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Padlin's avatar
Padlin
Explorer
Mar 02, 2015

Cable size for 160W portable solar panel

Have 2 trailers. Trailer #1 has an existing 30A PWM charge controller being fed by a single 160W roof mounted panel. The controller is about 2' from the 2 6v batteries with a shunt between them for the monitor. Trailer #2 has no solar.
Have a 160W portable solar panel with rear mounted 10A controller, came with 20' or 12awg to use from controller to the batteries.
Want to use trailer #1 late fall/winter bypassing the portables controller and running the cable to the existing 30A controller. Will use trailer #2 this summer feeding it's batteries directly from the panel mounted controller.

Portable Panel specs
Open Circuit Voltage (Voc): 21.0V
Short Circuit Current (Isc): 9.4A
Maximum Power Voltage (Vmp): 17.0V
Maximum Power Current (Imp): 10A


Fixed Panel Specs
Voc 22.2V
ISC 9.46A
Vmp 18.5V
Imp 8.65A


Using 10A of current I believe the following max cable lengths are correct.
12awg = 20'
10awg = 30'
8awg = 40'

Am I correct in assuming that the cable gauges and lengths mentioned above would work for both scenarios?

Do you see any other issues?

14 Replies

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  • jrnymn7's avatar
    jrnymn7
    Explorer
    Mar 02, 2015
    First off, that 160w portable's Isc is a little high for that 10a controller. Should be 8a, max. And usually, Imp is lower, not higher, than Isc.

    10a thru 20' of 12ga will have a v.d. of ~ 5.5%... too much.

    10a thru 30' of 10ga will have a v.d. of ~ 5%... too much.

    10a thru 40' of 8ga will have a v.d. of ~ 4.3%... still a little too much.

    Bump everything up two sizes, and you'll be good; thus allowing for additional losses at circuit breaker and connections, as well as temp compensated charging.
  • time2roll's avatar
    time2roll
    Nomad
    Mar 02, 2015
    As long as voltage drop is less than 2 I would call it good.
    My calculator says about 3x the distance is fine.
  • Bend's avatar
    Bend
    Explorer
    Mar 02, 2015
    OP-

    The secret of good solar PWM charging performance is conserving voltage. Once that is done, amps will take care of themselves. You need at least 16.5 volts at the controller for it to work and usually 14.8 volts at the batts. Your winter RV will probably need more solar watts and battery voltage due to low temps.

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