wire size

ws9876
ws9876 Solar Expert Posts: 448 ✭✭✭
in General Solar Power Topics #1
how long a no. 6 wire run would you do between a C 60 and a battery bank..????max..
the videos make it seem like it has to be too short..
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Re: wire size
    ws9876 wrote: »
    how long a no. 6 wire run would you do between a C 60 and a battery bank..????max..
    the videos make it seem like it has to be too short..
    Depends on the amps you are trying to put though it. If you have 20A of PV, you get a vastly different result from 58amps

    Use a wire calculator, shoot for <2% loss

    http://www.solar-guppy.com/forum/download/voltage_drop_calculator.zip

    Household 120V calculators work out 5-10% loss.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #3
    Re: wire size

    "Between a C-60 and battery bank"? That would also depend on the voltage of the battery bank, as for example delivering 300 watts to a 12 volt battery bank would send more or less 25 amps down the wire, while that same 300 watts delivered to a 24 volt battery bank would be only 12.5 amps, and best of all, going to 48 volts, your wire would only be passing more or less 6 and 1/4 amps. Thus the reason for going to higher voltages with more powerful systems. 6 amps is far easier for a wire to handle than is 25 amps.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: wire size

    More or less, I would recommend around 0.100 to 0.050 maximum voltage drop (at maximum charging current) for a 12 volt battery bank (24 volts: 0.2/0.1 volt drop; 48 volt: 0.4/0.2 volt drop).

    If you have more drop than the above--your run the risk of wasting energy while charging your battery bank (your controller will think the battery voltage is higher than it really is--and start cutting back on charging current).

    A few chargers have Remote Voltage Sense leads (MorningStar TS family and the Rogue MPPT to name a couple that I am aware of). These charge controllers will allow you to use longer/thinner leads than charge controllers that do not have remote voltage sense.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    Re: wire size
    mike90045 wrote: »
    Use a wire calculator, shoot for <2% loss

    http://www.solar-guppy.com/forum/download/voltage_drop_calculator.zip

    (note, in the spreadsheet, note that note #9 says:
    9
    When entering wire length use two way length.
    How long is each wire from the panel to the combiner box both ways?
    Same for all other wire runs.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
    Re: wire size

    from the controller to the battery bank is more critical than many think it to be. the reason for this is not the loss of power so much as undercharging your battery. the battery health can suffer far more greatly than the factoring of the small amount of power that is lost. if, for instance, you have a battery that needs to bulk up to say 14.4v before switching over to absorb. you see that a voltage drop will prevent the battery from ever seeing that 14.4v. now 14.3v isn't so bad, but when you start going farther out it gets worse and the battery suffers for it.

    btw, in my example that .1v drop represent about .7% for the v drop. you could probably get away with up to about 1% or so, but you can see the % here really should be ultra-low. there are controllers out there with remote voltage sensing to compensate for this, but it's better to just use the proper wire to overcome losses.

    remember, we are talking only of the voltage drop between the cc and the battery here and not the overall system v drop and respective %. whatever the v drop here between the cc and battery is gets added to other v drops like between pv and combiner and combiner to cc.
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