Noob Looking for Advice - Small Off-Grid Shed System

[skuldugger]

TL;DR
Proposed system for small backyard off-grid shed:

• 2 x Aptos 400W Bifacial Solar Panels | DNA-108-BF10
• 1 x Growatt 3kW Stackable Off-Grid Inverter | SPF 3000TL LVM-24P
• 1 x EG4-LL Lithium Battery (V1) | 24V 200AH | Server Rack Battery

Will this system work? Do I need any other hardware (other than panel mounts, wires, etc)?

Full description:
I have a small backyard shed that sits about 30 feet from the house and currently has no power. I have artificial turf in the backyard that I'd rather not dig up to run power from the house so a small solar system seems like a reasonable alternative (plus I like to tinker).
The shed is fairly small so I'm limited to only two panels and need them to be under 96" long and under 54" wide. The system would be used to run an overhead LED light in the shed, charge my re-chargeable power tool batteries, some corded power tools (one at a time), and some outdoor LED string lights.
In the event of a power outage in the house I'd run some extension cables from the shed to the house to power a few essentials (fridge, few LED lights, and maybe the (natural gas powered) furnace blower.
I realize the system is probably under-panelled but I think most of the time the battery would be fully charged as typical use would be very light. I want the larger battery capacity in the event of an outage and could supplement with a small gasoline powered generator I already have if needed.
Would greatly appreciate any advice on this.
Thanks in advance!

 

[E. Cho]

What is the Growatt idle consumption (nothing being powered)? These All in One /AiO inverter/charger/ MPPT charge controllers can consume quite a bit of battery power over night and during cloudy days.

Personally, I'd go with a low consumption Low Frequency inverter/charger and a separate MPPT Charge Controller such as a Victron for all, or other researched brands. Separate components might allow some use should one component fail whereas if you have to send back the AiO, then you have nothing? You don't mention budget.

LOTS of threads in the Beginner, General and other forums on VERY similar topic, where you can read at your own speed, absorb, question and figure out what works best based on the experience of others.

 

[MisterSandals]

In the event of a power outage in the house I'd run some extension cables from the shed to the house to power a few essentials (fridge, few LED lights, and maybe the (natural gas powered) furnace blower.

It would be wise to do an energy audit on what you expect to run and for how long to see how well your proposed system does to meet these energy needs.

Your system sounds reasonable except for the idle consumption of the Growatt. Do the math on daily idle consumption 24/7... it adds up.

What is the Growatt idle consumption (nothing being powered)? ...

Yeah, my thoughts too!

 

[skuldugger]

Thanks for the replies. I'll definitely investigate AIO idle consumption as that wrinkle never crossed my mind. I was leaning towards an all in one mostly for simplicity's sake as this would be my first attempt at a solar system.

 

[E. Cho]

The problem is that your specs might be okay but only for a perfectly sunny day, for a few hours with panels that have no shading and at the correct angle to the sun. Shading, cloudy days and night time must be taken into account in your energy audit (list of appliances using how much power/watts each). On a dark rainy cloudy day, panels only produce 5-10% of the watts of their sunny day (at the best angle too) capability. So if your high frequency AiO system uses 50-80 watts continuously, then you will not replenish just that use with 2 - 400 watt panels. Then add the 8-10 hours of night time (depends on time of year and panel location and angles) and your batteries without appliance loads will be continuously drawn down. As you list a refrigerator as an appliance and some motor power tools, you need to also account for inductive motor power startup surge needs and if the AiO can even handle it. Just because it says it's an inverter, they are far from all being equally capable and manufacturers omit or exaggerate or both the appliance types that an inverter can start and or run. Research here the threads on Low Frequency vs. High Frequency inverters, AiO's and that meet your budget and your energy audit and your future. Lots of info in the forums from already discussed topics of all of this for you to read and learn from.

 

[Rednecktek]

I have that same unit in my cabin, standby draw is about 30w on it. Don't panic.

