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Old 10-31-2018, 05:59 PM   #1
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Please critique/comment on/improve my solar plan

My wife and I are planning to do a small-ish solar array on our shortie. We've located a good deal ($0.35 per Watt) on some used 325 Watt panels that we'd like to make use of in our build, but we're not exactly solar experts. I've read quite a bit on DIY solar setups, but would appreciate any advice that can be given.

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120v AC:24v DC:
  • LED Lights
  • USB Wall Chargers for Phones, Etc.
  • Vent Fan
  • Water Pump

Solar Setup
We're going to obviously have to create a 24v DC Battery Bank and am open to suggestions as to battery type/brand/configuration.

Thank you in advance for your suggestions and help!
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Old 10-31-2018, 09:16 PM   #2
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Dunno the panel brand.

Good voltage to get a big output wattage boost from quality MPPT. I reco one Victron 75/15 SmartSolar controller per panel, each gets their own optimization, ideal handling of any partial shading issues.
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Old 10-31-2018, 09:20 PM   #3
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The best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries,

4x6V, around $400 per 200+AH @24V,

from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.

But why are you going 24V ?

Will be difficult / more expensive to find many device types, standard 12V much cheaper and easier.

If really justified, then look at Victron Orion DC converters to provide 12V circuits as needed.
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Old 10-31-2018, 09:22 PM   #4
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Fridge / freezers, laptop power and other screens much more efficient powered off DC, no inverter needed.

AIMS not a great quality inverter, but yes, crazy cheap compared to the good stuff.

But IMO inverters best avoided anyway for energy efficiency if possible.
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Old 11-01-2018, 09:07 AM   #5
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Good voltage to get a big output wattage boost from quality MPPT. I reco one Victron 75/15 SmartSolar controller per panel, each gets their own optimization, ideal handling of any partial shading issues.
Looking at the data sheet for those controllers, it doesn't seem that they're able to handle 325 Watts at 12 V DC (which is one of the reasons I've been considering 24 V). The 100/30 can take 440 Watts, but each controller goes up to $195.00

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Originally Posted by john61ct View Post
The best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries,

4x6V, around $400 per 200+AH @24V,

from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.

But why are you going 24V ?

Will be difficult / more expensive to find many device types, standard 12V much cheaper and easier.

If really justified, then look at Victron Orion DC converters to provide 12V circuits as needed.
My main reason for going 24v DC is to simplify our setup with only a single charge controller. Lots of DC lights that I've looked at are able to accept 12 or 24 V, as are the USB wall outlets. The reason I'm looking to invert is to keep costs down and avoid having to purchase many new things just for our Skoolie. We're planning to move most things from our house into the Skoolie, so it doesn't make sense to buy a new 12V TV or source a more expensive 12V Fridge. I may consider installing "Cigarette Lighters" around for charging our laptops to get the benefits of DC charging, but that'll depend on the cost and availability of DC chargers for our computers.
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Old 11-01-2018, 10:42 AM   #6
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Dunno the panel brand.

Good voltage to get a big output wattage boost from quality MPPT. I reco one Victron 75/15 SmartSolar controller per panel, each gets their own optimization, ideal handling of any partial shading issues.
Based on your comments I may consider using two of these Charge Controllers. They're a good price and can handle the wattage of our panels, which would give us the flexibility of a parallel install. I'll have to do a bit of reading on how to install multiple charge controllers on a single battery bank. Thank you for your input!
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Old 11-05-2018, 07:22 AM   #7
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I'm using a midnite solar classic 200. If your interested, this link has a good calculator for charge controller sizing of the midnite classic series

http://www.midnitesolar.com/sizingTool/
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Old 11-05-2018, 07:40 AM   #8
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I'm using a midnite solar classic 200. If your interested, this link has a good calculator for charge controller sizing of the midnite classic series

MidNite Solar - Classic Sizing Tool.
Awesome! I appreciate the resource!
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Old 11-05-2018, 09:55 AM   #9
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Looking at the data sheet for those controllers, it doesn't seem that they're able to handle 325 Watts at 12 V DC (which is one of the reasons I've been considering 24 V)
Well the reco was based on your saying it would be a 24V bank. At 12V need to double the amps capacity.

