Connecting broken panel in series

ismailkayaismailkaya Posts: 1Registered Users
Hi guys, i'm new in solar and trying to figure out basics. I have 4 100 watts solar panels and one 225 amp, one 100 amp and two 90 amp batteries. I'm using a 12 volt 1000 watt pure sine inverter. One of my solar panels is broken and giving max 2.5 amps on sunny days, others are working good. I'm planning to convert my system to 24 volts. I'm going to change the invereter to 24 volts. My charge controller is 30 amp 12/24 volts autoselect type. Is it a problem to connect the broken one and how should i set up the system? Or do i really need to convert it to 24 volts? Thank you and sorry for my english.


  • BB.BB. Posts: 28,088Super Moderators, Administrators admin
    When you connect solar panels in series... The Imp (maximum current rating under standard test conditions) need to match within 10% of their rated Imp (i.e., 5.0 amp and 5.5 amp maximum between high and low series panels).

    For charging your battery bank, you should look at 5% to 13% rate of charge... For a 24 volt @ 225 amp battery bank (2x12 volt 225 AH batteries in series):
    • 29.0 volts charging * 225 AH * 1/0.77 panel+controller losses * 0.05 rate of charge = 424 Watt array minimum
    • 29.0 volts charging * 225 AH * 1/0.77 panel+controller losses * 0.10 rate of charge = 847 Watt array nominal
    • 29.0 volts charging * 225 AH * 1/0.77 panel+controller losses * 0.13 rate of charge = 1,102 Watt array "typical cost effective" maximum
    Then there is the question of what your loads are like... For example, 1-3 days of stored energy and 50% maximum discharge (for longer battery life). We use 2 days of storage as a typical "optimum" battery sizing (for lead acid batteries):
    • 24 volts * 225 AH * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 1,148 Watt*Hours per night (2 nights)
    Note--A 2kWatt 24 volt AC inverter would drain your "daily battery" storage in about 30 minutes...

    As always, we like to start with your loads (average Watt*Hours per day, peak watts--such as starting a pump/refrigerator motor, where the system will be used--hours of sun per day, load variation by season) and such... Designing a system without knowledge of the loads is usually a money losing situation.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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