Hi! some noob questions

flyinghook

HI! I already have 500W of panels and 4.2kwh of batteries in service with a 40A MPPT charge controller and 3000W 12v to 120v inverter. This was to prove to the wife I know what I'm talking about and prove to me how well this works. Now it's time to turn it up a few notches nd turn this into what it's really supposed to be, a dry run for the off grid house I'm going to build in a few years. I'm buying 2 more banks of batteries and one more 500W array and I'm going to try powering the whole house.


I don't want to re buy anything I already have, and want to maximize my output per $, so I had a thought.

My rover charge controller is capable of charging 24v, plus wire for a 24v system is cheaper, but my inverter is 12v.

can I run 3x banks of 24v battery wise and somehow wire 2 12v inverters in?

as far as wiring the inverters to the home panel, once I have grid power disconnected, can I just hook each inverter up to each buss bar and have 2 banks of 120? I'm not expecting anything 220 to work.

petertearai

best to wait till your doing the project in 2 years . Save your money . If you do build a new of grid home ... then 48 volt inverter  or 24 volt is better . Adding batterys is not always the best .

oil pan 4

I wouldn't even attempt that.
Just get a 24v inverter.

petertearai

yep 12 volts for an off grid home isnt going to be the best in the long run . 
Lucky you have found this great site  , use the search facility to follow some older threads, many good discussions there.
In 2 years i would think panels will not be more costlier, they may be better and more efficient though .

mcgivor

Do a paper design based on load requirements before even thinking about buying, use a Kill-a-watt device as well as information from your electrical bill, also consider energy efficient appliances, learn to conserve because off grid is all about conservation, unless money is no object. 

MrM1

I would think 2 randomly connected inverters that are not stacked and designed to work together would cause some serious phase issues connected across the L1 and L2 of a main service panel

MrM1

Second issue I see, 12v inverter at 3000W = 250amps.  Better have some 4/0 battery cables. 

Photowhit

Why do you want to disconnect from the grid? Unless you have very expensive electric, the grid electric will be cheaper than solar.

flyinghook

mcgivor said:

Do a paper design based on load requirements before even thinking about buying, use a Kill-a-watt device as well as information from your electrical bill, also consider energy efficient appliances, learn to conserve because off grid is all about conservation, unless money is no object. 

kill a watts are not what I use. I use my electric company's data, which I would think gives me a much better picture of whole house use. either way, I've already done load calculations for daily use and peak load

flyinghook

MrM1 said:

I would think 2 randomly connected inverters that are not stacked and designed to work together would cause some serious phase issues connected across the L1 and L2 of a main service panel

not working together to get 220, as 2 separate branches of 120?

flyinghook

MrM1 said:

Second issue I see, 12v inverter at 3000W = 250amps.  Better have some 4/0 battery cables. 

as per my inverter manual, I have 0 gauge wire. then again, my packaging is optimized with the longest cable being 22 inches.

wellbuilt

I building a off grid home it’s about 3000sf and I’m useing a prewired inverter package from AWS out back flex power one 3600watt 48v it is a nice package . 
When you add up all the parts and pieces the 3500 bucks it cost is worth it in my  opinion . 
 The CC Inverter breakers and boxes would run 2800+- 2 strings of 8 battery’s 1500 bucks .
 I have 24  295watt  Solar panels with racking in pipes and disconnect battery cables fuses and other goodies around 5000 bucks . 
 Just call AWS and they will  design a system that work for you in about a day . 
 Then the guys on the forum can help with the set up , they are great .  
  My  electrical knowledge is minimal at best when it comes to solar 

flyinghook

Photowhit said:

Why do you want to disconnect from the grid? Unless you have very expensive electric, the grid electric will be cheaper than solar.

