Plans For My Solar System (Shortened Version)

[iambucket]

Hey everybody,

I'm going to be living out of a Sunline Que 5.4 TT for a job in Port Townsend, WA and want to set up a solar system. I most likely will not have a hookup so the solar will be my only source of power. I am starting to put together a plan and would appreciate any feedback.


CONSIDERATIONS
Fortunately, the area itself is in a temperate climate. I've never lived in a building out there with AC. However, I still have to keep the trailer cool because I will have two cats that will be staying in the trailer while I'm at work. There is no hookup to power the AC.

I would like some power for lights, fans (including a vent-fan) and for charging devices. I assume that’s about all I’m going to get without an extensive solar system.

My trailer itself only has 300# carry capacity when moving. So I will be keeping most stuff in the truck in between drives. This means I have to be conscious about any permanent weight I add to the trailer in my solar system. It also has limited roof space: 

The area in front of the AC is 30”(L) x 84” (W):

The area behind the AC is 42” (L) x 42” (W):

SOLAR SYSTEM

Ideally I'd set up panels totaling 400 W since the area is not sunny for over half the year. Realistically though, I may only be able to do 2 panels (200 W) due to my roof space and being hesitant to add much permanent heavy weight to my low carrying capacity trailer.

So I'm looking at doing what Dandelion did:
http://www.cheaprvliving.com/electrical/...solar-kit/

Because I'm concerned about overheating the cats I love being able to park it in the shade AND still get solar. Since my carrying capacity is small and the battery bank will add some permanent weight, I also like being able to keep the panels in the truck when on the road.

However, I’m wondering if 200W will be enough for me. The only ESSENTIAL thing in the summer will be fans. Can 200 W with enough battery bank run these 12 hours a day (making a bigger number than I think I'd need to be safe) if need and does anybody know from experience if fans are enough for cats in western WA? I'm also curious if 200 will give me anything outside of summer when the area is not so sunny.


SOLAR QUESTIONS
Do terms like “a 12 Volt System” or “24 Volt System” as in this post: http://www.cheaprvliving.com/basics-solar-power/, refer to the battery bank voltage? 

Also, I understand Volts and Amps as described by the garden hose analogy. And I understand doubling Volts through series wiring and Amps through parallel. Would somebody explain the advantages of doubling Volts vs. Amps? Either one would double the Watts so why is series recommend? Thanks.


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That's the beginning of my plan. Any feedback is appreciated. I'm especially curious if the fans will keep the cats cool enough (at least in my climate), if 200 W can power those fans for 12 hours a day, if 200 W will do anything significant in overcast, and abandoning mounted panels for unmounted.

Thank you for your help!

 

[GotSmart]

With a weight limitation, you are not going to be able to have much battery..  No more than 2.  (120 lbs) 

200 W of panels would work great.  

Renogy Monochrystaline panels are roughly 48" X 22"  and weigh 16.5 lbs each.  (Currently list $140 each)

By buying a kit direct from Renogy, and asking for a better price, you will save even more.  They will beat any Amazon price, as they are the seller, and do not have to give Amazon a cut of the sale. 

I had my cat with me full time, and between the vent fan, and and an ice chest with a rubber mat next to it, the cat was happy.  Those panels will produce something in most weather.  

I would reccommend setting up the panels paralell.  That way you will not be blocked by a shadow on one panel.

Unmounted panels are easy to grab, but mounted panels are too much work to try to remove.

 

[highdesertranger]

you wire two 6 volt batteries in series to make it 12 volt. 6 volt golf cart batteries are true deep cycle batteries and are readily available. 12 volt deep cycle batteries are hard to find and expensive. highdesertranger

 

[John61CT]

A LiFePO4 bank would be much lighter per usable AH, but expensive and/or risky.

Same with flexible panels, like 1/20th the weight, and don't last as long.

I'm looking at maybe mounting on big sheets that can stack in a roof rack, maybe get 2000 watts spread out on awnings or leaning around the campsite.

