why battery voltage drop much at bigining ?

[zolar]

hi all,,,
having 12v system consist of::: , 2x batteries 12v and 200amh each connected parallel ( means 12v with 400amp output ) charged by.. 1- sun yoba L60 charge controller as 60amp ( its not MPPT but equal to MPPT as written in catalog of the device ), and 3x panels of 200w each. connected parallel also , suppling 600w ( group of lights ), after sunset for about 8hours. all items in system new only 2 weeks ago connected. and having sun 8hours ~ 9hours daily , but I calculated as 7 hours when I build my system to be sure.

the problem is directly after the lights comes on the capacity of the batteries bank drop Significantly from 100% to 85% then keep reducing then Stabilizes at 81% , but after that it goes slowly to 50% for all 8 hours , is it normal or there is something weird .
btw I see the reading in the charger display ,
I am thinking that the charger reading not correct ( I mean either the batteris not fully charged or they are fully charged but the drop not correct ). any comments plz?

[SunEagle]

For a 400Ah battery bank you need about 40 amps of charging. Depending on what those 200 watt panels produce and how well they are aimed at the sun will determine you best charging ability.

As for the amount of useful sun hours I seriously doubt you get more than 5 hours so you can forget about any calculations using 7 hours a day.

[Sunking]

all items in system new only 2 weeks ago connected. and having sun 8hours ~ 9hours daily , but I calculated as 7 hours when I build my system to be sure.

You do not receive anywhere near 7, 8, or 9 sun hours in a day. Where did you come up with that nonsense? No place on earth receives that much sun. Well maybe here in Panama near the equator at high elevations on a mountain with freezing temps might touch 7 hours 1 or 2 days out of the year. . This is winter months and your Sun Hours are down to 2 or 3 Sun Hours. If you designed at 7, 8, or 9 Sun Hours will fail because that means you only have 1/3 the power you thought and your system will fail. First thing you will notice is your batteries keep getting lower and lower each day until dead because they are never recharged.

You cannot determine SOC by voltage on a working system. Only way to measure SOC on a working system is with a battery hydrometer.

Bottom line is you design for worse case. If you fail to do that, then you planned to fail. You used make believe fantasy numbers.

[zolar]

hi sunking ,, thanks for reply ,
first what is SOC please .
and actual sun hours daily now more than that , I am not living on mountain , I am living about sea level , sea only 400 meters from my house although I don't go to sea, and sunrise here 6:20 am and sunset 5:35 pm, and that's I think more even than 10 hours,and at summer more hours by the way,,
but as I said I calculate 7 hours to make sure that the sun mostly vertically to the panels , and I can be sure they have good sun shine.
and my batteries are GEL and sealed , I don't think I can use hydrometer also they are brand new.
but what you think ?::::: 3 panels of 200watt each can recharge the 400 amps in aday? putting in mind they are 50% discharged only...
according to my hours time I mentioned? or you think I have to add more panels?

[Sunking]

first what is SOC please .

State of Charge voltages you are expressing as 100 to 85%.

I am living about sea level , sea only 400 meters from my house although I don't go to sea, and sunrise here 6:20 am and sunset 5:35 pm, and that's I think more even than 10 hours,and at summer more hours by the way,,

That has nothing to do with Sun Hours. You are making a huge DIY mistake. You are associating daylight hours with Sun Hours. They are not the same thing. A panel never ever generates its rated power. At best for a few minutes around noon a panel might generate 90% of its rate power. If you look at the output of a panel is a Bell Curve. At first light the panel will generate 2 to 3% of rated power. As the day progresses power slowly rises and peaks at Solar Noon, then immediately starts to taper down till sunset.

So if you had say a 1000 watt panel operating into the grid where all power is harvested and utilized over the course of the day in Summer you may see 5500 watt hours produced. That would mean you had 5500 watt hours / 1000 watts = 5.5 Sun Hours despite having 14 hours of day light. In winter that can go down to 2000 watt hours or 2 Sun Hours. In that example you design for worse case winter 2 Sun Hours. You are using make believe numbers that are not based on reality.

Where are you located so I can look up your solar insolation numbers?

