# Off grid system questions



## norseman (Apr 17, 2013)

hello
I have a 25 by 34 metal Quonset hut I build on 25 acres, nearest power is 1/2 mile away and the community power company gave me a off hand quote of 15K to bring power to the line. I have access to some UPS batteries (108) of them, 12 volts at 9 amp hrs. Not know a heck of a lot about solar I was wondering if a 540 watt solar package from home depot would charge the batteries during the week and then run a 30 amps on and off on the weekend. Being in VA if I could get it to run a de humidifier or window ac it would be great.
Thanks for you assistance.


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## wy_white_wolf (Oct 14, 2004)

Paralleling that many batteries is dangerous. When one of them gets an internal short it will immediately try to balance all the others with it causing it to explode. 

You can overcome that by using fused interconnects on all the strings of batteries but that will add a large expense for such small batteries.

You will also have problems with balance of charge of all the strings. Even slight internal resistance of the batteries and interconnects will degrade them fasts

Thirdly UPS batteries are a poor choice for a solar system. They are designed for limited emergency use, not daily cycling. If they are new you would be lucky to get 100 cycles out of them.

WWW


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## AmericanStand (Jul 29, 2014)

What is the UPS battery?


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## coolrunnin (Aug 28, 2010)

AmericanStand said:


> What is the UPS battery?


Un Interrupted Power Supply for electronics mostly.


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## TnAndy (Sep 15, 2005)

coolrunnin said:


> Un Interrupted Power Supply for electronics mostly.



Also often used on things like emergency exit lights that mount over doors at stores/etc....the box under the set of lights holds the battery. Doesn't take much of a battery since they only need to run an hour or so at most.


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## norseman (Apr 17, 2013)

These batteries ran the computer server room for a large retail company for 4 to 6 hours


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## norseman (Apr 17, 2013)

wy_white_wolf said:


> Paralleling that many batteries is dangerous. When one of them gets an internal short it will immediately try to balance all the others with it causing it to explode.
> 
> You can overcome that by using fused interconnects on all the strings of batteries but that will add a large expense for such small batteries.
> 
> ...


Thank you, that is what I was looking for. I will start putting marine batteries on the list.


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## Steve_S (Feb 25, 2015)

AmericanStand said:


> What is the UPS battery?


 I think the correct question, is what Type of batteries, Sealed Lead Acid, AGM, Li-Ion or LifePO4. That will help determine next steps and best method. 

BTW: Many Telecom & Medical systems use LifePO4 Batteries within them, quite often they can be bought used / refurbished for a very reasonable price (IE: Lithium Ion Battery Modules U-Charge U27-12XP 12 volt 138Ah Lithium Iron Magnesium Phosphate battery modules, for LESS than $500 USD https://www.amazon.com/gp/offer-lis...0?ie=UTF8&condition=all&qid=1571994531&sr=8-1


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## wy_white_wolf (Oct 14, 2004)

norseman said:


> Thank you, that is what I was looking for. I will start putting marine batteries on the list.


I wouldn't put anything on the list until you figure out just how many watthours you will use in a weekend. If you want to put anything on your list make it a kill-a-watt meter to help determine that.

WWW


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## JeepHammer (May 12, 2015)

I'm going to go a different direction here...
This is with one assumption, the batteries you have aren't Lithium/metal.
I hate assumptions, but Lithium/metal is an entirely different story.

A thousand or two charge/discharge cycles,
And each cycle can be up to 80% of charge capacity.
Vs.
Lead acid batteries have a couple hundred, and you discharge below about 20% of charge capacity and you VERY seriously damage the battery.

Putting it simply,
That means you get 400% more charge back out of a lithium/metal battery,
And lithium/metal batteries store more to begin with.

Like Steve S said, what kind of batteries are they?

-----------------------

Now, that different direction,
Since you are looking for batteries, why not look for Lithium/Metal to begin with?

Lighter weight, no explosive/corrosive gasses, don't need water/corrosion maintenance constantly, have between 2x & 4x the charge density of lead acid (store & return more energy) for the same size, the list goes on...

Since they don't have a finite life span like Lead/Acid (Around 5-7 years if VERY carefully maintained), and can last up to 15 years, have thousands of charge cycles instead of hundreds, buying used Li-Metal batteries off the used or surplus market makes a BUNCH of sense.
The two things that will kill lead acid no matter how well maintained, age (5-7 years) and discharging/charging (charge cycles, a couple hundred with common automotive/boat batteries, twice that with dedicated solar batteries).
You need a lot more batteries so you don't discharge them deeply, and that's even more cost.

