different watt panels, a few questions for the experts please

[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 .

[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!!

[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.

[littleharbor]

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

[SprinterX]

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

Oooppps, finger trouble. Corrected now. Go HAWKS

[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?

[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.