[zolar]

when I said the time of sunrise and sunset only to tell you the day time but as I said i calculated the good sun shine as 7 hours just to be sure of sun hours for my panel
and sorry bro didn't understand much for last reply , but I am in united arab emirates close to abudhabi the capital

[Matrix]

hi sunking ,, thanks for reply ,
first what is SOC please .

Hi Zolar, Welcome to the forum. You are getting advice from some folks that really know (not including myself). Listen and Learn. SOC = State of Charge.

Also, to help you get your head around things, it might be helpful to do some load calculations for your daily need of Watt Hours (not watts). It is irrelevant to say "I have a coffee pot that uses 1200w" or "I plan to use 4 12w LEDs". Only you can determine how many Hours per day each of the devices attached to your system will run in a 24 hour period. That is the only way to determine:
- how large a battery bank you need
- The size inverter you need
- And the number of panels to provide the needed Amps to recharge those batteries as fast as possible when you have sun

You really need to do the work of Load Calculation so that you will know what your are demanding and what size system you need to avoid discharging more that 50% per day.

Where do you live? This will determine how much sun isolation you get each day. As SK said, it has nothing to do with the time from sunrise to sunset.

Here are 2 really helpful tools to help you get your head around your daily Loads (needs) and basic off grid system design. Look up the tools "Load Calculator" and the "Off Grid Calculator" at a place called the ALTE Store online - Both are very basic, but helpful in grasping the simplest of basic design. It will help you see visually want SunKing is saying. Simply Google search "alte store calculators" and you will find these calculators.

But as to sun hours for solar, here is a very basic chart ...

Solar Isolation Chart.JPG

[Matrix]

You are in the 5.0 - 5.9 part of the world. That is just the way that it is. 7 is never going to happen. The map above shows what you need to plan for.

[Matrix]

suppling 600w ( group of lights ), after sunset for about 8hours

Am I reading this correctly? You are running 600 watts of light for 8 hours a day? That is some huge lights. And that would call for a much larger off grid system than you currently have. That is 600w x 8 hrs = 4800 Watt Hours per day.

400ah of battery x 12v system = 4800 Watt Hours. So your batteries can only provide 1/2 of your need discharged to 50%. Your system is too small. But Perhaps I am misunderstanding what you are meaning in your opening post.

[J.P.M.]

hi all,,,
having 12v system consist of::: , 2x batteries 12v and 200amh each connected parallel ( means 12v with 400amp output ) charged by.. 1- sun yoba L60 charge controller as 60amp ( its not MPPT but equal to MPPT as written in catalog of the device ), and 3x panels of 200w each. connected parallel also , suppling 600w ( group of lights ), after sunset for about 8hours. all items in system new only 2 weeks ago connected. and having sun 8hours ~ 9hours daily , but I calculated as 7 hours when I build my system to be sure.

the problem is directly after the lights comes on the capacity of the batteries bank drop Significantly from 100% to 85% then keep reducing then Stabilizes at 81% , but after that it goes slowly to 50% for all 8 hours , is it normal or there is something weird .
btw I see the reading in the charger display ,
I am thinking that the charger reading not correct ( I mean either the batteris not fully charged or they are fully charged but the drop not correct ). any comments plz?

You have fallen for/into the common and needless trap of confusion brought about with the use of the term "sun hours".

Because the sun may be above the horizon for, say, 12 hours per 24 hr. day, that does NOT equate to 12 "sun hours" for that day.

The term "sun hours" is stupid, confusing and anachronistic. You need to think and understand a few things about the availability of the solar resource, beginning with getting rid of the term "sun hours". It only causes confusion - as you are now experiencing.

Begin by understanding that 1 "sun hour" is commonly interpreted to mean that 1,000 Wh of radiant energy from the sun will fall on a horizontal surface with an area of 1 m^2.

Then, stop using it and while doing do, also welcome yourself to the 20th and 21st century.

It's an anachronism whose time and usefulness has come and gone - if such usefulness ever existed in the first place compared to the confusion it caused and continues to cause.

Part of the problem is that that interpretation says nothing about how long it took for that 1,000 Wh to accumulate.

