Critique my system

mfolch

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May 4, 2022
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2
Totally new member and new to solar. We have a 24ft*12ft shed which we are attempting to convert into a writing studio. Hoping for some advice and critical feedback on the system I’ve put together (but haven’t purchased). Tell me where I’ve gone wrong and how to get it right. The shed is unfinished. So I’ll be adding insulation, lighting, wiring from scratch.

I live in Connecticut, and according to various online calculation tools, we receive an average of 4.1 peak hours of sunlight. However, one long side of the shed faces south, the pitch of the roof is roughly 20%, and it has direct, unobstructed sunlight from around 10am to 5pm during the winter and as late as 7:30pm during the summer.

The studio will be a primary workplace for either me or my wife. So our projected electricity needs are as follows:
  • 3 electric sockets: 2 for lamps and/or charging a computer; one dedicated for a window AC (see next bullet)
  • 8000BTU window air conditioner. For example, see this. (During summer: May to September; during the winter, we will use a fireplace insert for heating)
    • 115volt
    • 15amps
    • draws 6.2 amps
  • Overhead fan; for example, see this.
    • Volts 120
    • Watts 7.50 (medium speed)
    • CFM 5084
I have read online that for this system, we will need something like the following configuration. I would very much welcome knowing whether this is overkill. Precise information has been difficult to find. A number of ostensibly legitimate websites recommend smaller systems. I went mostly with one brand for the sake of simplicity and because it seems to have a good reputation. Very much open to other recommendations. The system below seems to cost about half as much as connecting the cabin to the house (which is about 4 acres away). Many thanks in advance—Marcus.
Panels:
  • Renogy 2PCS Solar Panel Kit 450 Watts 12/24 Volts Monocrystalline High-Efficiency Module: SKU: RSP450D-120X2-US
or
  • Renogy Solar Panel 200 Watt 12 Volt High-Efficiency Monocrystalline Module PV (x4): SKU: RSP200D-U
Battery
  • Renogy Deep Cycle AGM Battery 12 Volt 200Ah (x 3): RNG-BATT-AGM12-200-US.
Or
  • Renogy 12V 200Ah LiFePO4 Deep Cycle Lithium Battery with Bluetooth (x2): SKU: RBT200LFP12 -BT-US
Controller
  • Renogy 60A 12V/24V/36V/48V DC Input MPPT Solar Charge Controller: SKU: RNG-CTRL-RVR60-USRNG-INVT-3000-12V-P2-US
Or
  • Victron Energy SmartSolar MPPT Tr 150V 70 amp 12/24/36/48-Volt Solar Charge Controller
Inverter

  • Renogy 3000W Pure Sine Wave Inverter 12V DC to 120V AC: RNG-INVT-3000-12V-P2-US
Cables
  • extensions, battery cables, etc.: Various--and recommendations welcome!
 

Zil

Just another ass on the web
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May 27, 2020
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You are going to be disappointed by the power use from such small batteries when running air conditioner.
Just think. That 3000W inverter will want 250 amperes while it is running big loads.
 

MichaelK

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I would consider this Renogy system totally insufficient for operating the loads you are attempting to load. Please forget about 12V completely. Go with 24V, or better yet, 48V. I am successfully powering an 8000BTU air-con at my own cabin, but I have a 48V system with 4500W of panels.

I would also recommend that you stay away from Renogy. There are whispers that they might be going bankrupt. You'll get far better deals on solar panels on Craigslist with local pickup. Don't pay for panel shipping to your location. Instead of going with AGM, take a look at Trojan L-16s or Rolls-Surrette. Here is the battery I have right now as we speak. That's what I recommend.

I would also suggest going with a better quality inverter than Renogy. Take a look at the Magnum MS4048, the Outback Radian/VFX series, or a Schneider XW/Conext, all of which are quality tier-1 inverters designed to be hard-wired into the building's main electrical panel.

I power both my systems with Midnight200 charge controllers, though the Victron would be of equal quality.
 

12VoltInstalls

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suggest going with a better quality inverter than Renogy
Yes. And you probably need 24V system as it’s going to not be so amps to run your stuff.

If you want to power with solar to save money you may not experience that immediately as grid power is generally less costly than solar equipment per kWh

But for any other reason this makes sense n
 

mfolch

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Joined
May 4, 2022
Messages
2
Thank you for these very illuminating suggestions. The system I put together was in fact recommended by Renogy, so I am appreciative of the learned skepticism, recommendations for better products, and advice to go with 24v.

