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Lou Cetrangelo avatar image
Lou Cetrangelo asked

Charge Controller Max output current?

I am getting conflicting information. I have a smart solar 100/50 charge controller with four 170 watt panels connected in parallel. My dealer says I am pretty much maxed out in regards to input current. When i asked the panel manufacturer they said that each panel can put out up to 9.4 amps (i assume that would be at 18 vdc). So they said that by adding the fifth panel that would be only 48 amps.

I am thinking If you consider the output current (assuming no loss) when connected to a bank of lithium batteries the output voltage in bulk mode would be 14.4 vdc. With five panels connected the output current would be 59 amps. Am I correct here? Would this be exeeding the capacity of the controller? Does current limiting come into play?




charge current limit
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Alexandra avatar image
Alexandra answered ·

@Lou Cetrangelo

https://www.google.com/url?q=https://mppt.victronenergy.com/&sa=U&ved=2ahUKEwi4_rKXh93tAhUTWsAKHWpYBb4QFjABegQIBxAB&usg=AOvVaw3URawTb2ULNXeRD76LjZYp

No need to guess or argue. Go the mppt calculator and use it to see.

There is a sheet to work it out if you prefer on your computer

https://www.google.com/url?q=https://www.victronenergy.com/upload/software/VE-MPPT-Calc-2_4.xlsx&sa=U&ved=2ahUKEwi4_rKXh93tAhUTWsAKHWpYBb4QFjACegQICBAB&usg=AOvVaw2sgdM95-9oiMxpHeOp4tce

14.4volt bank charging at 50amps (the rated output of the charger) is 720W, sometimes more if the panels are cooler than 25° but it will waste anything above that as it is limited to the 50amp charging output.

That being said you can over panel slightly. There is about a 30% oversize allowed on the input except the 100v VOC input from the panels, never go over that.

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Lou Cetrangelo avatar image Lou Cetrangelo commented ·

Thank you for replying. I must not be understanding something. If you have 14.4 volts charging at the maximum current of 50 amps wouldn't you have 14.4 X 50 = 720 watts?



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Alexandra avatar image Alexandra ♦ Lou Cetrangelo commented ·

@Lou Cetrangelo

No my calculations are incorrect. 720W is the correct answer as you have worked it out.

I was playing with few configurations and for some reason typed the panel wattage instead of the output. My apologies for causing confusion.

Your proposed 4x 170W is good. Have you thought of two parellel two series? The higher voltage of series connected panels will help charging start up earlier in the day. As long as the total VOC is not over the 100W at min operating temperature higher string voltage is an advantage. But it does mean you have to stick to an even number.

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Lou Cetrangelo avatar image
Lou Cetrangelo answered ·

I must not be understanding something. If you have a solar charger putting out 14.4 volts and at its maximum current of 50 amps wouldn't you have 14.4 X 50 = 720 watts?

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Lou Cetrangelo avatar image
Lou Cetrangelo answered ·

No worries. I installed the spread sheet version of the calculator and set up a custom solar panel for my Zamp 170 watt panels. I was originally thinking of going to 6 panels and set them up as three sets of two in series and then connect them up in parellel. That would be within the max input current and voltage of my controller (smartsolar 100/50), However it would greatly exceed the max output currant of almost 90 amps by about 80%. The other point is that I have 5 m of 4 awg cable going to my controller with 4 panels in parallel. It is optomized for shading if my RV is parked partially under some trees.

What I plan to do is to install a 5th 170 watt panel in parellel on my current controller. This may be the most cost effective solution. I would be just over 30% over my max current. I will monitor it but I doubt I would every hit 50 amps in real world conditions. My panels are all flat on the roof. I have the ability to Tilt them but unless we were in one place for a long time with out shore power it would not be worth the effort. So they are not at top effecency


I may in the future add a 6th panel which would max out the area on my roof for solar panels. If I do I would also change the controller out to a SmartSolar 150/85 and probably add a 4th Battleborn battery but this would be a large expense.

Thank you for your help

Lou Cetrangelo


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