why battery voltage drop much at bigining ?

[SunEagle]

thanks mike but sorry I didn't understand this last part .
and why I can't go more than 2kw inverter ( if I increase panels and batteries )?

If you do the calculations you will find that a 2000 watt inverter at 24V can draw over 80 amps (2000w / 24V = 83.3A).

If you go with a bigger inverter you can easily exceed 100 amps which starts to get dangerous.

At 3000 watts & 24V you get 125 amps so going to 48v is safer for you and your system wiring.

[zolar]

Your panels can be wired for it, you are planning on the batteries for it, and the charge controller drops to a 20A requirement,

thanks mike but sorry I didn't understand this last part .
and why I can't go more than 2kw inverter ( if I increase panels and batteries )?

[Mike90250]

4, 320w panels can harvest 1200w , so for a 24V system, you need a charger rated for 40A.

If you have 400ah of batteries, you need at least 40A

With a 24V system, you should not plan on more than a 2kw inverter. If you want 3Kw, go for a 48V system. Your panels can be wired for it, you are planning on the batteries for it, and the charge controller drops to a 20A requirement,

[zolar]

thanks mike and nice hear from you again in this topic, and thanks a lot matrix for your reply,
but when I asked about the charger 60 amps before , its nothing to do with my old system.
I attend to build another system of 24v , already I bought 4 panels each 24v and 320watt and I bought another 2 batteries each 12v and 200amh I will connect them serial ( going to buy another 2 to increase the bank capacity connect them both serial then parallel with old 2 ).
now about inverter i attend to buy 3kw just for future load increase ( no brand in mind till now ) , at begining I bought hybrid ( mustsolar brand ) but after I read some negative comments about the hybrid system, so I returned it back , that's why now I am asking about charger , and about my using don't worry cuz I am just practicing and when i increase my system i will need only to buy more panels and batteries ( no need to change the charger and inverter unless i exceed the limit of amps ), but I think I will start with 300 watts daily 6hours

[Matrix]

Mike I believe he said that was for 8 hours. I went on the assumption that once the lights went off that was it for the day bc that's all the load he listed. But there could be more. And inverter idle use was also not factored, that could be another 600 to 2400 Watts per day .

[Mike90250]

If you like buying a small MPPT charger. and buying up to a larger one, and then replacing it because it broke, just start buying stuff.

But if you calculate out what your power needs are, what size and voltage the battery bank will be , and how much solar PV you will use, then we can advise you on a charge controller.
Sadly, solar PV systems are un-forgiving, they are hard to scale up, and yesterdays parts won't play well with tomorrows gear.

4800 Wh requirement - is that for a 24 hour period, or is 3 days already calculated into that ? I can't guess as to what your inputs to the calculator were.

[zolar]

mppt 3.pngmppt4.png thanks a lot J.P.M.
thanks a lot matrix , about my panel they are fitted in clean and clear place not even a cable shadow but as you said may be the orientation , and speaking about mppt I am going to buy one and thinking to start with ( makeskyblue 60 amp ) tell I increase my system I've read and seen some videos about it . I wonder if you can give me your openion about these 3 mppt charger plz.

mppt 1.png sorry I don't know how the pics comes that way , not in same line at end of the post

[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.

[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").

[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.]

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]

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 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.

[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.

[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.