Depth of Discharge under load

[Sunking]

Could you please cite your sources for this information? I've been interested in this for a long time and it's hard to find anything definitive.

Greencrusader
World peace through green energy

Well you are not going to find anything on Green Mafia sites. But to get you started. Sweeden IVL one of the most Green Minded countries in the world did a study on full life cycle of lithium batteries. Here is the link

https://www.ivl.se/download/18.5922281715bdaebede95a9/1496136143435/C243.pdf

The Life Cycle Energy Consumption and Greenhouse Gas Emissions from Lithium-Ion BatteriesA Study with Focus on Current Technology and Batteries for light-duty vehicles

Short version is a EV and its battery would have to last 20 years before there is EROI and CO2 offset. Here is some food to chew on:


Coal Plants generate roughly 50-75 times more energy that it takes to build the plant and mine the fuel.
NG plants 80 to 100 times.
Nuclear 200 times,
Hydro 100 times.
Wind Farm 10 to 15 times
Solar PV 5 to 7 times.

There is only one RE source that works, hydro electric. Bad news is in the USA there is no more land available for hydro. The most efficient means of Energy storage is Pump Back Lakes and Compressed Air of roughly 75 to 85% which is a negative EROI, and the lowest is any of the battery technologies.

So if anyone were really interested and deeply concerned about energy production and the enviroment, you would choose and use the most productive and highest EROI source you can possible get. Fortunately one of them is dirt cheap, highest EROI, with over 1 million years of proved fuel reserved and you are walking on it right now. Absolutely emission free of any pollutants and the safest energy source in the world.

[Sunking]

Over it's lifetime it will be able to store more energy than was used in it's creation.

Well that tells me and others in the battery industry you are either ignorant drinking Kool-Aid or a Liar. Which is it? When you compound the energy used to mine, smelt, assemble transport, and charge efficiency Pb battery EROI is roughly 50% and Lithium is not much better. Simple scientific fact that is not talked about by advocates and Green Mafia.

[tom rickard]

The battery is used to store energy from the sun.

Over it's lifetime it will be able to store more energy than was used in it's creation.

Sorry i had to dumb it down so much for you.

What you call reality is just not quite real..

I forgive you, i still hear people say PV cells take more energy to create than they will return.

Without full knowledge of the original posters power system i can't comment on if it will save him money, best we can do is offer him sound advice on making his batteries last as long as possible.

[J.P.M.]

Sunking is totally incorrect in saying you won't get more energy out of a battery than it takes to create it.

Don't worry about the negativity on this forum, it's just the way a few people communicate! Don't take it to heart.

For your batteries for as long as possible, make sure they all stay at equal state of charge, and don't discharge below 70%.

Your charge controller should take care of the rest of the requirements.

Good luck

Well, first and foremost, Disabuse yourself of the notion (if you have such a notion) that batteries create energy. They store some of what gets put into them, and never with 100 % efficiency. That means less comes out than went in. Always.

Second, and with that in mind, it may be helpful to keep in mind that batteries are no more than a temporary storage vessel for energy.

Those who draw some false equivalence between energy required to create a battery and the energy that passes through it (with some energy always lost in the process BTW) are looking at the whole thing incorrectly. Doing so is ignorant, incorrect and misleading, but suit yourself.

As for what you call negativity in the way some informed and experienced people see reality - some folks generally prefer to deal with reality as it is, not what they simply like. That's one of the traits and also a result of critical thinking rather than wishful or simplistic, or non thinking.

If some others say such more informed opinions express negativity, it may be because of those others' ignorance of such realities of the physics involved, and/or an inability to confront a Hobson's choice of either admitting their ignorance or making life more difficult than their ill conceived preordained and often ignorant notions can admit.

FWIW, by their very operation, batteries use energy due to their less than 100 % efficient input --->>>> storage --->>> discharge operation. That's OK, and unavoidable. The Second Law of Thermodynamics, or more generally the principle of Entropy striking as it always does.

But what all that means is your statement "Sunking is totally incorrect in saying you won't get more energy out of a battery than it takes to create it." is itself incorrect, totally or otherwise.

[SunEagle]

SunEagle, I'm not sure where all the negativity is coming from? I'm sorry if I've offended you. I'm just trying to ask a question and get an answer. Nothing I've said was meant to be negative. This has been a fun project for me creating an emergency power system, but using that solar power too. What would the expected lifespan of this battery setup be? If i'm doing something wrong, I'd like to fix it if possible before problems arise, or modify how I use it so it lasts longer.

Thanks in advance for any assistance,

I am trying to also be nice by pointing out that a large battery system made up of multiple parallel strings will never get you the number of desired cycles. Since the cycle count will go down so will the kWh output the system can generate over it's life. Even at $100 per battery and $0.30/kWh from the POCO I still don't believe you are saving money using a battery system.

If I can't convince you that batteries are will not save you $ then so be it.

[J.P.M.]

Could you please cite your sources for this information? I've been interested in this for a long time and it's hard to find anything definitive.

Greencrusader
World peace through green energy

I'd go the source: The Second Law of Thermodynamics, or, you can't fool Mother Nature.

