different watt panels, a few questions for the experts please

[inetdog]

MPPT = Multi Power Point Tracking. Gotta get the terminology right. Enjoy! Go Packers!

Actually it is Maximum Power Point Tracking, because the I versus V curve of the panel output will have one point which delivers the maximum power. That is called the Maximum Power Point, and the device tracks to always operate at that point as the panel I versus V curve varies with incoming light, temperature, etc. Hence (Maximum Power Point) Tracking.
The voltage at the current MPP is called V_MP and current is I_MP. The panel label gives those values assuming 1000W/sq. meter input and 25C temperature.

[Sunking]

I'm going to go with what has been the #1 suggested wiring schematic, the #2 example. Wire the 2x 50w in series, the 2x 100w in series and then both wired in parallel to the mppt controller.

The correct and only choice you have. Well Smart Choice anyway.

Thanx again for all your patience and help with this. My apologies for the frustration I must have induced.

No frustration on my part, glad to help those who really want to know, learn, and I am happy to answer all your questions. Go to the Off-Grid section and read STICKIES as it may help clear some of the Fog. When you have questions come on back now you hear?

[SprinterX]

MPPT = Multi Power Point Tracking. Gotta get the terminology right. Enjoy! Go Packers!

Oooppps, finger trouble. Corrected now. Go HAWKS

[littleharbor]

MPPT = Multi Power Point Tracking. Gotta get the terminology right. Enjoy! Go Packers!

[SprinterX]

I've read the replies over and over and over, trying to wrap my head around the theory. I think the fog is beginning to lift somewhat, but rather than continue to drive you guys mad with my grasshopper analogies I'm going to go with what has been the #1 suggested wiring schematic, the #2 example. Wire the 2x 50w in series, the 2x 100w in series and then both wired in parallel to the mppt controller.

Thanx again for all your patience and help with this. My apologies for the frustration I must have induced. Cheers boys and Happy New Year.

Best of luck against the Packers.

[Sunking]

I spent many hours yesterday researching the internet and youtube

You are welcome but you wasted hours on You Tube. Stop that. 90% of it is garbage from wannabes who know nothing.

In Example1 - the 2x 50w panels are wired in parallel to create one strand (18 Vpmax & 5.56A Ipmax). It is then wired in series with the other series wired 100w panels give a total 54 Vpmax & 5.56A Ipmax array.

From what I learned and what was written above I want to present the mppt controller with as much voltage as possible and let the CC do it's magic.

Here is your first mistake and has been explained a few times for you. You listened to John. When you put panels in series the voltage does add. However panel current is limited by the lowest panel current in the string. What is the 50 watt panel current? It is not 5.56 amps is it?. What are they? What did you come up with?

Did you answer something like 2.78 amps? Sure you did and that is the right answer. Watts = Voltage x Current. Now do a little math fun and take 2.8 amps x the 4 panels in series voltage. Hint I seriously doubt it is 54 volts. More like 72 volts. Look at the panel specs Vmp should be around 18 volts each right?. 13.5 volts would not charge a 12 volt battery. It takes at least 16 volts.

1) Doesn't paralleling the 2x 50w panels make them function the same as one of the 100w panels?

Yes but you are missing a very important point which I will make clear in a minute.

2) Doesn't this work the same as if I had 3x 100w panels all wired in series?

No Sir.

In Example 2 - the 2x 50w panels are wired in series to create one strand (36 Vpmax & 2.78A Ipmax ) . The 2x 100w panels are also wired in series to create a 2nd strand (36 Vpmax & 5.56A Ipmax). From there the two strands are wired in parallel to the CC.
1) Doesn't the differing amperage from the two strands cause problems at the Charge Controller with the result being a less efficient output to the batteries?

This is where I hope you light gets turned on and see. Back to what has been said already. With MPPT Output Current = Panel Input Wattage / Battery Voltage. That means Input Power = Output Power which is a great thing very efficient if conditions are met. It is the conditions you are missing and basic electrical fundamentals.

Example let's say you had 3 of the 100 watt panels in series. That gives you an voltage of 54 volts @ 5.56 amps. Do the math 54 volts x 5.56 amps = 300 watts every day of the week. In your Example #2 you have configured them as 2 x 2. So your 2 50 watt panel string produces 36 volts @ 2.78 amps (36 x 2.78 = 100 watts). Your 2-100 watt panels wired in series is 36 Volts @ 5.56 amps ( 23 x 5.56 = 200 watts).

Lights on time. For a MPPT with parallel strings each string shall have = Voltage because when you parallel solar panels, the panel or string of panels with the lowest voltage sets the voltage. So if you put a 100 volt panel in parallel with a 50 volt panel, your voltage is 50 volts and you just robbed yourself of 1/2 your power. Panels in parallel both Power and Current ADDS, and voltage remains the same. Now look above in your Example 2. 36 volts is equal in both strings, and the panel current adds so you end up with 36 volts @ 8.34 amps = what my friend?

36 volts x 8.34 amps = 300 watts all day long right?

