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Jan avatar image
Jan asked

Mppt 75/10 maximum amount of solar panels

Can someone please advise on what the maximum amount of solar panels I'm able to connect to a mppt 75/10. The only actual limitation (not considering the 10A maximum charging capability) it seems is the 75V Voc rating if I'm correct?

If a 100W panel with a 22.3v Voc is to be used...

It's my understanding: 75/22.3 = 3.36

Meaning a maximum of ×3 of the above mentioned panels

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1 Answer
seb71 avatar image
seb71 answered ·

You also have to calculate the string voltage in the lowest possible temperature for that place (in cold weather, panel voltage can be higher than Voc). This must remain under 75V (for that 75/10 charger).


Regarding the total power of your PV array, it depends on the battery voltage (higher is better). You can oversize the array (for cloudy weather/winter production), but do not exaggerate.

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Jan avatar image Jan commented ·

Thank you for the quick response


Considering I only have a limited amount of the actual solar panel specifications available, how does one go about doing this?

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seb71 avatar image seb71 Jan commented ·

22.3V x 3 = 66.9V


That is relatively close to 75V.


How cold can it be in your area (during the day)?


Did you already bought the panels and the 75/10 charger?

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Jan avatar image Jan seb71 commented ·
I bought the controller and 1× panel combined with a 100ah deep cycle gel battery a while ago, which I use to power my camping fridge/freezer, lights and etc when camping..

But I recently haven't had the opportunity to actually travel a lot..

Was planning on using the system to power a bunch of 12v downlights in my house (to keep the lights on during power failures)

But the only spot I can temporarily place my solar panels doesn't exactly get the best sun during the day.. hence the additional panels..


Temperatures normal vary between 20°c - 28°c (average maximum winter and summer temp.)

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seb71 avatar image seb71 Jan commented ·

I need minimum winter temperature (lowest ever recorded), not average, nor maximum.


If you only have that single 100W panel, don't be stuck on that model (if you can even get the same model).


For a house, better look at 60 cell PV panels instead. A single such panel can have 300W (or more). Price / W should be better.

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Jan avatar image Jan seb71 commented ·
As low as 5°c


Considering this still needs to be a fairly temporary/mobile setup (and there isn't a lot of space for big-surface-size objects while on the move) a 300w panel wouldn't be the best option....

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