Common bus bars

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System
System Posts: 2,511 admin
in General Solar Power Topics #1
I’ve looked at various system installations and there seems to be mixed views on whether the charge controller, battery charger (if separate), shunt (positive) and / or wind generator should have separate leads directly connected to the battery terminals.

Or, can you connect all the negative and positive leads to (separate) common bus bars and run one suitable sized cable to the battery terminals. Presumably the common positive must connect on the battery side of the battery fuse/breaker?
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  • System2
    System2 Posts: 6,290 admin
    #2
    Re: Common bus bars
    planetharman wrote:
    Presumably the common positive must connect on the battery side of the battery fuse/breaker?
    Not sure if I read you right - but if the common positive (from all sources and loads) connects to the battery side of the fuse/breaker, then what's left to connect to the other side of the fuse/breaker?
    Wayne
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: Common bus bars

    That’s part of my question really, as anything connected to the positive has it’s own fuse, does it have to be connected on the battery side of the battery fuse/breaker? I’m trying to avoid having a lot of connectors on the battery terminal and the associated leads.

    Again, I assume that there are no problems with a common neutral?
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Common bus bars

    OK, there should be no problems with a common neutral, however the positive from the battery, should pass through the battery breaker before it gets to all the other fuses/breakers, if you want to use it as a battery disconnect, otherwise the main breaker would be there just for good looks. If it's properly wired, and you have any problem, maintenance, lightening storm, just flip that main breaker and presto - everything is disconnected from the battery. And yes, each circut should also have it's own fuse/breaker as well, sized properly for that particular circut. Some may want the negative from the battery switched also. Mine aren't, my battery negative is earth grounded and not switched.
    There, I've given my experience, now I'll let the experts answer your question.
    Wayne
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,693 admin
    #5
    Re: Common bus bars

    You can have a master battery bank cutoff/fuse... But you still have to have a distribtution panel fuses/breakers too... For example, your solar charger may operate at 60 amps max and requiring a 75 amp fuse/breaker and wiring. But your 4 kW 24 vdc inverter may use 200 amps on a 250 amp fuse/breaker and wiring.

    The Solar Charger and Inverter circuits cannot share the same protective device because of the large differences in current.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: Common bus bars
    planetharman wrote:
    I’ve looked at various system installations and there seems to be mixed views on whether the charge controller, battery charger (if separate), shunt (positive) and / or wind generator should have separate leads directly connected to the battery terminals.

    Or, can you connect all the negative and positive leads to (separate) common bus bars and run one suitable sized cable to the battery terminals. Presumably the common positive must connect on the battery side of the battery fuse/breaker?

    i see no problem with using a buss and 1 wire going to the battery and could be protected by a fuse. many combiners use this methodology in going to the battery except that each branch is fused or protected by a circuit breaker or fuse. this holds true for loads of the battery as well as pv inputs as everything just tends to reverse in the same type circuitry. if your load is only an inverter then there won't be a bunch of 12v branch circuits although there could be if you combine 12v systems and a 115vac inverter system. oversize the buss in any case by 2 to 3 times so that the resistances are far lower on that buss than even the wire going to the battery. some can bolt the buss straight to the battery if sized right thereby eliminating another wire altogether.
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