Limiting Solar Charge Current from the Charge Controller

[SunEagle]

I am tired of the pissing match. This thread is closed

[Sunking]

You're saying I have some 400% higher efficiency loss solely because I have an all parallel set up which is totally untrue. You say 2% loss is great yet I'm only at 1%. loss in my wiring. You speak as if you don't know how long my wires are yet I've already told you. You haven't read my post thoroughly enough.

OK so you do not know anything about basic electrical fundamentals. You just pretend to know what you are talking about. We run pretenders off here.

Power = I x I x R or I^2R

Even a 5th grader knows the rules of squares. If the current is 10 amps into .1 Ohms, you loose 10 watts. Increase the current to 20 amps and you loose 40 watts or 400% more smart guy.

if I was a moderator I'd screen every single one of your posts.

30,000 post and counting, I have been here longer than the owners and all but one moderator. You are done here, now quit embarrassing yourself.

[travissand]

4. I believe you when you say you learned what you know 30 years ago because you are stuck in the past with antiquated techniques and technology.

Really? You believe what I never said? You have a habit of doing that I can tell. And I can also tell that you don't read my post. You keep on jumping to conclusions. I thoroughly explained myself and why I did what I did and financially it makes sense in my unique case which is likely not to apply two others. Your systems you design have a cheaper price tag because in your mind you keep reverting to starting from scratch. In reality a lot of people you are trolling are not starting from scratch like that and they have a lot of considerations that you are not willing to take into account as proven here by your obsessive blindness.
You're saying I have some 400% higher efficiency loss solely because I have an all parallel set up which is totally untrue. You say 2% loss is great yet I'm only at 1%. loss in my wiring. You speak as if you don't know how long my wires are yet I've already told you. You haven't read my post thoroughly enough. Nor have you read Matrix post thoroughly.

Either you don't know how to compute percentages or you can't get it out of your head that we are not talking about doubling the battery voltage as well for the sake of this argument. Halving the current does not make a 400% difference. Halving the current is actually a 50% reduction in power loss. Doubling the current is a 250% increase.
You're are babbling about the Midnite sizing tool in ways that has absolutely nothing to do with what I said about their tool being in error. You didn't even use it to demonstrate what I was telling you did you? You really do have no idea what I'm talking about do you? You're absolutely wrong about the graphs and you are putting meaning into them that isn't there. You're reading them upside down or you have dyslexia. They clearly show I am right. You're ignoring direct quotes by midnight. You're wrong on your wild ideas that more greatly varying voltage difference between incoming panel voltage and battery volts is more energy efficient. Honestly I wouldn't mind paying a little extra to keep my charge controller cool and quiet like the one out of four that I actually put in an all parallel configuration for the sole purpose of proving it.
It's written all over the internet everywhere that I am correct. Everybody agrees the larger the conversion = the more heat = a less efficient charge controller. No one here is claiming it's the cheaper design to run extra thick wires and pay for more Breakers. You're barking up the wrong tree. I'm sure you've been called out on this before. I'm having a hard time trying to figure out if you are just a troll or honestly confused. You couldn't be a because I've seen you spend a lot of time providing very valuable advice.
You say you helped Matrix design his system then why is he on a 24 volt system? I'm sure he has a good reason.
And obviously he's not heeding your advice as much as your big head thinks. I asked Midnite tech support about these subjects and they agree with me and say the N A is an error. Your communication, comprehension, attitude and reading skills are so horrible that Im done talking to you and if I was a moderator I'd screen every single one of your posts.

[extrafu]

I have a classic 200, running 180V into it to charge a "48V" bank. With my array and fitting additional wires into conduit, I had to go with higher voltage to get lower amps, to use thinner wire. With a 2Kw array it runs fairly hot, however, ALL classics run fairly hot, they have 2 stages of fans, and the turbo fan speed is quite loud and annoying.

Hey Mike. Just for your information, I have 2 arrays of 3360W each, all panels in series - each going to its own Conext MPPT 600-80 CC with 10AWG. DC input is at around 420V at each CC. Each CC is very cool, the fan doesn't even start.

