Stephen Miller avatar image
Stephen Miller asked

Output Voltage Requirements

Suppose I have four panels with the following statistics:

  • Module watts STC 380 Watts
  • Max power voltage (Vmpp) 40.00 Volts
  • Max power current (Impp) 9.50 Amps
  • Open circuit voltage (Voc) 47.80 Volts
  • Short circuit current (Isc) 10.01 Amps
  • Max system voltage 1500.00 Volts
  • Series fuse rating 30 Amps
  • Temp coefficient (Pmpp) -0.37%
  • Temp coefficient (Voc) -0.29%

Now, I want to buy a controller for them. If my battery bank is 12v, then my current out would be about 126v. Does that come into play? If it can't handle that output, will it ruin any of the components to run this or will it just limit my power output? How can I determine the current output for a controller?

I am running a 30w and 12/24v appliance so I don't need even close to all the power from the panels and am fine losing a huge chunk of it for the time being. I would then upgrade my battery bank in the not-so-distant future when it became important. I just don't want to damage any components in the interim.

I also have a second two-part question. First, do I connect my appliance(s) directly to the charge controller? If so, can I choose the output voltage? Suppose I have a 36v battery bank. Can I then choose to output 12v anyway from the controller for my appliance?

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1 Answer
wkirby avatar image
wkirby answered ·

You have some choices depending upon how you choose to wire your panels.
If you wire them all in series, then you'll need a 250/100 controller.
If you wire them all in parallel or two series - two parallel, then you can use a 150/100 controller.

These controllers will limit their output to 100A and work fine, you'll simply loose out of the upper ~320W when conditions are optimal.

It's always best to connect the appliances to the battery.
You controller will set it's selt initially to the battery Voltage, you'll need to change this later when you change your battery bank Voltage.
The charge controller charges at the battery bank Voltage, you cannot set it to 12V and charge a 36V battery.

To run 12V appliances from a higher battery Voltage, you'll need to use a DC-DC converter.
The 48V Orion DC-DC converters can accept a Voltage range of 32V-70V and output 12V.

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