Last light on the ole Xmas tree. Electric power is transmitted most effientlyu and economically at higher voltage. That is why electric utilities use high voltage up to 1 million volts. Remember Power = Volts x Amps. Amps are nasty, and if you lower your voltage, means current must go up at a given power level. Current = Power / Voltage. More math fun:

300 watts / 36 volts = 8.34 Amps all day long
300 watts / 54 volts = 5.56 amps all day long

More math fun.

300 watts / 150 volts = 1.5 amps all day long.

Why is lower current important? Because the higher the current is, requires larger more expensive wire, and current loses power along the length of of wire because wire has resistance. Power also = Current x Current x Resistance. Given that what happens if you increase current or resistance? Do the math on your own dime.

The only way to over come the losses with a lower voltage is use much larger more expensive wire. Best solution is to raise the voltage so you have less losses, and much smaller less expensive wire. Win Win with higher voltage. Low voltage is a LOSER. You have a 100 Voc MPPT Controller, which means you want to run panel voltage as high as you can, close to 100 volts as possible. However you are limited because you did not use matched panels. You only have one choice given what you have, 2 x 2 as in your Example 2. So quit wasting time and go with it. Quit watching You Tube.

Go Sea Hawks!!!!!!!

Speaking of Losers. Ganja is legal in Seattle and half the team is high. Go Cowgirls!!

[littleharbor]

Example #1, 54 volts@5,56 would work for either a 12 or 24 volt bank. MPPT controllers need higher voltages 150% or more than conventional PWM controllers. You can go higher, up to their limit and they still work although slightly less efficiently, (they get hotter).

Example # 2, 36 volts @8.34 amps would only work if charging a 12 volt bank. (which is what you are doing right?) . When you parallel wire the two strings here the amperage will simply add.

36 volts is the typical 24 volt battery charging voltage. Your batteries will clamp the incoming voltage to whatever they voltage they are at the time and will gradually rise as the charge. You still need higher available voltage from your array to "push" the amperage into your batteries. This allows for voltage losses in hot conditions while still being high enough to be able to equalize.

Either scenario will net you the virtually* the same amount of charging power with the MPPT controller doing the DC to DC conversion. * slightly less with higher voltage input .

[SprinterX]

Thank you Sunking, littleharbor. inetdog and mike90250 for your contribution to help me with my solar project. I spent many hours yesterday researching the internet and youtube to further understand the different aspects of what you presented. I still am a little confused on a couple things and hope you can see your way clear to offer up a little more clarification for me. The choice of these flexible panels was driven by their need to mount on top of a canvas bimini top on our boat.

I have drawn out two examples of how you thought I could wire up my panels.
Solar wiring example.jpg



In Example1 - the 2x 50w panels are wired in parallel to create one strand (18 Vpmax & 5.56A Ipmax). It is then wired in series with the other series wired 100w panels to give a total 54 Vpmax & 5.56A Ipmax array.
From what I learned and what was written above I want to present the mppt controller with as much voltage as possible and let the mppt circuitry do it's magic.
1) Doesn't paralleling the 2x 50w panels make them function the same as one of the 100w panels?
2) Doesn't this work the same as if I had 3x 100w panels all wired in series?

In Example 2 - the 2x 50w panels are wired in series to create one strand (36 Vpmax & 2.78A Ipmax ) . The 2x 100w panels are also wired in series to create a 2nd strand (36 Vpmax & 5.56A Ipmax). From there the two strands are wired in parallel to the CC.
1) Doesn't the differing amperage from the two strands cause problems at the Charge Controller with the result being a less efficient output to the batteries?

In Example 1 I'm producing a higher voltage (54 Vpmax) and equal amperage (5.56 Ipmax A) to the input of the mppt CC.
Where as in Example 2 I only deliver 36 Vpmax to the mppt CC and with differing amperages from the two strands.

Please correct me where I'm misunderstanding the theory or concept. I truly appreciate the help.

Go Sea Hawks!!!!!!!

[Sunking]

As a newbie to solar it made sense to me that the two 50w panels in parallel would retain their 12V rating but would sum up and accumulatively achieve the same amperage as the 100w panel. This would effectively make them equal to one of the 100w panels. From there I could wire the paralleled 50w panels in series with the two 100w panels. Again, I'm new to this..

As a Newb you made a lot of common mistakes. Not to worry though. Bottom line is it will cost you a more money than you needed to spend. Lucky for you not a lot of money lost. Example you chose to use very expensive battery panels, vs inexpensive grid tied panels.

The key is a PWM vs MPPT Controller, and using matched panels. Today any system 200 watts or larger should use higher voltage less expensive (1/2 the cost) higher voltage GRID tied panels with a MPPT controller. A 200 watt MPPT system = 300 watt PWM System in power generation. A 200 watt MPPT system cost less than a 300 watt PWM system. Not only that you could have bought a 300 watt GT panel and that would also save you a lot of money in hardware and materials.

OK with the panels you have assuming you have a Real MPPT Controller your best and smartest option is to wire the panels 2 x 2. Wire the two 50 watt panel in series, wire the two 100 watt panels in series, then connect both strings in parallel for 2 x 2. Any other option and you are screwed, So do not consider any other option as it is foolish like John suggested.