I explained this in my initial post, but let me elaborate. this first setup I built is not changing in function, but the parts will be easily separated from the rest once it is built. I am building a house in 2-3 years, where I am there is no electric at the site and I do not desire to have to have electric run before building my house. then I started thinking and calculating how much it would cost to run my new house off solar vs the grid, and solar came ahead. My electric is only 16c/kwh, but the fees/ect… end up being over $30 a month, which is insane, and this way I save the very likely $3k it would cost to have electric run to my site. so anyway, this initial setup is as I said, 500W of panels attached to 4kwh of batteries, and it is contained in a case to serve as my generator to build my house. as many of these components will be used in the next system as possible, but will be able to be removed to be my portable power unit. the system I'm building now will be a dry run for when I build my house, it will show what I need for capacities, and get my family used to living this way before we live in the new house.

flyinghook

wellbuilt said:

I building a off grid home it’s about 3000sf and I’m useing a prewired inverter package from AWS out back flex power one 3600watt 48v it is a nice package . 
When you add up all the parts and pieces the 3500 bucks it cost is worth it in my  opinion . 
 The CC Inverter breakers and boxes would run 2800+- 2 strings of 8 battery’s 1500 bucks .
 I have 24  295watt  Solar panels with racking in pipes and disconnect battery cables fuses and other goodies around 5000 bucks . 
 Just call AWS and they will  design a system that work for you in about a day . 
 Then the guys on the forum can help with the set up , they are great .  
  My  electrical knowledge is minimal at best when it comes to solar 

while I appreciate he input so much, my electrical knowledge in general is pretty good, I just haven't done solar and prefer to do everything myself. I am also limited to amazon and home depot for my sources. 

oil pan 4

Just about everything homedepo sells that's solar related is junk or over priced junk. Return any thing you bought from them.
There is a lot of cheap solar garbage on amazon that is junk, but you have to know what to look for.

We get someone coming on here about once a week that thinks they can run a whole house of 1 or 2 junk power inverters, a few batteries and solar panels. Don't worry it seems appealing but it's going to take a lot more that what you think it will

littleharbor2

flyinghook said:

Photowhit said:

Why do you want to disconnect from the grid? Unless you have very expensive electric, the grid electric will be cheaper than solar.

I explained this in my initial post, but let me elaborate. this first setup I built is not changing in function, but the parts will be easily separated from the rest once it is built. I am building a house in 2-3 years, where I am there is no electric at the site and I do not desire to have to have electric run before building my house. then I started thinking and calculating how much it would cost to run my new house off solar vs the grid, and solar came ahead. My electric is only 16c/kwh, but the fees/ect… end up being over $30 a month, which is insane, and this way I save the very likely $3k it would cost to have electric run to my site. so anyway, this initial setup is as I said, 500W of panels attached to 4kwh of batteries, and it is contained in a case to serve as my generator to build my house. as many of these components will be used in the next system as possible, but will be able to be removed to be my portable power unit. the system I'm building now will be a dry run for when I build my house, it will show what I need for capacities, and get my family used to living this way before we live in the new house.

 In your calculations showing solar will be cheaper have you factored in the fact that you will be replacing your battery bank every 3 - 7 years? This is usually the equation killer in off grid power.

Photowhit

I assume you will be using gas for heat, hot water? Will you need air conditioning?

If $30 user fees before buying electric and $3000 to install, it might be worthwhile looking into solar.

I ran my costs 7 years ago and it 'really' didn't make sense to do offgrid solar, but I already had a $2525 battery. 

It will be hard to do better than I did and I doubt a family would want to deal with adjusting daily loads so would need a generator as well. My energy profile closely matches my usage, the only way it can be close. 

BB.

FlyingHook,

What was the daily energy usage (kWH) and peak usage (Watts) did you calculate for your home... Just to give you some typical ranges (assuming cooking, hot water, heating are done with fossil fuels or wood):

• 500 to 1,000 WH per day (0.5 to 1 kWH per day, 15 to 30 kWH per month)--A cabin system for lights, cell phone/computer charging, RV water pump. 300 Watt AC inverter suggested
• 3,300 WH or 3.3 kWH per day (100 kWH per month)--About the minimum size off grid power system that will give you a "near normal" electrical life (Fridge, LED lights, LED TV, Laptop computer, clothes washer, well pump)
• 10 kWH per day (300 kWH per month)--A very efficient grid connected home. 1,500 to 3,000 Watt AC inverter suggested
• 33 kWH per day (1,000 kWH per month)--A typical North American home that has not done any energy conservation, does some cooking with electric. (500-1,000 kWH per month is typical North American Home energy usage). Around 4,500 to 9,000 Watt AC inverter suggested
• 100 kWH per month day (3,000 kWH per month)--Heavy energy usage. Electric heating, hot water, Air Conditioning, not much insulation or conservation.