As long as you have plentiful mains or genny power usually available, inverter based system with household appliances is fine.

But going off-grid, especially trying to be solar-mostly, the main investment needs to be on lowering consumption, being as efficient as possible.

Spending huge money on infrastructure just to enable using appliances designed for mains availability is silly.

Yes a conservation-first approach means some IMO minor compromises in lifestyle.
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Old 11-08-2018, 09:50 AM   #10
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We have a 600W solar panel array charging (4) 12v SLR155 lead acid batteries. The need to monitor Lead Acid Batteries so as not to draw down more than 50% of their capacity is turning out to be a major challenge (and expense - needing a $300 SmartGauge to avoid having to constantly monitor and calculate actual battery capacity). So my recommendation would be to invest a little more upfront to get Lithium batteries. It will save on price in the long run and stress worrying about over discharging and killing your battery life.
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Old 11-08-2018, 10:55 AM   #11
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We have a 600W solar panel array charging (4) 12v SLR155 lead acid batteries. The need to monitor Lead Acid Batteries so as not to draw down more than 50% of their capacity is turning out to be a major challenge (and expense - needing a $300 SmartGauge to avoid having to constantly monitor and calculate actual battery capacity). So my recommendation would be to invest a little more upfront to get Lithium batteries. It will save on price in the long run and stress worrying about over discharging and killing your battery life.

Is it not necessary to have a battery monitor when using Lithium batteries? I figured SOC was an important measurement no matter which type of batteries are used.
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Old 11-08-2018, 11:47 AM   #12
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Yes, in fact having to spend 5-7x more up front on just the bank makes it more critical to invest in proper protective infrastructure.

Letting an LFP bank go 100% dead flat usually turns it instantly into worthless scrap.

For those just starting to learn about this stuff, LFP is a very risky investment due to the very long ROI payback period.

Much better to start out with a better value / lower cost FLA bank.
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Old 12-04-2018, 12:31 PM   #13
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Alright - I may have actually found a really good deal on some brand new 310 Watt panels, so I think I'm going to go with three panels, each with their own charge controller. Now that I think the basic electrical design of the system is figured out, I wanted to turn my attention to the racking. I'd love to be able to do a fully adjustable array, but that's outside the scope of my plans, so I'm planning to do a system that's adjustable on just one axis (in my case, just left to right, not front to back). I've attached the sketch of my current plans here, please feel free to critique or offer improvements.