When I started out off grid 20+ years ago, I started with fork truck batteries. The fork truck place would sell me the steel case batteries for scrap weight, and just because they wouldn't power a heavy use fork truck through an 8 hour shift, didn't mean they wouldn't power my 1/100 the demand of a fork truck.
Even dead cells didn't matter since the connections between cells were external, you simply cut the connecting and jump over the dead cell with a jumper wire.

Now I search surplus places for Li-Metal, particularly for electric car batteries, large cordless tool batteries and battery back up equipment batteries.

It depends on how good you are at wiring, the Tesla Power Wall is a crap load of about double A size Li-Metal batteries, and it will power a house just fine, just incredibly expensive.
A soldering iron, terminal crimpers and you can save THOUSANDS.

There are thousands upon thousands of brand new tool batteries on the surplus market,
If you know how to wire in series to drive voltage up in a battery string,
Then know how to wire the strings in parallel to drive amperage up,
Connect those to an inverter, you are golden.

Charge controllers for each battery string connect to your solar panels, and you have a system that's modular.
Charge controllers are about $20 per battery string, and if any one string fails (batteries or charge controller) the system is redundant and doesn't fail.
The only singular failure point is the inverter, and since you are NOT paying the electric company, you can pick up another when you can afford it as a backup.

Wile some people tell you to 'Size' the system for what you use right now, I always advise modular and expandable.
Nothing can fail to stop you cold, and expandable means it can grow with your needs.

IF you have time to search state auctions, look for the road side 'Orange' trailers for road construction, and watch for 'Remodel/Refit' sales.
Those road sign trailers usually have two big, high quality solar panels, a set of 2 to 4 batteries, a charge controller on board. When people hit them or they get damaged they go to auction as scrap. I've bought them from $30 to $130.
Everytime the president's office changes political parties, there are either solar panels taken off government buildings for upgrades, or they are taken off because that party doesn't like solar.
Either way high grade solar panels, racking, switching/breaker boxes, even inverters for scrap weight prices.
The government always buys the best, and 20 year old panels often put out what they were rated for when brand new, and for $10 or $20 each, it's just too good a deal to walk by.


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## MichaelK! (Oct 22, 2010)

_Lead acid batteries have a couple hundred, and you discharge below about 20% of charge capacity and you VERY seriously damage the battery._

I think this one statement to total BS! I installed Trojan L-16s in my own system, routinely discharge them 20%, and I've have more than a thousand cycles now, and the batteries are still in almost new condition. Looking at my batteries, I'm expecting to get 15-20 years before they wear out. The number one reason batteries are destroyed is overly optimist charging from a too small array. My own system on paper is over-paneled, but it's likely the reason my batteries are in such good shape. It's one of the best things I designed into my system.


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## JeepHammer (May 12, 2015)

MichaelK! said:


> _Lead acid batteries have a couple hundred, and you discharge below about 20% of charge capacity and you VERY seriously damage the battery._
> 
> I think this one statement to total BS! I installed Trojan L-16s in my own system, routinely discharge them 20%, and I've have more than a thousand cycles now, and the batteries are still in almost new condition. Looking at my batteries, I'm expecting to get 15-20 years before they wear out. The number one reason batteries are destroyed is overly optimist charging from a too small array. My own system on paper is over-paneled, but it's likely the reason my batteries are in such good shape. It's one of the best things I designed into my system.


You missed the part about common AUTOMOTIVE/boat type lead acid batteries.
A Trojan L16 is hardly a common automotive/boat trolling motor 'Deep Cycle'.

Good luck on that 15-20 years, I hope you make it!

A 'Cycle' is fully discharged to fully charged, but every full discharge damages lead/acid, particularly flooded lead/acid battery.

50% discharged then charged is half a cycle.

20% discharge would take five times to make a single charge cycle. 20% x 5 = 100% charge cycle.
This next question would be how long have you had the batteries?
There are only 364 days in a year.
It takes 3 years to reach 1,092 (excluding leap year, 1,093 with a leap year).
It takes 5.5 years (excluding leap years) to reach 2,000 days, and if you are only discharging 20%, that's only 400 charge cycles in 5.5 years.
364 days x 5.5 years = 2,002 days (discounting leap years)
20% discharge x 5 days = 100% or 1 complete charge cycle.
2,002 days ÷ 5 days per complete charge cycle = 400.4 charge cycles in 5.5 years.
That's only 800.8 in 11 years discounting leap years which would be 1/5 of a charge cycle at 20% discharged.

*IF* you get 15 years (discounting leap years),
5,460 days (15 years)
20% discharge x 5 days per complete charge cycle = 1,092 charge cycles.

-----

I agree about being under panelled, no direct sun and you have chronically undercharged batteries. Too few panels and in winter short days the batteries will be chronically under charged until day light hours catch up with charge demands by the batteries.

---------------

The all time killer of flooded lead acid batteries is dimwit users.
Crap stuck to the plates, either being too cheap to buy distilled water and having contamination added to the electrolyte, or sulfidation collecting on the plates.

