Panel voltage question.

Seven
Seven Solar Expert Posts: 292 ✭✭
As I get closer to building my system I would like some input as to panel voltage and more directly, when does it go from low voltage to high voltage. Some of the panels and combiner boxes seem to have 48v as the cutoff between low voltage and high. My panels are 30Voc and I am trying to figure out weather to run them as 60v or 90v. Two or three in series.

So my questions are....
1. Is either setup a high voltage one?
2. Will it make a difference in reference to a combiner box?
3. Is there some code that states 48v as a max? (this is an offgrid setup)
4. Is there something that I am just totally forgetting?

The setup will be using the 210w Kyo panels and a Classic 150 controller going to a 12v bank at first, then 24v when I get enough panels. Im starting out with the cheap Costco batteries so I'm not worried about mixing at a later time.

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Panel voltage question.

    "High" and "low" are relative terms, not absolute. As long as the equipment is rated for "V @ A" compatible with your components there's no worries.

    Remember that Voc is open circuit: essentially zero Amps. The real concern here is to not exceed the charge controller's input with a Voc higher than its max. Cold temps will up the Voc. The midnight Classic 150 can handle 150 + nominal system Voltage: 162 Volts. No worries there.

    The combiner box & breakers are rated for 'X' Amps @ 'Y' Volts. This is an "under load" condition, so your panel Vmp is the Voltage that matters. The Vmp on these panels is 26.6, so two in series would be 53.2. I don't think you should exceed that is you're using breakers rated @ 48 V although the Amperage is quite low (less than 8). Unless you have a real need for the higher Voltage array (long wire runs) I'd stick with two in series.

    It used to be that the standard for nominal array Voltage on an MPPT controller was best at no more than 2X the nominal system Voltage. However, the Midnight Classc "breaks a lot of the rules" and probably will run almost as efficiently cutting 150 V down to 12 as it would with 48.

    Just my opinion. Others may have a different POV.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Panel voltage question.

    as far as the nec is concerned high voltage is anytime the voltage exceeds 50v. a 48v battery bank will be over 50v for a full charge and the pvs to charge it most certainly will be over it. even for a 36v battery arrangement (rare, but not unheard of) can have pv voltages that most likely will exceed 50v. 12v, 24v, and 36v battery systems and 12v and 24v pv systems will not be considered high voltage. remember the battery and pv voltages are nominal and are usually higher in reality just to head off some confusion.
  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    Re: Panel voltage question.

    Hi I would consider going to 24 volts from the start. Cables don't need to bee so big and efficientcys are better and so on . Also you wont need to change from a 12 volt inverter to 24 . Just a thought.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home