diy solar

diy solar

Battery size decisions

Ironman

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Nov 29, 2020
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Good Morning All,
I have made the decision to go with a solar system, not grid tied. Yearly average solar hours are 4.7 in my area.
Average consumption of my house and Machine shop is 28kw/day. This can be cut down a bit by shutting down the electric clothes dryer.
Present average daily use is 28kwh. With carbon tax, line maintenance charges, sales tax, my cost is .2626 per KWH.
I have a 5kw Lister diesel, 12kw Growatt, and a pallet of panels.

I figure I have to make the big battery purchase sooner or later. I could consider a small battery and running on generator power, as I do now when the power goes down.
If I have done my math correctly, I will need a 1200AH battery at 48 volts for 3 days stand alone power. I'm looking at everything including a forklift battery. LTO or LiFePo would be my first choice. Any recommendations you can give, or some one telling me I need less battery would be helpful.
 
Try calculating cost of electricity per kWh using PV panels and inverter.
Calculate cost per kWh cycled through each type of battery.

My math says batteries cost considerably more than PV panels.
Others have calculated cost of power produced with a diesel at $1.00/kWh. Of course, you already have the generator itself, so only fuel and maintenance costs count.
Likely you'll find it more cost effective to size the battery for one day or just one night, and start the generator on the occasions that isn't enough.
But if grid is available, use that not generator! (if it is 25% as expensive)

Other choices may be net metering with the utility, and putting in excess PV capacity (always produce more than you can use or store; use it or lose it.)
If net-metering isn't available, then zero-export. Use your own PV, then utility power, but no batteries.

My system is grid-backup, so as long as grid is up I bank surplus power as credits to later use for heating in winter. If grid is down, my battery is barely big enough to get through the night, but PV on a sunny day is enough to run A/C and everything else.

I use AGM, because my number of cycles over 10 years is expected to be low. For nightly cycling, Lithium sized for 80% DoD may be a good price point, especially the DIY ones people here assemble.
 
Is there any form of Net Energy Metering that you can use to leverage your investment in batteries? As @Hedges said there are options.

I have had good luck with the EVE LF280 regular LFP cells but their availability is in transition. There may be some newer versions of the LF280N cells from Amy at Luyuan in the near future. These will be matched cells and of a higher quality. Otherwise Lishen cells are coming in at around $100 per kWhr delivered to your door. 1200 Ahrs at 48 volts is between 72 and 80 kWhs of batteries depending on the size of the cells and how much of the capacity you want to use on a daily basis.
There is a general battery discussion here:

And a specific thread about Amy at Luyuan here:
 
Thanks for your input, Ampster and Hedges.
I will not ever take stolen tax dollars for anything I wish to do or build. And net metering is a expanding hairball that is already dictating the way a house faces and the number of panels you are allowed to have. Plus the line charges of $200/month to have a pole in my yard is something that just kills net metering. The cost of the system is not something that concerns me, and I have no intent to live with one light bulb for virtue signaling. I am more interested in staying on my 10 acres of heaven and living the life I have at present.

As we in my country are going into the Land of Mordor due to the government desire to crush energy use, the same gang in power now have turned the province of Onterrible into a place of $1300 dollar power bills, and forced people to chose rent or lights and food.
I live in the country and going off grid means one less tentacle they have wrapped around me. And one less power outage to face.

I appreciate the verification of my figures, three days are 84 kwh, and that's fine with me. I need to source a good 1200AH battery.
Lead is the most costly due to the 50% DOD and slow charge rate, so it is falling off the table. I am doing power meter readings at dusk and dawn and at 24 hr intervals to calculate the overnight usage and to verify the daily total is the same as the average. My plan is to buy this summer so I have time til I need the battery.
 
Is it $200/month minimum fee to have electric service?
For my net metering, fee is $10/month.

"Buy this summer" - meaning buy an off-grid property?
Certainly battery based systems are cheaper than connecting to the grid in many cases.

If you have grid available, when I checked prices of commercially available batteries, it did not make financial sense to store power in a battery. (DIY batteries are cheap enough.) So I would suggest a zero-export system. PV panels and grid-tie inverter, with a measuring device to ensure no power is ever exported to the grid but curtailing production. PV generates 100% of your consumption or its capacity, whichever is less. An additional power you buy from the grid.

