help with upgrade

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notsobright
notsobright Solar Expert Posts: 247 ✭✭
in Solar Beginners Corner #1
hi guys,

just ordered the MS suresine 300 from here (NAWS) and a PC adaptor to log into my MS SSD controller.


right now my system is on my mini RV (van) and consist of two keocera 40w panels rated at 3.3amps max each, one MK 100ah AGM batt., and the sun saver duo controller good for 25amps max.

I want to add another 130watt panel w 7.39 amps max


Im looking at probably 13 amps max with these three panels.

I have allready wired my system with #10awg and the run to the controller and battery is about 12 feet one way.

my question is: will I need to rewire or is the #10awg enough for the added panel?

Im thinking its OK but just making sure before I buy the panel. I dont want to rewire because it was a huge ordeal in this van in the first place.


thanks.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
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    Re: help with upgrade

    that would depend on what is acceptable to you. the voltage drop % is under 3%, but that is only for that section of wire. wiring going from the pvs to the controller are also to be needing consideration as it contributes to the voltage drop as well. if it is that difficult to rewire, then i don't see a problem living with the extra v drop if the vd from each of the pvs to the controller are held to under 2%, but that's your decision to make. i also don't believe you to be getting 3.3a from 40w pvs as it is more likely to be 2.3a each. i made my rough calculations based on the 3.3a though.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
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    Re: help with upgrade

    At least when you pull the most current (charging low battery) you can afford the drop, and as the battery fills up, current drops, and so does the V 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
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #4
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    Re: help with upgrade

    I double checked, I dont know why I was thinking 3.3amps on these

    heres the specs of the panels I have:

    http://www.e-marine-inc.com/products/solar_panels/kc40.html


    and the one I am considering adding:

    http://www.e-marine-inc.com/products/solar_panels/kc130tm.html


    my 12 foot run of wire is from the PVM to the Controller and the controller is 2 feet from the battery.


    sounds like I'll be allright with my existing wiring?


    thanks
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #5
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    Re: help with upgrade

    I hope you are aware that we sell the same panel for almost $200 less http://store.solar-electric.com/kykc130wasop.html ...
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #6
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    Re: help with upgrade

    Using:

    voltage drop calculator

    13 amps and 2x12'=24' round trip...

    Gives you around 0.3 volt and 1.84% voltage drop. And a 10 awg wire is good for 20 amps at least (using NEC conservative ratings) -- assuming appropriate insulation and routing of cable.

    Ideally, you should have a series fuse/breaker in each panels + output lead to protect internal shorts in panels from power supplied by the other panels. Usually, series protection devices are required when more than two panels (or panel strings) are connected in parallel to protect against fire.

    If you don't find the "series fuse" specification for the panels (here is the 130 watt panel PDF from Windsun/NAWS--no fuse listed; typically on the mfg. spec. sheet)--a little less than 2x the Isc should be fine (~5 amps for the two smaller panels; ~15 amp for the larger panel).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #7
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    Re: help with upgrade
    Windsun wrote: »
    I hope you are aware that we sell the same panel for almost $200 less http://store.solar-electric.com/kykc130wasop.html ...


    I am now.. thanks!




    BB. wrote: »
    Using:

    voltage drop calculator

    13 amps and 2x12'=24' round trip...

    Gives you around 0.3 volt and 1.84% voltage drop. And a 10 awg wire is good for 20 amps at least (using NEC conservative ratings) -- assuming appropriate insulation and routing of cable.

    Ideally, you should have a series fuse/breaker in each panels + output lead to protect internal shorts in panels from power supplied by the other panels. Usually, series protection devices are required when more than two panels (or panel strings) are connected in parallel to protect against fire.

    If you don't find the "series fuse" specification for the panels (here is the 130 watt panel PDF from Windsun/NAWS--no fuse listed; typically on the mfg. spec. sheet)--a little less than 2x the Isc should be fine (~5 amps for the two smaller panels; ~15 amp for the larger panel).

    -Bill

    great help thanks! I was wondering about the fusing too because when I added the second 40w I figured I had to increase the closest panel to controllers fuse amperage which is still in the safe range for the panel but if I add a 130w then they way I had it I would need a fuse that is higher amp than the panel would be safe at.

    thanks again, I'll read up on it.
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