Panel/array size vs battery bank & daytime only loads?

[georgerc]

lets try and stay on topic, this concept interests me,

the downside I can see is that 60A controller, likely the first time you power up that system something will go wrong.
,
I know what you are trying to accomplish but with a 60 amp controller it would get complicated.

say for example you size your battery needs to your overnight consumption needs, we'll assume you end up with a 48v bank ( this will make sense in a minute ) that can handle a 20A charge/discharge current and you go with a cheap 20A controller, and we'll say you slightly oversize the array, this will result in leaving some power on the roof, but 1 hour before solar noon on a really nice day you start running that 1000w saw, on and off making some cuts, that amounts to just about 48v at 20A, I rounded things up and didn't take into account losses and such, but for the brief seconds you run that saw the batteries wont take a charge, some will call it micro cycling or interrupted charge, but it should work for you if you size things just right,

on an ugly day you don't woodwork and your slightly oversized array still charges up your batteries some, for what you are trying to do you may be overthinking it, start with your overnight load, and work everything up from there, pick the winter solstice, throw an extra panel in there and if on a nice day you end up leaving some watts on the roof, oh well.

good luck and make sure you report back

[SunEagle]

This is extremely funny. How many years does it take to be so STUPID and IGNORANT. He does not even know the very basic fundamental Ohm's Law and the relationship of voltage current, power, and resistance. Ohm's Law is week one of any electrical course pounding it into the students head by working thouseands of equations. Fail that test at the end of the week and you are gone. He failed that very simple test.

But I followed exactly what the guy did in his YouTube video so it must be right.

[Sunking]

This is extremely funny. How many years does it take to be so STUPID and IGNORANT. He does not even know the very basic fundamental Ohm's Law and the relationship of voltage current, power, and resistance. Ohm's Law is week one of any electrical course pounding it into the students head by working thouseands of equations. Fail that test at the end of the week and you are gone. He failed that very simple test.

[littleharbor]

my panels are individually switched .. i know what im doing, i may be an as, but an aviation electrician as lol ... you want to know the 'real' truth of all this bs? the 'experts' here spent mega bucks on factory panels with inefficient cells that shut off at the tiniest little cloud .. THATS why they need high voltage and mppt chargers to make those '4' high dollar panels with crap cells actually charge their bank of 50 batteries haha .. thats something their smartas rears would know if they ever built their own panels with 'ebay' cells .. if you research you'll find you can get efficient cells that put out great even on a cloudy day, factory packed AND sealed .. theyre just factory blems .. guarantee theyre about 5X better than the ones in their old high dollar bs panels .. but no .. theyre going to tell me how it is and what works .. from my perspective its a joke lol ...

Please remind me to stay off any plane you have worked on. You truly don't know what you are talking about.

[SunEagle]

But I will ask you to post a comparison of your DIY panels power when new, and in 3 short years. That's what gets my attention, panels that work after 3 years.

Or don't work at all after one year in the rain.

[Mike90250]

my panels are individually switched .. i know what im doing, i may be an as, but an aviation electrician as lol ... you want to know the 'real' truth of all this bs? the 'experts' here spent mega bucks on factory panels with inefficient cells that shut off at the tiniest little cloud .. THATS why they need high voltage and mppt chargers to make those '4' high dollar panels with crap cells actually charge their bank of 50 batteries haha .. thats something their smartas rears would know if they ever built their own panels with 'ebay' cells .. if you research you'll find you can get efficient cells that put out great even on a cloudy day, factory packed AND sealed .. theyre just factory blems .. guarantee theyre about 5X better than the ones in their old high dollar bs panels .. but no .. theyre going to tell me how it is and what works .. from my perspective its a joke lol ...

So, for neophytes, I'm going to dissect this grossly erroneous post.
While I'm sure the originator means well, and thinks his cells outperform cells in 25year warranty panels, we'll see it isn't so.

Aviation is Never wrong,
Until they are: https://www.scientificamerican.com/a...he-dreamliner/

Inefficient cells that shut off at the tiniest little cloud.
Let's see a cell that does not drop power when Light Levels drop. Mfg & model. We never had NASA spec any for use, to use on their spacecraft.