I figure PV + inverter costs $0.05/kWh amortized over 10 years, $0.03 amortized over 20 years assuming one inverter replacement.
That's with my San Jose sunshine, Ontario will be less.
My AGM battery storage costs $0.50/kWh. Check out what people here are doing with DIY lithium. I think it is somewhere between $0.05 and $0.20/kWh over its hoped-for lifetime.

Try to minimize battery requirements by pumping water when the sun shines, store in a tank. Heat a tank (or rocks) to store heat for nighttime.
Your diesel generator only delivers 25% to 33% of energy as electricity. A considerable amount is given off as heat. "Combined Heat and Power" - use waste heat for the house.
 
I thought for a moment there that you were describing the regulatory environment of California. ;)
I think we share some of the same goals but I am constrained by the building code and that my existing structure is currently served by an Investor Owned Utility. Even though I may not be able to disconnect, due to the building codes, I am not required to use much of it.
There are many posters here from Canada including @Steve_S who as far as I know is entirely off grid. You have some time to find the best option fpr batteries, so enjoy the journey. It sounds like you have the the other items like inverters and solar panels figured out but there also great resources for those items here as well. I look forward to following your progress.
 
I'm jumping in this discussion as I believe I'm in the same country as Iroman and I was in the same boat before taking the decision to go off-grid. 5 years ago the hydro company in my area was quoted to bring hydro on my property at 40K which was ridiculous. The last hydro pole on my street is at 400ft from my entrance and our hose site is at 300ft from the entrance. They don't want to cover any cost so they asked 40K. In addition with that, because this is not my principal residency they will charge an additional 70CAD every month plus the price per KW is much higher as the population density is lower then city area. Because all of this we choose to go off-grid.
 
Yes, sounds right Rogerus. I've owned my place for 20 years, and if I never burned a watt in all that time, I would still have to pay $200/month, and have done. That's $4000, that would be half a battery bank.
Ampster I am pleased with everything I have got so far. The 12000T inverter is what I wanted for price and features. I picked up 20 x 550 watt panels for $137US each. I have the welding and machining skills so I will drive in some 2.87" oil well tubing pilings to make a 40 ft long ground mount frame. I will not have to rent stuff, so I am looking forward to this build.
 
Yep, completely OFF-Grid and Loving It !

Hydro One wanted $55,000 to bring power up here... closest pole is 1km away. Terrain is rough (I am on a Granite Ridge) which adds to the complexity for them. I built Hyper Efficient and structures are oriented to maximize solar potentials and to use Nature versus "brute force" imposition. House keeps its heat extremely well in winter, cools itself in summer, has NEVER been over 26°C inside in summer and I gave away my AC 3 years ago, no use for it... I'm running now with 910AH of LioFePO4 and 956AH of Heavy Lead Acid (my old bank, now as backup).

The reality is, that today we can build to R2000 or higher spec for a building without great difficulty. Solar Panels, Shingles have come down Massively and still falling. More & Better solar equipment is being released regularly and those prices have also gotten quite reasonable compared to even 5 years ago ! Battery Costs have changed a lot too and with MANY OPTIONS being available to people.

To my fellow Canucks.
Remember IF you want to be insured, CSA Stamped & Certified Gear. *(UL only does not cut it)
You will require an Electrical Inspection & sign off by Insurance Co.
If your not grid connected, you can IGNORE hydro one and their pile of ****
If Grid Connected but NOT pushing power to grid, ie using grid as backup only, you don't need to worry about Hydro Inspections as long as it is isolated BUT having an electrician inspect & sign off is still smart. It is also good CYA in case hydro goes stupid (they have done so many times with people).
No one can say you cannot have solar, no one can deny you going off-grid. You do NOT have to have Grid Power, anyone tells you that, drop LEAD between their eyes ! Show me how the various AMISH can have their homes, farms etc without ANY Powerlines running to their properties ?
 
So that's what I sound like! :0)

I was going to say .26C a Kwh hour is cheaper than I pay and a LOT cheaper than a lot of people here pay.
The $200 a month though is insane! I thought mine were stiff at $1 a day.

