Off Grid Solar - learning more from DIY users

xtry51

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Looking to see if anyone in NH or MA who has built their own solar system might consider letting my wife and I see it in person and pick your brain on ideas.

The current will-certainly-change situation. Kids are getting older, 2nd of 3 is a year away from leaving the nest. Wife and I are looking at buying a large piece of land or farm (>100acres) while we keep the current house and one of the 3 kids takes it over. Either we're going to build a new house or basically gut whatever we buy to the studs and start completely from scratch.

The ambitious long term power goal. Both the wife and I want an off grid solar for basic things lights, fridge, freezers, well pump up front. I would likely later clone whatever we build to take over as much as possible in house (TVs, computers, small appliances etc). We'd also have a garage with workshop and several sheds (chickens, goats, etc) and would like to plan independent systems to support those as well so possibly a 3rd and 4th smaller clones.

We realize doing this will each be high $ projects. We realize we will need to have regular utilities to support some items, especially the shop equipment I have. We have started making a list of current power usages and categorizing them into need, want and wish lists. We're also going to pull our power usage history for last two years.

We're trying to learn as much as we can and are not going to pay a company to do it for us as that would defeat the purpose of being self sufficient. The point is to understand how it all works and how to fix it if necessary ourselves. Plus we enjoy doing everything ourselves. So I'm basically reaching out to the hive here so hopefully someone can piss all over our cheerios and point out where not to go majorly wrong out of the gate and at least have enough knowledge to start a budgeting process. This is likely a 2-5 year from now move as we're hunting for exactly what we want in a property, not just jumping on what's available today.

So, any generous people who love telling engineers they are wrong and/or idiots? 🤣
 

Brewer

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Wouldn’t say you're wrong or an idiot but you can do a good thing in a wrong or idiotic way if you're not careful. Among your calculations be sure you do some dollar-cost averaging. And if you're going for it, time your purchases with subsidies.

When I was working in solar it was a 25-year service life you get out of the panels and they would pay for themselves after about 22 years. And those numbers are with gov’t subsidies on the front end and SRECs throughout the service life. Even the owner of our company was currently operating in Mass but based out of Pennsylvania -- he just moved where the legislation made his business profitable, was very frank that he might close up shop in this state if subsidies weren't renewed.

Going off-grid means at the minimum you won't get the return of SRECs sold back to the grid, so your cost spikes dramatically. Combine that with purchase/install during a period without subsidies and unforeseen maintenance due to something like hail and you could regret the whole venture.

Self-service can also be challenging even if you plan for it. Just one panel out of commission drains dramatically from the rest of the array. You'll have to decide if you'd rather just disconnect that bum panel and rewire the array without it or get the thing replaced. If it's a rooftop array, you might need to remove several panels just to reach the one you want to replace/disconnect, then put them all back. At least with a ground-mount system you can just walk or crawl under to mess with wires.
 
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xtry51

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Thank you for above and feedback on some points.

100% will not be rooftop. I'm going to build ground arrays slightly off ground to avoid snow buildup with catwalks so the panels can be cleaned/cleared of snow.

We have zero concern about ROI. Obviously mitigating purchase costs where possible is great, but we will not be selling power back to the grid and don't care if this project costs more money than other solutions.

We would plan on having spare panels on hand for swapping. We would also consider having spares of smaller items but the goal with cloning the setup for separate groups of items is to use identical parts for charge controller, invertern, etc so that we could scavenge parts off any of the other "grids" to keep the first and most important grid running. This is also why ROI is of no concern. We're gonna blow the cost out of the water having multiple independent setups completely isolated from each other.
 

strangenh

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Do you plan to backhaul to the house as DC or invert at each panel?

What's your shadow situation where you plan to install it? If it's pretty open with uniform shadow, you could get away with (depending on how big a system) hauling it as DC in strings to one or more inverters. There are a lot of ways now to achieve off-grid and hybrid systems.

Do you want a large battery setup or one of those "the inverters store some, and we'll just use less at night or run a generator every now and then?" If battery, what kind(s) are you comfortable with? How much maintenance? When you expand, do you want to centralize that battery setup?
 

xtry51

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Whatever property we buy will either have open fields or I will clear open fields. Ideally on a small incline facing south. Given this I would run DC to a building with inverters and battery bank. Then trench for underground AC distribution to other buildings. We have family experience with solar water heat, so the building would likely end up heated for battery efficiency in winter. I also have friends with heat pump experience so possible we use a heat well to dump any excess solar production for later use.

On size we are currently thinking going big battery bank for multi-day backup on the first grid. Say 2-3 days. With the battery research we've done leaning at LiFePO4 batteries due to low temp and ability to drain deeper. Yes, we realize these batts are not cheap but it seems like the increased cycle count offsets some of the cost. Also by the time this project starts there will be even more data on longevity, so I'm open to altering this decision when we execute, but for budgeting it makes sense to plan for the higher cost I think.

