how do you build an offgrid system gradually? i'm poor

I have some parts and am buying more in the next 8 days. i want to be able to power my kitchen when the power goes out...six times per year average,
usually 2 or 3 days, but one time for 9 days. i have totaled the max. watts I would need if using everything and the usual load; 4000 and 2500 respectfully.
350 ah per day should cover one day IMO. but for 3 days = 1050 ah would be better. especially in the winter (electric base board heat). i'm poor, so i'm going to have to buy major pieces like an mppt, solar panels, and batteries a little each month. i found 400 w solar panels @ 48 v for $229 each and think that i'll need
at least 4; 2 series/2 parallel. mppt appears to cost $3000 including taxes and shipping. 12v LFP Batteries could cost me $550 to ?? and i'd need 4 or $1500 for a set or a rack battery set for ??? All these big expenses total up to at least 8 months for me to buy. so my idea is to buy parts that i can use to grow my system as i can afford the parts and have a good 4kw system when finished instead of buying little system now, have to buy again later and have the small system which i can't use. i don't need blue tooth, but really want wifi monitoring and controlling. I usually spend 3 weeks new years and xmas out of town and want to be able to monitor the system and shut off the batteries if they go too low.
so what parts go together to make my intended system? thanks for your help.

I would start with an all in one unit. Then add batteries for backup (they can be charged from the grid at first). Then add solar panels for extended backup.

notarichman said:

350 ah per day should cover one day IMO.

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Is that at 120V?
350Ah x 120V = 42000Wh

42000Wh / 5hours solar = 8400W of panels

thanks. I think i'll have to save for 3 months to buy a good mppt inverter/charger. i already have some solar panels and am buying more in 8 days.
if they don't work with the mppt; then i have 2 ecoflow systems, a delta max and a delta river that i bought for camping and can use the panels for camping. otherwise, maybe i can use them for the mppt when i buy it. they are supposed to be 4 each 350 watt.

timselectric said:

I would start with an all in one unit. Then add batteries for backup (they can be charged from the grid at first). Then add solar panels for extended backup.

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The problem I noticed is that upgrading is not always possible because solar components have physical limitations (Voltage, Amp, Watt).

The most expensive is the battery, if you start with a 12V system, when going to 48V, you will not be able to reuse any of your original system.

I would start with a 48V battery, even if the AmpHour is small, to limit the initial over all cost.

I wil then search for the cheapest SSC with at least 2 mppt input and a 250V Voc, so I could add a large number of PVs for later upgrade.

48v is all that I would recommend.

MisterSandals said:

Is that at 120V?
350A x 120V = 42000Wh

42000Wh / 5hours solar = 8400W of panels

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500 watts @ 120 vac for 9 hours during the day= 4.5kwh + 4000 watts @ 120 volts for 1 hour (during day)= 4kwh + 1500 watts @ 120 volts for 7 hours (during night)=10.5kwh, leaving 7 hours when i only power for my fridge, 300 w??? total watt/hours used = 21.1kwh x 3 days = 63.3kwh.
apparently my math didn't have enough details and dropped a zero. however, with an estimated 4 panels @ 400w = 1600w x 5 hours sun in winter = 8000wh x 3 days = 24kwh. 63.3kwh - 24kwh = 39.3 kwh i'll have to make up at first with grid power. later with more panels + mppt + batteries;
i might be able to power my kitchen. 8 more panels and a lot more batteries.

MisterSandals said:

Is that at 120V?
350A x 120V = 42000Wh

42000Wh / 5hours solar = 8400W of panels

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You need to look at your priorities.


- My point is to avoid to buy cheap something that could not be upgraded later and will have to be scrapped.

i am guessing at 300 watts for my fridge and 180 watts for lights = 480 or about 500 watts x 14 hours = 7kwh. but during the winter i'll need some heat... 1500watts for space heater or baseboard? x 24 hours = 36kwh, but i'm usually gone a good portion of the day and i turn the heater down a lot, so 1000watts x 14 hours= 14kwh and during the winter, 21kwh per day, 63kwh for 3 days of lost power.
63kwh total of batteries / 48volts = 1312 ah of batteries or 14 each 100 ah batteries.

notarichman said:

63kwh total of batteries / 48volts = 1312 ah of batteries or 14 each 100 ah batteries.