They dump chlorine, lead, iron, calcium and everything else in tap water into the batteries and can't figure out why the crud collects on the plates.
They add water, but don't stop and think where the sulfur from sulfuric acid went when the water dumped it to escape, add more water and go on there marry way without running the de-sulfidator to put the sulfur stuck to the plates back in suspension...
And let's not forget the idiots that don't check battery water at all until the first set cooks themselves.

Then there are the semi-educated, figured out the batteries need regular CLEAN water, the inverter has an automatic charge leveler/de-sulfidator, but they don't own, and don't know how to use a specific gravity tester, so they don't have a clue how the battery string is doing until it irreparably fails.


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## AmericanStand (Jul 29, 2014)

MichaelK! said:


> _Lead acid batteries have a couple hundred, and you discharge below about 20% of charge capacity and you VERY seriously damage the battery._
> 
> I think this one statement to total BS! I installed Trojan L-16s in my own system, routinely discharge them 20%, and I've have more than a thousand cycles now, and the batteries are still in almost new condition. Looking at my batteries, I'm expecting to get 15-20 years before they wear out. The number one reason batteries are destroyed is overly optimist charging from a too small array. My own system on paper is over-paneled, but it's likely the reason my batteries are in such good shape. It's one of the best things I designed into my system.


I don’t understand this. Why do you call it BS and then explain you you follow the advice in it ?


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## AmericanStand (Jul 29, 2014)

JeepHammer said:


> You missed the part about common AUTOMOTIVE/boat type lead acid batteries.
> A Trojan L16 is hardly a common automotive/boat trolling motor 'Deep Cycle'.
> 
> Good luck on that 15-20 years, I hope you make it!
> ...


Interesting take on the definition of a cycle. Where does that come from ?


Do you know the difference between ignorance and intelligence? 
Let me help you out ,your ignorance is revealed buy your use of the word idiot .


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## JeepHammer (May 12, 2015)

AmericanStand said:


> Interesting take on the definition of a cycle. Where does that come from ?
> 
> 
> Do you know the difference between ignorance and intelligence?
> Let me help you out ,your ignorance is revealed buy your use of the word idiot .


Yes, idiots... They are everywhere.
You want to take me to task for calling someone that intentionally damages their own batteries idiots, even though they the education is printed in the instructions and often on the battery itself...
Education willfully ignored, idiotic move and that makes the purpetrator an idiot.

The instructions, even the label often say distilled water only.
It's not hard to follow, and yet you see batteries with oil in the cells where the oil funnel is used to get water into the cells.
White crusty calcium scale built up on plates from hard water.
Red iron rust built up under the cap line and on plate separator making them electrically conductive.

When someone wants warranty, you pull the top cap & plates, the 'Mud Tray' under the plates is full of scale & rust from impurities in the water added, enough the mud tray filled up and shorted the plates out.

Ever see what chlorine does to lead plates? Not to mention what it does to the electrolyte...

You can't fix what's wrong with them, you tell them 'Distilled Water Only', the instructions say 'Distilled Water Only', and yet there goes whatever is handy, through what ever is handy for a funnel or water container, oil, dirt, rust...

Education given but ignored, IDIOTIC action purpetrated, purpetrator is an IDIOT by definition.

--------------

A battery is charged to 100% DESIGNED RESTING CHARGE CAPACITY of a STATIC CHEMICAL BATTERY, that's 100% of 'Charge Capacity'.

Notice the use of 'DESIGNED', 'RESTING', 'CHARGE', 'CAPACITY', 'STATIC', 'CHEMICAL', 'STORAGE', 'BATTERY'.

Flooded lead acid batteries STORE ENERGY CHEMICALLY, they do NOT store 'Electrons'.
Electrical energy is converted into CHEMICAL storage, then converted back into electrical when a demand (called a 'Load') is placed on the battery.

If you have issues with these words, I URGE you to seek definitions.

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Then there is the MOVING ELECTRICAL components to a battery/load/circuit.
A lead/acid battery CAN be 'Charged' well above it's DESIGNED capacity, which will create a CHEMICAL imbalance and damage the CHEMICAL reaction components of said battery, but that state of charge IS STILL in excess of DESIGNED CHARGE CAPACITY.

Discharged is also an Imbalance of DESIGNED charge capacity, and will damage the battery.
The further discharge, or overcharged (electrical terms), the battery is, takes it out of CHEMICAL BALANCE, and the battery is damaged.

ANY use of a battery damages it...
LIFE SPAN depends on how badly you damage the battery.