[greencrusader]

Sunking is totally incorrect in saying you won't get more energy out of a battery than it takes to create it.

Could you please cite your sources for this information? I've been interested in this for a long time and it's hard to find anything definitive.

Greencrusader
World peace through green energy

Tom Rickard,

Thank you for the advice, and the kind words. It's kinda scary how a simple question about if I should go lower into my DOD, on my Solar Backup system, tuned into I'm an idiot, and should tear it all down lol. I thought this was a forum, for hobbyist into the idea of solar, but I think I'm going to find a nicer forum, where beginners can ask questions without being insulted by multiple members just for asking questions.

[tom rickard]

Sunking is totally incorrect in saying you won't get more energy out of a battery than it takes to create it.

Don't worry about the negativity on this forum, it's just the way a few people communicate! Don't take it to heart.

For your batteries for as long as possible, make sure they all stay at equal state of charge, and don't discharge below 70%.

Your charge controller should take care of the rest of the requirements.

Good luck

[Sunking]

I'd like to fix it if possible before problems arise,,

You cannot fix it, law of physics will not allow you to fix it. You have not offended anyone but yourself. You will soon figure it out when your wallet beats the crap out of you, gets your attention, and teaches you the hard way by loosing a lot of money.

What you do not know is batteries cost money and have a negative EROI. Basically that means they will never give you more energy than was put into them to make the. Sure the POCO is ripping you off at 30-cents per Kwh. Geez and rice where I live is less than 10-cents, si I understand why you think you are being robbed, you are. But what you do not understand if you buy quality batteries that give you the best rate of return for your investment the energy in battery cost alone is going to be $1 per Kwh. I do not know what math democrats are taught, but us independents and libertarians know 30-cents per Kwh is less than $1 per Kwh. However you can only get it down to $1 per Kwh by using optimum design and quality batteries which you are not doing, so in the end, you will be replacing your batteries more frequently every year or two when your wallet finally throws a fit and teaches you a lesson. There will be no one to blame but yourself for not understanding what you are doing.

Do you want to also talk about the cost of all the other equipment to make the batteries work? It really get ugly. Not only wil it cost you more, you just because a very heavy dirty polluter. Why? That negative EROI thing again. At 50% efficient overall you used twice as much power to make the batteries that is never recovered. You just robbed your children of resources and added a lot more pollution to the air.

There is no way to win with off-grid solar. The law of physics will not allow it. To bad schools today do not teach math and science anymore.

[Sunking]

At current power generation I save about $300 - $400 on my electric bill. .

You must be smoking some really good stuff, or drinking really bad moonshine. You are not saving any money, Whatever you take off grid will cost you 5 to 10 times more than buying it from the POCO. In 5 years you will be on your 3rd set of batteries. Just in battery cost alone you are looking at $1 to $2 per Kwh used. so much for that 30-cents per KLwh the POCO charges you is a bargain compared to how deep th ebattery guy is going to get into your pockets. He will be able to take a nice weekend vacation off you.

SunEagle, I'm not sure where all the negativity is coming from? I'm sorry if I've offended you. I'm just trying to ask a question and get an answer. Nothing I've said was meant to be negative. This has been a fun project for me creating an emergency power system, but using that solar power too. What would the expected lifespan of this battery setup be? If i'm doing something wrong, I'd like to fix it if possible before problems arise, or modify how I use it so it lasts longer.

Thanks in advance for any assistance,

[SunEagle]

I see where the confusion is. I did not pay even close to $500 each per batteries. I payed closer to $100 per each 12v 90 ah batteries brand new. It was part of a liquidation. I also payed only $100 per each 325 watt panel, also new, part of the same liquidation. I guess my upfront costs are not as much as you would typically pay for the system.

10 x batteries $1000
8 x 325 watt panels $800
2 x MPPT Charge controllers $300
1 x 1000 watt Pure Sign wave inverter $100

Total $2200. I guess It's technically somewhere between 5 - 7 years, but during that time, if we have a prolonged power outage, I can still run the hot water baseboard furnace, and select loads, which was my objective, over simply purchasing a generator.

So you have a 24v 450Ah battery system using 10 - 12V batteries wired in 5 parallel pairs and you expect to get more than 5 years out of them. Good luck with that.

But I do now understand the DOD better thank you for explaining why i should not go any further. Would you suggest only using 30% of the battery or even less?

I see where the confusion is. I did not pay even close to $500 each per batteries. I payed closer to $100 per each 12v 90 ah batteries brand new. It was part of a liquidation. I also payed only $100 per each 325 watt panel, also new, part of the same liquidation. I guess my upfront costs are not as much as you would typically pay for the system.

10 x batteries $1000
8 x 325 watt panels $800
2 x MPPT Charge controllers $300
1 x 1000 watt Pure Sign wave inverter $100

Total $2200. I guess It's technically somewhere between 5 - 7 years, but during that time, if we have a prolonged power outage, I can still run the hot water baseboard furnace, and select loads, which was my objective, over simply purchasing a generator.