[Sunking]

We're not talking about a 24 volt system versus a 48 volt system. We all agree a 48 volt system is more efficient than a 24 in every way.
Yes I agree with your statement but that is not what we're talking about here. We're talking about for a 24v system what voltage incoming is the most efficient. Sun King is saying the higher the better with the only limit i assume being the high incoming voltage spec for the charge controller.. I am saying the closer to battery voltage the better.

Hate to do this to you, but you have asked for it so I am going to put you out of our misery and clearly show you are a fool and a hack who can only find work outside of the USA

1. You clearly stated you are running 6 panels in parallel. That would mean you would need a very expensive combiner with 6-fuse units and those cost a great deal of money. For 6 inputs with the fuses is going to run you $500. Multiply that by two identical arrays and you have wasted $1000 of your money. Now you compound that foolish mistake by now having to use 2 controllers another $700 waste of money and materials. Now smart money would use none of that. No Sir if it were me I would be using a 600-volt controller and wire the 12 panels 2S6P requiring no combiner, no fuses, and only using very inexpensive 14 AWG wire and save myself or my clients $1500.

2. Midnite Solar Calculator is a Spreadsheet and will work with any numbers you want to throw at it. Only thing it checks for is over wattage and voltage. Instead of using 39 volts Vmp @ 55.1 amps Imp you are running try a lower voltage = to battery charging voltage of 28.8 Vmp 74 amps Vmp. It worked right? Sure it did , bu tin practice would not work because in practice you need 36 volts minimum. With a 1 to 3 volt drop on the FET would make it a very inefficient (65%) PWM controller running @ 100% duty cycle. Again a ignorant foolish mistake.

3. Additionally running 1S6P as you are, requires you to use at least 6 AWG wire from the very expensive combiner which ?I doubt you used and makes you very dangerous on top of a fool. That will will only work up to 15-feet 1-way @ 3% voltage loss. Want 20 Feet and now up the wire size and cost to 4 AWG and now you have exceeded what the Classic Terminals can support. Smart money does not do that and knows if you cut the current in half, yeilds 400% More efficient transmission for a given size of wire. Run at least 2S3P and you can use much less expensive 10 AWG wire up to 30 feet 1-way @ 2% loss. I would go one step beyond that and use 12S1P into 48 volt battery with 14 AWG wire (4.6 amps) up to 350 feet @ less than 2% loss if needed. Not you as you prefer to waste money and resources with a lot of copper and unnecessary hardware.

4. I believe you when you say you learned what you know 30 years ago because you are stuck in the past with antiquated techniques and technology. It clearly shows because you are throwing away all the benefits of MPPT Controllers. MPPT Controllers allow you to run much higher voltages and efficiencies. Today with MPPT Controllers Input Wattage is limited by battery voltages.

12 volts up to 1000 watts
24 volts up to 2000 watts
48 volts up to 4000 watts.

6 x 355 watts = 2130 watts. Granted the Midnite Solar Classic 150 can do that, but you have 6 x 355 x 2 Controllers operating at a input voltage that is NOT APPLICABLE. Matters not if you like it or not, manufactures specs matter and you have completely ignored them which makes you an ignorant fool. All you have to do is look at two Charts Midnite Solar publishes for fools like you to see. Please note N/A = Not Applicable when you look at the charts. I am sure everyone else will understand what that means is not to operate at 12, or 24 volt battery @ less than 90 Vmp.

Midnite Solar Power Graphs
Midnite Solar Wattage vs Voltage Table

Happy New Year.

[Mike90250]

The specific voltage and losses will vary between brands of controllers, battery voltage requirements and length of PV HVDC cable run.

Midnight publishes 1.3x battery voltage, however My opinion is that would be the Bulk/Absorb Voltage, since that's where the most power is required. Float and EQ don't consume a lot of current.

I have a classic 200, running 180V into it to charge a "48V" bank. With my array and fitting additional wires into conduit, I had to go with higher voltage to get lower amps, to use thinner wire. With a 2Kw array it runs fairly hot, however, ALL classics run fairly hot, they have 2 stages of fans, and the turbo fan speed is quite loud and annoying.