EDIT:
For clarity - the hinge also takes some of the burden off of trying to find or engineer a rail that accounts for the curvature of the roof. With that I won't have to ensure everything is perfectly parallel to use mechanical fasteners.
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Old 12-04-2018, 01:34 PM   #14
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I'm no sure what your plan is with using 3 solar controllers but I also can't think of any situation where it makes sense.
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Old 12-04-2018, 01:44 PM   #15
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I'm no sure what your plan is with using 3 solar controllers but I also can't think of any situation where it makes sense.
In order to prevent issues with partial shading and the like, we're running the panels in parallel, as opposed to in series. The problem with doing that is the expense of getting a charge controller that can handle all of that wattage. It's more cost effective to do three separate charge controllers than to source one charge controller large enough to accommodate three panels at our wattage.
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Old 12-04-2018, 05:52 PM   #16
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I would like? If you mind to second guess your hinge idea?
In your drawing.
It looks like even with the outside pieces of angle free to pivot that the hinges are still going to fight each other?
Issues first then suggestions.
How is it secured wile going down the road or one side or the other when parked and a storm with wind comes through?
The fixed points you show don't show a lot of adjustment if any to keep the panel's attached to the fixed points.
I don't have solar panels and can only daydream about them myself for my build but I have installed many water solar panels.
I can draw an idea of what's in my head if you want a visual for expanding on your idea if needed I suck on computer but can pencil/sketch an idea on pen and paper in a few.
Research standing seam roof s-5clamps and look at the other types. Then look at uni-strut spring nuts? They are both known buy many names but that will open up many an opportunity or idea? The spring nuts are adjustable and long term if the spring is gone the nut is still adjustable.
The best for these in the plumbing/mechanical/HVAC/hanging hospital machine world is Hilti but they think something of it/Hilti.
Erico is an electrical supplier that can do it,Fastenal thinks something of there stuff and might have a piece or two but are. More than happy to charge you shipping to have when you need it.
Find you local plumbing and electrical supply houses and ask.
The ones I posted were commercial construction and they are local for me.
Just research unistrut systems and you see how universal it is.
Not a salesman? Just a man that have used many a different styles and strut and if I have a choice over cutting/ drilling/welding angle iron over using strut that is rated to hold the weight that it is supporting. I am doing strut.
Good choices and good luck
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Old 12-04-2018, 06:33 PM   #17
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I would like? If you mind to second guess your hinge idea?
In your drawing.
It looks like even with the outside pieces of angle free to pivot that the hinges are still going to fight each other?
Issues first then suggestions.
How is it secured wile going down the road or one side or the other when parked and a storm with wind comes through?
The fixed points you show don't show a lot of adjustment if any to keep the panel's attached to the fixed points.
I don't have solar panels and can only daydream about them myself for my build but I have installed many water solar panels.
I can draw an idea of what's in my head if you want a visual for expanding on your idea if needed I suck on computer but can pencil/sketch an idea on pen and paper in a few.
Research standing seam roof s-5clamps and look at the other types. Then look at uni-strut spring nuts? They are both known buy many names but that will open up many an opportunity or idea? The spring nuts are adjustable and long term if the spring is gone the nut is still adjustable.
The best for these in the plumbing/mechanical/HVAC/hanging hospital machine world is Hilti but they think something of it/Hilti.
Erico is an electrical supplier that can do it,Fastenal thinks something of there stuff and might have a piece or two but are. More than happy to charge you shipping to have when you need it.
Find you local plumbing and electrical supply houses and ask.
The ones I posted were commercial construction and they are local for me.
Just research unistrut systems and you see how universal it is.
Not a salesman? Just a man that have used many a different styles and strut and if I have a choice over cutting/ drilling/welding angle iron over using strut that is rated to hold the weight that it is supporting. I am doing strut.
Good choices and good luck
Thank you very much for your input. I realized that I should have shown my plans from the end, as well, to show how I anticipated the raise/lower mechanism working. My plan is to secure the angle brackets to the roof rails with two bolts, per leg, which I think should offer pretty solid stability, when necessary.

I had been thinking about unistrut, as well, but haven't ever worked with it before but have plenty of experience with angle iron, so that was my first instinct. I'll look into the material suggestions you've offered.

As to the hinges fighting each other, it's certainly possible and I'm open to suggestions. I was thinking that door hinges would offer a decent range of motion in either direction, but I haven't mocked things up, yet.
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Old 12-05-2018, 06:56 AM   #18
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In order to prevent issues with partial shading and the like, we're running the panels in parallel, as opposed to in series. The problem with doing that is the expense of getting a charge controller that can handle all of that wattage. It's more cost effective to do three separate charge controllers than to source one charge controller large enough to accommodate three panels at our wattage.
I'm afraid I do not understand this. Perhaps I haven't had enough coffee yet today.

I agree that parallel is ideal.

The link to the proposed panels is no longer working so please allow me to assume they output about 6 amps @ 50 volts. Three of them wired in parallel would result in approximately 18 amps @ 50 volts.

There are many charge controllers that can handle this so I'm confused by your statement above.

I'm running four, 435 watt panels in parallel, thru a Morningstart TS-MPPT-60 and into a 24 volt lithium battery bank. Nearly twice the total wattage that you are talking about. That charge controller cost me $530.

The Morningstar TS-MPPT-30 is all that you would need (more than you need) and it costs something around $390. In my way of thinking, one $390 name brand charge controller is less expensive than three $209 controllers.

I did not download the manual for the listed controller but I assume you have confirmed that they can be networked so that they operate "together" to properly charge a single battery bank.

Where did my number crunching go wrong??
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Old 12-05-2018, 07:05 AM   #19
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Victron 75/15 is usually ~$125
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Old 12-05-2018, 07:35 AM   #20
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I stand by my earlier post. Connecting 3 charge controllers to a single battery bank sounds like a mistake. Electricity doesn't just flow downhill like water.
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