The other grids we build later we figured would be 24hr backup or less as they would be serving the "wants" or "wish" items not critical items. And again they could be pillaged for spare parts if needed.

I don't think we would ever centralize the battery bank to a shared situation as that would put all the grids at risk.

We plan on buying an inverter that accepts generator power input. We have been looking at the Schneider Conext 6848s which seem to meet these desires.
 
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I lived off-grid for 5+ years. A couple pieces of advice:

1) Buy my book: Tiny House Engineers Notebook: Volume 1, Off Grid Power: Tiny House Engineers Notebook: Volume 1, Off Grid Power: Haynes, Chris: 9781530936038: Amazon.com: Books

2) You want to be looking at LiFePo4 batteries....lead acid is obsolete IMO.

3) Do not buy new Lithium batteries there are much better deals. I use Batteryhookup.com and have gotten some smokin deals!! Sign up for their email list....every couple weeks something interesting comes along.

Here is an example of a pack I am building for my van conversion:

IMG_1167.JPG
Its made from 25AH cells and has an overkill solar BMS. Its 3 cells in parallel for 75AH and 4 of those wired in series to produce 12V. The discharge characteristics of LiFeP04 cells are much better than lead acid batteries...meaning you will actually get 75AH from the pack. The downside is cold temperature charging...if you need that then golf cart batteries are a better solution.

These cells were $12 each!!! 12 cells @$12 = $144, BMS was $115....thats $259 for a 75AH pack that can be discharged at 225A (BMS limits it to 120). And it comes with a bluetooth module that lets you adjust params, and monitor the pack from a phone app.

EDIT: This just came in 2 minutes ago (8AH 200A discharge for $12):
 
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Duxprep

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Other solid resources to learn from
Diy solar with Will Prowse on youtube. Also his forum. Diysolarforum.com is filled with excellent resources and people.

Solar panels are cheap. Wiring, batteries and electronics are not.

Design a system so you optimise wiring to use smaller gauge. Build your own lifepo4 batteries (not hard and lasts 3-5000 cycles) like 10 years. You can buy 16 new Lishen 270ah cells for like 1600 bucks right now. That's 13,000kw of power Depending on criticality you can get by with chinese all in one inverters. They are fraction of the cost and you can buy extras to have on hand. Just remember to de-rate them (use less than max). If you're looking for set it and forget it then buy top tier stuff like schneider, magnum, sol-ark, midnight solar, victron etc

When ready to buy the Alt-e store in boxboro Ma is a great resource. Order online and pick in person to save shipping
 

whatluck

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I lived off-grid for 5+ years. A couple pieces of advice:

1) Buy my book: Tiny House Engineers Notebook: Volume 1, Off Grid Power: Tiny House Engineers Notebook: Volume 1, Off Grid Power: Haynes, Chris: 9781530936038: Amazon.com: Books

2) You want to be looking at LiFePo4 batteries....lead acid is obsolete IMO.

3) Do not buy new Lithium batteries there are much better deals. I use Batteryhookup.com and have gotten some smokin deals!! Sign up for their email list....every couple weeks something interesting comes along.

Here is an example of a pack I am building for my van conversion:

View attachment 453492
Its made from 25AH cells and has an overkill solar BMS. Its 3 cells in parallel for 75AH and 4 of those wired in series to produce 12V. The discharge characteristics of LiFeP04 cells are much better than lead acid batteries...meaning you will actually get 75AH from the pack. The downside is cold temperature charging...if you need that then golf cart batteries are a better solution.

These cells were $12 each!!! 12 cells @$12 = $144, BMS was $115....thats $259 for a 75AH pack that can be discharged at 225A (BMS limits it to 120). And it comes with a bluetooth module that lets you adjust params, and monitor the pack from a phone app.

EDIT: This just came in 2 minutes ago (8AH 200A discharge for $12):

Looks good. Did you fabricate your own bus bars?
 

Duxprep

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I meant to add - Tons of channels on youtube to see people's system installs, Battery builds etc. Here are a couple

One family I've been watching recently is these guys - Built the house themselves -run their farm, solid parents and values - They have a schneider system - They've continued to upgrade it as well. Oh and she is VERY easy on the eyes
View: http://youtu.be/C-aeOzBn6YE


Another one is this guy - not an off gridder, but instead has a resilience/prepper mindset. He did a very substantial DIY off grid setup with top tier equipment and has a nice video series of the entire install

View: http://www.youtube.com/playlist?list=PLkTIWHBRRyi6NyWsyl03VuC2-JdBx0M46
 

mibro

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Awesome plan, xtry51.

