Need some help getting started

[mshoward82]

I found myself a new hobby and it involes solar power.

I'm new to this and dont know too much. I have been doing a little research and I think I have everything sized right as best I can tell. But I still need some help getting started.
I'm not too familiar with the wiring side of it.

Here is my project:
- Small shed about 100 yards from my house with no power.
- Create enough power to run a flood light at night, a light bulb or two inside the shed, some small power tools, and some yard equipment like a weed eater.
- Use soalr panels to charge a battery bank to supply power when needed.

I have decided on some of the basics I need.
- about 250w solar panel 1-2
- looking at 4-6 batteries, 6v 200ah at 24v
- some kind of charge controller
- a power inveter 1000-2000w
- and a breaker box to run power to a couple outlets, a light bulb, and a flood light

Now i have learned some basics about the panels and the batteries and I think I have those well figured out.
What I am having trouble with is all the wiring and the stuff in the middle.
I have tried looking arouond for some good diagrams, but didnt find anything I felt was too helpful to me.
I'm not an electrical engineer and some diagrams are a little over my head. Something easy to follow would be great.

There are some things I'm not too familiar with:
- Where and what size of fuses to use
- What is a shunt
- How to incorporate a meter and charge controller
- any disconnect switches
- anything else i might need

I want to get a good plan in place before I start buying stuff.

Thanks for any help.

[thastinger]

I don't know how many specifics you will get on wiring and fusing here. When I was going through this with my off-grid system, I just asked for places to find the references so I could do my own reading on it. IMHO, you should consider the NEC as a min safety standard even if you don't intend to pull an electrical permit for the installation.

Search the internet for "SAND 2005-0342-N". That document should get you started coupled with the present NEC.

[SunEagle]

I found myself a new hobby and it involes solar power.

I'm new to this and dont know too much. I have been doing a little research and I think I have everything sized right as best I can tell. But I still need some help getting started.
I'm not too familiar with the wiring side of it.

Here is my project:
- Small shed about 100 yards from my house with no power.
- Create enough power to run a flood light at night, a light bulb or two inside the shed, some small power tools, and some yard equipment like a weed eater.
- Use soalr panels to charge a battery bank to supply power when needed.

I have decided on some of the basics I need.
- about 250w solar panel 1-2
- looking at 4-6 batteries, 6v 200ah at 24v
- some kind of charge controller
- a power inveter 1000-2000w
- and a breaker box to run power to a couple outlets, a light bulb, and a flood light

Now i have learned some basics about the panels and the batteries and I think I have those well figured out.
What I am having trouble with is all the wiring and the stuff in the middle.
I have tried looking arouond for some good diagrams, but didnt find anything I felt was too helpful to me.
I'm not an electrical engineer and some diagrams are a little over my head. Something easy to follow would be great.

There are some things I'm not too familiar with:
- Where and what size of fuses to use
- What is a shunt
- How to incorporate a meter and charge controller
- any disconnect switches
- anything else i might need

I want to get a good plan in place before I start buying stuff.

Thanks for any help.

I'm glad you haven't spent any money yet.

Before you start sizing your panel wattage and batteries you really need to determine your actually watt hour load. The electrical load for the light bulbs, power tools, weed eater and flood light can end up totally a lot depending on their wattage and length of time you plan on using them. There is a tool called "kill a watt" that allows you to measure the electrical load of small appliances like your power tools. You may be surprised how much they use.

You should start reading the "stickies" located here in the off grid electrical design like this one for battery sizing. http://www.solarpaneltalk.com/showth...Battery-Design

Please be aware that if you need to have an inverter the size of 1000 - 2000 watts your batteries will end up costing you thousands of $$ every 3 - 5 years, plus the initial cost of solar panels, battery charger, inverter and wiring.

Do all the research on equipment sizing before you need to worry about wire size and fusing. If you are only looking to light your floodlight and light bulbs it might not cost you much to install the solar pv system and batteries, but the power tools will run up the cost. You will probably find out that a small generator or even running a power line to the shed will end up at a much lower cost.

[Naptown]

For about 1/4 of what you will spend initially on a solar set up you could rent a trencher and buy enough UF wire to power 10 times what you can power from solar. And with no battery replacement costs. Just a little to the POCO on a monthly basis.

[mshoward82]

This is more of a hobby then a necessity, and it's to give myself a better understanding of how solar power works.
I understand that I could physically run power to my shed and be all good to go for a lot less. But this is something I would like to do.
I am setting a budget at ~$2,000.
I'm looking at getting 6 - 200ah/6v batteries. For a 12v system producing 7,200wh. Maybe 8 for 24v if i can find a good deal or increase my budget.
And 1 or 2 panels to charge the batteries. And not to support constant power.
This isnt something I will be living off of, but would be nice to have a little power to light a lightbulb at night if I need to get in there.
And support a 300w flood light for a few hours at night.
The biggest thing that I can see using would be a small electric pressure washer I have. I'm not sure on the wattage, but I do know that it pulls 13 Amps. I'm not sure but I think that calculates out to about 1500 watts.
And that would only be used for a MAX about 1 hour. And that would be used like twice a year.