[SunEagle]

We're not talking about a 24 volt system versus a 48 volt system. We all agree a 48 volt system is more efficient than a 24 in every way.
Yes I agree with your statement but that is not what we're talking about here. We're talking about for a 24v system what voltage incoming is the most efficient. Sun King is saying the higher the better with the only limit being the high incoming voltage spec for the charge controller.. I am saying the closer to battery voltage the better. I trust Midnite when they say it works best when the voltage is at least as high as 1.3 times the highest expected charging voltage. My test showed for a 24 volt system a incoming voltage of 40 was better than an incoming voltage of 80 in my climate with my weather type. Which is 4000 FT elevation temperature between 45 and 65 degrees day and night. Ocean views both sunrise and sunset. And mostly sunny to partly cloudy with little to no rain year round.
I originally was thinking putting 3 in series and taking huge advantage of the voltage conversion might even be able to charge off of really dim light. But the amount of amps coming from panels in that situation is so low it's dwarfed by the heat loss in the conversion. Solar panels are limited by their amps that's why a pwm system has such huge losses. On a pwm 24 volt System a 40 volt 9 amp panel would only put out battery voltage at 9 amps which is a huge loss of potential power versus a mppt system which would bring in 40 volts at 9 amps. Where the mppt takes the best Advantage is when the battery voltage varies. For example my 24 volt battery range is between 24 on up to 29. An mppt controller will very it's voltage conversion to put out the right amount of Volts for the situation. A pwm can't do that, a pwm simply connects and disconnects the panel there's no voltage conversion at all and no way to increase the amperage out higher than the amperage in. It's within this tiny range between 24 and 29 that an mppt gains the majority of its advantage in a 24 volt system.

I agree with what you state concerning PMW CC's. They waste a lot of wattage due to how they work (amps in = amps out).

Since I do not have hands on experience with any Midnite CC's I will bow to those with more experience. But based on what I have read concerning MPPT type CC's they work very well with an input voltage that if it stays below their max input rating yet can be much higher then the battery voltage they are charging.

Again the Midnite CC that you have may be different when it comes to input voltages but when you are discussing electrical circuits at any voltage the higher it is on the wires the lower the losses and higher the efficiency of the circuit..

[travissand]

In basic electrical circuitry the higher the voltage the more efficient a piece of equipment runs as long as you do not exceed the voltage rating.
.

We're not talking about a 24 volt system versus a 48 volt system. We all agree a 48 volt system is more efficient than a 24 in every way.
Yes I agree with your statement but that is not what we're talking about here. We're talking about for a 24v system what voltage incoming is the most efficient. Sun King is saying the higher the better with the only limit i assume being the high incoming voltage spec for the charge controller.. I am saying the closer to battery voltage the better.

I trust Midnite when they say it works best when the voltage is at least as high as 1.3 times the highest expected charging voltage. My test showed for a 24 volt system an incoming voltage of 40 was better than an incoming voltage of 80 in my climate with my weather type. Which is 4000 FT elevation temperature between 45 and 65 degrees day and night. Ocean views both sunrise and sunset. And mostly sunny to partly cloudy with little to no rain year round.

I originally was thinking putting 3 in series and taking huge advantage of the voltage conversion might even be able to charge off of really dim light. But the amount of amps coming from panels in that situation is so low it's negligible and it's dwarfed by the continuous heat loss in the larger conversion.
Solar panels are limited by their amps that's why a pwm system has such huge losses. On a pwm 24 volt System a 40 volt 9 amp panel would only put out battery voltage at 9 amps which is a huge loss of potential power versus a mppt system which would bring in 40 volts at 9 amps. Where the mppt takes the best Advantage is where the battery voltage varies. For example my 24 volt battery range is between 24 on up to 29. An mppt controller will very it's voltage conversion to put out the right amount of Volts for the situation. A pwm can't do that, a pwm simply connects and disconnects the panel there's no voltage conversion at all and no way to increase the amperage out higher than the amperage in. It's within this tiny range between 24 and 29 that an mppt gains the majority of its advantage in a 24 volt system. For some reason Midnite wants me to have at least 40 volt panels so that's what I have. Something about the way the buck converter operates requires this. Any higher than that and the charge controller gets unnecessarily warmer.