With 11 Kw of panels and the listers, I don't think I'd be worried about a 3 day battery reserve. even if you live in some place where there is snow, you can get around some of that by vertically mounting the panels or have a swing mechanism that will tilt them vertically. 11Kw isn't a bad size array and getting a 3x Kwh rate shouldn't be that hard. 550W panels must be Huge. I
I do get my feathers ruffled up when I think of it, sorry.:oops:
I was talking on the phone as I typed and after I went to bed, I realized I had fat fingered the amount $200/month over 20 years is $48000. To make it worse the guy I was talking to is off grid.:eek:
I live in an area where we get cold weather. It was -18C or 0F last evening, and has warmed up to -13 this am. My Lister is in a pout at that temp and needs a block heater. I put a 200 watt magnetic heater on it, so that is a draw to consider. OTOH, about 5 years ago, I drug a Witte Oilwell E20 pumpjack engine home for scrap and instead fixed a few things and set it up on propane. It is battery start and because of propane, it lights up instantly in the cold. Of course, with a 6.25" bore and 8" stroke it takes a huge dude to crank it so the electric start is good.
My panels are 1/2 cell PERC with 96 cells, 77"(6.4') tall x 51.57"(4.3') wide. The local Tech Institute did a 5 yr study, and concluded that on a year-round basis a tilt angle of 53° at 180 deg South, generated the most energy with snow clearing. And at 53 degrees snow does not stick on it.
In the shop, I have to start motors up to 5hp, so a battery bank makes that surge a lot easier, even with the big flywheels on the Lister. Years ago, I looked at the Changfa diesels, they are everywhere in east Africa, but the noise is brutal. The 650 rpm of a Lister is a sweet sound and not hard to silence.
Remember IF you want to be insured, CSA Stamped & Certified Gear. *(UL only does not cut it)
You will require an Electrical Inspection & sign off by Insurance Co.
If your not grid connected, you can IGNORE hydro one and their pile of ****
If Grid Connected but NOT pushing power to grid, ie using grid as backup only, you don't need to worry about Hydro Inspections as long as it is isolated BUT having an electrician inspect & sign off is still smart
I was expecting that, and it is one question I wanted to ask. I have never failed an electrical inspection, but am concerned that this being a new 'thing', the inspectors are going to CYA on everything. I plan to use best practices when wiring, but DC may have them spinning. Breakers from Midnight Solar do not cut it as they are Chinese UL,but there are limited options at the local electrical wholesaler. I see the Chinese circuit breakers are sold up here. So I will be inspected and told to use CSA only and then I will do nothing to change it.
Insurance is not a worry, they rejected us years ago for heating with wood. What they allow here fore grid tie is the inverters that shut down when they don't get a 60cycle signal from the powerline. This is handy when a beaver goes logging and your powerline doesn't get out of the way soon enough.
 
Forklift packs can be bulk charged at high rates much against the common internet mantras and they are also warranted by the Manufacturers to 80% DOD NOT 50.
George, re-reading your post, I can see you have been down the same path as I have. I will have a chat with the local forklift battery co, and see what they offer. I am building in extra capacity into what I do, because I want it as user friendly as I can so if I am not around my wife can handle it. I had not planned on a heated powerhouse for the batteries and componants, but with lead batteries, I may have to have a battery blanket. My plan is to use a 10ft seacan out near the panel bank and run AC from there.
Oh, time to take my power meter reading.
 
"Battery blanket" - Trukinbear tried insulating his forklift battery and discovered it heated up fast while being charged. LA is maybe 70% efficient, more or less, so if you insulate it to keep it from cooling off too fast make sure you also open vents to allow plenty of airflow when it warms up. Or how about earth sheltered? How deep is the frost line? Below that, the earth maintains a fairly constant temperature.

Propane engine vs. electric heater for diesel - How about exhaust heat from water heater (if fuel not electric) ducted over engine to keep it warm. Or an antifreeze loop double-isolated from the hot water line, pumped out to heat the oil pan in advance of starting the engine?

You're going to put your PV panels on a pipe frame. You could put each column of panels on a pivot for manual seasonal tilt.
Having one setup aimed SW and one SE reduces peak current and extends hours of production. That would reduce cycling of battery during the day.
Usually active trackers aren't cost effective compared to more panels. Commercial systems often have a single-axis East/West tilt, but then the angle for season or latitude isn't convenient, panels need to be spread out to avoid shade. But if you have a hill facing South, a long pipe on it rotating for tracking throughout the day might be good. It would require bearings taking significant thrust and radial load.

Lead-acid batteries - how well they are charged affects their longevity. Don't know about the Growatt, but people say SMA Sunny Island has exceptional management of the batteries. So long as you have more than sufficient power, of course.

