiFePO4 24v Electrodacus Sbms40 quad breaker chest freezer to fridge- Samlex PST 1524 - Samlex pst3024  - 1hp shallow well pump-Marey 4.3 GPM on demand waterheater - mama bear Fisher wood burning stove, 30" fridgarair oven ,fridegaire dishwasher  Unique 290l stainless D.C. Fridge-unique 120l portable fridge/freezer 
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