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DaJTCHA
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# Posted: 24 Apr 2012 18:42 - Edited by: DaJTCHA
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We're just about at the point where I'm ready to install two ridge peak windows on the North and South walls of the "Shed Mahal" so my mind is wandering to air flow, temperature and venting.
I plan on purchasing two Fan-Tastic Endless Breeze Fans and HFT Solar Panel Array. I've got a coupon for the solar panel set for $149, so I can't beat that.
Here is my plan and I'd like to hear critiques please:
(1) Solar Panel Array
(2) Exterior Mounted Marine Deep Cycle Batteries Wired in Parallel
(2) Fan-Tastic Fans Bracketed to fit either window in a push pull configuration
I wish to make a receptacle plug mount that will accept the leads from the panel so that I can move the array in / out of the cabin and reposition it to the track the sun. I figured with the appropriate gauge wire and a "plug" of sorts, this would be quite convenient. I have over 30" of room from ground level under the high side of the joists and figured this would be the best place to permanently mount the battery box housing the two batteries. I'm thinking that I can purchase a pair of jumper cables and use the HD wiring to handle the paralleling from battery to battery and then run the 12volt leads into the structure from underneath. My biggest need is to vent the loft area (where we'll sleep in the evening) during the day to remove the excess heat build up. Because we're in Pa. and in the mountains, in the evening it turns considerably cooler than daytime...sometimes the swings are crazy like 70-80 degrees down to 45-55 degrees! So the fans will likely be running at full throttle while the sun is providing the most free energy to recharge the batteries. Our energy demands will be quite low in the evening and likely be in the form of LED lighting. But realistically, during the hottest of the summer/fall months...we'll be consuming the most energy from 12-6pm and then nothing until the following day. I should also mention that we usually only camp for 2-3 days at a time because of the demands of work, so keep that in mind when considering whether I'll "run out" of energy. I'm thinking not...
What do you guys think of this plan?
Thank you,
Dj
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Rob_O
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# Posted: 24 Apr 2012 19:37
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How much power do those fans use? I bet two of them use more than the 45 watts that kit claims to make
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DaJTCHA
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# Posted: 24 Apr 2012 19:42
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They are listed to consume a maximum current draw of 3 amps each and I believe this is on the highest setting. So let's just say 6 amps total. This is the reason I mentioned having two deep cycle batteries in parallel. I figured during the early morning hours until the sun really started to heat up the loft area and the times we weren't running the fans, they could be recharged by the panels.
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Rob_O
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# Posted: 24 Apr 2012 20:21
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Some rough math suggests you will get about an hour of fan time for 2 hours of sunshine, plus you want to run other loads. If you want to take the panels in when you go home I don't see you having much success with this setup
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DaJTCHA
Member
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# Posted: 25 Apr 2012 12:53
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Rob_O-
If both batteries were fully charged...how does this affect run time calculations? Thank you for your help!
Dj
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VTweekender
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# Posted: 25 Apr 2012 17:18 - Edited by: VTweekender
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Well, lets say you parallel 2 batteries that are 120AH to come up with 240AH, you only want to draw down to 50% to 60% of that as you don't want to draw the batteries down to nothing and damage them as a rule. If you draw the 2 fans at 6 amps per hour for about 6 hours, and lets say you draw another 10 amps over that day with other devices you will be using up about 46 to 50 amps per day of your available 120-140 amps stored at a full charge.
The 45 panel in your area may only get about 3 hours of good sunlight to recharge the batteries on a sunny day, which will give you maybe 5 to 8 amps per day recharge. So, simply put, USING about 50 amps per day, RECHARGING about 8 amps per day, equals you will not keep up with usage.
If you let the batteries fully recharge before you go for a weekend you will most likely make it through, but if you take the system home and the batteries are drawn down lets say 40% when you start the visit, you won't make it as the panel won't keep up with the draw.
A 400 watt panel array would be closer to what you would want to handle those needs.
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Rob_O
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# Posted: 25 Apr 2012 21:10
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Quoting: DaJTCHA Rob_O- If both batteries were fully charged...how does this affect run time calculations?