So, for example, if the sun were to be above the horizon for 12 hrs. at some location on some day near the equinox, but that day had solid cloud cover at that location, the total irradiance on a horizontal surface for the whole of those 12 daylight hours might be something like 600 Wh/m^2, which, by common interpretation might be [(600Wh/m^2) per day]/[1,000 Wh/sun hour] = 0.6 sun hours/day. Calling that 0.6 kWh/m^2/day rather than 06 "sun hours" avoids any confusion about how long it took for the 0.6 kWh of energy to arrive. Still not a complete description of the insolation situation for that day in question, but better, more useful and above all, less confusing that "sun hours".

Nor does the term "sun hours" say anything about how much insolation is received by a (usually) flat surface that is inclined at some angle to the horizontal, and also oriented at some azimuth that is probably not equator facing. The term has some use mostly in comparing different locations for relative suitability for energy production from solar energy. Without more information about equipment, location, device orientation and other things, the term "sun hours" is mostly and otherwise useless and as seen here, confusing.

One easy way to avoid the confusion often and commonly brought about by the use of the term "sun hours" is to not use it. A much less confusing and more technically useful term used by serious solar designers is " kilowatt-hours per m^2" per day. At least the use of kWh/m^2 has some useful and identifiable units and is less confusing as your confusion serves as a common and obvious example.

That term - kWh/m^2 per day - is still not as good or as complete as the idea of "clearness index", which is easier to understand and explain, and is the accepted standard when talking about suitability comparisons among various areas or sites with respect to solar resource availability.

The clearness index is simply the ratio of insolation on an unshaded horizontal surface on the ground at a location on the earth to the insolation over the same time period on a surface parallel to the other one (the one on the ground) but at a point just above the earth's atmosphere (say 100 miles above the earths' surface). The clearness index can be and is given as any period of time - hour, day, month, year, or any length of time.

At the end of the day, to get a serious handle on system design, none of the three concepts discussed here - Sun hours, kWh/m^2 per day, or clearness index are sufficient in and of themselves for system design. They are pretty much limited to comparing relative solar potential between or among various sites or locations or at different point in time - little more than that.

Of the three, the clearness index is the most straightforward, easiest to understand, and the one serious solar designers and reseachers use.

"Sun hours" is, as continues to be demonstrated, the most confusing and probably the most useful at leading the solar ignorant to easily reached, bad assumptions and conclusions. Your confusion is the latest but probably a textbook example of how the term "sun hours" can waste time, lead people astray and into bad conclusions and design.

It's a B.S. term that needs to be dropped.

[zolar]

hi again,,,
great thanks matrix and J.P.M.
I start with J.P.M. cuz only shortly ,,,, believe it or not brother I got confused much after I read your reply (read it about 3 times ) , BUT, BUT, BUT, great thanks for reply and explaination for me and some others like me . your time to read my topic and replying really appreciated

matrix I did calculated total watt hours as I said its group of lights ( 60 led light each 10watts around the house outside ) and cuz they start 6pm till 2am after midnight is 8 hours
I do calculated 4800wh , and I know that altestore site , I used to use their off grid calculater but didn't care about the map , I WILL FROM NOW ON ,
but now here some questions plz :
A. do you think I am discharging my batteris more than 50% ?
B. do you think I need more than 3 panels each 200w ?
C. is it right to know output current from my panel dividing watt by voltage ( 200 / 12 )? if its like that ,,, then I have problem cuz when I read the amps in the charger 1 by1 ( I mean every time I read 1 panel separately ) I have 8amps in panel number1 , and 4amps in panel number 2 , and 4amps in panel number 3 .
D. if you don't mind show me how to calculate manually ( mathmaticlly) the panel needed for 400amh batteries , cuz I used altestore site calculator and renogy site calculator and there is difference between both.

[J.P.M.]

hi again,,,
great thanks matrix and J.P.M.
I start with J.P.M. cuz only shortly ,,,, believe it or not brother I got confused much after I read your reply (read it about 3 times ) , BUT, BUT, BUT, great thanks for reply and explaination for me and some others like me . your time to read my topic and replying really appreciated

I have been accused (with a lot of justification at times) of overexplaining stuff. I often add "Take what you want. Scrap the rest" to the end of my written spoor for that reason.