To address a few comments, I’m not exactly trying to save money. This is for a large shed quite far from our house, which I’m hoping to turn into a writing cabin. I’ll use it only during the day, probably for not much more than 6 hours at a stretch. I live in Connecticut. Summers are hot but short, winters are long and cold, but I’ll use a wood stove to heat the space. So, a few lights and lamps, somewhere to plug in my laptop, a fan, and the 8000btu AC is really just about all the space will have and need. Connecting to the house is a possibility, but even if I double the cost of the system I posted above, it will cost just about the same as digging a trench, burying cables, and wiring the place. I can see from the price and build quality that the products you guys recommended are of a different caliber altogether, and in general I also prefer to cry once, but I’m not living in this space, not spending nights there, and have no plans to use as backup or alternative power for an existing system (I have a generator that will run the house for more than two weeks).

What’s wrong with hybrid inverter/controllers and battery banks? E.g.,
  • Rich Solar 3,000 watt pure sine inverter charger- 48Vdc - 120V
  • 4 (6) x 200 Watt Monocrystalline Solar Panels 12V
  • 1 x 5.3KWH HSKY Lithium Battery Bank
In similar vein, not sure whether Growatt is any good, but why not have a Growatt 3000w inverter system, with 1200watts solar panels, and 2 300 watt lithium iron batteries, all of it at 24v?
 

MichaelK

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What’s wrong with hybrid inverter/controllers and battery banks? E.g.,
  • Rich Solar 3,000 watt pure sine inverter charger- 48Vdc - 120V
  • 4 (6) x 200 Watt Monocrystalline Solar Panels 12V
This is why not...

1652496266433.png

Dirtiest powered inverter I've ever seen.
 

Rednecktek

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Location
On a boat usually.
Thank you for these very illuminating suggestions. The system I put together was in fact recommended by Renogy, so I am appreciative of the learned skepticism, recommendations for better products, and advice to go with 24v.

To address a few comments, I’m not exactly trying to save money. This is for a large shed quite far from our house, which I’m hoping to turn into a writing cabin. I’ll use it only during the day, probably for not much more than 6 hours at a stretch. I live in Connecticut. Summers are hot but short, winters are long and cold, but I’ll use a wood stove to heat the space. So, a few lights and lamps, somewhere to plug in my laptop, a fan, and the 8000btu AC is really just about all the space will have and need. Connecting to the house is a possibility, but even if I double the cost of the system I posted above, it will cost just about the same as digging a trench, burying cables, and wiring the place. I can see from the price and build quality that the products you guys recommended are of a different caliber altogether, and in general I also prefer to cry once, but I’m not living in this space, not spending nights there, and have no plans to use as backup or alternative power for an existing system (I have a generator that will run the house for more than two weeks).

What’s wrong with hybrid inverter/controllers and battery banks? E.g.,
  • Rich Solar 3,000 watt pure sine inverter charger- 48Vdc - 120V
  • 4 (6) x 200 Watt Monocrystalline Solar Panels 12V
  • 1 x 5.3KWH HSKY Lithium Battery Bank
Add in a decent 30a MPPT controller and you're good to go.
In similar vein, not sure whether Growatt is any good, but why not have a Growatt 3000w inverter system, with 1200watts solar panels, and 2 300 watt lithium iron batteries, all of it at 24v?
It's easy and the AIO is usually going to cost a little less than the individual parts AND come with a transfer switch to draw power from an extension cord/generator/micro-nuclear reactor if your batteries get too low to feed your loads.

Also, to throw it out there, there is a 3Kw Growatt that comes in 48v so you could use that with your HSKY battery.


This is why not...

View attachment 94566

Dirtiest powered inverter I've ever seen.
In engrish for those of us who aren't familiar with the EE side of things? Doesn't that just mean it can use 24v +/- 10% for its input voltage?
 

12VoltInstalls

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‘Distortion’ is power that gets expended but doesn’t do work. In non technical terms. “Technically“ that’s not a good description but it’s how you’ll experience it. So add normal conversion losses and it wastes a LOT of electricity you can’t use
 

MichaelK

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Messages
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In english for those of us who aren't familiar with the EE side of things? Doesn't that just mean it can use 24v +/- 10% for its input voltage?
No, it refers to the level that the sine-wave output deviates from the perfect curves they show in the textbooks. Don't actually know that fine details as to how it is calculated, but what I know is that in the real-world, distortion means higher amp draw, hotter running appliances, and a shortening of lifespan. By how much, I have no clue.
 
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