 

[TucsonAZ]

To answer a simple question you asked, if you double the volts and half the amps you don't need as heavy gauge of wiring so there's either a savings in cost, the ability to run wire longer distances or less voltage drop. I will also mention, make sure you have no shade on the panels, say from that tv antenna you have up there. Also, it get's VERY hot under the panels, I would never do another install that didn't allow me at list 3-4 inches or more under the panels.

For your needs an EPSOLAR charge controller along with a single grid tie (aka 24v) panel around 300 watts may work well. That along with with two batteries should get you where you want to go along with room for expansion and the ability to do a 12v or 24v system. If you're near Tucson I have some AGMs with life left in them I'm not using and will give you for $70 for the pair.

 

[Optimistic Paranoid]

To answer your question as to why a "12 volt" battery is half discharged at 12.4 volts instead of 6 volts . . .

1: A nominal 12 volt battery is made up of six individual cells wired together in series.  Due to the nature of the chemistry, each cell, fully charged, is 2.1~something so a fully charged "12 volt" battery is actually somewhere between 12.6 and 12.7 volts.

2: Volts is not a measure of electrical QUANTITY, it's a measure of electrical PRESSURE.  The reason that long distance power lines operate at voltages like 240,000 volts is because you need that much pressure to drive electricity for hundreds of miles.

3: A battery does not actually store electricity.  In 9th grade science class we were told that a battery converted electrical energy into chemical energy while being charged and converted chemical energy into electrical energy while being discharged.  A somewhat better way to look at it is to call a "battery" a chemical generator.  It generates electricity by way of a chemical reaction when called upon to power a circuit.  Once discharged, if hooked up to a higher voltage - between 13 and 15 volts - the greater pressure forces electrons into the battery, and the chemical reaction is reversed, restoring the battery - eventually - to full charge.

4:  Due to the nature of the chemical reactions, by the time the battery has delivered half the power it is capable of generating, it's voltage has fallen to around 12.4 volts.  By the time the chemical reaction is complete, and the battery can no longer generate any meaningful current, a meter will still read 11 point something but the battery is considered fully discharged.

 

[iambucket]

I had my cat with me full time, and between the vent fan, and and an ice chest with a rubber mat next to it, the cat was happy.  Those panels will produce something in most weather.  

I would reccommend setting up the panels paralell.  That way you will not be blocked by a shadow on one panel.

Unmounted panels are easy to grab, but mounted panels are too much work to try to remove.

Thanks for the real-experienced cat report.

Are you saying that parallel and series have a necessarily different physical layout of the panels? I thought the panels could technically be set anywhere and it was the terminal connections that determines if it is series of parallel. Am I understanding you correctly?

 

[iambucket]

A LiFePO4 bank would be much lighter per usable AH, but expensive and/or risky.

Same with flexible panels, like 1/20th the weight, and don't last as long.

I'm looking at maybe mounting on big sheets that can stack in a roof rack, maybe get 2000 watts spread out on awnings or leaning around the campsite.

Since this is my first install I'd rather learn on something less expensive to mess up on than Lithium. Maybe when I get this down  Is that what you meant by risky?

If you can roll up flexible panels within an awning that would be awesome! I love the redundancy of having something over you that blocks out heat from the sun AND collects its energy.

 

[iambucket]

Also, it get's VERY hot under the panels, I would never do another install that didn't allow me at list 3-4 inches or more under the panels.  

For your needs an EPSOLAR charge controller along with a single grid tie (aka 24v) panel around 300 watts may work well.  That along with with two batteries should get you where you want to go along with room for expansion and the ability to do a 12v or 24v system.  If you're near Tucson I have some AGMs with life left in them I'm not using and will give you for $70 for the pair.

Would you stay away from flexible stickies then because of no airspace underneath?

I think since a lot of the kits came with 100 W panels I just assumed that was the biggest size. I now see there are 300s though so far I haven't seen one small enough to fit on my roof space or conveniently fit in my truck. What do you mean by grid tie?

