FAQ:Solar Panel without the Technical Stuff

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Re: FAQ:Solar Panel without the Technical Stuff

Postby eamarquardt » Mon Oct 28, 2013 8:40 pm

eggsalad wrote:What about battery/solar systems on a MUCH smaller scale?

My "battery pack" consists of 2@ 6v 12AH batteries wired in series, for a combined total of 12v 12AH. I like them because they are small and free (out of the recycle pile at work).

The whole system draw is 0.05A for the LED lighting, and 0.3A for the fan. Some quick math tells me I'm not going to need a whole pile of solar panels to keep a charge! A 25W panel gives off 2 amps, right? So 6 hours would be the max charge I'd need for totally depleted batteries?

Seems cheap enough, or can somebody tell me where the errors in my figures lie?


Just that an LED drawing 0.05 amps isn't gonna be very bright and a fan that draws 0.3 amps isn't gonna move much air. But......if yer getting enough light and moving enough air to be comfortable then it works. Also you should figure on only getting about half of the amp/hours out of your batteries that they're rated for.

Cheers,

Gus
The opinions in this post are my own. My comments are directed to those that might like an alternative approach to those already espoused.There is the right way,the wrong way,the USMC way, your way, my way, and the highway.
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Re: FAQ:Solar Panel without the Technical Stuff

Postby eggsalad » Mon Oct 28, 2013 10:12 pm

eamarquardt wrote:
Just that an LED drawing 0.05 amps isn't gonna be very bright and a fan that draws 0.3 amps isn't gonna move much air. But......if yer getting enough light and moving enough air to be comfortable then it works. Also you should figure on only getting about half of the amp/hours out of your batteries that they're rated for.

Cheers,

Gus


Gus, I don't want to question your knowledge, but the LED lighting is a strip of 15 SMD LEDs I found in the junk pile at work. Draw was tested using both the ammeter in the benchtop power supply we use for testing and also with a Fluke 87 DMM. 0.05 amps at 12.6 volts either way. It lights up my TTT quite nicely - I certainly can't stare into it very long!

As for the fan, I found it using a link in another thread.

http://www.amazon.com/gp/product/B000V6 ... UTF8&psc=1

If the specs given on Amazon aren't lies, this fan can move 134 cfm at 0.3 amps draw. The cubic volume of my trailer is approximately 80 ft^3. If my math is right, this fan can refresh the air in my TTT every 36 seconds.

What am I missing?
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Re: FAQ:Solar Panel without the Technical Stuff

Postby eamarquardt » Mon Oct 28, 2013 11:51 pm

Hi,

Rule of thumb you can get 1/2 the rated output in amp/hours out of your batteries w/o serious degradation of their health. So yer looking at about 6 amp hours of use before the batteries are effectively 100% discharged.

As far as the amount of light goes, if you can do what you want to do with the amount of light your string is putting out that's all that matters and they "work". You might want to try reading by them for a reasonable amount of time or doing whatever you plan to do with them on. Real world experience is the "best test". I'm not arguing the point that they don't put out enough light for you.

As far as the fan you referenced goes, I just dug into my "stash" and found a couple of 1.5 inch fans. They draw, according to the label, 0.1 to 0.25 amps at twelve volts. The three inch fan I found says it draws 1.3 amps.

I have no idea how much air they move but given a week or so I can borrow a test instrument and get a reasonable value.

I have installed Fantech vent fans in my bathrooms. They are centrifugal fans so they might draw more compared to an axial fan but the 150 cfm fan draws 55 watts or so. Nearly 150 times more than the Antec fan you referenced.

Fantastic vents are kinda the "standard" on the forum. To move 920 cfm they draw about 3 amps. http://www.fantasticvent.com/products/m ... _6000.html

It just seems a bit "fantastic" that Antec (the fan referenced in your post) can move nearly 50% more air than the Fantastic fan and use 1/10th the power. Maybe they're using Kryptonite magnets? :shock: :twisted: :thinking: :thumbsup: :applause:

Having used a Fantastic fan I wasn't overwhelmed with its output.

I'd be surprised if the Antec delivers 50% more air than the Fantastic fan for 1/10th the power.

Just don't want you to be disappointed with your system but it seems to me that yer planning on getting an awful lot out of 6 amp hours.

A 6' X 4' X 3' space is nearly 80 cubic feet. That seems a bit cozy for a Teardrop sleeping quarters.

Hope this helps.