The first system is a good emergency backup/learning system. The 3.3 kWH per day system is about the largest I would suggest as a first time DIY type system (and it will not be cheap--Something like $10,000 to $30,000 if you do all the labor, shop for good deals, etc.).

The reason a Kill-a-Watt type meter is suggested--You pretty much need to know the energy usage of every AC appliance/system you plug into your solar power module.

For a 3.3 kWH per day system, we are talking about a ~120 Watt refrigerator (~600 Watts when defrosting), less than 50 Watts for lighting, 1,000 Watts for a washer, possibly >2,000 Watts for a smaller well pump, 30-60 watts for a computer and LED TV, etc...

In the above system, the refrigerator is something like 1,000 to 2,000 WH (1 to 2 kWH) per day by itself (an Energy Star Rated full size refrigerator). That is 1/2 of your daily load or more...

To build out a system that can run a "modern" North American home on 500-1,000+ kWH per month ($50 to $200 per month power bill), is highly expensive. Add replacing batteries every 5-7 years (typical), new inverter+charge controllers every 10+ years, you are looking at $1 to $2+ per kWH burdened costs for you solar electricity. Compare that to $0.10 to $0.40 or so per kWH for electricity for most utilities in the US.

Even generator AC power is in the $1+ per kWH range (as we approach $4.00 per gallon gasoline costs again--That $1 per hour is just for fuel costs).

If your present electric bill was 10x as much (the cost for going off grid solar), would your electric usage be the same (and you paid $50,000-$100,000 up front for your next 10 years of power costs)?

If I recall correctly, Photowhit's present off grid solar power costs are around $0.50 per kWH--But he works hard at that (managing daily loads, got really good pricing for hardware, did the work himself, etc.).

-Bill

Estragon

I'd also add that location is important. At altitude in Colorado or AZ desert will have much different performance than (eg.) my location, where using solar alone is pretty impractical from late Oct to March as the days are too short and the sun too low.

flyinghook

oil pan 4 said:

Just about everything homedepo sells that's solar related is junk or over priced junk. Return any thing you bought from them.
There is a lot of cheap solar garbage on amazon that is junk, but you have to know what to look for.

We get someone coming on here about once a week that thinks they can run a whole house of 1 or 2 junk power inverters, a few batteries and solar panels. Don't worry it seems appealing but it's going to take a lot more that what you think it will

I'm getting my wire and tape, housings, conduit from home depot, and renogy panels and charge controllers

flyinghook

I'm  new, not dumb, lol

flyinghook

littleharbor2 said:

flyinghook said:

Photowhit said:

Why do you want to disconnect from the grid? Unless you have very expensive electric, the grid electric will be cheaper than solar.

I explained this in my initial post, but let me elaborate. this first setup I built is not changing in function, but the parts will be easily separated from the rest once it is built. I am building a house in 2-3 years, where I am there is no electric at the site and I do not desire to have to have electric run before building my house. then I started thinking and calculating how much it would cost to run my new house off solar vs the grid, and solar came ahead. My electric is only 16c/kwh, but the fees/ect… end up being over $30 a month, which is insane, and this way I save the very likely $3k it would cost to have electric run to my site. so anyway, this initial setup is as I said, 500W of panels attached to 4kwh of batteries, and it is contained in a case to serve as my generator to build my house. as many of these components will be used in the next system as possible, but will be able to be removed to be my portable power unit. the system I'm building now will be a dry run for when I build my house, it will show what I need for capacities, and get my family used to living this way before we live in the new house.

 In your calculations showing solar will be cheaper have you factored in the fact that you will be replacing your battery bank every 3 - 7 years? This is usually the equation killer in off grid power.

batteries every 5, inverter and charge controller every 15, inverter every 10, panels every 25

flyinghook

Photowhit said:

I assume you will be using gas for heat, hot water? Will you need air conditioning?

If $30 user fees before buying electric and $3000 to install, it might be worthwhile looking into solar.