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Since a Voltmeter is used to check the ElECTRICAL component, it's NOT an accurate way to check on the CHEMICAL component of said flooded lead acid battery.
The proper, and specific tool for that job is a hydrometer for checking/gauging specific gravity of the electrolyte, corrected for temperature.
The little 'Floating Ball' units don't correct for temperature, so a proper hydrometer is required, and the education to properly read a hydrometer is also required.

Proper tools for the job is common sense, you don't use a tape measure to see what the temperature is... If you do you are an idiot when you know thermometers exist and what their function is...

---------------

20% DEPTH OF DISCHARGE is 20% reduction of capacity, or 1/5 total DESIGNED CAPACITY of that flooded lead/acid battery.
The POTENTIAL (not realized or produced electrical capacity) electrical capacity has nothing to do with the CHEMICAL imbalance going on inside the battery.

I know you have an issue with definitions so here goes,
To a layman, the COMMON USAGE term for any amount of discharge & recharge is 'CHARGE' CYCLE'.
1% OR 100% 'DISCHARGED & RECHARGED', IT'S STILL '*1 CHARGE CYCLE*' IN COMMON USAGE TERMS.

The question is, do YOU believe, in your personal experience, that you can discharge a flooded lead/acid battery to ZERO, a 100% discharge of designed capacity, no electro-chemical reaction at all, 
And recharge it to 100% of designed charge capacity and the battery won't be damaged, will continue to operate as nothing happened? 
That would be 1 charge cycle under 'Common Usage' of 'Charge Cycle'.
That's exactly what the poster did when he stated he had 'Thousands Of Charge Cycles' (common usage) and as you pointed out, turned right around and said he only discharged to 20%...

----------------

Since we are talking specifically about batteries,
And in all scientific, and most common usage applications, we all (pretty much) agree that DEPTH OF DISCHARGE determines life span,
AND,
Since science proves, and application teaches us that deep discharging, or overcharging damages the battery,
AND,
Since groups like Battery Counsel Internation (BCI), and Manufacturers use AVERAGED Depth Of Discharge to determine totals for 'Charge Cycling' based on the DESIGNED CHARGE CAPACITY for determining the damage done to the batter to estimate life cycle.

It would make sense for the common, layman, home user to do likewise, and determine the actual discharge depth to figure the cycles based on designed charge capacity to determine longevity since a battery bank can cost several thousand dollars to install, and replace.

And since it can cost several thousand dollars to install & replace, that brings us back around to being educated and following that education with it's rules, or being an idiot and scrapping the battery bank by undersizing it (depth of discharge), or dumping contamination into batteries, etc...


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## JeepHammer (May 12, 2015)

'Ignorant' isn't an insult since it simply means lack of education in a particular field.

Jumping on someone that points out the science, or common usage doesn't apply since the subject goes specific enough to discount common usage doesn't apply anymore doesn't do anyone any good.

The layman or common use of 'Charge Cycle' goes right out the window as soon as you start talking about life span of batteries.
Common useage is 1 discharge + 1 charge = 1 'Charge Cycle'.
This completely ignores the 'Depth Of Discharge' of that battery, which is specific to each battery type.

Ignorance creates fear & confusion which leads to anger.
That explains the angry angry rants on so many specific & scientific topics.
It's also why I tried to explain the Depth Of Discharge principal in a conversation SPECIFIC TO LONJEVITY of a specific type of battery.

Either the science clicks or it doesn't, what someone absorbs or accepts has noting to do with specific definitions or the science.
Scientific or legal definitions often have little or nothing to do with 'Common Useage' definitions, it's context that matters.

Since the chemical storage battery doesn't care about 'Common Useage', and will be used up sooner when 'Depth Of Discharge' is higher,
Consider the context, compensate for the heavier use damage that accumulates, and you will get a fairly accurate estimate of life span of that battery.
There is only so much plate material in any given lead/acid battery, and when it's used it's damaged, and that damage accumulates over the entire useage period.
The amount of use/damage can be estimated when considering how hard the battery worked before recharge, therefore, any estimate of life cycle has to be based on the rate of decay (damage) from use.
The 1% Discharge/Recharge = 1 Charge Cycle
Or,
100% Discharge/Recharge = 1 Charge Cycle model can't estimate the life span of the batteries, and in this case it's flooded lead/acid batteries, the most easily damaged battery type by deep discharging.

Either you connect the dots and accept the science or you don't.
It won't change the science or the math either way...


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## MichaelK! (Oct 22, 2010)

AmericanStand said:


> I don’t understand this. Why do you call it BS and then explain you you follow the advice in it ?


Well, I suppose the central issue is how you define a cycle? Jeephammer is the very first person I have ever seen that defines a cycle as he does above. Each and every other person I've ever read thinks a cycle is a 24 hour day. I can though see his logic, coming from his point of view. But, if everyone else in the world measures time in days and years, I'll measure time in days and years. I won't bother thinking in terms of a 1/5 of a cycle.

