diy solar

diy solar

100% off-grid system from the ground up, literally.


 
You're getting some good advice here. The 100 watt panels are really not suitable and buying stuff before you have a system design is a sure fire way to waste money and make an underperforming system. EMP hardening is a fantasy, at least in the apocalypse sense. Too many wires and whatnot that will induce voltages.

Good to see someone mention considering FLA batteries. While I would love to go lithium I simply couldn't afford it. I got 10 years out of my last bank of FLA's and no way would lithium be cheaper per year. I would say that the idea of having three days of power storage is an outdated notion. I simply charge every day, if the sun isn't cutting it I fire up the genny. This limits the DoD and makes FLA's last much longer.
 
My system is grid-backup. Grid power costs me $0.15 to $0.45/kWh (3 different rates depending on time of day)
PV panels and grid-tie inverters together with balance of system cost me $0.05/kWh
Batteries alone cost $0.20 to $1.00/kWh (by the time they wear out) depending on chemistry and type. Battery inverter and balance of system not included

So obviously batteries are the biggest cost in a system, and probably won't save on utility bills unless rates are even higher (can be for some commercial users.)
My approach is to over-panel and throw away excess production. (curtail production in the case of backup/off-grid, backfeed utility to the point of having a surplus at end of year for net-metering rather than buying extra power from them.)
For the batteries, I undersized the bank so it barely gets me through a night with the grid down, and used maintenance-free AGM batteries at the higher cost end of the scale.

In the case of grid failure and overcast skies, maybe my batteries will recharge at 0.05C or below. I'll turn off extra unneeded loads. As boondox said you could run a generator if you really needed power.

My battery bank cost $5000 for 20 kWh. Could probably have downsized to $1250 for 5 kWh if I bothered to load-shed four refrigerators/freezers when the sun went down.
 
Greetings Experts: It's time for me to get serious about creating a power station for my soon to be built barn style home in Southern Utah. I understand a bit about the differences between a 12, 24, and 48 volt system so I've settled on a 48 volt system. I am in the process of drawing out the various circuits and determining the inverter type, wattage, and number. What I have not settled on yet is which cells to use to build my system and what BMS to use. There are so many to choose from and I've watched so many great videos that I'm overloaded with information and there's no clear leader in the industry, at least to my knowledge.

I would sure appreciate some input from anyone who has experience building with raw cells and BMS to make a 48 volt system suitable to power my barn/home that will have a living area of 20 x 40' (2 bedrooms, bathroom, and kitchen/dining/living area) with an equal sized basement right below. Along side that there's a RV garage that's also 20 x 40' and above that there's a loft, again, 20 x 40'. Another 20 x 40' garage is next to the RV garage but it won't need too much in the way of power, at 1st.

Your advice would be much appreciated. George
I didn't peruse the comments to your questions but, take a look at David Poz's new battery build he made from new cells he got from Battery Hookup. He built a terrific new 48V Lipo4 battery for a little over $400 that will match most commercially made batteries. He does amazing work with everything he does.
After all of my research I don't think you will find anything better for your system than a Sol-Ark 12k. I am in the process of building a new 12K system for my off-grid farm. You will have to go with a 48V system to meet your needs. The Sol-Ark 12k is a plug and play system and you can piggyback up to 3 of them for a 27Kwh system that will provide high amounts of AC power without touching your battery bank during high panel performance. It is almost bullet proof and easily set up.
 
Last edited:
I think lifetime cost is also lower for an oversized bank you normally only discharge partially.

Please allow me to be the first one to disagree with your conclusion.

My oldest LiFePO4 batteries are only a bit over 5 years old but they have been "microcycled", stored for months at 100% SOC in warm temperatures and generally mistreated.

They blow the doors off any FLA batteries I have that are 5 years old even adjusting for cost.

I will be sure to update this thread after another decade or two of abuse on these batteries but I suspect they will still have working capacity that I use :cool:
 
Real datapoints are good.
I have a 5 kWh AGM bank I bought 10 years ago for $1000 but it has only seen float or periodic recharge life. I haven't tested its capacity.
My new bank is 20 kWh AGM for $5000 and only 6 months old. I've test cycled it to 70% DoD a couple times.
So I don't have personally obtained data for many cycles and many years.

How many Ah are your LiFePO4, and what did they cost? DIY or ready to use commercial product?
 
Case in Point.
I have 8 Rolls Surrete S-550 Heavy Lead Acid solar batteries. Configured at 24V, 4S-2P.
Each 6 Volt battery = $424.00 CDN / $325 USD or $3392 CDN / $2600 USD
Total Power = 856AH or 428AH useable Amp Hours.