May I suggest you also look at DIY low grade geothermal energy which heats/cools to 52F year round. With solar powered fans and low grade geothermal you can both heat in the winter and cool in the summer.

My ideal setup would be a highly insulated house with off grid solar and low grade geothermal heating/cooling.

This dude growing oranges in Nebraska in winter is a visionary.

View: https://www.youtube.com/watch?v=ZD_3_gsgsnk
 
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Really appreciate all the input here. I bought the book @GomerPile.

I'll have to dig into making our own batteries I honestly didn't even realize that was a thing.
there are a bunch of DIY power wall videos on youtube. If you are willing to do some battery recycling you can build huge packs for pennies compared to new cells.
 
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Not sure where in NH you are but take a look at the link below for Hillsborough County. They buy in bulk and do most of the install work as part of a volunteer group. You put in the volunteer hours, purchase the gear through the coop like unit, and are reportedly put on their project list sort of like an Amish barn raising. Haven't participated in it yet but its on the to do list

Hillsborough County Area Renewable Energy Init
 

mibro

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Every time I think about a build, this is the core of my energy plan

🤯 That's fantastic!

It's a pleasure to share the information.

The Nebraska dude has a web site and will send you all kinds of plans and materials at low cost.

This is the direction the country should be going to lower our energy usage. Windmills and grid tie solar are just more industrial mess.

The 52F low grade geothermal is so easy and truly low cost, unlike the big money forms of "Green Energy" - lol. All you need is a backhoe and some plastic pipe.
 

Waher

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Awesome plan, xtry51.

May I suggest you also look at DIY low grade geothermal energy which heats/cools to 52F year round. With solar powered fans and low grade geothermal you can both heat in the winter and cool in the summer.

My ideal setup would be a highly insulated house with off grid solar and low grade geothermal heating/cooling.

This dude growing oranges in Nebraska in winter is a visionary.

View: https://www.youtube.com/watch?v=ZD_3_gsgsnk
Don't forget solar hot water + back up water heating from the ground sourced heat pump system. Failsafe is a wood stove for heat, hot water, and cooking. Greenhouses are such a big deal for off grid year round farming, yet they get how much attention in most prepper planning?
 

xtry51

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We already use wood heat and the new location will also be primarily wood heated likely with oil for when we are on vacation.

I'm also considering coal instead of wood given coal is easy to store in large quantity.
 

xtry51

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Does anyone have any personal examples/experience of the cost to presently build a 100ah LiFePO4? I see I can buy a Battle Born for $899n which seems to be a popular brand when looking around.

What are "cheap" brands I should avoid?
 
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Pic is my 16P4S 80AH main battery. A 100AH version would be 20P4S and a diy cost of $260 (with overkill solar 120A BMS).

Beware the battle bourne batteries are limited to 100A which is barely enough to run a 700w microwave.

217BE44E-FA1A-4B0A-A625-D147E23B350B.jpeg
 

strangenh

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By "ah" - do you mean at the nominal voltage of one cell, or of a 12V pack? (I really hate the use of "ah" without the cell nominal voltage in these conversations.) Looks to me like you're stacking the numbers correctly, so a 100ah battery pack as you're using the term is 1.2KWh, yes?
 
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By "ah" - do you mean at the nominal voltage of one cell, or of a 12V pack? (I really hate the use of "ah" without the cell nominal voltage in these conversations.) Looks to me like you're stacking the numbers correctly, so a 100ah battery pack as you're using the term is 1.2KWh, yes?
I use AH (amp hours) in my head when dealing with 12v nominal packs because it’s easier to make comparison to lead acid batteries.

If you prefer KWH then yes 1.2KWH for a 12v 100AH pack. The pack in the pic is 0.96KWH.
 

smokey-seven

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I'm also considering coal instead of wood given coal is easy to store in large quantity.

I've heated a house with coal for 2 years. It's a little dirtier, hauling the stuff in and ashes out, but lots less bugs and critters. Learn how to bank a fire. I could make a grate of coal last all night, well stocked banked. Make sure you buy a COAL stove and not a wood stove. The metal is thicker and well put together. Follow manufacturers recommendations for distances from and safe insulation below. You cannot hurt to increase these specs. Plan your flue (exhaust system) well.

Check your delivery capabilities in your prospective area and plan for a drop into a holding facility that can gravity distribute your stove needs. (driveway for heavy truck, access to coal storage)
 

strangenh

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I use AH (amp hours) in my head when dealing with 12v nominal packs because it’s easier to make comparison to lead acid batteries.

If you prefer KWH then yes 1.2KWH for a 12v 100AH pack. The pack in the pic is 0.96KWH.
Yeah, that's cool. Larger off-grid solar uses 48V strings, often with 6V lead-acid cells, so I am careful about assuming ah equivalence.

