Wiring solar panels

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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #32
    A 3 panel string will have a 1.8% drop with # 10 AWG and 1.2% with a #8 AWG.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #33
    Seems better to use a combiner box then due to higher voltage I guess. Thanks again.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #34
    Agreed
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #35
    Ok so just to run it by and also for your info these are the circuit breaker I decided to go with

    This is going between my charge controller and batteries 1P 63A DC 125V Circuit breaker MCB C curve
    http://s.aliexpress.com/q6jquMbA
    (from AliExpress Android)

    These are going on my panel strings 1P 16A DC 125V Circuit breaker MCB C curve
    http://s.aliexpress.com/nueI7J3U
    (from AliExpress Android)

    These are going on each battery string of 51.2v 100ah 1P 100A DC 250V Circuit breaker FOR PV System C curve MCB
    http://s.aliexpress.com/VjI73mMZ
    (from AliExpress Android)

    ABD for added protection I'm going for these on each string of solar panels 5 pcs/lot Solar Panel MC4 PV Connector with Built in 15 Amp Diode
    http://s.aliexpress.com/Nb6Ffyua
    (from AliExpress Android)

    Can never be too safe :smiley:
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #36
    I would recommend a 175 amp breaker between the inverter and the battery. Also, many use fuses instead of breakers on the battery strings. Tends to enable shorter cable lengths. But, your choice.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #37
    But my max current draw is 100 amps on each string. Which I would never be able to do. What's the reason for going for 175 amps?
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #38
    I didn't see an inverter breaker on the list, which is what @Raj174 is suggesting. It protects the inverter, and the wire from the inverter to the point of parallel battery connection. The inverter manual should specify size. Likewise, max size should be specd by pv panel maker. Some breakers can operate at near normal max running currents (no derating), others need to be sized bigger (but still small enough to protect wire, etc).
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #39
    For battery wiring you will need a minimum 2/0 AWG or 9.266 mm cable. You need that size or larger to keep losses low. Your bank will be 51.2 volts 600AH correct? It is actually capable of delivering 1800 amps continuous. 
    What is the wattage of your inverter? 3600 to 4000 watts requires a 175 amp breaker.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #40
    I have 8 100 Ah 12.8 V batteries I will wire 4 in series and 2 series in parallel. Each of the 2 series will have a 100 amp dc breaker . So 2 breakers for my whole battery bank. My bank will be total 200 A 51.2 v nominal.

    My inverter is a quattro 10kva. I will protect that with a 200 amp fuse.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #41
    Sorry, I thought you had 24 battery packs. Ok, that will do.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #42
    I drew a diagram to make things a bit clearer. I hope it helps.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #43
    Hi Yerf,
    I would advise that another breaker be installed on the positive incoming line between the combiner box and the charge controller. This should be installed near the charge controller with the breaker for CC to battery, same size.

    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #44
    I have connected it to main busbar connecting the inverter, battery and cc. Is this wrong? And I think I'm going to change the breaker from 63amps to 100 amps 250vdc. O also plan on adding a 65 amp fuse on the cable coming out of the charger just incase.
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited October 2017 #45
    It's a good idea to use a single breaker to shutdown the entire array because if you have to shut down the charge controller while the array is producing power, the PV input needs to be switched off first, then the battery breaker is switched off and back on to reset the controller. After which, the PV input can be switched back on.

    My calculations indicate maximum charging amperage at 71 amps. Although with hot panels at midday, 55 amps will be more likely. I would use an 80 amp breaker on the charging cable,  A # 4 AWG or metric equivalent is only rated for 70, 85 or 95 amps depending on wire type, insulation and temperature. Type THHN would be my choice. ( see ampacity chart here: http://www.armstrongssupply.com/wire_chart.htm )

    The 65 amp fuse will be redundant, but your choice. The breakers and fuses are there to protect the cables, and have to be rated lower than the maximum amperage the cable can carry.

    Rick 
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #46
    Thank you so much for your reply. I plan on using 3Awg cable from the panels to the controller and from the controller to batteries inverter etc., thus my reasoning to use 100 amp breaker and 65 amp fuse. I don't trust a breaker on its own to be safe. I've seen those things catch fire. Although I'm not sure on the proper usage of neither fuses or breakers.

    The victron BMS is connected to the bus bar and controlled by a 3 a switch. When this is switched off the BMS shuts down the charge controller and inverter effectively shutting down the system. According to victron.

    I've attached a more detailed diagram with the various victron components. Sorry for the shoddy drawings.
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  • Yerf
    Yerf Registered Users Posts: 65 ✭✭
    #47
    Also battery fuses, where should they go ideally? At the end of the bank or in the middle?
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #48
    They go on the same cables as the breakers since they preform a similar function and are either on or near the battery terminal depending the type of fuse holder used.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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