# Small solar idea.



## ihookem (Jun 13, 2015)

I have a cabin back in da woods. I have a Honda EU 2000 generator and been using it for 11 yrs. It works very good and is no problem at all. I am however looking into a 100 amp 12 volt marine battery to take along to run 75  watts of incadecent  lights. However, I was thinking , I could easily go with an inverter to stay 120v and just use 3 LED lights. How long though, would 3  8 Watt 800 lumen run on a 100 amp with an inveter? Does the inverter take a lot of power?  And, just a small solar panel should work,, I think.It would be nice to not here the generator and not have to take it along in the car. ( I refuse to keep it up there) . I imagine I need a voltage regulator too huh. What is the cost of something like this?


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## TommyTally (Jun 13, 2015)

Watts= Amps x Volts. Assuming the inverter does not take a significant amount of energy, running 24 watts at 120 volts total per hour is 0.2 amps, so you're talking around 50 hours of runtime with 100 amps. However, I have always heard/read that you don't typically want to completely discharge your batteries. Maybe someone with more experience with these types of setups can chime in as well.

The cost of the system can depend on the type of solar panel/battery bank/inverter you use. I was looking for a small scale startup kit from Renogy awhile back that came with the panels, inverter, and cables (http://www.amazon.com/Renogy-100W-M...1434245019&sr=8-1&keywords=renogy+solar+kit); seemed to be a decent price for that package. You have to keep in mind the sun hours you would get per day and the location of the solar panel to roughly determine how much you can recharge your batteries with a smaller kit like this as well.


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## woodgeek (Jun 13, 2015)

Three 8W lights is 24W.  At 12V that is 2A, not 0.2A.  IF you don't want to go below 50% discharge, a 100 Ah battery will still run the lamps for 25 hours.  The specs on the inverter will tell you what the background load is, they vary a lot.

If you ran the 3 bulbs for 6 hours a night, you would use only 144 Wh (0.144 kWh).  A 40-60W panel would likely be able to keep up with that load in the summertime.  I always found that fleabay had the best prices on small panels.  You would also need a charge controller.  I have found the small/cheap ones to be unreliable (mostly they 'turn themselves off' from time to time, killing the battery.)

I just did a search on fleabay, and 100W panels are as low as $129 buy it now, with free shipping.  The charge controllers are $20 and up.  This one seems popular:
http://www.amazon.com/VicTec-Intelligent-Regulator-Controller-Environment/dp/B00MB0N8K6/ref=sr_1_1?s=automotive&ie=UTF8&qid=1434246667&sr=1-1&keywords=solar charge controller

A 100Ah marine battery and a 100W panel would be a nice cabin system in terms of running a few lights, keeping phones charged, etc.  With those loads, your car/truck could run a 100W inverter as your 'backup' on the cabin system.  Don't forget to put a fuse in the battery line for safety!

I would shop around for a 180W or 400W pure sine inverter, which can be had under $100.  I like the 'Wagan' brand.


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## TommyTally (Jun 13, 2015)

woodgeek said:


> Three 8W lights is 24W.  At 12V that is 2A, not 0.2A.



Right, I was assuming he wanted to stay at 120V with the 3 LED lights as he stated.


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## woodgeek (Jun 13, 2015)

TommyTally said:


> Right, I was assuming he wanted to stay at 120V with the 3 LED lights as he stated.



Sure, 2A at 12V, 0.2A at 120V.  Both 24 Watts.


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## begreen (Jun 14, 2015)

For a solar powered system you might want to consider installing 12v led bulbs and fixtures instead in order to eliminate the loss due to the inverter. A 3 watt 12v LED bulb will provide about 250 lumens. They make dual bulb fixtures that shed a decent amount of light. Then you could use the small 100w inverter that Woodgeek described when you want to run a laptop. Otherwise there are lots of 12v accessories, USB chargers etc. made for RVs and boats.


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## ihookem (Jun 15, 2015)

I would like to stay with 12v but the problem is , if I go back to the generator I have to switch lights back to 120v. We have people using the cabin sometimes and once in a while someone will bring their own generator. If I forget to tell them the lights are 12v , it will ruin the lights. 12v would be cheaper and easier though. My BIL got his solar panel kit from somewhere. It cost him about 500 bucks. It seems like a lot of money but he got a battery that is supposedly just for solar and that was 250 dollars or so. 500 dollars seems like a lot though.


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## begreen (Jun 15, 2015)

The house could be set up with a 12v charger/converter, the same as an RV. When a generator is hooked in, allow it to only power a sub-panel that has 120v circuits for dedicated loads like kitchen outlets for a toaster, refrig or microwave. On the panel there should also be a 120v breaker feeding the charger/converter that will power the all the 12v loads and charge the house battery if it needs it. If you go this route, get a decent unit that has 4 stage charging. This is a good one. http://www.bestconverter.com/PowerM...tage-ConverterCharger_p_412.html#.VX7-8RNViko


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## Dune (Jun 15, 2015)

Begreen beat me to it. Use 12 volt LEDs and skip the inverter. The inverter waste energy and lessen your lighting hours.