[SunEagle]

You know you have a lot of things understood but more you speak here in this thread less faith I have in you. Here's a quote straight from the Midnite webpage "With MPPT controllers the higher the input voltage the less efficient they are."

if you want to see for yourself go to the classic string sizing tool do a calculation and read the notes.

http://www.midnitesolar.com/sizingTool/

In basic electrical circuitry the higher the voltage the more efficient a piece of equipment runs as long as you do not exceed the voltage rating.

Now for Midnite they may have a lower voltage limit where they peak on efficiency but for most charge controllers that is not true.

So I hope you and Sunking can come to an agreement as to what voltage provides the highest efficiency because you are both correct yet are still arguing with each other.

[travissand]

The higher the input voltage, the more efficiency the controller is period.

I know you have a lot of things understood but more you speak here in this thread the less faith I have in you. Here's a quote straight from the Midnite webpage "With MPPT controllers the higher the input voltage the less efficient they are."

if you want to see for yourself go to the classic string sizing tool do a calculation and read the notes.

http://www.midnitesolar.com/sizingTool/

[travissand]

The order a solar system should be designed in is first the batteries according to your storage need.

then size the charge controller according to the batteries Requirements no skimping on this one..

Then after you've done all that make sure you get enough panels to satisfy the batteries requirements and if you can afford two or three times that requirement it will help you greatly on cloudy weeks. Of course greatly oversizing the panels only works with charge controllers that can deal with the oversized solar panels properly and if you really have that many extra Watts you may as well add another charge controller and dump power somewhere that saves you money

[travissand]

Complete nonsense and proves you do not know what you are talking about. All MPPT CC are Buck Converters and as such input current is always lower than output current, and input voltage must be higher than output. Putting more panels in series raises the Input Voltage and lowers the Input current. Output is unchanged. The higher the input voltage, the more efficiency the controller is period. That is why you use the manufactures efficiency tables to determine the sweet spot which you refuse to believe. That makes you a fool.

Why must you insist on me being a fool? I don't know why you think I don't know how a buck converter operates. You are jumping to conclusions again. Since you've been back you appear to be a different more angry person. You quote me when I say adding a 10th panel could push him over his Midnight's max? That's kind of what Matrix set himself. What does that have to do with your rebuttal?
To my knowledge Midnite says the higher the incoming voltage the lower the efficiency but they don't make a big deal of a negligible loss. If Matrix adds another panel as he quoted himself that would put his Midnite into amp limit mode.
I was quite clear and I'll reiterate adding a panel to a system increases the max amperage the controller can put out if you're still under its Max. With matrix's particular panel wattage The Sweet Spot was 9 panels and the calculator recommended 3 in series versus all in parallel. Midnight's calculator tool could be in error when it comes to parallel versus series parallel. This becomes obvious when you punch in the specs for a 40 volt panel on a 12-volt system and it still forces you to put some in series. Matrix was worried about the heat that's why I brought up what I learned with my experiment. I wonder if anyone's done any long-term temperature experiments to see how much life you actually shave off of the charge controller by running it hot but within spec?


It's okay for you to be completely ignorant to the fact that I have done the experiment and I know for myself what runs cooler and what puts out more power. I understand you aren't here measuring things yourself and that's okay. Why are are you preaching about input voltage must be higher than output voltage, obviously I'm bringing in 40 volts and putting out 24. Midnite recommends incoming voltage at 30% more then maximum expected charge voltage. So if I'm equalizing at 31 volts I need 40 volts in which is exactly what I have.

[Mike90250]

To clarify..... We should panel for Winter and then take panels offline in the Summer?

No, the controller just does not utilize the excess panel power - IF you have limited it to the design specs. Putting way too much panel (3x would be too much) into a controller, can cook even a well made MPPT when it reaches the limit of what it can throttle back.

[Sunking]

To clarify..... We should panel for Winter and then take panels offline in the Summer?

No, you size the panels for winter. In summer no changes, you just do not utilize the extra energy available or find ways to use it.

[PNW_Steve]

FWIW the way it is intended to limit charge current is panel wattage.

To clarify..... We should panel for Winter and then take panels offline in the Summer?