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diy solar

DIY off-grid solar system with the grid backup

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tommyt

New Member
Joined
Mar 22, 2023
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6
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Hi All,

I would like to play with solar at home without messing with the grid, existing wiring, and huge investments. I’m going to install a small (about 600W) off-grid system with the battery and power up a mini-fridge and a desktop PC. So, loads are powered by panels during the day and by the battery during the night. However, I would also like to have the possibility to plug a controller into the outlet, so in case of bad weather, it’s able to switch to the grid and keep loads powered.

The main requirement is reliability. I would like to use only more or less wide-spread components that have been on the market for a while.

When you hear about a project like this, solar generators are the first that come to mind, but unfortunately, I’m not aware of any particular models that can work in this way. Some generators can work in pass-through mode, but they won’t use the battery until the grid is off. And they cannot be connected to the grid and panels simultaneously.

I also found this device on Amazon https://www.amazon.com/dp/B09PQL8KWH. It fits the purpose but it’s too exotic. I’m not ready to experiment with the high-voltage device with just 8 reviews.

Could somebody please advise any other option? The all-in-one solution would be perfect, but I’m ready to build the system from the components. It’s easy to find an inverter and MPPT controller, but what I'm really missing is a device that can draw power from the grid automatically.
 
Last edited:
What you need is a small aio watts24/7 sells the small ones and will give you support, highly recomend buying from a us based supplier being new at this, off shore support can be lacking and leave you pulling your hair out
 
tommyt said:
Hi All,

I would like to play with solar at home without messing with the grid, existing wiring, and huge investments. I’m going to install a small (about 600W) off-grid system with the battery and power up a mini-fridge and a desktop PC. So, loads are powered by panels during the day and by the battery during the night. However, I would also like to have the possibility to plug a controller into the outlet, so in case of bad weather, it’s able to switch to the grid and keep loads powered.

The main requirement is reliability. I would like to use only more or less wide-spread components that have been on the market for a while.

When you hear about a project like this, solar generators are the first that come to mind, but unfortunately, I’m not aware of any particular models that can work in this way. Some generators can work in pass-through mode, but they won’t use the battery until the grid is off. And they cannot be connected to the grid and panels simultaneously.

I also found this device on Amazon https://www.amazon.com/dp/B09PQL8KWH. It fits the purpose but it’s too exotic. I’m not ready to experiment with the high-voltage device with just 8 reviews.

Could somebody please advise any other option? The all-in-one solution would be perfect, but I’m ready to build the system from the components. It’s easy to find an inverter and MPPT controller, but what I'm really missing is a device that can draw power from the grid automatically.
Click to expand...
I started almost the same way just taking a handful of devices off grid power, but I didn't worry about having a way to connect back into the grid. I just ran some extension cords to the inverter to get my feet wet, then if I needed grid power, I just plugged back into the regular wall outlet.

There are a lot of different options out there, it all depends on your needs and budget.

If I had to throw something out to look at, it might be this one. https://watts247.com/product/pip-3048lv-mk/. Now I have no personal experience with it, but comparing to what you were looking at on amazon, it seems close in features and budget. Most of the MPP inverters have a great track record.

2 places I would look at are https://www.currentconnected.com/ and https://watts247.com/. Both are staffed with helpful, knowledgable folks that do a lot to work with you.
 
The OAE (Ampinvt) LF solar inverter you linked from Amazon I was recently thinking about acquiring (posted about it in the AIO Forum) but decide against it due to the modes of operation. It is more of a UPS and less a solar power device (except for charging purposes). Many of the other off grid AIO's out there would serve your purpose better.

Typically an off grid solar inverter will be select-able for which is the preferred power source. Modes may be SBU, SOL, SUB or Uti. These devices incorporate a ATS (auto transfer switch) for maintaining power from either grid or solar/battery to inverter.

Yes an off grid soalr inverter can be set to use solar during the day and battery afterwards until battery voltage drops to a setpoint at which time it auto transfers back to your home's AC supply for the load.
 
tommyt said:
Hi All,

I would like to play with solar at home without messing with the grid, existing wiring, and huge investments.

The main requirement is reliability.
Click to expand...
Are you thinking of expanding later? Do you need 120vac split phase for 240vac stuff ? Are you thinking of starting larger inductive loads like ac or well pump? Will you need UL listing?

Do you want reliability and trouble free set and forget operation ?
 
If you only need 120v the MPP LV3048 is a good choice. 600w is really small for a system and you lose a lot of expandability in the future.

How are you envisioning plugging your stuff into all of this? Extension cords and power strips? Do you envision seperate breaker panels hard wired into outlets in the wall? Is this going in a shed/garage or in the main house?

If you went with a small system you can just wire an extension cord to the AC Input terminals and plug it into the wall. Something like the LV1012 would be about all you can do through that before you run the risk of tripping a wall outlet. Anything larger than that will need a 30a breaker and wire to feed it.

The wiring and settings are pretty easy to do once you figure out what you're after.
 
rodrick said:
here’s one that might fit the bill https://watts247.com/product/pip-1012lv-ms/
Click to expand...
A very nice unit, I have one on my solar dolly. I don't know if it can be stacked for additional output but can easily feed from a wall outlet for your AC backup.

Set it to SBU and it will power everything from the panels, then take from the batteries when the sun gets low, then pull from the walls when you drain the batteries too far.