Cheers,

Gus
The opinions in this post are my own. My comments are directed to those that might like an alternative approach to those already espoused.There is the right way,the wrong way,the USMC way, your way, my way, and the highway.
"I'm impatient with stupidity. My people have learned to live without it." Klaatu-"The Day the Earth Stood Still"
"You can't handle the truth!"-Jack Nicholson "A Few Good Men"
"Some people spend an entire lifetime wondering if they made a difference in the world. The Marines don't have that problem"-Ronald Reagan
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Re: FAQ:Solar Panel without the Technical Stuff

Postby eggsalad » Tue Oct 29, 2013 12:37 am

eamarquardt wrote:Hi,


A 6' X 4' X 3' space is nearly 80 cubic feet. That seems a bit cozy for a Teardrop sleeping quarters.



Quite cozy, indeed. My TTT is 6'10" long. The height tapers from 40" to 30", and the width tapers from 48" down to 28"

If you're curious, you can see the build here:

viewtopic.php?f=50&t=57667

Thanks for your help and input, Gus.
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Re: FAQ:Solar Panel without the Technical Stuff

Postby Shadow Catcher » Tue Oct 29, 2013 7:05 am

The interior of Compass Rose is about 400 cu feet and we are using two Antec 120mm three speed fans. Antec claims they put out about 100 CFM each on high, I for one am a bit skeptical. What I can tell you is we seldom have them more than medium speed and at night often on low and they work just fine. As to the amp draw I would buy that as well. I have ours set up with a DPDT switch and I can power both or one with center off. On medium and low they are very quiet.
The right price (free) is always a good thing and he did not say what kind of batteries they are, they might not be subject to the 50% SOC rule.

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Re: FAQ:Solar Panel without the Technical Stuff

Postby Bogo » Tue Oct 29, 2013 10:05 am

Looking out at fans at Digikey, I see for 3.6W (0.3A @ 12VDC) and under. I see a maximum of 94.2 CFM. CFM ratings from 80 CFM to 95 CFM have wattage ratings of 1.92W to 3.5W.
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Re: FAQ:Solar Panel without the Technical Stuff

Postby Jdhiker » Tue Oct 29, 2013 10:44 am

eggsalad wrote:
eamarquardt wrote:Hi,


A 6' X 4' X 3' space is nearly 80 cubic feet. That seems a bit cozy for a Teardrop sleeping quarters.



Quite cozy, indeed. My TTT is 6'10" long. The height tapers from 40" to 30", and the width tapers from 48" down to 28"


That's about what mine is also. Only 24 sqft floor space. That's about it for a 4x8 teardrop. And plenty of space to sleep.
If you're curious, you can see the build here:

viewtopic.php?f=50&t=57667

Thanks for your help and input, Gus.
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Re: FAQ:Solar Panel without the Technical Stuff

Postby eggsalad » Tue Oct 29, 2013 12:11 pm

Shadow Catcher wrote:The right price (free) is always a good thing and he did not say what kind of batteries they are, they might not be subject to the 50% SOC rule.



For the record, these are the batteries in question:

http://www.batteriesplus.com/product_search/32641-Werker-6V-12AH-AGM-Battery-WKA6--12F.aspx

We use them for the emergency floodlights, and they are replaced annually, regardless of whether or not they've been used. After a year, most of them are still just fine, but rules is rules.
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Re: FAQ:Solar Panel without the Technical Stuff

Postby Esteban » Wed Oct 30, 2013 10:54 am

AM Solar amsolar.com specializes in solar systems for RVs. Their RV Solar Education pages rv_solar_education seem like a good primer on basic solar concepts. Their pdf downloads system_wiring_overviews wiring diagrams for various sized systems are instructive and helpful. With some alteration for teardrop sized trailers they can help you plan your own solar installation.

I strongly suspect that AM Solar sells solar panels from Grape Solar. Probably ones from their Small Off Grid line of solar panels. Like this 100 watt panel GS-S-100-TS and the 160 watt GS-S-160-Fab8

Many of their panels are sold by Amazon.com, Costco, Lowes and Home Depot.
Grape Solar has a 100 watt flexible panel PhotoFlex 100W that is 21.26" x 41.34" and weighs just 3 pounds that looks like a good one for a teardrops roof. :thinking:
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Re: FAQ:Solar Panel without the Technical Stuff

Postby wtcreaux » Sat Feb 08, 2014 11:13 pm

After reading through the various posts and searching online, I'm left with a question - should the controller be closer to the battery or the panel?? :thinking:

Thanks
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Re: FAQ:Solar Panel without the Technical Stuff

Postby eamarquardt » Sat Feb 08, 2014 11:26 pm

wtcreaux wrote:After reading through the various posts and searching online, I'm left with a question - should the controller be closer to the battery or the panel?? :thinking:

Thanks


Battery.

