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Old 05-21-2018, 06:20 PM   #11
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A couple more points:

The inverter will require the same watts in as it puts out. If you pull 300 watts from the inverter you will have to feed it 300 watts. Well almost true. Your inverter will not be 100% efficient so you have to feed it a tiny bit extra.

120 Volts x 2.5 Amps = 300 Watts

12 Volts x 25 Amps = 300 Watts

24 Volts x 12.5 Amps = 200 Watts

Batteries.... You mentioned "6 batteries". Are they AA or 8D? There are a lot of different batteries out there.

I am going to guess that you are looking at GC2's as they are one of the most popular. If so, you would wind up with a 36 Volt battery bank if connected in series. If you want 12 Volts you would connect them by paralleling 3 strings of 2 batteries in series . BAD idea. Trying to properly equalize 3 parallel strings can be very challenging.

I am rambling....

I would suggest taking a look at https://handybobsolar.wordpress.com/ and spend some time on https://www.solarpaneltalk.com/

It is WAY too easy to spend a lot of money on a system that does not perform up to your expectations. The best tool to avoid this is knowledge.
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Old 05-22-2018, 10:57 AM   #12
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That's what I am trying to avoid. We have 4 255w panels and I bought a Renogy 60Ampt MPPT controller that cannot handle over 800w so it's useless to us. We were looking at T105s, but decided on something a little bigger since the Amp hours was greater. I just don't want to keep buying stuff (like the controller) just to find out that it won't work as needed, or we didn't need as much power as we thought because we end up with a 12v refrigerator (which we don't want). I think we are going with the Trojan AEM series.

I am on several forums, but there's never really any clear answers and everyone just starts arguing that their setup is best and know what they are talking about more than the next guy.
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Old 05-22-2018, 11:15 AM   #13
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Do you have the Energy Commander 60 Amp controller? if so, you can run up to 2800 watts. Depends on battery bank voltage.

Let's back up a bit now, what is your daily power requirement?

That is the first question that needs to be answered in the design process.
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Old 05-22-2018, 11:21 AM   #14
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That's what I am trying to avoid. We have 4 255w panels and I bought a Renogy 60Ampt MPPT controller that cannot handle over 800w so it's useless to us.
"Useless" may not be 100% accurate. Firstly, many controllers will clip off the excess power that they cannot handle. I'm not familiar with your model but something to look at. Secondly, if you flat mount your panels, you are likely to see only about 80% of rated output. So, 816 watts on the best of days.

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Let's back up a bit now, what is your daily power requirement?
Good call Steve!
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Old 05-22-2018, 11:31 AM   #15
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Oh... also... refrigerator power use is fairly difficult to measure and/or predict. Big variables (outside temperature, amount of time you like to stand there with the door open staring at the inside, etc.) have a significant impact on it's duty cycle. I mention this as just using the data on the label may not be indicative of actual power consumption.

I have a rather large residential refrigerator (Samsung RF24FSEDBSR - 23 cu. ft). Power consumption was measured over a 54 day period and averaged 64.4 Wh (5.12 Ah @ 12VDC). However; this was a single data point during not very challenging conditions so I don't consider it to be 'good' data but possibly interesting. This amount of power is easily supplied by the sun when, as Steve points out, the solar charging and power storage parts are properly designed/sized.
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Old 05-22-2018, 12:17 PM   #16
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As JD stated there are significant variables that come into play.

I monitored my Frigidaire 10.9cf power consumption over a 3 month period of normal usage with ambient temperatures ranging from around 62F-78F. Daily consumption varied by as much as 20%.

I used my "highest day" when creating my energy budget.


Off topic: JD, have you measured power consumption of your LED lights while using the dimmer?
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Old 05-22-2018, 01:44 PM   #17
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This is the refrigerator we have.


This is the charge controller we have.


I don't have any numbers on me, but we will also have a 32" Samsung TV, a computer, router, led lights, cell phone chargers. Nothing that takes up a ton of electric.

Thanks for all the help.
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Old 05-22-2018, 01:53 PM   #18
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Off topic: JD, have you measured power consumption of your LED lights while using the dimmer?
Just posted them over on my build thread.
http://www.skoolie.net/forums/f32/mi...tml#post270861
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Old 05-22-2018, 02:05 PM   #19
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This is the refrigerator we have.


This is the charge controller we have.


I don't have any numbers on me, but we will also have a 32" Samsung TV, a computer, router, led lights, cell phone chargers. Nothing that takes up a ton of electric.

Thanks for all the help.
I hate to say it, but you have work to do!!

An energy audit requires some time on your part. The items that you have in hand need to have their current draw measured. A tool like the Kill-A-Watt is invaluable. Plug your item into that you can see EXACTLY how much power it is using. Leave it plugged in for a day and you get a nice average. Next, you need to apply an anticipated time element to each item. How long are you going to use it each day? I can't explain it any better than I did here:
Energy Audit - Watt For? - JdFinley.com

If that doesn't make sense, there are plenty of other similar posts out there on the Internet.

Without data, all you can do is guess. Guessing usually results in the what your friends experienced - disappointment. I understand this stuff can be confusing and people may seem to be saying different things but data will eliminate all that. Data eliminates the need to guess.

I thought you previously said that your refrigerator was "300 watt", where are you getting that? Forget I asked, have you measured the current draw over the course of a day? If not, get a kill-a-watt, load it up with food, let it stabilize for a day or so and then start recording (for a couple of days).
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Old 05-22-2018, 02:11 PM   #20
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Ok, I will do that with everything.
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