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Old 30-06-2016, 08:55   #1
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How to match solar panel voltage to controller

I am installing three 305 24v panels. The label on the back of the panel reads "Open current voltage 45.6" and "Max power 36.9" I have read this is normal for 24v panels but how to I apply this to the charge controller? Will a Victron that shows 12V 24V 48V 70A MPPT work? I have read 36v will not work some controllers. The Outback 80a shows 12V 24V 36V 48V 60V
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Old 30-06-2016, 09:08   #2
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Re: How to match solar panel voltage to controller

The controller will adjust the solar panel voltage for the best power point. When you first up the system you will connect the output and the controller will measure and set the voltage, then apply the solar panel input and the controller will track to MPPT.
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Old 30-06-2016, 09:16   #3
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Re: How to match solar panel voltage to controller

Does it matter if the controller is rated for 36v if the 24v panel shows max power as 36.9v or is the controller rated at 24v the correct one?
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Old 30-06-2016, 09:21   #4
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Re: How to match solar panel voltage to controller

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Originally Posted by Formosa Scott View Post
I am installing three 305 24v panels. The label on the back of the panel reads "Open current voltage 45.6" and "Max power 36.9" I have read this is normal for 24v panels but how to I apply this to the charge controller? Will a Victron that shows 12V 24V 48V 70A MPPT work? I have read 36v will not work some controllers. The Outback 80a shows 12V 24V 36V 48V 60V
I think you will find the 12V 24V and 48V refers to the battery voltage not the solar panel voltage, so with a 12v (or 24V) battery system you should be fine. Be careful to check the max input voltage of the controller. It will be buried in the specs somewhere. If this is exceeded the controller will almost instantly be fried.

If you connect your solar panels in parallel the maximum open circuit voltage is 45.6V, but in rare cases solar panels can exceed this voltage so you need a reserve. Most controller manufacturers recommend the maximum input voltage should be at least in the order of 20% greater than the open circuit voltage of the array (so around 55v+ for your panels in parallel). If it is close to this number it is worth checking with the manufacturer.

It would also be worth checking with the manufacturer that the unit self protects if over 70 A are produced. Most, but not all controllers will do this. You will very rarly exceed 70A, but in exceptional circumstances it is possible (assumining you have a 12v battery system)
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Old 30-06-2016, 09:29   #5
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Re: How to match solar panel voltage to controller

The voltages you mentioned are the battery bank voltages that the controller will output to. Input voltage will be stated as a range or max voltage. Also need to calc the output current. The controller will only output up to that limit. If your panel input (volts X Amps) is more than the controller can put out you will be wasting/not using some of the power from the panels during parts of the day.
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Old 30-06-2016, 09:52   #6
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Re: How to match solar panel voltage to controller

Thanks for the help.
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Old 30-06-2016, 16:24   #7
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Re: How to match solar panel voltage to controller

if you go to the Outback controller website there is a selection tool. I think for the most part the controllers are rated based on power in and amperage out.
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Old 30-06-2016, 23:13   #8
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Re: How to match solar panel voltage to controller

The specifications for the controller should state what the "maximum input voltage" is. The voltage specified will most probably be the maximum voltage the lowest rated voltage of the components in the regulator exposed to the open circuit voltage output of the panel.


Since your regulator states that it is suitable for the regulation of "The Outback 80a shows 12V 24V 36V 48V 60V" I would guess that the maximum input voltage of the regulator would be well in excess of the 60V stated and consequently easily able to handle your 24V system wherein the open circuit voltage of the panels is stated as 45.6V which is 14.4V less than the 60V system rating for the regulator.
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Old 30-06-2016, 23:32   #9
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Re: How to match solar panel voltage to controller

Both Victron and Outback MPPT controllers in the 80 Amp range can handle up to around 145-150V inputs.
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