Cheers,

Gus
The opinions in this post are my own. My comments are directed to those that might like an alternative approach to those already espoused.There is the right way,the wrong way,the USMC way, your way, my way, and the highway.
"I'm impatient with stupidity. My people have learned to live without it." Klaatu-"The Day the Earth Stood Still"
"You can't handle the truth!"-Jack Nicholson "A Few Good Men"
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Re: FAQ:Solar Panel without the Technical Stuff

Postby stoneal » Sat Feb 22, 2014 7:44 am

I have a 100 watt panel that I mount on a position able stand to get the perfect angle. My charger controller is 15 amps. I have a group 31 battery. I also have a folding 100 watt panel when space is needed and can't take the larger set up. Either one recharges my system even in minimal sunlight to keep lights, microwave, fan and toys running day and night. I have seen mounted panel but you have to put teardrop in the correct angle which is not always obtainable when camping.116998
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Re: FAQ:Solar Panel without the Technical Stuff

Postby BigBlueToe » Sun Nov 23, 2014 1:44 pm

I'm getting ready to wire my teardrop and I want to make sure I'm doing it right.

Here's what I have:
    I bought a 100w Renogy panel from Amazon that came with a 30A charge controller.
    I bought a deep cycle battery from Batteries Plus for about $100.
    I also have a Battery Tender Jr. from when I had a motorcycle.

What I want it to do:
    Power LED lights - 2 reading lights in the cabin, 1 cabin dome light, 2 porch lights (one over each door)
    Power 12v cigarette-lighter-type receptacles for charging phone, charging Ipad, charging Kindle, running 12v DVD player

My question has to do with how to wire all that up. The charge controller has a place on it for powering lights (it cautions to use low power.) Is that where I draw the power for all my stuff? I was thinking it made more sense to get the power from the battery, but the Renogy how-to videos talk about getting power for lights off the charge controller.

Here's what I was thinking of doing:
    Running wires from the charge controller to the battery. (Do I need a fuse on this? On the positive or negativewire?)
    Running wires from the battery to a fuse panel, and from there sending power out to all the 12V stuff - the lights, the 12v sockets, etc.
    I would also hook up the battery wires from the Battery Tender Jr. to the battery. These would be dead except when I'm parked by shore power.

My assumptions - please tell me if I'm wrong:
    The charge controller will keep the panel from overcharging the battery.
    It will also detect when the Battery Tender Jr. is charging the battery and will reject any electricity "going the wrong way" - into the solar panel.
    I can run all the lights and socket directly off the battery terminals as long as I have fuses to protect everything.

I'm certainly no electrical engineer, so I won't be offended if someone tells me my assumptions are foolish and my plans won't work. Please comment. I would appreciate all the help I can get.

Thank you!

Gordon
Central Coast of California
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Re: FAQ:Solar Panel without the Technical Stuff

Postby MtnDon » Sun Nov 23, 2014 3:21 pm

BigBlueToe wrote:My assumptions - please tell me if I'm wrong:
The charge controller will keep the panel from overcharging the battery.
Yes

It will also detect when the Battery Tender Jr. is charging the battery and will reject any electricity "going the wrong way" - into the solar panel.
Yes, and also keep power from flowing from the battery to the panels at night

I can run all the lights and socket directly off the battery terminals as long as I have fuses to protect everything.
Yes. But there may be an advantage to using the load terminals on the charge controller. I am not totally familiar with that CC, but the load terminals are usually provided with a circuit / programming that cuts off the load if the battery voltage drops to a preset low point. The better CC's have that voltage user programmable. Some only have a preset value and often that is set way too low. Check the user manual specs or of possible find an online copy and list the link so we can have a look. The load terminals also can have other built in functions like turning on a light when it gets dark. That can vary a lot between makes and models.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: FAQ:Solar Panel without the Technical Stuff

Postby MtnDon » Sun Nov 23, 2014 3:31 pm

BigBlueToe wrote:
Here's what I was thinking of doing:
Running wires from the charge controller to the battery. (Do I need a fuse on this? On the positive or negativewire?)
Positive lead for fuses or breakers. I would do a main fuse as close to the battery as possible, to protect the wire from battery to fuse panel, unless the fuse panel was "right there" at the battery. A good ANL type can be used. My ideal is to also have a battery disconnect switch at the battery so all power can be cut off if desired w/o needing tools or having to pull fuses.


I would also hook up the battery wires from the Battery Tender Jr. to the battery. These would be dead except when I'm parked by shore power.
I would connect the battery charger / tender on it's own positive connection. Separate from the wire that takes power to the loads. Reason; that way all loads can be shut off for sure while the battery can still be charged or maintained. And vice versa. There might be no power coming in to the unit when not connected to shore power, but if connected at the battery end there would still be battery power in the wires between battery and charger. So, ideally another fuse would be a good idea; one near the battery again to protect against accidental shorts.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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