I'd call the numbers VTweekender provided a very good guesstimate to start with. You will need to do some more detailed load calculations to see just how far you can get with the power you have available
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DaJTCHA
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# Posted: 25 Apr 2012 22:52 - Edited by: DaJTCHA
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For conversation's sake....we get about 6 hours of good sunlight as our location is on top of the mountain and we've got an excavated area free from obstructions and in direct sunlight.
We'll do a little adjusting of the numbers in the equation and please critique from there...
240AH batteries (fully charged from home)
(2) Fans total draw of 6amps/hour run for 6 hours = 36AH usage
(4) LED Lights "modules" Run for 3 Hours = 3AH
(1) 45 Watt Panel Array Recharging @ 8AH (conservative guesstimate here)
Max of 3 day stay at a time...
39AH X 3 = ~120AH usage
Recharge = ~24AH
Total usage = 95AH
We're looking at a 40% reduction approximately. Hmmm...you're right guys, I may wish to consider something larger, Maybe buying two of this arrays and a larger charge controlling might be the ticket.
Please comment, I appreciate the learning experience.
Dj
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Rob_O
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# Posted: 26 Apr 2012 00:04
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The solar kit is going to cost about the same as another battery. If you can charge at home the money will be better spent on another battery
Hauling batteries will get old real quick. You will also wish you had more power on the third day camping. Maybe something around 400AH of battery with a 100W panel charging the system all week would be about right for your needs?
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DaJTCHA
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# Posted: 26 Apr 2012 00:09
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I'm thinking that I may find out quickly (maybe our first multi-day camp out) that your suggestion of purchasing another set of panels and another battery will be the route to go. I'll let you guys know how this works out. I think the biggest factor(s) is 1. How much sunlight the panels see. 2. How much amp draw the fans exhibit and how long we use them to cool the space to a desirable temp.
Thank you,
Dj
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Sarge
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# Posted: 27 Apr 2012 09:53 - Edited by: Sarge
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HFT (3 15w panels) will produce roughly 2.4 amp hours in perfect conditions for $150 bucks. Plan on about half of that with cable loss etc. So lets say 1.5 amps per hour. Lets say you have (realistically) 4 hours of direct sun on your panels you may produce approximately 6 amps per day.
With 6 amps of solar power you should not exceed 60 amp of battery capacity. You also should only calculate usage of 30 amps of usage per day maximum.
I looked up the fans you mentioned. They draw around 1 amp, 1.5 amps, and 2.6 amps for the 3 speeds each. So if you are on high on three fans you suck down 7.8 amps per hour. So you could run your three fans for about 45 minutes before you have drained your supply for the day.
So...if I wanted to run those three fans on high for say 6 hours....(I will go backwards from the fans/hours)....my usage requirement is
46.8 amps. So I would need (minimum) 100 amp hours of batteries and 10 amps of solar power. 10 amps of solar power equates to (voltage multiplied by amps=watts) roughly 10 amps to 120 watts in a 12v battery system.
Today (right now) I see a 120 watt panel on sale for $160 delivered. Rated at just shy of 8 amps. 100 amps of deep-cycle batteries is roughly $80 bucks each.
If it was my system, and depending on how many hours of direct sun I had, I would go with (2) 120 watt panels and two 100 amp deep cycle batteries. 20 amp charge controller and you are in good shape.
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DaJTCHA
Member
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# Posted: 27 Apr 2012 10:49 - Edited by: DaJTCHA
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Excellent advice Sarge! Can you provide me a link to this panel and the 100AMP batteries please? Any chance you can provide me with the link where it spells out the AH for the Fantastic Fans based on the three speed settings as well?
The only mistake I see is the calculation of three fans. I'll be running just two, but knowing that they consume 1.5amps on the medium setting gives me some room.
Thanks to all!
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Sarge
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# Posted: 28 Apr 2012 09:00
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Sure. I do not know the rules here (forum rules) so I will PM you a link to the panels. The batteries you can get at any Sam Club or Costco. Even WalMart Deep Cycle Marine batteries work well.
The amp info on your fans comes from a review of them on amazon.com a guy did.