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If your buying LFP batteries you are already in the $20,000+ range on batteries alone no matter how you do it.
Are you sure you want 3 days of backup power or have you changed your mind about using a tight budget?

Impossible to pick both.

If you are looking to power your kitchen a few days a year, a generator would be the cheapest solution. If you are trying to power your kitchen most of the year, a solar system, with batteries would be worth looking into.

robby said:

If your buying LFP batteries you are already in the $20,000+ range on batteries alone no matter how you do it.
Are you sure you want 3 days of backup power or have you changed your mind about using a tight budget?

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my village loses power about 6 times per year for an average 3 days. one time, no power for 9 days - i left!!!
once i figured out 63.3kwh for 3 days, i may just power my fridge for 3 days and leave during the winter. i tried to look up power use
for my fridge, but couldn't find it on the internet. so i estimated 300 watts x 24 x 3 = 21.6kwh. with 8 each 400w panels x 5 hours sun
= 3200w x 3 days = 9.6kwh. so i'd have to have 3 times that if the fridge ran all the time. but in winter i could turn off my heat and the
temperature would be about 32 degrees in my kitchen and the fridge would only run about 1/3 the time? so 8 panels would be enough.
batteries for 3.2kwh per day @ 48v = about 65 ah. so one 100ah 48 v battery set should be enough.

48V 50Ah Smart Lithium Iron Phosphate Battery $1700 plus taxes and shipping - would need 2 = $3600?​

signature solar's gyll battery = $1500 only need one. +plus tax + shipping

EG4 48V 100AH LiFePower4 Battery $1500 only need one.+plus tax + shipping​

and it is rack mounted.

If it's a combination fridge freezer. You will have to install a thermostat heater. Otherwise when the temperature gets below 40, everything in the freezer will thaw out.

i don't keep much in my freezer, so i'll just empty it before i leave and take it with me to eat at my sister's house.

Regarding refrigerator for your village, you could try this

I use a small 7.1 cubic foot freezer chest. Freezers work better when they are 100% filled. I saved about two dozen 1 gallon water bottles, and refilled them 90% so that when they freeze, they don't crack open -- a little needed extra room to expand. They're inside of it now.

When I run my generator every other day for 1 or 2 hours to charge my battery for off grid, the generator also runs the freezer chest. Just 1 or 2 hours a day is enough to freeze some of the water bottles.

Slowly over the week the water bottles have been freezing. It's been 5 days and half of them are half frozen. That's good enough to refrigerate things for me.

It's cold enough to be a refrigerator but not frozen enough yet. If and when it does totally freeze and it is 100% filled, it will stay frozen for "4 days".
without power. Then it will stay as a refrigerator for probably a week or two.

It's like a reverse battery: store frozen water.

Eventually I'll have the freezer chest hooked up to solar. If I keep it full of frozen water, and take a frozen gallon out when I need room, it should be extremely efficient. It should hardly ever run because it has so much stored frozen water. We're talking just a couple hundred a watts per day if that if I can get to that point.

Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the PVwatts.com or JCR Solar Uber-Sun-Hours calculator sites to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that. If you're looking at the All-In-Ones check for correct voltage outputs (120v or 240v Split Phase for North America, 220v Single Phase for European type areas) and make sure it has enough capacity for a little bit of growth and fudge factor.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round ) and help figure out which parts and pieces you're going to want to get.