Summary: Scrap the term "sun hours". It only causes more confusion. Instead, use kWh/m^2 per day in its place, and then get more informed about solar availability and how to determine it. Your designs will be better and you'll waste less time in a confused state.

[zolar]

no brother J.P.M. ,, you really done veeery well to explain but , its me that I couldn't understand , I really appreciated your time and what you wrote and as I said even if I didn't understand ( may be cuz of my mind lvl about solar comparing to your as an expert ) I am sure some 1 who will read , he will get it and will be helpful for him
plz don't get upset ,,, but really I am new to solar and most of terms I don't understand them , our electricity here is ok we have no problem , also prices low but I wanted to do my own project and when I do something I like to do it perfect and knowing what I did and why. not only buying items and do connection , so what you wrote is a base that I must depend on it to go ahead. thanks again brother, but if you can answer any of questions I wrote plz?

[J.P.M.]

no brother J.P.M. ,, you really done veeery well to explain but , its me that I couldn't understand , I really appreciated your time and what you wrote and as I said even if I didn't understand ( may be cuz of my mind lvl about solar comparing to your as an expert ) I am sure some 1 who will read , he will get it and will be helpful for him
plz don't get upset ,,, but really I am new to solar and most of terms I don't understand them , our electricity here is ok we have no problem , also prices low but I wanted to do my own project and when I do something I like to do it perfect and knowing what I did and why. not only buying items and do connection , so what you wrote is a base that I must depend on it to go ahead. thanks again brother, but if you can answer any of questions I wrote plz?

I honestly and sincerely believe you, or most anyone on this planet, can understand anything you choose to understand and indeed master provided you apply yourself and persist in the quest, and also that the material is presented and explained in a way that you can understand.

My explanations often lack the elegance of brevity often necessary for true clarity which is one of many the reasons I'm not a good teacher.

BTW, I usually write to the larger audience as well as the OP, keeping in mind that others may read any particular post - not just the original poster (the "OP").

[Matrix]

I do calculated 4800wh , and I know that altestore site , I used to use their off grid calculater but didn't care about the map , I WILL FROM NOW ON ,

Yes i saw from your other thread on this forum that you had used the AltE Store Calcs. It is a good and quick little calc. I based most of my whole system design from it, long before i found this forum. My daily Watt hour needs are 3400 and my system has performed flawlessly for a year - thanks in part to the tireless help of many here on this forum and other forums. But my system is MUCH larger than yours.

As to your questions, I am not qualified to give you a serious answer, especially based on the limited info you have provided about your total system design. But in general I would say ...

A. do you think I am discharging my batteris more than 50% ?

Yes. And for a 4800 Watt hour need you probably need a much larger battery bank. Somewhere close to 1000Ah. And when we get into system this large, it would be best to get away from 12v system. I would do 24v at a min and would not hesitate to jump up to 48v

B. do you think I need more than 3 panels each 200w ?

Yes, According to the calculator you need at least 7 at 200w. But how do you have your present panels wired? I think you would also benefit from a true MPPT controller

C. is it right to know output current from my panel dividing watt by voltage ( 200 / 12 )? if its like that ,,, then I have problem cuz when I read the amps in the charger 1 by1 ( I mean every time I read 1 panel separately ) I have 8amps in panel number1 , and 4amps in panel number 2 , and 4amps in panel number 3 .

That could be the orientation of each panel and how it is being effected by shading, a leaf, a shadow from a power line or vent pipe, etc. hard to say without knowing your full setup and install specifics.

D. if you don't mind show me how to calculate manually ( mathmaticlly) the panel needed for 400amh batteries , cuz I used altestore site calculator and renogy site calculator and there is difference between both.

Over my pay grade. This for the likes of SunKing, J.P.M., Mike etc.

Everything I have told you here is just generalities and best guesses. There are definite ways to answer every one of your questions, but with out knowing specifics it is hard to say, and I would hate to see you just keep throwing money into a never ending pit. It is best to design good first and then spend once.