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diy solar

off grid cabin system

mrlocdown

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Feb 4, 2021
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Hi guys I'm in the midst of designing a small system for my off grid cabin, which will be used for weekend getaways. My system will consist of 6 Rich solar 170 watt panels, a renogy Rover 60 amp controller, a Aims 2000 watt 24 volt inverter/charger, 4 battle born 12 volt batteries 2s2p, and of course the needed circuit breakers and other hardware. My question is should the panels be wired in series or parallel. they are 170 watt, vmp 18.4v, imp 9.24a, voc 22.6v isc 9.79 amps, vmax 600vdc. Please any help would be appreciated. the renogy has a max pv input voltage of 150v and a rated load current of 20 amps.
 
I understand the Renogy to accept upto 150v DC input. Depending on how cold it gets in your area you could run all 6 of your panels in series as 6*22 = 132v

I feel compelled to also mention there are some alternate choices for hardware that would be considerably less expensive and or offer much larger capability for the same money.
 
https://santansolar.com/ Offers several options for high watt low cost panels. Many of the forum members have been pleased with the cells they buy from them. 250-350w panels are likely going to be the best watt/$ you can get.

Your use case matches well with an all-in-one unit like a growatt. the 3kw 24v or 48v unit will give you an inverter, mppt charge controller and grid/generator charger options in one ~$700 unit . https://watts247.com/

There are those that think the china units dont have a place in 24/7 off grid applications however considering the quality of the components you have already spec'd its sorta an china-apples to china-apples comparison.

BB are high quality LFP batteries however they are extremely expensive. If you have 2 months to wait you might consider looking at the 270-280ah LFP cells that are being offered in the group buy here on the boards. 16 cells runs about $1700. (thats 13,000 w/hr of battery for half the cost, 560ah @24v or 280@48v)
 
https://santansolar.com/ Offers several options for high watt low cost panels. Many of the forum members have been pleased with the cells they buy from them. 250-350w panels are likely going to be the best watt/$ you can get.

Your use case matches well with an all-in-one unit like a growatt. the 3kw 24v or 48v unit will give you an inverter, mppt charge controller and grid/generator charger options in one ~$700 unit . https://watts247.com/

There are those that think the china units dont have a place in 24/7 off grid applications however considering the quality of the components you have already spec'd its sorta an china-apples to china-apples comparison.

BB are high quality LFP batteries however they are extremely expensive. If you have 2 months to wait you might consider looking at the 270-280ah LFP cells that are being offered in the group buy here on the boards. 16 cells runs about $1700. (thats 13,000 w/hr of battery for half the cost, 560ah @24v or 280@48v)
How do I access the group buy?
 
I have contemplated the Growatt. Looks a little daunting to program. However, it would save me some money..
 
Use a solar string calculator like the one at www.midnightsolar.com to determine what the actual Voc will be for your winter low. A quick calculation at 1.12X suggests that on a frosty morning, the Voc would go above 150V. So, a 3S2P array might be safer.

Will your cabin be wired as straight 120VAC, or standard 120/240 split-phase AC? Will you be running any power tools? A good split-phase low frequency inverter might be a better choice for the inverter. BTW, the measured distortion (10%) on the Aims inverters is the highest I've seen in the inverter industry.
 
it wail be straight 120. Didn’t know about the distortion in regards to the aims invert.
 
it wail be straight 120. Didn’t know about the distortion in regards to the aims invert.
What kind of main electrical panel will you be fitting for the cabin. Most main panels you can pick up at Home Depot are for split-phase? It's an opinion, but I feel that the best inverters are the ones already designed to put out split-phase AC, because they are being built to power a whole house.

For the inverter, you need to dive into the detailed specifications of the inverter, not usually advertised on the top page. Look for a button designated "SPECS" or such.

In terms of inverters, you really do get what you pay for. A budget price likely means budget performance. Pay close attention to the "surge rating" of the inverter you shop for. A serious inverter might say 200% surge for 5 seconds, or 10 seconds, or even 60 seconds. A high-frequency (cheap) inverter might quote "200% surge for 8ms". That's 8 milliseconds, which is a joke. It will power your TV, but not a circular saw.
 
How do I access the group buy?

you can PM @Michael B Caro he is the one that has been handling the group buy for these cells. I have bought a set from him, he was great to work with. He can give you updates on what cells he can currently get ahold of (it changes weekly) and when his next order will be.
 
I would highly suggest getting something besides the AIM inverter. The distortion in it will cause any kind of motor (fridge, freezer, fan, AC) to die real fast... I have the Magnasine 4448, it will run air compressors, my AC, circular saws, I cut down a tree with a Skillsaw with a chain attached off it... I would not expect the AIM or any of the budget inverters to do this, you really do get what you pay for and the inverter is the piece that determines the life of everything running on it.
 