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## Where2 (Jun 15, 2015)

I'd suggest the 12V 48 SMD (5050) LED panels (warm white) to light up your cabin. They put out a great deal of light, and are dirt cheap on fleabay. Put them in whatever decorative lamp casing you wish.

I'm presently rebuilding some old 12V RV fixtures that originally used two 18W 1141 bulbs using the 48 SMD LED panels I suggested. I was working with a single 24 SMD (half a 48 SMD panel) unit last night, and although it is plenty bright to keep you from stumbling over furniture and pets, you'll want at least 48 SMD's to try to read without eye strain. The 48 SMD panels draw ~430mA each.


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## woodgeek (Jun 15, 2015)

Personally, I like a good sine wave inverter (with a second cheap one as a backup).  Folks are going to bring 120V tech to use, and will be frustrated without a 120V supply.

Just switch off the inverter when you leave, the parasitic load when you are there is no concern on a 100W+ panel.


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## iamlucky13 (Jun 18, 2015)

ihookem said:


> I have a Honda EU 2000 generator and been using it for 11 yrs. It works very good and is no problem at all



I've heard good things about these little generators. Any idea how many hours you have on it, and how many times a year you use it? Any maintenance besides oil changes and winterizing?



ihookem said:


> However, I was thinking , I could easily go with an inverter to stay 120v and just use 3 LED lights. How long though, would 3 8 Watt 800 lumen run on a 100 amp with an inveter? Does the inverter take a lot of power?



It's not uncommon for a basic inverter to draw a few Watts regardless of whether there's a load plugged in, so first of all, disconnect it when not in use (or wire in a switch). I've also heard the efficiency of cheap inverters is usually around 70% under load, so 24 Watts of LED's on an inverter will probably draw 35-40 Watts. That's still better than running 75W incandescents, but not as good as using LED's designed for 12 V.



ihookem said:


> I imagine I need a voltage regulator too huh. What is the cost of something like this?



$250 or so for a deep cycle battery online, $300 from a boating store. $150-$200 per 100 Watt solar panel (about 2' x 4'). $50-100 for a decent charge controller. So ballpark $500 for a pretty decent kit, not counting the nice AC-DC charge-converter begreen suggested, which would be a bonus feature for more flexibility.

That buys you more peace and quite, a little less wear on your generator, and some gas savings. If I were lucky enough to have a cabin out in the sticks, I'd definitely spend $500 to do something like this.

In the summer, on a sunny day without shade, a 100 W solar panel should get you 500-600 Watt-hours per day, or almost half of what a 100 Amp-hour battery will hold. So that's more than enough for the amount of lighting you're talking about. If you want to use a fan or radio, you could do that sparingly, too. Much more than that will require a bigger system.

If you really need nothing more than lighting, you can get by with a smaller panel and a smaller battery and save a bit.

The charge controller regulates the voltage from the solar panel to what the battery needs, and cuts off power when the battery is fully charged to avoid damaging it.



TommyTally said:


> However, I have always heard/read that you don't typically want to completely discharge your batteries. Maybe someone with more experience with these types of setups can chime in as well.



You will get the best life from your battery if you avoid fully discharging it. The general recommendation is to avoid regularly going below 50% (a multimeter gives a rough estimate - try to stop using when it drops to 12.1V). A deeper discharge here and there won't kill it, but it will slightly reduce the useful life. Around 80% or so (about 11.6V), the life reduction starts to get more pronounced.

That's for a deep cycle battery. A decent quality marine deep cycle can be run to 50% hundreds of times. Marine dual purpose batteries are still fairly robust and might reasonably get 100 cycles or so. Don't use a starting battery like this unless you're really in a pinch. A few dozen deep discharge cycles can potentially be enough to wear out a starting battery.


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## ihookem (Jun 21, 2015)

Lucky 13, I wish I had an hr meter on it. I use it for work sometimes but mostly for the cabin. I imagine I have 30 hrs a yr for 11 yrs at the cabin and another 50 hrs for work. So, 350 hrs. I only change oil every yr and started running Amsoil 5 w 30 . I have some left over from our car. I let it run out of gas if Im not going to use it for several months. I am sure I could get away with a very small solar panel. I used to bring an old battery from a car . It lasted one night at best with 50 watt 12v incadecents. With LED's I am sure it would last 2 nights with a decent battery. I will look on Craigslist and see if I can get something foe a solar panel. I also might just take my Marine battery ( 105 AMP)  and see how long it will last with a small radio, and 3 7.5 Watt light bulbs.


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## Seasoned Oak (Jun 26, 2015)

It will be nice when LI-ion are cheap enough for this application. My cell phone recommends  taking the charge down below 15% before recharging. THey are lightweight compared to Lead acid and more power dense.


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