cable thickness?

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higgins
higgins Solar Expert Posts: 56 ✭✭✭✭
in Solar Beginners Corner #1
On my 10 amp Charge controller,the terminals for the wire to the battery only allows for a small wire thickness,what size should it be going to battery?
Higgins
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #2
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    Re: cable thickness?

    Part of the question is how far away is the battery from the charger...

    Current wise--14 awg house wiring is rated at 15 amps - 20 amps maximum.

    It is always a good thing to have the voltage drop between the battery charger and the battery bank be as low as practical--even a 0.1 volt error in voltage is ~10% change in level of charge.

    Using a generic voltage drop calculator... 10' run (20' total of 14 awg wire, carrying 10 amps will have a 0.6 volt drop...

    That 0.6 volt drop will cause the charger to think it is charging at 14.4 volt volts, and the battery is seeing 13.8 volts--So, the battery will be taking longer to charge (as the current drops, the voltage drop falls too) as the controller cuts back on the current (enters absorb phase of charging) when it could really still be cranking out 10 amps.

    Of course this depends on the type of charge controller you have and the settings you are using for charging...

    For computer system power supplies, we always had remote sense wires that measured the bus voltage at the point of use (such as local bus bar). It allowed us to use smaller gauge cable (more voltage drop) and still have an accurate voltage at the bus.

    I wish solar and AC charge controllers used remote sense leads more often (I think I remember one older charge controller that had remote sense option).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: cable thickness?

    IF the connectors on the charge controler only allow a small cable to be connected then use a small length of cable about 4" to connect to the controller say #12 then twist connect longer lengths of say #8 or#6 to go to the battery/ies dont use connectors to join the cables bare about 2" of the thin and thick cables and long ways twist them tightly together I also solder as well to make sure no corosion happens over time then put heat shrink over the join
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