I'm finishing my final LFP setup with 910AH. 2x24V/280AH (560AH) + 2x 24V/175AH (350AH)
Current Costs: the 16x 280's $1700 USD + BMS, Fuse & Casing. (that is already MORE USEABLE POWER , just with these)

The numbers say it all... AND there is no watering, maintenance, desulphurating runs or any of that "extra" to deal with.

Also, about 90% of folks always abuse their First FLA and only get at most 50% of their lifecycles because of it. Don't wanter them, allow them to discharge too low, do not regularly desulphate them, never rotate them across the banks....

LEAD IS DEAD ! Good Lead batteries are NOT Cheap, the cheap ones are what you get for buying cheap. Rolls, Trojan and only a very few others still make Real Heavy Lead Deep Cycle batteries anymore, most companies have been sold off to Investment Companies who shifted production off shore an are now making them as cheap as possible for the most MSRP they can get from the gullible folks still buying them. Lead is following the Steam Train to history, this is the 21st Century !

PS: Anyone saying how Great Their System is and what they use and yet do not have an "About my System" page with photo's, diagrams, products/devices used in their build, yadda yadda - credibility is iffy .... SHOW US U ARE REAL ! so many Youtube University Couch Warming experts annoy the bejeezus out of most of us....
 
Well, lead is ALMOST dead. There is no one size fits all for batteries. Cold temperatures are still a problem for lithium and extreme heat can be as well. The up front cost of lithium can be too much for some, it was for me. While FLA's do require maintenance, lithium needs a BMS that can crap out.

I don't think there is any need for the fancy, expensive FLA's like Royce. I got 10 years out of sam's club golf cart batteries. Just charge them every day and don't run them down below 75% SoC. Water them once a month. Hardly onerous. I have plenty of panels so that they get charged quickly in the AM and I fire up the genny if the sun isn't doing it.

I am not plugging FLA. If I could afford lithium I would have. But each use case needs to be evaluated to determine the right battery for the job.
 
Well, lead is ALMOST dead. There is no one size fits all for batteries. Cold temperatures are still a problem for lithium and extreme heat can be as well. The up front cost of lithium can be too much for some, it was for me. While FLA's do require maintenance, lithium needs a BMS that can crap out.

I don't think there is any need for the fancy, expensive FLA's like Royce. I got 10 years out of sam's club golf cart batteries. Just charge them every day and don't run them down below 75% SoC. Water them once a month. Hardly onerous. I have plenty of panels so that they get charged quickly in the AM and I fire up the genny if the sun isn't doing it.

I am not plugging FLA. If I could afford lithium I would have. But each use case needs to be evaluated to determine the right battery for the job.
You got 10 years out of Golf Cart Batteries bought 10 years ago. If you went and bought the exact same brand, model today, it would certainly not last 10 years, it would be lighter (thinner lead plates, less ABS plastic and other "economies" . The "Brand" may be the same even but more than likely just a label owned by an Investment company. There are not that many Lead Acid Battery makers left anymore... Even Exide isn't Exide anymore... not like what it was
 
For me the first criteria was compatibility. I stated out with SMA Sunny Boy, intending to add Sunny Island. Those only speak one language of BMS for lithium. I've heard from others on the forum that if only used to generate AC from lithium and not charge it, Sunny Island can be used with DIY lithium. But my application is with AC coupled GT PV inverters, and excessive PV vs. battery capacity. Sunny Island is happy to curtail production 90% to hit my target 0.2C or 0.1C charge rate. If DC coupled you need a way to manage that (although with lithium, 0.5C can be OK.)

So for me, an off the shelf UL listed AGM battery that is easily interfaced to Sunny Island was the choice. I don't care as much about $/kWh because most of my PV generation is used-it-or-lose-it, not stored in batteries for a rainy day. It's first job is to light up my local island grid so Sunny Boy powers the house when utility grid is down. Keeping the lights on at night is secondary. So long as they last 10 years in my application I've done OK. And that was AGM not FLA so I never have to touch them, just rely on Sunny Island to count coulombs and manage their SoC.

"Ain't what they used to be" ... that's my experience with Optima for vehicles. Hope the SunXtender in my PV system doesn't suffer from the same beancounting. We'll have to see how the various lithium batteries turn out in terms of lifespan and defect rate. Catastrophic losses were in the news in years past (cargo causes aircraft crash, etc.) of course LiFePO4 is supposed to be inherently safer. My AGM batteries are approved for air transport; perhaps LiFePO4 could be although it isn't yet.
 