My shed isn't really a hobby shop or anything. I spend little time out there. And would like to have some power when I do need to access it.

Again, I am just trying to find some help in how to wire everything together and what devices i would need in between my panels and my batteries and then out to my outlets.

Thanks.

[Sunking]

I'm looking at getting 6 - 200ah/6v batteries. For a 12v system producing 7,200wh.

You are way off base here. While you are correct 12 volt 600 AH has a capacity of 7.2 Kwh but only 3.6 Kwh is usable, and only 1.44 Kwh if used daily. The minimum solar panel wattage you can run on that size of a battery is 650 watts with a 60 amp MPPT controller. No way is $2000 going to cover that.

[FloridaSun]

I am setting a budget at ~$2,000.
This isnt something I will be living off of, but would be nice to have a little power to light a lightbulb at night if I need to get in there.
And support a 300w flood light for a few hours at night.
The biggest thing that I can see using would be a small electric pressure washer I have. I'm not sure on the wattage, but I do know that it pulls 13 Amps. I'm not sure but I think that calculates out to about 1500 watts.
And that would only be used for a MAX about 1 hour. And that would be used like twice a year.

With a $2,000 off grid investment seems you can get about 1Kwh a day use or about $36.50 a year of grid electricity @ $.10 a Kwh. Only a 50 year pay off rate except... battery replacement comes along and you or your grandkids (or their grandkids) will never break even. Don't even thinkabout trying to pull 1500 watts out of a 7000w bank for an hour. It won't happen. Do the math.

http://www.solarpaneltalk.com/showthread.php?10450-Inverter-Size-vs-Battery-Size-Tutorial

[mshoward82]

ok so i think i figured out that i wont be able to pull 1500 watts.
From what i get is that 600ah/8 = 75amps. 75 * 12v = 900 watts. Since I am looking at FLA battery.
and if i went with 8 batteries in a 24v I would get 400ah/8 = 50amps. 50 * 24v = 1200 watts.
ok so don't use the pressure washer at 1500 watts. Got it

Now for needing a 650 watt panel I don't get. I was looking at a 250 watt panel.
I don't feel that I will be draining my battery bank every day and require a full charge every day.
Maybe doing a 50% drain on a rare occasion and about a 10% on a daily or even less since it won't be used on the regular.
So taking away any high watt items, I don't foresee using that much from my batteries.
If I kept my battery usage to a minimum would I need that large of panel to slowly recharge my batteries? Or am I looking at this the wrong way?
And if I went with a 250 watt panel at 12v I would need a +20amp MPPT. Or at 24v a +10amp MPPT controller.

And as for the investment side of this, I'm not doing this as an investment. I'm not looking to recoup my money or try and break free from the POCO.
However i would like to still stay within my $2000 range. If i decide I wont be able to get what I want out of it, then I will decide that.
This is just a new hobby for me. Sorry if you guys don't understand this.

[SunEagle]

ok so i think i figured out that i wont be able to pull 1500 watts.
From what i get is that 600ah/8 = 75amps. 75 * 12v = 900 watts. Since I am looking at FLA battery.
and if i went with 8 batteries in a 24v I would get 400ah/8 = 50amps. 50 * 24v = 1200 watts.
ok so don't use the pressure washer at 1500 watts. Got it

Now for needing a 650 watt panel I don't get. I was looking at a 250 watt panel.
I don't feel that I will be draining my battery bank every day and require a full charge every day.
Maybe doing a 50% drain on a rare occasion and about a 10% on a daily or even less since it won't be used on the regular.
So taking away any high watt items, I don't foresee using that much from my batteries.
If I kept my battery usage to a minimum would I need that large of panel to slowly recharge my batteries? Or am I looking at this the wrong way?
And if I went with a 250 watt panel at 12v I would need a +20amp MPPT. Or at 24v a +10amp MPPT controller.

And as for the investment side of this, I'm not doing this as an investment. I'm not looking to recoup my money or try and break free from the POCO.
However i would like to still stay within my $2000 range. If i decide I wont be able to get what I want out of it, then I will decide that.
This is just a new hobby for me. Sorry if you guys don't understand this.

They understand. What they are trying to do is convince you that your "hobby project" is going to cost you thousands of $$ and they feel that maybe you will end up regretting spending it. They' like me' are just trying to help you understand the costs, rewards and liabilities of your project.

[FloridaSun]

If I kept my battery usage to a minimum would I need that large of panel to slowly recharge my batteries?

