Solar array amperage drop help please???

[hay4man]

That shouldn't be a problem. You might see slightly less power output from each individual panel because the charge controller will try to pick the best point for the combined panels, but more overall power.

[P34CHY]

Thanks for the reply.
the resultant loss should not be a factor, lots of sun here in spain,
and i have a bank of 750 amp deep cycle batteries i was concerned about
going up in a blue flash tee hee.

[Mike90250]

Hi guy's
I'm quite new to all this (first post). I hope you can help with this.
I have two kyocera 130w panels with vmp of 17.6v and imp of 7.39amp. these are wired in series for 24 system.
I also have four photon panels with vmp of 32v and imp of 3.35amp wired in parallel.

would it be safe to wire the kyocera series in parallel with the photon panels to creat
one string. if not any suggestions welcome.

Your output will be about 32V. the kyocera panels will be operating about 10% below their power.

Panels in parallel, will always be pulled to the lowest voltage panel (the photon @ 32V) The higher voltage panels will never realize their full power, and will be operating below their Vmp.

This is if you use a PWM charge controller.

If you use a MPPT controller, you may get a voltage between the 2 different panel voltages, and the MPPT down converts the input voltage, to the battery charge voltage.

Good luck.

[P34CHY]

Mike90250

THANKS MIKE.
Just found this forum today (what a find) you guy's seem to know
plenty about all this scary electric stuff.
Really big thanks for your help.

[P34CHY]

mixed panels

Just had a thought.
(unusual for me),
what would th resultant wattage and amps produced from such
a string.

[Mike90250]

Just had a thought.
(unusual for me),
what would th resultant wattage and amps produced from such
a string.

PWM or MPPT controller ?

[P34CHY]

at the moment PWM
but hoping to get my hands on an outback mppt soon

[Mike90250]

I have two kyocera 130w panels with vmp of 17.6v and imp of 7.39amp. these are wired in series for 24 system.

I also have four photon panels with vmp of 32v and imp of 3.35amp wired in parallel.

PWM, charging a 24V battery, you will see about 27V @ 12A
This is a GUESS, as I don't have the IV curves for either panel.
Your battery will hold the voltage below the max AMPs of either array.

A MPPT controller will be closer to 25A. It will run your 700W of panels much closer to their peak power. PWM runs your panels just above your 24V battery voltage, I'm using 27V as my guess.

[hay4man]

That is a tough question. Depends on the power curves for the panels, and whether you are using an MPPT or not.

I did some more thinking about the blocking diodes. If you are planning to put a bunch of modules in parallel, it is dangerous to not put blocking or isolating diodes in series with each module.

The logic is that if one panel gets shaded, it will become forward biased, and all the other panels will dump their power into the shaded panel. This could mean several hundred Watts being dissipated in the shaded module. If the shading lasts for longer than a few minutes, the solar cells will heat up rapidly and likely become damaged.

[rootytootie]

OK hay4man. I have off all this weekend. If I get some good sunlight I will go out there and test each panels Open circuit voltage and post them on here for you to help me out. I will also take off the 80 watt panels out of the circuit and see what amperage they put out by themselves. They are 6 15-watt panels wires in parralel together to 1 wire. Then I have that 1 wire run into my distribution block where they meet the other 80 watt panels. They are all nominal 12v though. But I will also post the information I can find on the back of the panels to and post them up. Thanks everyone for your time and effort and helping out a fellow solar hobbyist. Much is appreciated on this side.

Glenn

[Mike90250]

The logic is that if one panel gets shaded, it will become forward biased, and all the other panels will dump their power into the shaded panel. This could mean several hundred Watts being dissipated in the shaded module. If the shading lasts for longer than a few minutes, the solar cells will heat up rapidly and likely become damaged.

That's not how I've understood it. Panels are a CURRENT SOURCE. When there is any light at all, they develop a voltage. As the light gets brighter, the voltage stays pretty much the same, and they output more current.