You got 10 years out of Golf Cart Batteries bought 10 years ago. If you went and bought the exact same brand, model today, it would certainly not last 10 years, it would be lighter (thinner lead plates, less ABS plastic and other "economies" . The "Brand" may be the same even but more than likely just a label owned by an Investment company. There are not that many Lead Acid Battery makers left anymore... Even Exide isn't Exide anymore... not like what it was
There is truth to that for sure. I went with Crown for my most recent bank in the hopes that they will be of decent quality, time will tell. And again, I am not plugging FLA as 'better". Cost is an impediment for some. And lithium does need balancing and a BMS while FLA just EQ a few times a year and you can set that to automatic. My system has been quietly plugging away for many years without any major failures and a low cost of operation. While lithium may be "better" there sure isn't anything wrong with the cost, performance and reliability that I have gotten from my system.
 
How many Ah are your LiFePO4, and what did they cost? DIY or ready to use commercial product?

10 batteries total ranging in size from 6Ah to 100Ah.

Mix of DIY and cheap chinese commercial.

Cost from under $50 to around $1250.
 
10 batteries total ranging in size from 6Ah to 100Ah.

Mix of DIY and cheap chinese commercial.

Cost from under $50 to around $1250.
Is that $1250 for 12V 100 Ah 1200 Wh?
If so would be 4x the price of my SunXtender AGM, and hopefully 4x the cycle life, so cost-parity per Wh of life.
If 48V 100 Ah then same capital cost and lifetime cost expected to be 1/4 as much.
 
Well maybe this is controversial topic I'm sure, but just FYI, Will Prowse posted a video saying Lithium is cheaper than lead acid, I'm sure we could find all sorts of pros and cons to both sides, but just to see his take again:
 
Is that $1250 for 12V 100 Ah 1200 Wh?
If so would be 4x the price of my SunXtender AGM, and hopefully 4x the cycle life, so cost-parity per Wh of life.
If 48V 100 Ah then same capital cost and lifetime cost expected to be 1/4 as much.
48v on the 100Ah in question. My 48v batteries range from 20Ah to 100Ah.

The 12v nominal ones range from 6Ah to 60A. 12v and 48v are the only two nominal voltages I use for my applications.

Rather than get into a pissing contest about FLA vs LiFePO4 I would just like to say that I am fairly analytical and have read a ton about LiFePO4 for more than 5 years while continually experimenting along the way to confirm what I am reading. I have convinced myself that LiFePO4 has a superior cost/benefit ratio and I am spending my money accordingly.

I did start small with my stable of batteries and have diversified my range of batteries and gained experience as I have gone along. I have learned a ton over the years but I am firmly convinced that LiFePO4 is the absolute best/most cost effective for ME and MY APPLICATIONS.

I routinely take my batteries into the field and move them from property to property. That (and my less than stellar physique) is the only thing that has kept me from building a large, relatively heavy 280Ah 48v battery to date, but I'm getting there once I figure out the best place for me to keep what may be the largest battery in my stable. Of course the heaviest LiFePO4 I will ever build pales in comparison weight wise to a serious FLA battery bank. The weight, physical space required and necessary maintenance are also a major downside FOR ME and my less than stellar physique.

I doubt there is anything else I can add to this conversation and hope my opinion was helpful to someone.
 
Yeah I respect this approach a lot, it is a learning curve for me as well (even with all the planning I thought I knew how to do, some things still went sideways to a certain degree and I'm not even deployed fully yet). I decided to plan with using the 48v DC in my initial solar setup, but my RV already uses a 12v 6-battery setup (with a Magnum inverter, and a few tiny solar panels on the roof with a pmw charger), and also has an Onan 6.5 kW propane generator I wish could be good for charging the 48v or something. Then my Toyota Prius has a 207.2v DC hybrid lithium traction battery setup where I added in an APC rackmount 240v/120v 3.5kW / 5.2 kW surge UPS/inverter connected to it (for backup generator function), however, I have not found an easy way to interface all these system voltages together, other than use a 240v AC output on the Prius APC/UPS to potentially run a generator input on an a Sol-Ark all-in-one or something. Or one guy used a midnight classic MPPT solar charge controller to convert his Prius Hybrid battery 207.2v DC directly, to charge his solar 48v battery bank. For the most part my 48v system should be pretty scaleable by itself, but I wish I could tie some of these systems together to the RV and the Prius, so I could move DC power around in the most efficient way. Then there's all the EMP resistance planning as well (thanks to Steve_S for all that info as well), I plan as much as possible, but as I learn more things evolve and change in my plan. So far not too bad though. Will try to run as many things off raw 48v as possible, and if I get a Sol-Ark later, it will only be a luxury item really, to use AC sparingly, like for power tools, air compressors, and such where DC doesn't make sense. My particular off-grid location has no electricity for 45 miles, so have to build a solid system. If I add in more solar panels later, I would use the MPPT chargers in the Sol-Ark I'd plan to get, to scale out and add those in. For now though I wish I had a way to get more solar to the RV 12v system, might need to buy more panels, since it isn't easy to move power around.
Keep us posted on your Prius project - we've got three 2nd generation Prii and have done a bunch of experiments with an eye to using the ICE and MG1 as a generator/cogen provider and running the 207.2VDC thru solar-type charge controllers to work with my inverter. Too many other projects taking priority now.
 