I'm going to be taking 80 to get back to WA so Tuscon is a ways out, unfortunately.

 

[Optimistic Paranoid]

What do you mean by grid tie?

They're talking about using panels originally designed to go on the roofs of stick and brick buildings.  These are usually tied to the electrical grid.  The house draws it's power from the grid at night or on cloudy days, and in sunlight, the excess power the panels produce are fed into the grid for a credit against their electrical bill.

 

[John61CT]

Is that what you meant by risky?

Yes, very $$$$ to get a canned system safe for newbies. Less $$ but riskier to DIY.

Just mentioning because weight will be such a limiting factor for you.

If you can roll up flexible panels within an awning that would be awesome!

No, they're called flexible, but just for one-time fixing direct to a slight curved surface as on boats. You can walk on them with soft shoes, but actual flexing in use will break the cells quickly. Forget about rolling!

My idea is mounting on thin light panels, pulling them out and leaning/laying them down around the van. Including awnings, supports but not fixed to them.

 

[GotSmart]

Thanks for the real-experienced cat report.

Are you saying that parallel and series have a necessarily different physical layout of the panels? I thought the panels could technically be set anywhere and it was the terminal connections that determines if it is series of parallel. Am I understanding you correctly?

Series or paralell is all wiring.  

Series is when one panel feeds power through another, then to the controller.
Paralell is both wires coming together then to controller.

 

[John61CT]

https://www.smartgauge.co.uk/batt_con.html

 

[iambucket]

https://www.smartgauge.co.uk/batt_con.html

That's very interesting how much "negligible" difference adds up. Do you think it would still occur with a two battery bank?

I'm confused that it shows one end starting at the top battery and the other going "to installation." Which Shouldn't both be extending past the battery bank? Which end is to appliances and which one is from the charge converter?

 

[iambucket]

If I did a combination of one 100 W on the roof and two unmounted...
or two 100 Ws on the roof and one unmounted.

Does each group, the group of one and the group of two panels, need a separated charge converter?

 

[John61CT]

That's very interesting how much "negligible" difference adds up. Do you think it would still occur with a two battery bank?

I'm confused that it shows one end starting at the top battery and the other going "to installation." Which Shouldn't both be extending past the battery bank? Which end is to appliances and which one is from the charge converter?

Yes improper wiring causes imbalance even with just a pair.

Why would you think the charger and loads would be on different "ends"?

Yes some have a load buss separate from charge buss, but they both come off the same terminal, it's all one circuit in normal operations.

 

[John61CT]

If I did a combination of one 100 W on the roof and two unmounted...
or two 100 Ws on the roof and one unmounted.

Does each group, the group of one and the group of two panels, need a separated charge converter?

One converter is fine as long as V/A within specs.

Cabling gauge needs to be larger with distance to reduce voltage drop.

 

[DLTooley]

AC is a heavy duty use, even in Port Townsend. A 200 watt panel system with two golf cart batteries is a solid starting point. You will have to do the math to figure out how high to set your thermostat given likely temps. If your AC draws 1500 watts then you won't get much more than an hour of use. One good thing about AC is that battery storage is a bit less of an issue as use corresponds with sun - the marginal difference between your solar bank and the draw is where you need battery. It would be very easy to destroy batteries on a smaller solar bank.

A fan is a light duty use.

 

[GotSmart]

Air conditioning on a 200W solar system with only two GC batteries?   :huh:

It is doubtfull if it will even start up, much less operate for one hour

 

[DLTooley]

Air conditioning on a 200W solar system with only two GC batteries?   :huh:

It is doubtfull if it will even start up, much less operate for one hour

Nice graph, but a bit severe. The Whynter freezers pull a max of 4.5 amps when running.  100 watts covers that easily, but will of course limit your load.  If you cool to substantially below 32 Fahrenheit during the peak solar you should be able to turn it off - or at least in the areas I frequent!