diy solar

diy solar

New and confused

Yknotr

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Apr 15, 2021
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Im super new to solar power and just cant quite wrap my mind around all the intricacies of it. Ive watched videos and researched write ups on solar but still am lost. For ex:

-do i want an MPPT or PWM charge controller?

-are these 4 amorphous solar panels left at camp by former owner worth using or should i buy all mono crystalline panels? Id hate to junk them because they are new in box.

-Someone asked me the million dollar question recently, “how much power do you need?” Well I could throw a dart at a board with amps, watts and volts and could be closer to an accurate answer. Lol. Truth is I dont know but Id say some lights at night, a fridge through the day (prob weekends only as we might shit it off when bot there) a vacuum cleaner at times, microwave on occasion, but at least I know ill prob need the generator to make toast in morning...

-and several other questions.





Heres what i have so far:

Cabin in woods with fairly open view of South but roof angles toward east and west

4 -25 watt amorphous panels (free)

6 -6 volt gc2 duracell lead/acid deep cycle batteries from Sams Club

An existing generator plug that enters on side of cabin and feeds a panel box inside.

Panel box with 8 breakers (120) that feed to outlets, lights and 15 cu foot fridge freezer within cabin.

The cabin is completely off grid and has no sewage or water (yet) but id like to hook up a pump of sorts to run water in from 275 gallon ibc tank that will sit 6 feet high on a frame so gravity will provide some pressure.



My hope is that I can connect the battery bank as 12v source to an inverter and then to the panel box so that Ill have option to use battery bank to power camp and so i wont have to use generator as often.



Although I think I can grasp the basics Of how solar works, Im clueless in how many of this and how much power of that, that ill need.

Charge controllers: size and type??

Charge regulators ??

More panels Im sure will be needed but what type and how many watts will be sufficient?

Cabling: what gauge and how long can I go with a particular gauge wire.

Im not adverse to spending some

$$ on project but Im not independently wealthy either.

I sort of need my hand held here, if anyone is willing to do this. Lol. Here is a few pics of the camp as well as specs on my six 6 volt batteries (intend to use for 12v)

Specifications

  • 20 amp hour rate:215
  • 5 amp hour rate:157
  • 6 amp hour rate:156
  • Battery Electrolyte Composition:Acid
  • Battery End Type:Top Post
  • Battery Purpose:Deep Cycle
  • BCI Group Size:GC2
  • Contents:ONE EACH
  • Freight Class:65
  • Minutes at 25 amps:395
  • Minutes at 75 amps:105
  • Terminal Type:DIN
  • Volts:6


IMG_2783.png

IMG_2781.png

IMG_2782.png

Hopefully i can post these but if not its a 30x16 foot footprint with metal roof.

I thank you in advance for any “hand holding” you folks are willing to do for me. Im sure i left out some ?’s I should be asking as well.
 
Nice little cabin. That should be fun.

MPPT shines where there's over about 150watts and very little shade. But can be made to work better with diodes.

You aren't going to get much with those 4 times 25watt panels.
I would suspect it's a Harbor Freight kit.

The Microwave will likely require the generator.
The fridge would need around 1000 watts startup if it's a full size fridge.

An 3 cubic foot fridge requires much less, maybe 400watts so think about a small fridge.

For the fridge I would say you want at least 120Ah capacity
My 2 cents.

I'm sure others will chime in with more.
Good luck.
 
Give the solar panels to a child working on a school science project. They are basically useless for anything else. How many feet is it to the nearest clearing that gets full sun for a good part of the day. As 45N observes in your pics, there are numerous trees that will shade the panels.

With six 6V batteries, you really only could design a 12V system. Wire them 2S3P. Outback used to make 36V components, but those appear to have been discontinued. Assuming each battery is ~200Ah then what you have would be 200Ah X 3 strings X 12V = 7200Wh of electricity. Assuming you don't want to ever use more than 50% of the battery, that gives you about 3.6kWh of power. With the frig running 24/7 you might consume 1.8kWh per day. So, you'd get two days of use in cloudy weather before you need to start up a generator.

That would need far, far more panels than what you now have. Charging at 1/8C (0.125C) you need {(200Ah X 3 strings)/8 } X 13V X 1.25X fudgefacter = 1220W of panels, roughly 12 times what you have right now. You would need a very high amperage controller to handle that at 12V.

MPPT is definately the way to go. You can shop for cheap high-voltage grid-tie panels on Craigslist. You can then wire them in series to bump up the voltage, and then position the panels in a clearing up to 100-150 feet away from the cabin.

Alternatively, pick the 4 best batteries, and string them in series for a 24V cabin system. At higher voltage, you can use thinner, cheaper wire, a smaller capacity charge controller. Over time, 24V will allow greater growth/expansion.
 
Give the solar panels to a child working on a school science project. They are basically useless for anything else. How many feet is it to the nearest clearing that gets full sun for a good part of the day. As 45N observes in your pics, there are numerous trees that will shade the panels.