Here we are October 20th, 2020 and there are certain "characters" that still argue the Planet is Flat. Amazing but true... and in the Western "Apparently Educated Nations with Good Schools" this bafflegab still has traction...
Mad Mike even killed himself with his home made rocket trying to prove the Planet is Flat... Talk about taking being a DORK to the extreme.


when-youre-arguing-with-a-fool-make-sure-he-isnt-doing-the-same-thing-quote-1[1].jpg


So for those who insist on PONTIFCATING, here's the hero of the day below....
Now remember what little Chicken Hawk said about Ol'Foggy.
tumblr_nun6jpICFw1tf48o1o3_500.gif
 
Keep us posted on your Prius project - we've got three 2nd generation Prii and have done a bunch of experiments with an eye to using the ICE and MG1 as a generator/cogen provider and running the 207.2VDC thru solar-type charge controllers to work with my inverter. Too many other projects taking priority now.

Sounds great, will do... For now, you can read up on the other guy who already used a Midnight Classic MPPT charger on a tweaked wind profile to charge his 48v using the Prius: https://www.solarpaneltalk.com/foru...idnight-classic-as-voltage-converter-possible

Mine is a Prius Gen IV with the lithium 207.2v, and the earlier ones used nickel-metal hydride 201.6v (although both types have quite a operating voltage range, like maybe 190-240v DC), if I don't try this later using an MPPT charger, then for now I will use the APC SURT5000XLT UPS I have now and pipe the 240v AC output to a gen input on an all-in-one inverter like the Sol-Ark, to use it as a backup source for charging the 48v bank.
 
I wholeheartedly agree you should have a really good plan before you start buying equipment. Sad to say some things are hard to estimate without actually doing them, your off-the-grid lifestyle might change your estimates in ways you can't anticipate. My situation was odd, I thought I was just temporarily without store-bought power - I scrounged and built 3 different systems from used parts (except the batteries), and learned a lot along the way. Sure, you can record your on the grid power use, but once you start having to really watch what you do (after you are off the grid) your behavior will likely change. Once I realized my situation wasn't just a temporary blip in my life was when I got serious and started buying new equipment and putting together a system that will last. 48V all the way, but since you aren't doing FLA you might even think of a higher system voltage than that. Think about future changes and leave some room for expansion. In my case, I thought - what is the worst thing they can do to me after I've put in my expensive off-grid solar system? - let me have power again, and/or MAKE me have it, so I designed my system to have the capability to do grid-tie even though I have no intention (chance) of hooking back to the grid, so the worst-case scenario is I make the meter spin backward all summer and use them as my battery in the winter. Left myself room for 50% more panels without having to add any more equipment. I know had I tried to do all this from the start my end result would have been vastly different, so I'm grateful for my 'learning' systems along the way.
Thanks for your post. I will wait a little while, at least until the barn/house is framed and weathered in, to buy the big ticket items like the bigger inverter or inverters, batteries, and charge controllers. Our 35' 5th wheel is my temporary home when I'm on the property so I will probably try my hand at designing a small system for that just to get some experience working with solar systems. Currently, I just have 4 standard deep cycle lead acid batteries up there that I plan on running in parallel but need to do a little research as to which inverter to buy so I can power up the micro occasionally and use the furnace and fridge as needed. Shouldn't be too hard to figure out what my consumption will be. I already have an epever 40 controller so I'll work with that and see if I can keep from frying it. I found the link to batteries and panels that one of the other commenter's posted very helpful and was surprised to see how much cheaper, per watt, the panels on the site he suggested were. I'm sure I'll use the 40 100 watt panels in varying configurations since I do need to power my 40' shipping container and property gate opener as well as a few security cameras, so there's plenty of need for low wattage system builds I can think of. I really appreciate all the comments and suggestions.
 
I didn't peruse the comments to your questions but, take a look at David Poz's new battery build he made from new cells he got from Battery Hookup. He built a terrific new 48V Lipo4 battery for a little over $400 that will match most commercially made batteries. He does amazing work with everything he does.
After all of my research I don't think you will find anything better for your system than a Sol-Ark 12k. I am in the process of building a new 12K system for my off-grid farm. You will have to go with a 48V system to meet your needs. The Sol-Ark 12k is a plug and play system and you can piggyback up to 3 of them for a 27Kwh system that will provide high amounts of AC power without touching your battery bank during high panel performance. It is almost bullet proof and easily set up.
Thank you sir! The Sol-Ark 12k is definitely on my radar. I really like David's videos and have watched many of them. I'll look for one where he builds the 48v system. I really appreciate your comments.
 
Back
Top