Now in my own case, I evaluate the quality of my battery bank in terms of it's specific gravity, that is the weight of the acid itself. Too many people completely ignore specific gravity, and judge the quality of their batteries by voltage only. That's another reason batteries die. After three years, (so what is that, 219 cycles?) my batteries still have a SG of 1.290. That's how I interpriate the quality of my bank as being well maintained. This is a system that I can use 8 hours a day to run a 240V well pump, so its no primadonna.

Another point brought up is the fact that lithium batteries can be drained to 90+% of their capacity. But comparing on an amphour by amphour basis, and assuming the lead-acid batteries are only drained 20% vs 90%, the lead-acid still wins on a dollar by dollar standpoint.

One last comment I could make is the maturity of the lead-acid platform. The metal technology is still too new, with the people rushing them to market not fully understanding the potential dangers of it's chemistry. These batteries have started fires that have brought down airplanes, and ended human lives. Doesn't anyone here remember Samsong? Are the same kind of engineers that designed the 787 flight control system going to be designing batteries too?


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## JeepHammer (May 12, 2015)

MichaelK! said:


> Well, I suppose the central issue is how you define a cycle? Jeephammer is the very first person I have ever seen that defines a cycle as he does above. Each and every other person I've ever read thinks a cycle is a 24 hour day. I can though see his logic, coming from his point of view. But, if everyone else in the world measures time in days and years, I'll measure time in days and years. I won't bother thinking in terms of a 1/5 of a cycle.
> 
> Now in my own case, I evaluate the quality of my battery bank in terms of it's specific gravity, that is the weight of the acid itself. Too many people completely ignore specific gravity, and judge the quality of their batteries by voltage only. That's another reason batteries die. After three years, (so what is that, 219 cycles?) my batteries still have a SG of 1.290. That's how I interpriate the quality of my bank as being well maintained. This is a system that I can use 8 hours a day to run a 240V well pump, so its no primadonna.
> 
> ...


Glad to see you will at least consider it.
I learned it from BCI, which are engineers that classify, quantify and categorize batteries on a world wide basis.
Back about 1995 or 96 I got the BCI news letter and it had an article about figuring life span of 'Placement' batteries, including RE.

It's good to hear from someone that uses specific gravity tests to determine state of charge instead of a volt meter to check electrical production potential.
One of the things I do for new lead/acid owners is give them a printed tutorial on using a proper hygrometer with built in thermometer so it's accurate. 

For whatever reason, really good hygrometers are always available on the government/military surplus market so a lot of times I give them away when someone bought batteries. I figured it was cheap insurance against NOT having warranty returns and trying to explain I can't warranty something they killed through ignorance/neglect.

As for 'Cycle', how else would you estimate lifespan without considering depth of discharge?
It's a math problem to determine what daily usage is to size the battery bank for a 20% average depth of discharge,
It's easy to figure out how much you need from charge source to recharge batteries.

You have to consider how much use/damage the plates will sustain, at optimum charge & maintiance, the battery degrades faster the deeper it's discharged, even if it's recharged immediately.

Without figuring depth of discharge and the damage done, how else could you estimate the lifespan of the battery?
How could you quantify the average number of partial sun days, no wind days, no sun days, etc. (All averages),
So you could factor the deeper discharges into the shortened life span?
Now, I didn't include that into your example, but that was what the article was about, the average number of partial sun sun, no sun days mapped out by region.
It also considered wind, which made me test my area for wind averages, and that just wasn't going to work, so I went solar.

Most places take data points from pervious systems and battery life in those systems and 'SWAG' (scientific wild "butt" guess).
The BCI formula was the only one I've seen that considers actual use, but like figuring watt/amp/volt conversions and uses of Ohm's Law, it takes a little math which scares the crap out of 99% of people.

Do what works best for you, this works best for me for over 20 years.


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## Steve_S (Feb 25, 2015)

From Wikipedia, the free encyclopedia

A *charge cycle* is the process of charging a rechargeable battery and discharging it as required into a load. The term is typically used to specify a battery's expected life, as the number of charge cycles affects life more than the mere passage of time. Discharging the battery fully before recharging may be called "deep discharge"; partially discharging then recharging may be called "shallow discharge".