THATS why they need high voltage and mppt chargers to make those '4' high dollar panels with crap cells actually charge their bank of 50 batteries
NO, I run 160V @ 12A because the wire is cheaper for 150' of #8 wire. Feel free to continue to buy 20V wire that can handle 100A from the PV array,
I can't afford the wire, let alone lift it, to install it into 150' of 4" conduit. And it's a 40 battery bank, not 50. All in series, no nasty parallel paths.

if you research you'll find you can get efficient cells that put out great even on a cloudy day, factory packed AND sealed .. theyre just factory blems .
Actually, my panels ARE factory blems, but electrically good. The "Floor Sweepings" sold on flea bay have failed one of about 50 electrical tests, Some of those tests are designed to prevent fires (reverse leakage) and only a couple of those tests could be performed in a modest electronics hobby garage shop. Most of the sweepings have not had the edge anneal process done, so in a couple years, they will crack apart all on their own, have fun,

but no .. theyre going to tell me how it is and what works .. from my perspective its a joke
No, I'm not going to tell you anything, I'm going to tell the neophytes what I've found to actually work, and you can follow your own light. But I will ask you to post a comparison of your DIY panels power when new, and in 3 short years. That's what gets my attention, panels that work after 3 years.

[ButchDeal]

they ever built their own panels with 'ebay' cells .. if you research you'll find you can get efficient cells that put out great even on a cloudy day, factory packed AND sealed .. theyre just factory blems .. guarantee theyre about 5X better than the ones in their old high dollar bs panels .. but no .. theyre going to tell me how it is and what works .. from my perspective its a joke lol ...

You know that those factory blemish BS cells you bought on Flebay are exactly the same as the ones in the commercial PV modules EXCEPT that yours failed the tests on the line.
Not blemish tests but performance tests. So there is no way your cells will outperform by 5X ones that passed the tests.

[jflorey2]

my panels are individually switched

Ah. So more wiring and more switches. Higher cost, more losses and lower reliability.

i know what im doing

Funny how everyone says that.

you want to know the 'real' truth of all this bs? the 'experts' here spent mega bucks on factory panels with inefficient cells that shut off at the tiniest little cloud .. THATS why they need high voltage and mppt chargers to make those '4' high dollar panels with crap cells actually charge their bank of 50 batteries haha .. thats something their smartas rears would know if they ever built their own panels with 'ebay' cells .. if you research you'll find you can get efficient cells that put out great even on a cloudy day, factory packed AND sealed .. theyre just factory blems .. guarantee theyre about 5X better than the ones in their old high dollar bs panels .. but no .. theyre going to tell me how it is and what works .. from my perspective its a joke lol ...

Would you trust a car mechanic to rewire an aircraft you were responsible for? But hey, he knows a MUCH cheaper way to wire an ARINC bus!

[badley]

Because you are about to add ~120 amps of current to an already "sizable" (240 amp?) system, perhaps?

You might want to "change things" to prevent a fire when that battery sees 360 amps going through a single terminal. Or not; some people have to learn through experience.

my panels are individually switched .. i know what im doing, i may be an as, but an aviation electrician as lol ... you want to know the 'real' truth of all this bs? the 'experts' here spent mega bucks on factory panels with inefficient cells that shut off at the tiniest little cloud .. THATS why they need high voltage and mppt chargers to make those '4' high dollar panels with crap cells actually charge their bank of 50 batteries haha .. thats something their smartas rears would know if they ever built their own panels with 'ebay' cells .. if you research you'll find you can get efficient cells that put out great even on a cloudy day, factory packed AND sealed .. theyre just factory blems .. guarantee theyre about 5X better than the ones in their old high dollar bs panels .. but no .. theyre going to tell me how it is and what works .. from my perspective its a joke lol ...

[jflorey2]

i have a sizable 12v system ive been using for ~6 years and im in the process of adding 12 more panels and 2 more C60's to have more overhead simply to do it because it does work so good and i love it . . . explain to me why i need to change things ...

Because you are about to add ~120 amps of current to an already "sizable" (240 amp?) system, perhaps?

