I have a 4 panel setup that is pushing 20a to a SmartSolar 100/20 controller 150' away. In theory the 150' run should be using 1 AWG but the controller connection for PV input supports at max 10 AWG. How does one overcome this?
asked
PV wire length vs CC connections
You didn't mention if the panels are wired in parallel or in series or their voltage. At 150', I'd definitely try to increase the voltage by wiring the panels in series. Volts times amps equals watts. Wiring in series means you add the volts, but the amps stay the same.
So for a given number of watts coming from your panels, if you increase the voltage you decrease the amps. The trade off for wiring in series is the output of all the panels significantly degrades if any of them are shaded. You also need to ensure your charge controller can handle the voltage from the panels if they're wired in series -- not all controllers can. You wouldn't have to wire all four panels in series. Splitting them into pairs of two wired in series with the two pairs then connected in parallel is an option.
Sorry, I didn't specify the config because I thought the part important was the current, length of wire, and controller limitations. They are 4 Trina 325w panels configured as 2S2P with each panel spec at 40.4v/10.3a
@Billy Myers run your figures through this Voltage drop Calculator .
Higher array voltages (panels in series) will result in lower currents (copper savings).
However you must ensure that the array Voc at low temps is safely under the mppt's PV input 100v limit. Use the online calculator .
Sorry, I didn't specify the config because I thought the part important was the current, length of wire, and controller limitations. They are 4 Trina 325w panels configured as 2S2P with each panel spec at 40.4v/10.3a
Regarding the Voc input limit, I thought the CC input limit is a soft one and the current was what damaged the controller. On these charge controllers I'm not seeing a reference to damage from over voltage, the damage is caused by exceeding the current. Going over voltage will just limit it. By the way thanks for the help, learning from everything we're discussing.
@Billy Myers the mppt voltage input limit should never be exceeded. blue smoke will eventually leak out, and that results in a dead mppt.
The mppt will limit the battery current output to 20a. The mppt will also limit the pv input current, though you have to be careful should you exceed the mppt's input current limit. Reverse polarity connection of the pv may damage the mppt should you exceed the input current limit.
Your problem lies with the distance between the array and mppt. Keeping the voltage drop to acceptable levels requires thick and expensive cables.
How much money do you want to spend on copper?
What is your battery voltage?
48v lifepo4 battery
If I put the array any closer than 150ft away in any direction they will be in direct shade any season and any time of the day year round due to tall tree's that I cannot cut.
Am I missing something of the optimal configuration between panels and controller? My only limitation is how close I can put the panel array to the controller. With the 2S2P array I'm at 80.8v/20.6a max being pushed to the SmartSolar 100/20. I don't believe there's any better configuration for the array or a smaller guage of wire to use to get from panels to CC without real loss of power across 150' distance.
@Billy Myers My only limitation is how close I can put the panel array to the controller.
Total cost of mppt and cable? Ability of array to charge a 48v battery? (you never mentioned batt voltage)
Assuming a 48v battery. Your array and mppt wont charge a lead acid battery. Your array and mppt will struggle to charge a 16 series lifepo4 battery at higher array temperatures.
Where I live a 100-20 is $230, and 100m of 2awg cable is $1600. $1830 for PV that dont work.
I would suggest 4 series panels, a 250-60 mppt and 100m of twin 6mm pv cable. A 250-60 is ~$1050, and 100m of twin 6mm pv cable is ~$400. About $1450 for PV that will happily charge a 24-48v battery regardless of array temps.
Your money, how much do you want to spend for a system that works?