As far as working with the space you've got, that's not a bad system at all! If you don't already have a generator, make sure you get an Inverter style so that Growatt will talk to it without complaining too much. Something in the 1500-2000w range will easily provide all the power that Growatt can use for its battery charging. If you're really paranoid, a 3Kw inverter generator will fill the batteries AND run all your loads at the same time.

Make sure when you start planning out your wire runs and such you have a breaker/disconnect for your PV that does 2 legs (the Chitaxi 2-pole DC breakers work well) for troubleshooting, the main fuse/breaker to the inverter should be 150a, and I would recommend a small breaker panel for all your 120v breakers to come out from and some skinny twin breakers.

The most confusing thing you'll have to worry about is the grounding (because it's really confusing!) and you'll need to decide if your G-N bond will happen in the breaker panel OR do you want the Growatt to do it. If you do it in the breaker panel you'll have to pull a couple screws in the Growatt to make that work right. Not difficult, it took me about 5 minutes to get mine open, pull both screws, and get it back together.

Don't let the people tell you that "OMG VICTRON OR DEATH!!!", your system is perfectly fine for your use case.

 

[yodamota]

I believe our inverter uses 8w when in searching mode. and 25w when powering loads. There are times in the winter when the inverter being on is to much of a draw.

 

[skuldugger]

I have that same unit in my cabin, standby draw is about 30w on it. Don't panic.

As far as working with the space you've got, that's not a bad system at all! If you don't already have a generator, make sure you get an Inverter style so that Growatt will talk to it without complaining too much. Something in the 1500-2000w range will easily provide all the power that Growatt can use for its battery charging. If you're really paranoid, a 3Kw inverter generator will fill the batteries AND run all your loads at the same time.

Make sure when you start planning out your wire runs and such you have a breaker/disconnect for your PV that does 2 legs (the Chitaxi 2-pole DC breakers work well) for troubleshooting, the main fuse/breaker to the inverter should be 150a, and I would recommend a small breaker panel for all your 120v breakers to come out from and some skinny twin breakers.

The most confusing thing you'll have to worry about is the grounding (because it's really confusing!) and you'll need to decide if your G-N bond will happen in the breaker panel OR do you want the Growatt to do it. If you do it in the breaker panel you'll have to pull a couple screws in the Growatt to make that work right. Not difficult, it took me about 5 minutes to get mine open, pull both screws, and get it back together.

Don't let the people tell you that "OMG VICTRON OR DEATH!!!", your system is perfectly fine for your use case.

Thanks for the input.
I do think I'll look at some potential alternatives to the all in one; might actually be less expensive as well. I'm just in the research/planning phase and probably won't actually proceed with a build until Spring.
My primary use case is just to have some power in my shed for light and occasional power tool use; the backup power use case is secondary but definitely appealing where running my fridge is the main concern. I've had to throw away a lot of food more than once due to power outages that lasted up to a couple days.
I bought a generator last year that I haven't needed to use yet. It's a 3700W continuous 4500W peak inverter style. But I'd prefer not to have to run it 24/7 so the small solar system seems like a decent investment and should meet my primary use case.

 

[Rednecktek]

I do think I'll look at some potential alternatives to the all in one; might actually be less expensive as well. I'm just in the research/planning phase and probably won't actually proceed with a build until Spring.

It's really hard to beat the AIO's in price when you price out the inverter, the SCC, the transfer switch, and the AC charger. If you spend a LOT of money going component you might get down to 15-20w of standby, but at that point is it really worth it? You can't buy a 3Kw 24v inverter for less than the $500 a full Growatt costs you, much less the 60a SCC for it, AND the 30a AC charger.

How much are you willing to spend to save that 240Wh a day, and how much of that could have paid for an entire battery?

Whichever way you go you're heading in the right direction.

I believe our inverter uses 8w when in searching mode. and 25w when powering loads. There are times in the winter when the inverter being on is to much of a draw.

Yeah, "Sleep Mode" which is worthless. Most of the unit's I've looked at require 50w+ to wake up so you have to turn on every single light in the place to get any of them to turn on and your coffee pot says it's 12:00 12:00 12:01 12:01 12:02 12:00 12:00