Basically, it looks like you are building Li packs that deliver KWh at under 1/4 the retail price, making them effectively equivalent in cost to (quality) deep discharge AGM lead-acid batteries, which are around $0.24/wh right now (up 10% from a year ago!), with the advantage of space-saving (50%) and no deep discharge damage. That's excellent. Not to mention you can keep spare cells around more readily to replace sub-pack cells.

How "used" are the cells you're getting? What kind of lifespan (years or # of cycles) do you expect out of them?
 

cstockwell

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We already use wood heat and the new location will also be primarily wood heated likely with oil for when we are on vacation.

I'm also considering coal instead of wood given coal is easy to store in large quantity.
I believe it was you that I spoke with about our mutual acquaintance who had the truck that ran on wood gasifier? I still haven't gotten around to trying to make the setup with an older generator I pulled from an RV years ago. Did you consider having that type of setup to help periodically charge your battery banks when solar is not at peak?
 

xtry51

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I believe it was you that I spoke with about our mutual acquaintance who had the truck that ran on wood gasifier? I still haven't gotten around to trying to make the setup with an older generator I pulled from an RV years ago. Did you consider having that type of setup to help periodically charge your battery banks when solar is not at peak?
That was me. I am definitely interested in exploring, though I am strongly considering diesel with bulk storage. With diesel I can heat the house, run tractors, run trucks and run generators.

I've also been looking at old Lister full mechanical diesel engines for generators. Hand crank. Little to fail. Can be open bath water cooled.
 
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Yeah, that's cool. Larger off-grid solar uses 48V strings, often with 6V lead-acid cells, so I am careful about assuming ah equivalence.

Basically, it looks like you are building Li packs that deliver KWh at under 1/4 the retail price, making them effectively equivalent in cost to (quality) deep discharge AGM lead-acid batteries, which are around $0.24/wh right now (up 10% from a year ago!), with the advantage of space-saving (50%) and no deep discharge damage. That's excellent. Not to mention you can keep spare cells around more readily to replace sub-pack cells.

How "used" are the cells you're getting? What kind of lifespan (years or # of cycles) do you expect out of them?
Batteryhookup discloses the source of the cells they sell. For a while, they had 18650 cells from Ring cameras that were brand new cells just in a plastic housing you had to crack open. The green cells in my latest pack were surplus from a manufacturing run. They are grade A cells that met specs, just not enough of them for anyone to use them in a new product (at least that's my guess).

The 32650 cells in my other pack were manufactured for batteryhookup and so far I have had zero issues with them. Time will tell on how long they last. A lot of DIYers are using them and have not reported any issues. Even if a cell goes bad it should be pretty easy to fix. Word of advice on these: I'm fairly sure the 5AH and 6AH cells are identical! The only difference is grading...the 6AH cells tested above 6AH and are being sold for more. Personally, I bought the 5AH versions which test out at well over 5AH and are IMO a better deal.

Historically, I've used golf cart batteries in my systems. Those are about $225 for 200 amp hours. These are crappy consumer batteries that work ok for a while but degrade quickly. Some of that is probably my lack of maintenance and the rest is that they are just shit. My gut feeling is that a 100AH LiFeP04 pack will perform as good or better than a pair of golf cart batteries over time. If your application is large drain over a long time then of course the lack of capacity hurts you. Off grid power is seldom that kind of load. It's running the microwave for 3 minutes, full sunlight for 4 hours, some lights for a few hours, more full sunlight, etc etc. In the typical off grid power profile shit grade golf cart batteries become unusable after 24 months. My feeling is that LiFerP04 packs will easily last 24 months and probably longer. The only issue is charging in low temperatures...they need to stay warm to accept a charge (my BMS has low temp cuttoff). An unheated cabin up in northern NH will need some lead acid cells to give you power while the place warms up.

Random thoughts....
 
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strangenh

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Good stuff, GP! Thanks. I believe in the "buy once cry once" for lead-acid batteries and usually push people to the Concorde Sun Xtender line, which are zero maintenance (though proper floating is a good idea!) and I've seen them run about 10 years before enough start to perform poorly to recommend replacement. They are about 1.5X the price of the golf cart types. Obviously, that's with the system set up for a little better than 2X the expected daily discharge, which you don't need to do with LiFeP04, though the Concorde AGMs can take a deep discharge better than most lead cells.

It sounds like OP is thinking about a larger system than a tiny house off-grid setup, but that is all very interesting stuff you can scale up from if you're willing.
 

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Not exactly what you are looking for but a friend built their retirement home with passive solar placement of the house.
It helps keep the house warm in winter and cool in summer so less use of power. They used a website that evaluates the plot of land you are building on and then how to place the house.


 
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