You might want to "change things" to prevent a fire when that battery sees 360 amps going through a single terminal. Or not; some people have to learn through experience.

[Sunking]

well i can agree with you on not wasting my time lol .. i have a sizable 12v system ive been using for ~6 years and im in the process of adding 12 more panels and 2 more C60's to have more overhead simply to do it because it does work so good and i love it .. ..

I rest my case, you just proved are a bigger fool than I or anyone else thought. If you only know how much money you have wasted would make you very angry. Fools and their money soon part ways.

Like I said you have no biz answering any questions. You have no clue what you are doing or talking about.

[badley]

I second that. He has absolutely no understanding of Day 1 student Ohm's Law. Badley you should not be answering any questions and your flawed opinions show how foolish you are. You do not understand the fundamentals or basics.

well i can agree with you on not wasting my time lol .. i have a sizable 12v system ive been using for ~6 years and im in the process of adding 12 more panels and 2 more C60's to have more overhead simply to do it because it does work so good and i love it .. its been in operation and seen me through several multiple day power outages in storms ect so i have 'some' idea of what works and what i want, like a better way to take care of batteries which i worked out, but telling you isnt going to happen because i 'dont know what im talking about' lol, ya know, ... if you could explain to me why i need to go mppt and high voltage on a system that works great and powers about anything during the day im all ears .. explain to me why i need to change things ...

[jflorey2]

i understand the logic in designing an 'efficient' system and for small ones hey why not ... theres alot of misinformation about what works though, and a large array of panels on a well set up 12v system does fine

Small array? Definitely. Large array? No, it doesn't.

Let's take a typical large array - a 10kw solar system. At 12 volts that's 833 amps. There are no commonly available battery terminals that exist that can handle that current.

Now let's downsize it to a smaller 1kwh solar system. At 12 volts that's 83 amps. That's doable. And if your inverter doesn't draw more than 1kW (with an occasional surge to 2kW) then that can work too.

the 'mppt vs pwm' debate though irks me .. you dont need mppt OR high voltage to make a high output system, what does it do? save you money? increase your 'real output? make your batts last longer?

Yes, yes and no.

It saves money since you can buy cheaper HV panels. It increases your output by using the entire output of your panels, not just the battery voltage times Impp. It does not make your batteries last longer; things like keeping them at a high state of charge and not cycling them too hard are what matters there.

the system just needs to be designed well if its 12v larger wires ect

The hardware does not exist to go that "large" on wires within solar power systems.

. i wouldnt try saving on wire when you have thousands in panel, inverter, batts ect even if its high voltage .. thats ignorant lol ..

Personally I think spending money you don't need to on 12V panels, multiple charge controllers and multiple battery banks is more ignorant. Why not save money by buying cheaper HV panels, save money by not having to buy multiple controllers and save money on thinner wire?

[Sunking]

You have no clue what you are talking about.

I second that. He has absolutely no understanding of Day 1 student Ohm's Law. Badley you should not be answering any questions and your flawed opinions show how foolish you are. You do not understand the fundamentals or basics.

[badley]

That is not required. A charged up battery does not charge or accept current. The battery voltage will be equal to the charger voltage, thus no current.

in the morning though it will bang them if you got 24 panels smiling at them lol ..

Well, I disagree with your opinion. Many factors get decided when designing a system. One is the decision from PWM to MPPT, and another is efficiency and Voltage

i understand the logic in designing an 'efficient' system and for small ones hey why not ... theres alot of misinformation about what works though, and a large array of panels on a well set up 12v system does fine .. too many people try to rely on battery in a solar setup imo, but also i realize theres many applications for solar .. the 'mppt vs pwm' debate though irks me .. you dont need mppt OR high voltage to make a high output system, what does it do? save you money? increase your 'real output? make your batts last longer? .. i think its 'NO" in all cases by the time you get down to putting that 500w load on 'X' amount of 20 hour capacity .. the system just needs to be designed well if its 12v larger wires ect .. i wouldnt try saving on wire when you have thousands in panel, inverter, batts ect even if its high voltage .. thats ignorant lol .. all my opinion of course .. sorry so long ...