In general, number of cycles for a rechargeable battery indicates how many times it can undergo the process of complete charging and discharging until failure or it starting to lose capacity.[1][2][3][4]

*Apple Inc.* clarifies that a charge cycle means using all the battery's capacity, but not necessarily by discharging it from 100% to 0%: "You complete one charge cycle when you’ve used (discharged) an amount that equals 100% of your battery’s capacity — but not necessarily all from one charge. For instance, you might use 75% of your battery’s capacity one day, then recharge it fully overnight. If you use 25% the next day, you will have discharged a total of 100%, and the two days will add up to one charge cycle."[5]
-----------------------------------------------
REF: https://en.wikipedia.org/wiki/Charge_cycle

If you really want to understand batteries, charge cycles & the various issues with different chemistries etc check out *The Battery University* here: https://batteryuniversity.com/learn/

BTW: I'm sure Norseman hoped to get some quick answers to make a decision / choice that is going to affect his wallet and the side excursion the thread took, likely didn't help. Every question is an opportunity fore some to learn and others to share knowledge for the betterment of ? oh well, such a shame....


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## AmericanStand (Jul 29, 2014)

I think in common usage a cycle is simply a discharge and a recharge.
I can see some reasons for considering a cycle to be a 24 hour day. 
The definition jeep hammer uses seems to be very accurate and precise.
So for now I’m going to go with the idea that context matters.
For communication purposes it really doesn’t work well when your singular definition is not used by the people you are communicating to.


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## JeepHammer (May 12, 2015)

Looks like Apple uses the same FORMULA I do, but they deal with the little devices that are on and off chargers before they reach 100% charged.
I wouldn't want to guess how many times a phone gets partly charged/discharged, that would make me pull my hair out...

And I'll be the first to admit I'm the worst at it. Phone charges for 15-20 minutes, off the charger until the low battery warning pops up, back on the charger for 30 minutes until I need it, back off the charger for 3 hours, etc. etc...
I leave it lay on the desk, tool box, night stand and not charge it nightly, so there is no base line for 100 charge to start from in my case.

It's a testament to what Lithium/Metal batteries will take! I'm still running an iPhone 5, I can't even remember when I got it, no idea how old it is or how much I've abused the battery...
That's what I'm almost done bringing to my solar system, the last two lead/acid strings are being replaced with metal when they fail, which should be in about 2 years.
The golf cart runs fine on USED metal batteries, which reduces the cost from $ thousands to $ hundreds, and the all weather charge controller was $66.

Instead of reducing the number of battery strings as 4X increases in capacity metal batteries replaced lead/acid, I already have the space dedicated, I simply increased reserve capacity, I can run house & shop 3 days without sun and barely put a dent in reserve capacity.
With lead/acid, one day without sun and I had to fire up the generator to use the shop on the second day without sun.
When the last two lead/acid battery strings go metal, I estimate I'll have a 5 day reserve capacity at normal consumption rates.

----------------------

As for Norsman, use what you have.
Use what you have as a learning experience, realizing it's not 'Optimum',
Or buy a system that's specific and someone already figured it out for you.
Learning this is steep for about a day or two, the biggest issue you will have is learning to put knowledge into practice, you think there are a lot of battery types, wait until you get into connectors and wiring!
I keep mine dirt simple, anything under 50 amps is Anderson connectors (cheap off eBay), wires get a stick on tag (mailing label) marked for voltage.
Anderson's are idiot proof, I can't plug them in reversed polarity no matter how tired or distracted I am...

----------------

My warning was don't fall into the automotive/consumer battery trap...

I did that at first and it's expensive while not being nearly as productive.
It's battery design, consumer automotive batteries are designed to start the vehicle, then be fully charged, work more or less like a capacitor for the charging system the rest of the time.
'Marine Deep Cycle' is a little better, but they are still basically a starting battery.

Common batteries come in three basic types, Consumer, Commercial & Industrial.

Consumer is a crap shoot, consumers are fairly ignorant of manufacturing processes and get inflated ratings, bright colors, mostly packaging (Eye Candy),
Almost no consumer battery will reach it's published specifications, it's built to expire as close to warranty end as can be estimated, and the manufacturers have a lot of experience in determining just how long the battery will live.

Commerical has to meet claimed specifications simply because truck, tractor & heavy equipment garages have testing equipment and track life cycle, warranty fails, etc.
Guys in the shops know the difference between 1,000 Cranking Amp (CA) and 1,000 Cold Cranking Amps (CCA) and have actual load testers to check the batteries.
If the battery doesn't live up to specifications, the manufacturer will get caught...

Industrial batteries are built to take a beating and stay alive, and people working with industrial batteries daily know even more about them, have better testing equipment, and track everything.
Think steel case fork truck batteries... They are built for use/abuse.

Golf cart batteries are much better for the application, but designed to throw a lot of amps quickly to move the golf cart which limits them somewhat in lifespan.
The sheer product number of golf cart batteries make them cost attractive, and they do the job MUCH better than consumer grade starting batteries.
The rules are pretty simple too, don't freeze or over heat, don't let them get low on water, recharge fully when possible, do a de-sulfidation charge every month or so.
Check on the health with a hydrometer to see how you are doing.

If you are trying to decide between two different brands of batteries that are pretty much equal in published specifications, weigh them.
Plate material weighs more than case or electrolyte, the one with the most plate material wins.