It's not the every day minimal use that will snag your system. You need to design for worst case as in your battery is near 50% discharge after several dim days, it's sunny today and that battery needs to charge now. A 250w panel is not going to do it for your 3600+ watt need. A 250w panel will not even give you 1Kwh a day of end power with four hours good sun. There are losses involved. Would you rather buy $400 more of panels now or after you kill $800 worth of batteries?

And as for the investment side of this, I'm not doing this as an investment. I'm not looking to recoup my money or try and break free from the POCO.
However i would like to still stay within my $2000 range. If i decide I wont be able to get what I want out of it, then I will decide that.
This is just a new hobby for me. Sorry if you guys don't understand this.

haha, I did get off on a ROI rant there. The point is $2000 will not get you where you want to go, buying and supporting a 7200Wh batt bank with solar. Scale down the system or add $$$$.
I have a 'hobby' system too and have spent almost $1800 for 600w panels, quality 45A MPPT (coming this month hooray), cheapo walfart hybrid marine batteries (24v, 200Ah bank) and 24v 400w PSW inverter. Add wiring, boxes, fuses and holders, panel mounting brackets, etc, another $200+ spent even with scrounging up spare parts around here. A good 24v 25amp charger added more... etc etc... and that's for a 4800Wh battery bank.
My little hobby project started as a simple 12v cheap learning tool system, used to charge the several 18v batteries for tools and lights I have here. With the help of this forum's knowledge it grew into a good solid system and can be expanded when I eventually replace the battery bank. Understand the sticky threads in off grid section. Have fun.

[Sunking]

Now for needing a 650 watt panel I don't get.

Real simple a FLA battery needs a minimum C/12 charge current.

A 650 watt solar panel with MPPT charge controller supplies 650 watts / 13 volts = 50 amps. 50 amps x 12 volts = 600 AH maximum battery it can support. Without a C/12 charge current your batteries will stratify and lead sulfate crystals cannot be dissolved.

One work around is use AGM batteries but there is a trade off. AGM batteries cost twice as much and last half as long. FLA gives you roughly 400% more bang for the buck.

Understand now?

[mshoward82]

Ok so I am starting to see where you guys are going with this.
From my calculations(using you battery design tutorial), let say I expect to use 2kwh a day.
Using 8 FLA batteries at 6v/225ah. For a 24v system at 450ah.

I would need 750w in Panels with a 4 sun hour day.
Now will this change depending on the voltage of the panels?
I have seen some at 12v and 20v and others. Which should be used for a 24v system?

And need a battery size of ~417ah for 5 days of cloudy coverage.
which my setup has 450ah. Is this OK? or should my 5 day coverage not exceed 50% of my 450ah?

And then also a +31amps MPPT controller.

And not exceed more than 1350 watts at one time.

Am I on the right track here?

Also you guys have been great helping me out. I am starting to see the cost inefficiency with this type of system. But like i said this is not an investment. I look at it more like me putting a lift on my truck kind of thing. My truck used to get about 19mpg, then I spent money, raised it, and put bigger tires on it. Now I am getting about 13mpg. Winning! However I am seeing that this may be out of my budget to get my desired effect. It may be something that I will have to play around with more on paper to see if its worth it to me. I really enjoy plotting things out and seeing what the paper says, and the putting into real world action and see how my results compared. I think I am challenging myself to make a plan, learn something, and see what my results are.

I still have a lot to learn first.
A couple things I am still lost on...
C/8 for FLA batteries? Why 8 hours? Is it something to do with not going more than 8 hours on a 20 hour rated battery?
What if one was to use the 100 hour rating vs the 20 hour rating?
And C/12 charge current for the batteries? I still don't understand this. Where does this come from? I didn't see it on any of the stickys.

"A 650 watt solar panel with MPPT charge controller supplies 650 watts / 13 volts = 50 amps. 50 amps x 12 volts = 600 AH maximum battery it can support. Without a C/12 charge current your batteries will stratify and lead sulfate crystals cannot be dissolved."
(Sorry I don't know how to do the quote thing)

where did you get 13 volts? where does the requirement for C/12 come from?

[PNjunction]

Do not pass go (translated to don't open wallet) until you see this:

http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design

All will be revealed.

[mshoward82]

I doesn't tell "ALL". But it is a good starting point.
I didn't see anything explaining why the C/12 charge current. Or why you use a C/8 for FLA batteries.

[FloridaSun]

I doesn't tell "ALL". But it is a good starting point.
I didn't see anything explaining why the C/12 charge current. Or why you use a C/8 for FLA batteries.

The C/8 - C/12 charge and discharge guidelines involve internal chemistry of FLA battery and how much can be pushed in or pulled out. Dereck is much better in explaining it than I and has done so in previous posts from time to time. This may help you, http://www.smartgauge.co.uk/peukert_chg.html