With MPPT you want to run panel voltage as high as possible. That means wiring as many panels in series as the Controller will allow you. Example if you had three of the 100 watt panels would allow you to wire all 3 in series. But to do that the panels Current Specs have to be the same because the lowest panel current rating dictates the maximum current a series string will pass. As Dave indicated if you put the 50 in series with the 100 wat panels can force them into bypass and burn them up. If it did not bypass, would result in turning you r100 watt panels into 50 watt panels.

With PWM Output Current = Input Current. Wire all your panels in series and current is limited to 2.9 amps (50 watt panels) in and out of the Controller. Do the math. 2.9 amps x 12 volt battery = 35 watts from your 300 watts of panels.

With MPPT assuming the panels are matched so power adds. Output Current = Panel Wattage / Battery Voltage. So with say three of your 100 watt panels in series input current is only 5.8 amps, however output current = 300 watts / 12 volts = 25 amps. Do the math again 25 amps x 12 volts = 300 watts, same as input power. Which is the larger number? 35 watts or 300 watts?

[littleharbor]

Both ways described here will work. The difference is with paralleling the two 50 watt panels first and series wiring them with the other series wired 100 watt panels you will end up with 54 Vmp @6.4 amps. If you go series 50 watt parallel with series 100 watt is you end up with 36 Vmp @9.6 amps. Your controller can handle either voltage and each is the same amount of power, BUT. 36 Vmp. is basically 24 volts nominal (think PWM) charging voltage and not what your MPPT controller wants to see when charging a 24 volt bank of batteries. 36 volts will work great for a 12 volt bank though and is actually a better voltage to use if charging at 12 volts.
After rereading back a few entries I see you are planning on going 12 volt for your fridge so Sunking's wiring method would be best, by a small margin because of a small loss of effiency at higher voltage through your MPPT controller. I hope this makes sense.
BTW, the parallel branch connecters will work in either scenario.


Littleharbor

[SprinterX]

Who rewrote the rules of series circuits? A total lack of any understanding basics.

In a series circuit with panels, the lowest Isc dictates the maximum current. What you end up with if you put 100 watt panels in series with 50 watt panels with same Voc, you turned every 100 watt panel into 50 watts.

OP you have two options depending on your controller type being PWM or MPPT.

If PWM you have no choice to put all the panels in parallel. At best 200 watts from 300

If a real MPPT wire the two 50 watt panels in series, and parallel them with the two 100 watt panels in series. You wil get the full 300 watts.

If you put them all in series as John recomend if it is PWM you get 35 watts from 300 watts of panels, If it is a real MPPT you get 200 watts out of 300.

Thanx again for the feedback guys. Just when I thought this was sorted out I'm struggling to make any conclusions as how to wire them up. Several have posted alternative methods.

MPPT controller.jpg

Here's the 30 amp MPPT charge controller I ordered around Christmas. From various reviews it's suppose to be a true MPPT CC of good quality.
Here's a link to it's manual. http://www.epsolarpv.com/en/uploads/...0581526220.pdf

As a newbie to solar it made sense to me that the two 50w panels in parallel would retain their 12V rating but would sum up and accumulatively achieve the same amperage as the 100w panel. This would effectively make them equal to one of the 100w panels. From there I could wire the paralleled 50w panels in series with the two 100w panels. Again, I'm new to this.

There appears to be a couple trains of thought here. I'm not looking to generate any drama or issues, just wanting to sort out the correct way to wire my panels up to achieve their maximum performance and efficiency.

Thanx again guys.

[Sunking]

Since they all have the same Voc and Vpmax and your controller can accept up to 100v input I'd just wire them all in series. Since the 50 watt panels have a lower Isc I'd wire them in the ground end of the series.

Who rewrote the rules of series circuits? A total lack of any understanding basics.

In a series circuit with panels, the lowest Isc dictates the maximum current. What you end up with if you put 100 watt panels in series with 50 watt panels with same Voc, you turned every 100 watt panel into 50 watts.

OP you have two options depending on your controller type being PWM or MPPT.

If PWM you have no choice to put all the panels in parallel. At best 200 watts from 300

If a real MPPT wire the two 50 watt panels in series, and parallel them with the two 100 watt panels in series. You wil get the full 300 watts.

If you put them all in series as John recomend if it is PWM you get 35 watts from 300 watts of panels, If it is a real MPPT you get 200 watts out of 300.

[Mike90250]

Current (amps) in a series circuit is the SAME everywhere in that circuit. If you put a half size PV panel in, it will be the choke point and limit ALL the current in the circuit.

[John Galt 1]

I thought the smaller panels would simply add their voltage and the current would flow if they were on the end of the string.

[SprinterX]

Thanx very much for the input guys, much appreciated. I was afraid I had made a huge blunder adding in the 50 watt'rs. With the 300w total I should be able to sustain the 12V fridge, the odd use of the inverter and the array of LED lights. Our little boat has a pretty good house battery package with 4x 6V golf cart lead acid batteries giving 465 amp/hrs.

My panels have the MC-4 connectors and I've ordered additional connectors to make the cables needed to connect to the CC. I will need to order a pair MC-4 connectors for paralleling the 50w panels.