If you buy retail and not from a high volume distributor, learn to read date code stickers for month/year of manufacture. Batteries CAN sit on a shelf for a year or more, not at 100% state of charge and be damaged before you get them.


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## JeepHammer (May 12, 2015)

AmericanStand said:


> I think in common usage a cycle is simply a discharge and a recharge.
> I can see some reasons for considering a cycle to be a 24 hour day.
> The definition jeep hammer uses seems to be very accurate and precise.
> So for now I’m going to go with the idea that context matters.
> For communication purposes it really doesn’t work well when your singular definition is not used by the people you are communicating to.


Context...
In this case, it was estimating the lifespan of lead/acid batteries.

Context... Why I explained how I estimate a 'Discharge/Charge' cycle...
I'm not the super genius, or team of regular geniuses that came up with the formula,
I use a simplified version since I don't normally allow for clouds, storms, short days, etc...
But with the BCI formula you could drill down into all that should you want to.

I just found it a helpful tool that got me closer than the hit & miss approach I had before I ran onto it.

I knew basic electro-magnetic and DC electrical before I started with my solar system, but being the KING off getting in over my head and working 4 times harder to get out of any situation, this just clicked in my head as a way NOT to screw up yet again...

Education in estimation, theory, etc takes you so far,
Then it's time to get your feet wet, and learn about crap cables, crap terminals, corrosion everywhere, condensation on everything creating yet more corrosion,
I started with a cheap little yard barn the neighbor didn't want on his rental property, and with lead/acid batteries, I learned about wood rot & floor strength... 

The usage/damage curve to lead/acid batteries isn't liner, it's exponential.
20%-25% is about optimum for battery life short of not discharging batteries at all.
A 100% discharge, no electro-chemical activity at all, and the battery is usually damaged beyond use in just half a 'Charge Cycle' since a common charger won't recharge a completely discharged battery.

That chemical component jumps in the further the battery discharges and damages the plates MUCH faster the deeper the battery is discharged.
Keeping to 20%-25% discharge the battery chemistry doesn't go haywire and destroy the plate surfaces and the battery keeps working...

That's as simply as I can explain it without a bunch of chemistry, which even I'm shaky on since since electro-chemical chemistry is not my field of study.
I know just enough to NOT kill my batteries anymore...


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## MichaelK! (Oct 22, 2010)

Instead of being overly verbose, I can just cut and paste Trojan's own graph illustrating battery longevity. This I think reinforces the concept that a cycle should be considered a discharge/charge cycle, which in the real world is mostly one day(with proper design). I myself designed my own system with a <20% discharge rate in mind, and looking at the SG of my batteries as a gauge of their health, I think I did a very good job.


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## markt1 (Dec 15, 2013)

If you are going to go with lead batteries, buy a small forklift one. 20 year real lifespan. The company I retired from last year had a forklift battery in it dated 1997 and it was still going strong. Common RE batteries from Trojan and such have 7-10 year warranties. I have four 125Lb ones for an array of 100ft2. For a larger array you'd need a proportionally heavier lead battery. I would have gone for a forklift battery myself, except the weight prevented me from getting it down in a steep-stepped basement at the time. Lithium batteries are much more expensive, and some car ones have been known to catch fire, so consider that before keeping one in your basement. Edison iron cells are also available, are both safe and expensive, can be deeply discharged, have very long lifespans, but are not all that efficient in returning stored energy back to an inverter. IMHO the best site for solar info is: https://forum.solar-electric.com/categories


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## Steve_S (Feb 25, 2015)

LifePO4 Batteries are the most suitable at this point for Renewable Energy and more cost effective than Li-Ion and LifePO cannot catch fire or present any risks like that. I'm buying a new pack for my system. 24V, 400AH complete with BMS and an external Charger for 2999 USD. https://www.amazon.com/dp/B07TWD17TZ/ref=twister_B07TRQ48GW?_encoding=UTF8&psc=1 

Stay up[ top date on Factual Information on Battery Tech here: https://batteryuniversity.com/ Don't let social media and word of mouth misinform.

BTW: 12VDC/138AH Drop In LifePO4 $350 USD (from medical equipment, testedf & verified and come with BMS. https://www.ebay.com/itm/153700424107


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## JeepHammer (May 12, 2015)

I honestly hope Michael K. Gets 5,000 charge cycles, that's a big chunk of money he shelled out and I hope it pays off for him.

Markt1 is correct about fork truck batteries, they are stupidly overbuilt, and I've written about using them before. I bought used/defective fork truck batteries and jumped the dead cell (external bridges between cells) and they chugged along just fine even when abused.
The biggest issues I had were corrosion (a never ending battle with any lead/acid) and getting them properly de-sulfidated/balanced, there weren't a bunch of heavy duty units back then and making the amperage volume was a challenge working with 25 year old solar panels only, which is what I had (opposed to what I actually needed).