OK, now that I've got that out, there's a few things I'd like to add in:

(electric base board heat)

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There is no way even Elon Musk could afford enough batteries to keep a house warm on baseboard heat. Look into alternative methods of heating be it wood stove, diesel heaters, whatever you can do to get off the baseboards. I have a similar doodle project for off-grid heat in a Idea Doodle Thread that might give you some ideas. Every dollar you can spend to reduce your consumption is about $5 in solar equipment you DON'T have to buy.

i'm poor, so i'm going to have to buy major pieces like an mppt, solar panels, and batteries a little each month

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There are some places you can cheap out and some you can't. A couple things right off the bat that will save you cash is 1: consider getting used solar panels instead of new if you can afford the space. A pallet of 23 200w panels cost me $53ea after freight. 2: The WallyWorld 29DC 120Ah FLA batteries are about $100ea out the door with tax and core charge. Yes, you might only get 5 years out of them, but for the $1600 that single 48v 100Ah rackmount battery you can get 48v 240Ah usable in lead acid and step up to nice LiFe's in a few years. Or get less batteries and use that money elsewhere. Yes, a little more maintenance and more space, but LOTS cheaper up front.

Places to NOT skimp are your inverter, wires, and fuses. Fires are EXPENSIVE!!!

i found 400 w solar panels @ 48 v for $229 each and think that i'll need
at least 4; 2 series/2 parallel.

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When you see something listed as a "12v Panel" or "48v Panel" those aren't actual numbers that you'll use. What that means is that a "12v Panel" can generate enough voltage to charge a 12v battery, but not enough for a 24v battery. A "48v Panel" will create enough to charge a 48v, 24v, 36v, or 12v battery. Your charge controller will take the voltages of the panels and convert them to whatever the battery needs. Don't worry about trying to find "48v Panels" when you can just put 2 "24v Panels" in series and get the same effect.

mppt appears to cost $3000 including taxes and shipping.

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Where are you getting your SCC and where are you sending it??!!??!! That's obscene even for Victron. There are many, MANY other brands that will turn solar panel power into battery power. Don't let the Victron fanboys tell you that it's "Victron or Nothing", especially when you're on a budget.

OK, more later, the boss just showed up.

notarichman said:

i'm poor, so i'm going to have to buy major pieces like an mppt, solar panels, and batteries a little each month

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notarichman said:

these big expenses total up to at least 8 months for me to buy. so my idea is to buy parts that i can use to grow my system as i can afford the parts and have a good 4kw system when finished instead of buying little system now

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I’m here to inform you that if you can do that in 8 months you are rich. Richer than much of the world is anyway.

OK, got a quick minute while the boss isn't looking. A couple more thoughts for you.

I would suggest skipping the AIO's and going for a component system for a couple of reasons. First, the standby draw on AIO's is notoriously bad and since you're on a budget you really need to maximize every watt hour. As an example my camp system will be 24v based and a 3Kw AIO (for simplicity because my nephews are jocks) and I'll have 6 of the 120Ah batteries in there. Of those batteries, 1/3 of them are JUST going to power the standby draw of the AIO while I'm up there. Going with components allows you to cherry pick your inverters and SCC to get the most out of every watt both in standby draw AND efficiency.

Secondly, since you're going to be building the system up gradually going for a component based system will make it easier to grow in the future as you'll be able to add SCC's or increase the inverter size much easier if you don't have to throw out the entire $1000 AIO when you want to make a big change.

Yes, AIO's are super simple, but they're really best for a Set-It-And-Forget-It type system.

I usually spend 3 weeks new years and xmas out of town and want to be able to monitor the system and shut off the batteries if they go too low.

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Is there any reason you couldn't just turn the system off when you leave? Are there loads you'll need to have on all the time? How about just securing the breakers to the non-essential stuff and leave the fridge on? A good quality shunt can probably do all that and will be much cheaper than a SCC or something that will do the same thing. I think you'll have to fork out $RealMoney for the ability to do that. Affordable and Online Control are pretty mutually exclusive.

Winter is always the hardest on solar systems since you usually don't get krap for usable light and systems have a hard time keeping up depending on where you live. Definitely hit up PVWatts and the JRC solar map and see what you have to work with. You can check out my How Low Can You Go thread and see what kind of info you're going to get. The JRC site is really good for throwing in battery size and panel size and seeing how well you system will hold up.

Now is the time to do all the doodling and number crunching BEFORE you spend anything on parts that you might not be able to use.

I’m here to inform you that if you can do that in 8 months you are rich.

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I could do a really nice system in 8 months of pay if it weren't for those pesky cats and wife and house all wanting money.