With six 6V batteries, you really only could design a 12V system. Wire them 2S3P. Outback used to make 36V components, but those appear to have been discontinued. Assuming each battery is ~200Ah then what you have would be 200Ah X 3 strings X 12V = 7200Wh of electricity. Assuming you don't want to ever use more than 50% of the battery, that gives you about 3.6kWh of power. With the frig running 24/7 you might consume 1.8kWh per day. So, you'd get two days of use in cloudy weather before you need to start up a generator.

That would need far, far more panels than what you now have. Charging at 1/8C (0.125C) you need {(200Ah X 3 strings)/8 } X 13V X 1.25X fudgefacter = 1220W of panels, roughly 12 times what you have right now. You would need a very high amperage controller to handle that at 12V.

MPPT is definately the way to go. You can shop for cheap high-voltage grid-tie panels on Craigslist. You can then wire them in series to bump up the voltage, and then position the panels in a clearing up to 100-150 feet away from the cabin.

Alternatively, pick the 4 best batteries, and string them in series for a 24V cabin system. At higher voltage, you can use thinner, cheaper wire, a smaller capacity charge controller. Over time, 24V will allow greater growth/expansion.
Ok. You have def put many things in perspective. Thank you kindly for your time. I have no panels yet (seeing how the others are junk) and the 6 batteries are all new (manuf 4/21) im regretting getting those now because i have learned since purchase that agm or lithium are so much better (in long run) but these were on sale and cheap. $69/ea)
i could return these as they are unused still and go with something more appropriate. In some ways, i just wish they offered a kit with everything needed and that were set up as small to larger set ups that i could pick from.
i did find a site that has some variation in options and if you know of one that is similar please say so.
Thank you again for your time
 

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Those batteries are no more junk than a Toyota is junk. Sure, having a BMW is better, but the Toyota will still get you where you're going. Same with those batteries. I would however not let them sit unused very long. They will eventually drain dead sitting for months. Put them on a table-top charger every few weeks and keep the water levels topped off. Treat them well and they will give you years of service. Abuse them and they last a year. Care for them properly, and expect 5+ years of service.

What I would NOT do is buy a kit. You can put together a cheaper, higher quality system buying individual components. Don't buy panels through the internet. You pay more for the shipping then you do the glass. Look for local sellers on Craigslist. Expect to get 4-5 watts per dollar.

Find a clearing where you can position a ground mount, then wire several high-voltage grid-tie panels in series to get 90-120VDC. Then you can run a few hundred feet of wire to the controller to charge the batteries. Look at Epever's higher voltage limit Tracer series. If you get one with the 200V limit, you can run wire a long way.
 
Those batteries are no more junk than a Toyota is junk. Sure, having a BMW is better, but the Toyota will still get you where you're going. Same with those batteries. I would however not let them sit unused very long. They will eventually drain dead sitting for months. Put them on a table-top charger every few weeks and keep the water levels topped off. Treat them well and they will give you years of service. Abuse them and they last a year. Care for them properly, and expect 5+ years of service.

What I would NOT do is buy a kit. You can put together a cheaper, higher quality system buying individual components. Don't buy panels through the internet. You pay more for the shipping then you do the glass. Look for local sellers on Craigslist. Expect to get 4-5 watts per dollar.

Find a clearing where you can position a ground mount, then wire several high-voltage grid-tie panels in series to get 90-120VDC. Then you can run a few hundred feet of wire to the controller to charge the batteries. Look at Epever's higher voltage limit Tracer series. If you get one with the 200V limit, you can run wire a long way.
I really love your analogies. Im full of them myself. Also really like the candor you offer!! Ok so you again, have narrowed my options (which is exactly what I need). I will look up the info you provided (still learning the electrical verbiage) and would really like your continued support as I navigate through this. However, I def do not want to wear out the welcome you’ve offered thus far. I have topped off the 6 batteries and will continue to monitor them for discharge.
my local Craigslist is awful with options and I find Facebook Marketplace to offer more. There are a few guys there who sell used panels and Im uncertain if I should stick with poly or mono. An inverter is another dilemma. How big (wattage) and whether pure sine or modified. Im the type who will buy a 20x40 garage if I wanted a 15x30 just because i want room to grow. I cant thank you enough for your help so far.
 
my local Craigslist is awful with options and I find Facebook Marketplace to offer more. There are a few guys there who sell used panels and Im uncertain if I should stick with poly or mono. An inverter is another dilemma. How big (wattage) and whether pure sine or modified. Im the type who will buy a 20x40 garage if I wanted a 15x30 just because i want room to grow. I cant thank you enough for your help so far.
Don't let used dissaude you. My best performing panels are used Astronergy's that I bought off Craigslist. Just ignore the poly vs mono discussion. Solely base your decision on watts/$. If you shop locally, you can bring a voltmeter with you and test each panel before you pay for it.

I use the 2X rule for everything solar. Figure out what your largest single load (or loads) you are likely to run, and get an inverter twice that value. Do NOT buy a MSW inverter. They are very hard on things running on electrical motors. Stick with sine-wave. The best inverters won't have NEMA plugs. They are designed to be hard-wired directly into the main electrical panel.
 
I see a lot of trees shading the roof.
That is a good thing. Will discourage putting panels on roof running in wrong direction..
4 25w panels. Place beside parking space and use to float charge your car battery, and snowmobile.
 
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