Can I combine multiple different panels into mppt?

I have two hundred watt 12 volt panels with their own pwm controllers on my 12 VDC trailer system. I'm looking to upgrade to a 24 volt system to run a freezer, microwave, computer and TV.  If I buy a 1000 volt 40 amp mppt controller can I hook up those two panels to it, as well as other panels I get? Or will different spec panels cause issues, and i should just get matching panels to connect to the controller?

From what I ve read you are best to go with similar panels. I believe how it works is the voltages can be different its the amps which need to be the same. otherwise the amperage from the lowest panel will be a bottle neck the larger panels. Meaning the larger amp panels will operate at the lowest amp panel.

if you had 5 panels at 10 amps and you have 1 panel at 4 amps. all of the 5 panels at 10 amps would operate at the 4 amp panels rating.

really I would try to find another use for those 2 -100 watt panels. I just bought 6 - 360watt panels

What I think you mean is a 1000watt 40 amp charge controller?

I think you will want more solar if you plan to use a microwave/freezer. I would advise doing an energy audit https://diysolarforum.com/resources/system-energy-audit-and-sizing-spread-sheet.12/

What inverter are you wanting to use?

Thanks for the link!

The sine wave inverter i have is too small, and I read you don't want to use a regular inverter on electric motors. So I will need to acquire one.

I'm still reading about mppt controllers, but my understanding is you wire your panels in series up to the voltage capacity of the controler, and can wire groups of those panels in parallel up to the amperage capacity of the controler. Is this correct?

R Webber wrote:

I'm still reading about mppt controllers, but my understanding is you wire your panels in series up to the voltage capacity of the controller, and can wire groups of those panels in parallel up to the amperage capacity of the controler. Is this correct?

Yes, you are correct.  You can have any type of panel in parallel as long as the series voltages of the two strings are equal to within 5%.  Let's say your 12V panels put out each 18V.  Wired in series, they would be 36V.  You could then pair that with a 72-cell residential grid-tie panel putting out 36-37V.  Then the amperage produced by the first string is added to the amperage being put out by the large grid-tie.

Since most budget MPPT controllers can handle at least 100V, you could wire four of your 12V panels in series for string #1, and two of the 72-cell panels in string #2.

Just remember though that solar panel voltage goes up as the temperature goes down.  A series string that was just fine in the middle of summer, could fry your controller come winter.  Staying 20% below the MPPT limit is a conservative way to do it.  That's the Voc, not the Vmp.

R Webber wrote:Thanks for the link!

The sine wave inverter i have is too small, and I read you don't want to use a regular inverter on electric motors. So I will need to acquire one.

I'm still reading about mppt controllers, but my understanding is you wire your panels in series up to the voltage capacity of the controler, and can wire groups of those panels in parallel up to the amperage capacity of the controler. Is this correct?

You can create a mixed panel load but the way the mppt brain works it will always tend to favour one string over the others. That gets worse when any shading gets involved. I have found that 12 volt panels sell for a premium used. Selling off my 80 watt 12 volt panels was enough to purchase my 60 cell 250 watt panels when I redid my personal array. Also worth watching out for is a lot of 12 volt panels have a limited maximum string voltage that is not compatible with the newer high voltage charge controllers ..
If you are starting new I would suggest matched strings.
Cheers, David

David Baillie wrote:
You can create a mixed panel load but the way the mppt brain works it will always tend to favour one string over the others.
If you are starting new I would suggest matched strings.
Cheers, David

That is not how electricity works.  You need to remember the electrical mantra, "In series volts add while amps stay the same, but in parallel amps add while volts stay the same.  There is no favoritism as long as the voltage of each string is the same.

Let's go back to the above comparision, the putting of two 12V panels in series as one parallel string, and a second high-voltage grid-tie panel.  For the sake of keeping the math simple, let's assume the 12V panels are putting out 11.1A at 18Vmp, while the HV panel puts out 6.9A at 36V.  Wired in series as mentioned above, the two 12V panels will be putting out 11.1Amps at 36Vmp.  See how the math in the first part of the mantra works?

The second string, consisting of the single HV panel, is putting out 6.9Amps at 36Vmp.  The two parallel strings together put out a total of 11.1A + 6.9A = 18A at 36Vmp.  See how that follows the second part of the mantra?  So, panels may be mis-matched as long as you keep the voltages the same.  Keep in mind that in the real-world, output never matches pen&paper calculations.  There is always some loss.

Shading is a completely separate issue.  If shading is a problem, it's because your choice of panel positioning could be better.