I ran my costs 7 years ago and it 'really' didn't make sense to do offgrid solar, but I already had a $2525 battery. 

It will be hard to do better than I did and I doubt a family would want to deal with adjusting daily loads so would need a generator as well. My energy profile closely matches my usage, the only way it can be close. 

gas or wood for heat, and hot water. this house will be engineered to not need ac. My family is resistant to daily throttling, too, but will have to adapt, as I want my new house to be as self reliant and sustainable as possible.

petertearai

still , i would wait and learn , then buy what is needed once you are about to construct your system . possibly the only thing i would buy at the moment is  an outback fm80 or midnight charge controller,  or simlar good quality high voltage charge controller . This piece of kit will most likely not end up redundant .

Photowhit

I don't know where you live, but some places defy "engineering not to need Air conditioning". You could likely do a Berm shelter in Missouri and be okay, but I use to live in Florida and it just could not be done. It is possible to tolerate anything, but likely to create difficulties in many area. I went 'native' in Missouri for a few years before building a place I could run an air conditioner off solar.

I suspect you haven't gotten far enough along to figure out that the best pricing is often not the 100 watt 1 volt nominal panels. And if you intend to have refrigeration, You will likely benefit from a 24 or 48 volt system voltage. Less charge controllers, smaller wiring... It's the reason solar systems are somewhat hard to 'grow'

Consider you are already have a 3000 watt, 12 volt inverter, so I guess you don't plan to have a code compliant home or insurance on the home. Only 1 UL 1741 3000 watt inverter that I'm aware of and they wouldn't suggest "...as per my inverter manual, I have 0 gauge wire..."  Might work for open air marine use... but I doubt it. 0 gauge wire is not designed to handle 250 amps;


Not sure why you would want or need a 3000 watt inverter, I'm doing okay and running a bit more including a window unit with a 1800 watt inverter.

12 volt systems also have problems with running too many batteries in parallel. Which creates it's own set of problems, heck I'd be running a 48 volt system if my battery wasn't for a cabin system I designed 13 years ago. I'm likely to go ahead and switch once my battery hits the dust. The reason I haven't spent the money on a higher wattage 24 volt inverter.

...and it looks like you want to run another inverter?  

Do you have a final system size in mind for this home? Do you have a daily and season energy budget? Do you know your solar Insolation? A lot of people here with experience setting up off grid homes. Perhaps we can help. You  admit to being new to solar. Don't be these people, I actually tried to help them with some info a couple years ago...

https://youtu.be/16rC650s69I

flyinghook

The 3000watt inverter was so I have plenty of overhead when building I'm not tripping the inverter, and how is 150amps not enough capacity in the wire? am I missing something? I'm going to go proper 24v, I have no problem spending the money if I have to. What size panel is most cost effective? I'm open to input. My average daily usage is 9kwh with electric stove and central air. I'm hoping to go with a 3000-5000watt inverter, 1400kwh of panels, 16200 of batteries. I have a 2Kw/day energy star large fridge, a small ish chest freezer, a small furnace, microwave, washer and dishwasher, countertop appliances, and two window air conditioners in the summer, since this house isn't built to not need ac. I live in the upper peninsula of Michigan, on the Wisconsin border, so engineering a new house to not need air conditioning isn't impossible. Those people in that video clearly weren't committed to making solar work for them, as obvious by their attitude and constant use of a generator, stating most people use more than just solar. I also have financial incentives to go with solar

flyinghook

never mind the amps, my tired brain has failed me. I don't plan on running 3000Watts continuous, and my wires are short, very short, for what I'm using it for, it should be fine, plus I always monitor my projects for overheating from time to time. The whole home system will be appropriately robust, I assure you, and if this proves inadequate, I'm not above revising what I've done.

flyinghook

I also have one led tv, small home theater, wifi/cable, modern laptop

petertearai

maybe look to get an inverter  fridge . newer ones use less than 1kw a day 

mcgivor

The inverter refrigerators are the way to go, conservation is cheaper than production. 

flyinghook

yeah, I was considering a fridge upgrade, just need to find one around 25 cu ft that the wife likes and isn't all full of features like see-through doors