Panel wiring - can I use both parrallel and series

Hi

I know how to wire in series and parrallel for an even number of panels. I was given 1 panel by a friend.

How can I best add this 1 panel to my array?

Can I wire 2 panels in parrallel - then link with 1 panel in series.

i.e. 2 panels parrallel - 12v x 7a = 12v @ 14a

then tied to another 12v @ 7a panel in series.

Would that get me 24v @ 21a?

(all numbers for example only - I know actual voltage/amps not correct - I just want to know if this will work)

Thank you.

Comments

  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: Panel wiring - can I use both parrallel and series

    No, that would give you 24 volts at 7 amps. The power on the odd panel would be pretty much 100% wasted, and you would also run the risk of burning out the diodes in the single panel. You have to have an even number of panels, or more specifically the amperage must match in each part of the string.
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: Panel wiring - can I use both parrallel and series

    Not the way you describe...

    When you connect panels in series, their Imp (current maximum power) ratings should be within 10% of each other.

    And when you connect panels in parallel, their Vmp should match to within 10% too.

    When you put two panels in parallel, you get a sub array with Vmp~17.5 volts and Imp~14 amps (two 7 amp panel in parallel).

    Attaching to a third panel in series with Vmp~17.5 and Imp~7 amps will not work correctly... This is (sort of) like placing a flashlight battery in series with a car battery. The system will only pass ~7 amps maximum--and there is a good chance you will over heat and cause the single panel to fail.

    If you have three panels and want to charge >12 volt battery bank, you can use a MPPT charger. They could take the ~3x17.5Vmp=42.5Vmp @ 7amps and efficiently down convert it to the ~14.5/29 volts needed to recharge the battery bank. The "useful" power from such a setup is:
    • 17.5 volts * 3 panels in series * 7 amps * 0.77 panel+charger deratings * 1/29 volts charging = 9.8 amps typical maximum charging current into a 24 volt battery bank.
    The only draw back is that MPPT (maximum power point tracking) solar chargers are around $300 to $600+ vs the $50-$150 for a PWM (Pulse Width Modulation) charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CMcDCMcD Registered Users Posts: 6
    Re: Panel wiring - can I use both parrallel and series

    Thank you for your prompt replies.

    Since the extra panel did not cost me anything, I think I will just set it up as a charging station to maintain lawn tractor and other batteries.

    Thank you again for your assistance.
  • CocirecaCocireca Registered Users Posts: 1
    Re: Panel wiring - can I use both parrallel and series

    Hi, combine all 3 panel in parallel and use a 30A charge controller @ 12V
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