Being I was a product of the 'Boomer' generation, I completely discounted Edison (NiFe) batteries in the beginning... (Stupid is as stupid does)
Between a big turn of the century to present railroad yard, and several underground mines I had access to them, but just vapor locked on 'Stupid' mode and discounted them...

I don't make that mistake anymore, so when I run into NiFe batteries (scarce now) I set them aside, rebuild and get them ready for service. 
I have a nice collection of 'Antiques', glass jar Edison & Exide rebuilds since the rebuild kits are still available. 
That's about as close to 'SHTF' planning as I get, all but a few are dry, but I roll out some filled & charged ones on 'Pioneer Days' to display.

The biggest money suck/stupid mistake I made was consumer automotive lead/acid batteries.
Between mistakes in type, size & age matching, I could kill at least one a month, sometimes more... 

Since I owned a lead/acid battery, starter/alternator/generator/welder rebuild business (mostly industrial) for several years, I still have those connections (no pun intended) and I've been switching to LiFePo4 batteries.
Gently used and MUCH deeper depth of discharge without significant damage I'm seriously thinking these are the way to go.
The cost is coming down S-L-O-W-L-Y, and they are showing up on the used/surplus market fairly regularly.
Since I set up for BIG lead/acid batteries, I actually have a surplus of storage capacity now which reasonable priced surplus/over run capacity is never a bad thing...

Between DoD and charge density in a small, light weight package, the traditional limits are pushed way back for solar applications.
No matter what people say, safety is an issue for me, and LiFePo4 are as close to 'Safe' as you can get considering there is 1kw per battery...
When they are certified 'Safe' for hospital operating rooms, that's about as close as you can get...


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## JeepHammer (May 12, 2015)

A link on batteries I found interesting...
https://edisontechcenter.org/batteries.html


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## Steve_S (Feb 25, 2015)

*BYD 24V LIFEPO4 4-4.5 kWh BATTERY MODULES RV POWERWALL*

Regular price $450.00
https://batteryhookup.com/collectio...tery-modules-rv-powerwall?rfsn=2267412.b1bf25
*Samsung SDI ESS Energy Storage Battery 16S 60 Volt - Used 13.2 kWh Rack Mount Mega 3.3 - Four Pack[Mega 3.3]*
*Price: $1,720.00* https://www.evwest.com/catalog/product_info.php?products_id=486

Attentive folks can find incredible deals if they pay attention & search a bit. Just a sample, there is a LOT more to be had if looking and if someone does not mind importing from Europe there is even more opportunities to save big and build a great system.


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## JeepHammer (May 12, 2015)

Steve_S said:


> *BYD 24V LIFEPO4 4-4.5 kWh BATTERY MODULES RV POWERWALL*
> 
> Regular price $450.00
> https://batteryhookup.com/collectio...tery-modules-rv-powerwall?rfsn=2267412.b1bf25
> ...


13 kW is a screaming good deal!
I've messed with those units and the BMS/charge controller is a common flat 8 wiring connector.

Rack mount makes them stupid portable.
Park an inverter on top the rack box and you have an entirely portable 13 kWh whole house backup system!


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## JeepHammer (May 12, 2015)

This summer we socked in a solar system for my niece & her husband, and it was about 90% used stuff.
Panels from government building remodel bought at auction, along with grid intertie inverter.

I told him to spend his money on insulating the old (50s) house and sealing up air leaks, all new thermal windows, doors, sealed every crack, blew insulation into the walls and ceiling...
So he & his friends did their part, about $7,000 in materials costs.

The panel mounts cost more than the solar panels & other random crap did, they have about 10kWh of backup and all they have been paying since the install/net metering is the $58 line connection fee.
0*F to 30*F weather last year was costing up to $1,300 a month, and they were using a wood burner part time...

I'm REAL interested in seeing how that 'Used' system performs in short winter days. It's over paneled for that very reason, and in our state it's net meter only, the rural electric doesn't pay for any excess production.
If it goes like I think it will, they can go off grid after the winter.

He's already used the backup two or three times, once for two days since rural electric is slow about fixing anything.
We already planted the wiring to increase system size by another 1/3 and the posts for panels are already installed waiting on another panel deal.
He's got a backup inverter installed (since they were used & cheap) and all I had to do was locate the backup switches, since it was grid intertie they weren't ordered with the backup switches, I have to assume what ever government building they came off of didn't have a generator.
About $40 each for the switches and 15 minutes to install.

The next round of LiFePo4 batteries we are going to bump up reserve also. 
At surplus/scrap prices it's stupid to pay the idiotic prices they do...


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