If you have a AAA battery and a D battery, both fresh and new, and you connect them +to+ and -to- (wait for it......) Ta Da NOTHING HAPPENS. They just sit there.

I've installed 2 strings of 11 panels each for a 4.5KW GT array. With only 2 strings, not even fuses were required for the combiner box. Only 3 strings and above need fuses. But no diodes. I've never seen any diodes in GT arrays.

By the time one row of panels gets blacked out, the higher row is in shadow too, so there is no reverse/backfeed power.


Now my off grid install of 1.5KW, has 5 strings of 3 panels and a fuse on each string. But still no need for diodes in it. Every diode wastes power.
My GT array would burn (as heat) about 20 watts. My off grid, 32watts (more diodes)

[P34CHY]

PWM, charging a 24V battery, you will see about 27V @ 12A
This is a GUESS, as I don't have the IV curves for either panel.
Your battery will hold the voltage below the max AMPs of either array.

A MPPT controller will be closer to 25A. It will run your 700W of panels much closer to their peak power. PWM runs your panels just above your 24V battery voltage, I'm using 27V as my guess.

HI Mike.
the kyocera panels are both 130 watt and the photon panels are 110 watt
each
the kyocera's in series give me almost 7.5 amps and the four photons at present are giving just over 13.5 amps.
does this mean that if i wire in the series kyocera in parallel with the four photons that i will get circa 32v, 700watts / 21amps

[Mike90250]

Almost, your voltage will drop to your battery charging voltage (I guessed at 27V) and while the amps of each panel will add, you will be dragging the voltage down, the amps may suffer, but not much below 12A. Very good of the 4 photons to be giving 13A !

[P34CHY]

happy now

Almost, your voltage will drop to your battery charging voltage (I guessed at 27V) and while the amps of each panel will add, you will be dragging the voltage down, the amps may suffer, but not much below 12A. Very good of the 4 photons to be giving 13A !

The photons are performing better than anyone expected and some friends
had to see to believe . not bad cosidering 1,200 euro for four, panels are
expensive here in spain but not half as expensive as back home in scotland.

thanks again mike.
peace of mind can be a difficult place to find if you dont have the proper map

[astrayan]

Gord, Mike the moderator has a job for life educating you guys!

I remember when I was 12 years old, and was afraid of a resistor. I can't imagine still being that way as an adult, but I know how confusing it must be to be given bad electronics advice - or any at all - if you don't strongly understand the principles behind it all.

Solar panels are mystifying, because they are strange beasts that produce power/current/voltage on a power curve which changes as they age.

With a voltmeter, you can measure "open circuit" voltage of 21V on a standard 12V panel. Or, you can measure "short circuit" current, of say around 5 Amps using a high quality ammeter. Neither of these measurements give you any precise information about how the panel will perform when attached to a battery, if you don't know the age or problems of the panel.

Short curcuit current will give you a grunt rating, which tells you if the panel is alive or not. A new panel will likely generate about 1A lower than the short circuit current when attached to a battery. Old, clapped out panels (like mine), will generate about 50% of the short circuit value in hot weather

The original poster's array of panels should produce about 21 Amps

90 watt harbor freight kit -> 5A
2 80 watt mono -> 8A
2 80 watt poly panels -> 8A

If you rate a battery at 14V during charging, this produces about 294W, instead of the 410W which is expected. This is the standard rip-off factor when using batteries. Solar panel manufacturers give you excess voltage of 17.4V, because they know that even this voltage will be consumed by age, heat/temperature, and bad wiring.

As to why the original poster's array is only producing 14A, I can only speculate that his regulator is blocking it. New regulators will go so far, and then switch into a panic mode, or switch off totally. I would suggest measuring the current without a regulator in place, or, as another poster has suggested, measure the panels one at a time. Beware, that they will not add up to the expected sum, if they are older panels.

Blocking diodes are not necessary, because the panel cells are diodes, and don't let a hell of a lot backwards. If they did, then connecting them to a battery in the dark would result in poofsky.