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Sarge
Member
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# Posted: 28 Apr 2012 09:03
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Well I admit being challenged sometimes but I cannot figure out how to private message. Oh well....
Here is the source for panels http://www.solarblvd.com/
Great customer service and excellent products.
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MtnDon
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# Posted: 28 Apr 2012 10:36
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There are no PM's here
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Anonymous
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# Posted: 28 Apr 2012 12:54
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Thanks man....that makes me feel better.....
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Sarge
Member
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# Posted: 28 Apr 2012 12:54
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No I am posting "Anonymous".....man I am talented this morning....
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Icebear
Member
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# Posted: 28 Apr 2012 15:42
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Just a thought but with such a temperature swing, have you considered using a convection system that doesn't need fans, or much smaller computer style fans??
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DaJTCHA
Member
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# Posted: 28 Apr 2012 15:53
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Because this is all theoretical at this point, I'd really like to see the real world application of what we're reviewing. We don't spend much time in the loft during the day, we do have some very nice trees that will throw shade on the roof during the day and combined with the temperature swings I mentioned...I may not need to actually vent the area but for an hour or two when the temperature starts to drop. If this is the case, getting the loft cool may be easier than I thought. This is situation will have to be reviewed "live" during the summer months to see how it all pans out.
Sarge- Awesome link! Thank you!
Icebear- I have thought of this and might just go that route.
Can someone comment on the cost of running the fans off an inverter tied to car battery on a running car? I know it is likely to be a PITA, but running a lead from my running car to the shed is a possibility. This might be the first step to discover how much time I need to run the fans to accomplish the goal.
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Sarge
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# Posted: 28 Apr 2012 17:23
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Do you have wind that is fairly average around 8mph-up?
I mean if you are looking at just 2 fans running for a short period of time you could go with a simple wind generator and a small 12v sealed battery of say 12 amps +/-.
I have a small 150watt wind gen just for trickle charging along with 1000 watts of PV. It turns so easy and does not require all the "towers" etc. that large wind gens do. Here in South Texas I would say it turns more than enough to keep a small sealed 12v battery charged up around the 12-15 amp range.
Here is mine on the edge of the shop.
The thing cost like $125 bucks and that included shipping. No controller as it just goes straight to the batteries with a in line 10 amp fuse. 15 amp sealed batteries are like $35-$40 bucks at home depot.
Just thinking out loud here.
I would have a portable battery that I could charge off my car and wheel in the cabin before I would run a cable from my car to an inverter but that's just me.
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DaJTCHA
Member
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# Posted: 28 Apr 2012 17:25
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We do get wind, it isn't reliable or steady...Sometimes we get alot and other days...nothing.
Thanks for the suggestions.
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Sarge
Member
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# Posted: 28 Apr 2012 19:35
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For "testing" I think I would go for a 10-12" battery fan for a few bucks before I bought batteries/inverters/panels etc. Shoot....use rechargeable D cell batteries 
Then you can have a better idea what type of air flow etc. you need without spending much money at all.
I know these things do move some air. We had a couple in our tent a few years back and they do work well and last.
http://www.amazon.com/O2COOL-Battery-Electric-Portable-Black/dp/B002VEDG5Y/ref=sr_1_2 ?ie=UTF8&qid=1335655933&sr=8-2
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DaJTCHA
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# Posted: 29 Apr 2012 21:42
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Sarge-
Well, I cut the holes and mounted the windows today at camp. What a difference. Although it was only 60 degrees, clear sky and sunny...the moment I cut the second hole on the North wall, it was like a vacuum. The air flow through these two little windows is impressive, especially with a moderate breeze. The temperature in the loft dropped significantly and this was without fans.
BTW< thanks for the link...these were the exact fans I was looking at. I was also pondering wiring them to run off a 12volt battery to get more life out of them.
The reason I want the solar system is because it is so cheap with the coupon and we've always talked about getting something "eco friendly" to help us out once the shed was complete.
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Sarge
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# Posted: 2 May 2012 07:38
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Man your cabin looks great. Glad to hear things worked out for you. Ventilation is often an overlooked commodity
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