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Marchandiso
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# Posted: 1 May 2015 02:00pm
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Reviving this old thread to give an update and to thank everyone that helped me get a better understanding of things
Last year I chose to go with a "small step" approach. I wired everything except the 12v lighter socket and chose not to buy any solar pannel as I was waiting for a deal to come by. I only used electricity for light purposes with 3w bulbs and was carrying my battery back and forth to charge it when needed.
After a year of waiting for a deal, I was pretty dead set on getting a 100W solar kit for 260$ but I got lucky yesterday and found a brand new 225W kit for 320$ that someone had bought but ended up not needing it. Its a lot more than I need but for the price, I coulnd't pass up. Products are as follow:
Pannel
http://www.canadiansolar.com/product/cs6p-p.html
Controller
http://www.westech-solar.com/download/westmppt.pdf
I'll set it up in the next few weeks and post pictures.
Thanks again for all the help people!
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offgridjunkie
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# Posted: 1 May 2015 05:02pm
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Quoting: Marchandiso After a year of waiting for a deal, I was pretty dead set on getting a 100W solar kit for 260$ but I got lucky yesterday and found a brand new 225W kit for 320$ that someone had bought but ended up not needing it. Its a lot more than I need but for the price, I coulnd't pass up. Products are as follow:
I am running a very similar system as you and you are really not going to regret this decision. By stepping up to 24 volt panels you are going to have less loss from the panels to the Charge Controller and using the MPPT is really going to keep your batteries happy.
Now lets talk battery- I hope you went with an AGM battery - Reason for this is they do not freeze and can handle a higher charge rate of c/5 rather than c/8.
You are going to be pumping out 18.75 AMP per hour of real sun, so battery size is going to be:
c/5 = 100 AMP-hr (AGM only)
c/8 = 150 AMP-hr
c/10= 187 Amp-hr
I currently use a 210 Watt 24 volt panel, 40 AMP MPPT controller and a 100 amp-hr AGM battery. I run a Dometic 12v fridge, cell phone charges, cell phone booster, and lights - never needing the generator. My battery is in float mode by 11:30AM even in the winter.
Nice work on the system.
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Marchandiso
Member
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# Posted: 5 May 2015 12:57pm
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Quoting: offgridjunkie I currently use a 210 Watt 24 volt panel, 40 AMP MPPT controller and a 100 amp-hr AGM battery. I run a Dometic 12v fridge, cell phone charges, cell phone booster, and lights - never needing the generator. My battery is in float mode by 11:30AM even in the winter.
This is very interesting.. I recently bought an old RV fridge that runs on 12v or propane. I was going to run it using propane but now I'll double check ifn I'd be better off plugging it in the electrical system. Thanks!
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razmichael
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# Posted: 5 May 2015 01:46pm
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Two-way RV fridges do not use condensers but are absorption fridges. The propane has a small flame to heat the ammonia. When run on 12v (or some also have 120v options), a small electrical heater does the job of the flame and is a power hog. In an RV you really only use the 12v while driving as it will run down a battery in very little time.
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offgridjunkie
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# Posted: 5 May 2015 02:36pm - Edited by: offgridjunkie
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And to clarify, My Dometic fridge is the Ice Chest style (12/24 volt or 120AC). It draws 275 Watts per 24 hr period. I agree with Razmichael, the RV fridge will drain your battery in a hurry at 12 volt.
My Fridge/Cooler URL
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Marchandiso
Member
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# Posted: 6 May 2015 10:07am
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Ok, looked into it and you're right, propane it will be. Little worried about the smell and having to cut a hole in the wall to vent it though.
Side question:
A friend asked if I needed a 3000W modified sine power inverter for the summer as he wont.
At the moment I'm using battery tools to do all my work at the cabin but using corded tools would speed up the work.
Question is 3 fold
I would mostly need it to run a circular saw and a 12amps, 1.5hp compressor.. Enough power or am I pushing it?
If I use it only in peek sun time (11am to 3pm) will it grind power out of my battery or will the pannel be providing enough power to run the inverter?
If I use it only in peek sun hours can I plug this straight out of the charge controller?
Chart shows only out of the battery http://www.westech-solar.com/download/westmppt.pdf
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offgridjunkie
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# Posted: 6 May 2015 02:36pm - Edited by: offgridjunkie
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That 3000 watt inverter will cook your batteries fast. To use power tools with a small system, you really need to use a generator. A good rule of thumb is to use an inverter matched to the number of watts of Solar panels you have. For example, if you have 500 watts of panels on the roof, you would not exceed a 500 watt inverter. For your panel, I would not exceed 300 watt inverter. This has to due to the discharge rate and charge rate your battery bank can handle (C/8 vs c/10). Also, you always want to run the inverter directly off the battery. As you use power from the battery, the charge controller will step up the power it is adding back to the batteries. But no matter how much you spend on a CC, it will only put in as much power as it is getting from the panels and what the battery will take. You need to have a balanced system.
What are you using for batteries?
You will not smell the propane from your fridge. Unfortunately you have to vent it to the outside.
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creeky
Member
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# Posted: 6 May 2015 03:50pm
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Quoting: offgridjunkie . But no matter how much you spend on a CC, it will only put in as much power as it is getting from the panels and what the battery will take.
just to clarify. a cc will output the full range of power coming from the panels, regardless of the state of the batteries, to your loads. your inverter can draw all that power plus power from the batteries if it is powerful enough.
In my case I can output 1600 watts of power in full sun from my panel sets. If my batteries are full (in float) the power coming to the appliance can come fully off the panels.
In fact i do this regularly. Two days ago I ran my dishwasher which draws 1200 watts in the heating cycle. I watched as my inverter went to max and my CC read just over 1600 watts being output. My batteries stayed on "float." which is fully charged and typically requires around 150 watts (i have small loads still running).
Two important points to consider:
1) it's now recommended to put your inverter and your CC power cables on the bus next to each other. this allows the CC to move power directly to your inverter most efficiently.
2) MSW inverters can toast some portable power tool batteries. I recommend only using pure sine inverters. They are pretty cheap now.
Finally. That's a nice rule of thumb offgridjunkie. And it makes perfect sense. I have a 1600 watt inverter after having a 3kw inverter. I way prefer the new one. Draws way less on idle. And is more than enough for my needs.
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offgridjunkie
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# Posted: 7 May 2015 12:56pm
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Quoting: creeky 1) it's now recommended to put your inverter and your CC power cables on the bus next to each other. this allows the CC to move power directly to your inverter most efficiently.
Exactly, this is the correct way to do it. My warning was to not connect the inverter to the Load terminals on the Charge Controller.
If you are going to do a really small system, use one of these: URL This way everything is fused at the battery for ultimate protection and keeps things neat and tidy for small spaces. With the Dual Terminal, you can run different amp fuses to match your controller and inverters recommended fuse.
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creeky
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# Posted: 29 May 2015 12:28pm
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didn't see this but 
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