Class T fuses are the best we know of for battery circuits. For parallel strings of PV panels, I have a concern about polarized breakers (available from both Midnight and Schneider). Touch-safe fuseholders are good so long as not opened under load.

Big motors - If you use 3-phase and VFD, they are easy to start. The harmonics or power factor of the diode/capacitor front-end may cause issues with transformerless inverters, at least I saw an error message. I wouldn't think Growatt would be particularly good at starting induction motors. Sunny Island or Victron, which can be stacked for lots of watts, should do it. You can do either split-phase or 3-phase.
 
"Battery blanket" - Trukinbear tried insulating his forklift battery and discovered it heated up fast while being charged. LA is maybe 70% efficient, more or less, so if you insulate it to keep it from cooling off too fast make sure you also open vents to allow plenty of airflow when it warms up. Or how about earth sheltered? How deep is the frost line? Below that, the earth maintains a fairly constant temperature.

Propane engine vs. electric heater for diesel - How about exhaust heat from water heater (if fuel not electric) ducted over engine to keep it warm. Or an antifreeze loop double-isolated from the hot water line, pumped out to heat the oil pan in advance of starting the engine?
Good to know there is heat produced, so an insulated shed would be fine for it, just have to vent the gas out. Not sure but if I go to a forklift battery, maybe a separate room for the battery, or is gas venting a big issue. On motors, the Growatt has a huge transformer, the unit weighs 201lb and the windings are copper.
Our waterlines are put 7ft deep, although personally I have not dug through frost any deeper than 4 ft. Having been an underground miner for 34 years, I know and love ground heat but sometimes it is too much work to harvest.
So, to help you guys visualize things:
My shop is a bit over 100 meters from the house. The array is going to be about 20 meters east of the shop. I have a power distribution center in the barn, about 20 meters closer to the house, in between the shop. That is where the solar inverter and the generator tie into everything. At present, all my power lines are underground. The place I have chosen for the array has no trees or buildings to shade the south and west view.
With the overkill on panels, and the max input on the Growatt at 7000Watts, I expect to clip the output most days in the middle of the day, and fatten the output morning and afternoon. Thus I want to KISS and not deal with rotators and trackers. If I was trying to squeeze the last dying watt out of panels that would be necessary, but not this way. We have wind here also, most times not at all worthy of wind generation...I tried.
But about twice a year we get 40-60 kmh winds. One of those setups on a pole would make a good windmill on those days. I want a setup that will not be low enough that a stray cow wants to scratch it's ass on it. Sometimes they get loose and come to visit us. So I plan for the bottom of the panels to be 3ft up and at 53 degrees the top will be 12 up. It will put the panel edge profile to the prevailing West winds.
Just my thoughts and plans at present.
 
I would suggest looking at splitting your array and offsetting it 2 different directions, SE and SW.
I have been experimenting with Multiple directional arrays, namely north, west and east for me and found very good results. For battery charging especially the goal is the most constant power, not the highest peak output... that like me you will shave anyhow. Offsetting the direction can make gains early and late and reduce the wasted power from clipping in the middle of the day which is a win all round.

It may be worth looking into this and see how it could work in your situation. Requires no more cost or effort but could make a good amount more KWH per day for you which may be helpful in winter when you do tend to need all the power you can get.
That's an interesting idea. I could easily put half the frame angled east by 15 degrees and the other west by 15 from solar south. Especially in winter when the sun is low on the horizon. I've been reading some say as high as 20 deg. offset from south, but I guess I should talk to a local solar pimp. I really didn't want to deal with them, but I maybe can just phone. Covid makes it so nice to go shopping. Some times it helps to talk to someone doing it, and the only one I know is a straight line of panels and grid tied.
But I do like the flattened out V idea. Logic says you should get gain from it.
The other orentation that probably would be no good for you but is helpfull for me is Flat. Gives the best possible generation in the worst condition ( overcast) and the best Conditions ( summer). I have found the dirt buildup etc is no where near as bad as the parroted mantras make out even at just 5o.
Think Snow.:giggle:
There is enough data out there saying right angles to the latitude gives the best results in this region. That's how we get 53 deg because we are at 53 latitude. That's at a fixed position, mid summer can be 15 degrees less, and mid winter would be at 68 degrees. I'll stay at a fixed angle that gives the best average over all.
 
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