Something like that also pairs very well with a DIY battery. 12v 4s batteries are a great starter battery and very simple. They are also cheaper than high capacity Off-The-Shelf batteries.
 
I would like to thank everybody for your valuable suggestions! It helped me a lot!

MrM1 said:
Are you thinking of expanding later? Do you need 120vac split phase for 240vac stuff ? Are you thinking of starting larger inductive loads like ac or well pump? Will you need UL listing?
Click to expand...

120 V only. I think it makes no sense to expand it a lot in this setting. If I like the idea I will have to hook up it to the main panel eventually and in my state, it will require a professional installation and probably different equipment.

Rednecktek said:
How are you envisioning plugging your stuff into all of this? Extension cords and power strips? Do you envision seperate breaker panels hard wired into outlets in the wall? Is this going in a shed/garage or in the main house?
Click to expand...

In the one room of the main house next to the garage. I'm going to use the extension cords. So it will be completely independent of the current 120V wiring. I would love to connect my entire home to solar at some point, but I will hardly be able to reuse this AIO in the future because a professional installer may require some different equipment. And for the whole home, it would rather be 7-10kW.
 
I would recommend going with a rackmount battery if you're doing a 48v system. It's one piece you dolly up against the wall and leave there until you move out, no worries about getting the battery right the first time (because there are quite a few ways you can mess up your battery that get riskier as you add more cells in), has a warranty, and is compatible with anything.

About the only place I would recommend using a DIY battery is if you went with the LV1012 system because a 4s battery is much less risky than a 16s battery, a Noco box for the battery is about $20 and fits nicely, and you can get 300Ah of 12v battery into a box the size of a truck battery.

If you want to keep it simple, the Chins/PowerQueen/Clone batteries for a 12v is pretty cheap and available.

With the LV1012 they are also stackable so if you needed more than 1000w you could add a second unit and let them work together off the same battery.

Either way you go there are good options. About the only reason I would lean you towards the 1012 instead of the 3048 is that your estimated wattage is so low (600w) that a 3000w unit is overkill and will draw a lot more power from your battery than a 1000w unit just to exist. The other big advantage is that the 1012 you can plug right into a wall outlet and never worry about popping a breaker, it just can't draw that much power from the wall. A 3Kw unit on the other hand can very easily ask for 30a out of a 15a outlet and that's not going to work for very long.

Just my thoughts from a total beginner standpoint. :unsure:
 
I'd invest a wee bit of time in the design (calc) stage ... verify on paper that everything will do what you want. All too common mistakes are guesstimates, buying first then planning, designing while assembling, and so on ... get the design done on paper, and verify that everything should work the way you need it to.

Design stage costs you nothing but some time, and is something like:

1. Go here, and enter in each appliance's values (watts, hours/day you want to run it, etc.):
https://unboundsolar.com/solar-information/offgrid-calculator

2. Go here, using numbers from above, and fiddle with various entries/components, and you'll see in real-time what your system component (inverter, mppt, panel) sizing is:
https://www.altestore.com/store/calculators/off_grid_calculator/

There are many similar website pages/calculators, but these two pages should help you get through most of the necessary calculations. This helps you quickly decide if you can do what you want to do, and you can vary component choices for what-if scenarios ... for example, changing from 12v reference voltage (inverters, battery-bank) to 24v ... you'll see the changes in real-time.

In essence, you're likely to be at an AIO inverter, a battery-bank (even if just one battery for now), and solar panels, along with connecting bit & bobs (cables, fuses, etc.) If your estimate of 600w system holds true, then a common AIO inverter size is 1000w, the next step up (at some reference voltage of 12v, 24v, or 48v). If you end up with 1500w of loads for some reason, then a 2000w system might be the next step up.

This could very well be a "solar generator" on a hand-truck, just without the hand truck, and without costing you as much as a solar generator but getting a lot less capacity.

If desired for a sanity check, run the design past the folks on this forum ... then you'll be buying with confidence from a supplier with a local US warehouse, and assembly will be fun and stress-free.

Hope this helps ...
 
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tommyt said:
Hi All,

I would like to play with solar at home without messing with the grid, existing wiring, and huge investments. I’m going to install a small (about 600W) off-grid system with the battery and power up a mini-fridge and a desktop PC. So, loads are powered by panels during the day and by the battery during the night. However, I would also like to have the possibility to plug a controller into the outlet, so in case of bad weather, it’s able to switch to the grid and keep loads powered.

The main requirement is reliability. I would like to use only more or less wide-spread components that have been on the market for a while.

When you hear about a project like this, solar generators are the first that come to mind, but unfortunately, I’m not aware of any particular models that can work in this way. Some generators can work in pass-through mode, but they won’t use the battery until the grid is off. And they cannot be connected to the grid and panels simultaneously.

I also found this device on Amazon https://www.amazon.com/dp/B09PQL8KWH. It fits the purpose but it’s too exotic. I’m not ready to experiment with the high-voltage device with just 8 reviews.

Could somebody please advise any other option? The all-in-one solution would be perfect, but I’m ready to build the system from the components. It’s easy to find an inverter and MPPT controller, but what I'm really missing is a device that can draw power from the grid automatically.
Click to expand...
To answer the question you want an automatic transfer switch

MOES at on Amazon

It switches to house power if battery is low
 
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