12 parallel wiring best or better?

Captain chunky
Captain chunky Registered Users Posts: 18 ✭
in PV Installers Forum - NEC, Wiring, Installation #1
Which of these two parallel wiring diagrams is right or I guess the better of the two? I guess my question is should the inverter and charge controller be wired to one lead battery or split the positive and negative between both 12 V batteries, newbie obviously. I just want to have the better of two connections, i've had the first battery for about two months and I'm adding a second to it, just trying to figure the best wiring. Thanks.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: 12 parallel wiring best or better?

    The first one is called "laddering" and is totally wrong. Uneven current sharing between the two batteries is guaranteed.

    The second one is called "diagonal" and is the best choice for keeping current even.

    The thirs one is diagonal as well, only drawn differently.
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  • Captain chunky
    Captain chunky Registered Users Posts: 18 ✭
    #3
    Re: 12 parallel wiring best or better?

    At the moment I have one 145 AH battery running a .58A pump 24 hours a day with 2 100w panels and a 30A CC, at night after sunny days the battery is 12.74 and in the a.m. I'm at 12.06 50% but if we get two days of clouds I am shot so a bigger battery bank is what is usually done right?
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  • Captain chunky
    Captain chunky Registered Users Posts: 18 ✭
    #4
    Re: 12 parallel wiring best or better?

    So the bigger bottom pic wiring "diagonal" diagram is the proper way to wire a 12 V battery bank, thank you. I knew I wasn't just going to watch a video on YouTube and be like oh sweet it's that easy right on.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: 12 parallel wiring best or better?
    Captain chunky wrote: »
    At the moment I have one 145 AH battery running a .58A pump 24 hours a day with 2 100w panels and a 30A CC, at night after sunny days the battery is 12.74 and in the a.m. I'm at 12.06 50% but if we get two days of clouds I am shot so a bigger battery bank is what is usually done right?

    Providing you have enough charging power to support a larger battery bank. 200 Watts of PV is probably giving you around 11 Amps of peak current, which is minimal for the battery you have now. If you add another battery of equal capacity the charge rate will drop to <5% and neither will get recharged.

    If I were you I'd increase the amount of PV first, and see how the battery responds. If it has been deficit charged repeatedly it may be time for more battery and panel in order to get the system up to snuff. Adding a new battery to an old one isn't such a good idea either.
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  • Captain chunky
    Captain chunky Registered Users Posts: 18 ✭
    #6
    Re: 12 parallel wiring best or better?

    My battery usually goes into float mode around 11am and its winter here in San Diego. Their in float mode now at 13.63. I guess I just thought if I added another 145 amp hour battery that it would help me on cloudy days from going below the 50% discharge.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: 12 parallel wiring best or better?
    Captain chunky wrote: »
    My battery usually goes into float mode around 11am and its winter here in San Diego. Their in float mode now at 13.63. I guess I just thought if I added another 145 amp hour battery that it would help me on cloudy days from going below the 50% discharge.

    It will, but if you haven't got the ability to recharge the larger battery bank you'll soon be in trouble from deficit charging.

    The rapidity with which your battery reaches Float is not necessarily a good sign; this will occur more quickly as battery capacity goes down due to sulphation.

    Looking at your 0.58 Amp 24 hour load we see 13.92 Amp hours per day, or about 10% of the battery's capacity. That is good sizing. It means you should have another 3 days capacity stored for cloudy days. So why are you not getting that? Well if the recharging is insufficient then you lose tiny amount of stored energy every day and the battery slowly goes down in capacity. This would be due to insufficient solar not just on cloudy days but sunny ones as well.

    I think you should test that battery to see if it ever gets to 100%.
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  • Ethan Brush
    Ethan Brush Solar Expert Posts: 235 ✭✭
    #8
    Re: 12 parallel wiring best or better?
    Captain chunky wrote: »
    Which of these two parallel wiring diagrams is right or I guess the better of the two? I guess my question is should the inverter and charge controller be wired to one lead battery or split the positive and negative between both 12 V batteries, newbie obviously. I just want to have the better of two connections, i've had the first battery for about two months and I'm adding a second to it, just trying to figure the best wiring. Thanks.

    Another good way to connect batteries in parallel is to take each battery or string (with same length cable) to a common busbar, then you also have a nice connection point for other stuff.

    http://www.stormcopper.com/design/Electrical-Ground-Bars.htm
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  • Captain chunky
    Captain chunky Registered Users Posts: 18 ✭
    #9
    Re: 12 parallel wiring best or better?

    do I charge it and let it rest before I check the voltage? how do I test to see if it gets to 100%? , and I think I will purchase another panel asap.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: 12 parallel wiring best or better?
    Captain chunky wrote: »
    do I charge it and let it rest before I check the voltage? how do I test to see if it gets to 100%? , and I think I will purchase another panel asap.

    Charge it first until your controller says it is charged. Then check SG on each and every cell. If you can't do that let it rest at least three hours and then check the Voltage. It should be near 12.75. Let it rest another three to six hours with no load and see how much it goes down from the initial setting. Yes, this is impossible to do on a system that is in use. That's another reason why being able to test SG is desirable.
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  • Captain chunky
    Captain chunky Registered Users Posts: 18 ✭
    #11
    Re: 12 parallel wiring best or better?

    After charge controller started blinking signaling full charge state, I Unplugged and tested after resting 3 1/2 hrs and it read 12.6 / 12.57 V. Hope I'm in the clear.
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  • Captain chunky
    Captain chunky Registered Users Posts: 18 ✭
    #12
    Re: 12 parallel wiring best or better?

    The battery is looking good, now to get MORE POWER! Have a good day all.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #13
    Re: 12 parallel wiring best or better?

    Which reading is correct after 3 hours of rest? 12.57 or 12.76? 12.57 would be a bad sign. 12.76 is a good start but you should test again 3+ hours later, as suggested above.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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