I would highly suggest getting something besides the AIM inverter. The distortion in it will cause any kind of motor (fridge, freezer, fan, AC) to die real fast... I have the Magnasine 4448, it will run air compressors, my AC, circular saws, I cut down a tree with a Skillsaw with a chain attached off it... I would not expect the AIM or any of the budget inverters to do this, you really do get what you pay for and the inverter is the piece that determines the life of everything running on it.
Can you suggest other inverter manufacturers? I was looking at the examples below.

CONEXT SW 4048 4000W INVERTER/CHARGER, 120/240VAC

https://www.invertersupply.com/inde....renogy.com/48v-3500w-solar-inverter-charger/
 
I would highly suggest getting something besides the AIM inverter. The distortion in it will cause any kind of motor (fridge, freezer, fan, AC) to die real fast... I have the Magnasine 4448, it will run air compressors, my AC, circular saws, I cut down a tree with a Skillsaw with a chain attached off it...
I can second this. AIMS appears to have the highest distortion levels in the industry, 10%.

I have the Conext SW 4024 in my workshop. It runs all my shop tools. I'd expect the 4048 to do even more so.
 
Well, it is getting warmer up here in NY and I plan to start purchasing some equipment. Below is my first stab at a list of equipment I am going to purchase, (thank you MichaelK!). I will build the prototype at my house for proof of concept then disassemble and bring to cabin.

- (6) 250W grid-tie panels - Santan Solar
- (8) 6V batteries - I have a friend in the battery business
- Epever 50A MPPT controller 12/24/36/48V - Amazon
- Schneider 4048 48V Sine Wave 120/240VAC split-phase inverter - Amazon
- Transfer Switch, Lugs, heat shrink, cables, etc.

My next step is to figure out the last item on the list, (Transfer Switch, Lugs, heat shrink, cables, etc.). Is there a site/can someone help me decide all the miscellaneous items and specifications of these items that will be required.
 
Well, it is getting warmer up here in NY and I plan to start purchasing some equipment. Below is my first stab at a list of equipment I am going to purchase, (thank you MichaelK!). I will build the prototype at my house for proof of concept then disassemble and bring to cabin.

- (6) 250W grid-tie panels - Santan Solar
- (8) 6V batteries - I have a friend in the battery business
- Epever 50A MPPT controller 12/24/36/48V - Amazon
- Schneider 4048 48V Sine Wave 120/240VAC split-phase inverter - Amazon
- Transfer Switch, Lugs, heat shrink, cables, etc.

My next step is to figure out the last item on the list, (Transfer Switch, Lugs, heat shrink, cables, etc.). Is there a site/can someone help me decide all the miscellaneous items and specifications of these items that will be required.
Sorry wrong thread.
 
My next step is to figure out the last item on the list, (Transfer Switch, Lugs, heat shrink, cables, etc.). Is there a site/can someone help me decide all the miscellaneous items and specifications of these items that will be required.
This is off-grid, right? If that is the case, you do not need a transfer switch. The Conext 4048 is designed with both AC-in and AC-out terminals, so you simply go to Home Depot and purchase a standard split-phase main panel like this one. https://www.homedepot.com/p/Siemens...Indoor-with-Copper-Bus-PN2020B1100C/312138640

The L1 terminal of AC-out is wired to the top terminal 1 of the panel, and L2 of AC-out to the right-hand terminal. The Neutral, N, goes to either of the vertical bussbars on either left or right. The ground connection on the AC-out terminal gets wired to the bussbar with the green screw. All the ground wires that come into the panel from outlets, recepticals, ect, get connected at the green bussbar.

For proper grounding, you may use multiple below-ground metal elements, like water-pipes, steel well casings, pounded ground rods, ect, that are all connected together. You also may have multiple above-ground grounding elements like light-fixtures, power sockets, ect all connected together. BUT, all the below-ground elements and all the above-ground elements may ONLY be connected and one and only one spot. That may be at the main panel pictured below, or inside the inverter housing. Follow the instructions in your installation manual.

In North America, you also need to bond Neutral to Ground, also at one and only one location. Again, this is either in the main panel, or in the inverter. Follow the instructions.
1617809221015.png
Lastly, you may connect a generator directly to the inverter, via the AC-in terminals. You wire a plug like this into the wall, and run a 4-wire 240VAC cable from the generator directly to the plug. The inverter will receive the power, and convert it into DC to charge the batteries.
 
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