Continuity works but no voltage

I am installing on a zamp "solar ready" RV.   Had a real hard time finding the wire on the roof from the combiner box. Once i found it I did a continuity test to make sure it was the right one. Continuity beeps, but i get no voltage when the panel is plugged in.  I get voltage from the panel, I get voltage from the other plugs on the combiner box when the panel is plugged in but no voltage at the end of the wire. I have no idea why i wouldn't get voltage when the continuity works.  Please Help!

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,175 admin
    Welcome to the forum MRCC1,

    Obviously, solar panels need some direct sun on the panels. If there is any shading, it will dramatically reduce their output.

    Under sun, and if using a "simple" PWM charge controller, the panel(s) should read near Voc (voltage open circuit) or 20+ volts if not connected/under load, and around Vbatt when connected and charging the battery bank (at the Vpanel input terminals of the charge controller).

    So, I would disconnect the two wires at the Vpanel input of the charge controller, and measure the voltage there. Note the polarity, it is very easy to mix up positive and negative connections. It is possible that if you have +/- reversed on the charge controller, it may "short out" the panels and read zero volts (I do not know, just guessing).

    If you still read zero volts with the Vpanel terminals disconnected, go back up to the solar array and measure the voltage up there. If zero, then disconnect from the RV wiring and check again. Make sure if you have several panels in parallel, that they are wired + to +, - to -, etc. (if wiring in parallel).

    Solar panels are not really "solar batteries" in the sense that they output 17.5 volts at any current level... They are "current sources" that will output (approximatly) X.X amps based on the amount of sun hitting the panel (100% sun, then 100% of Imp rated current. If 25% sun, then 25% of rated current). So the measured voltage from the panels depends on the amount of sun, amount and type of load, etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mrcc1mrcc1 Registered Users Posts: 2
    Thanks BB. The idiots that manufactured the RV wired the "solar Ready " box wrong. Put the wrong wires on the terminals to the fuse. Thats why i got continuity but no voltage! Just affirms my belief that "solar ready" on an RV is just a money grab!
  • BB.BB. Super Moderators, Administrators Posts: 30,175 admin
    At least you found the problem, and hopefully fixed it.

    Take care,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Wheelman55Wheelman55 Registered Users Posts: 79 ✭✭✭
    mrcc1 said:
    Thanks BB. The idiots that manufactured the RV wired the "solar Ready " box wrong. Put the wrong wires on the terminals to the fuse. Thats why i got continuity but no voltage! Just affirms my belief that "solar ready" on an RV is just a money grab!

    FYI. It is my understanding that ZAMP reverses their polarity on purpose so that only ZAMP gear is plug and play on ZAMP ready trailers/ RV’s. 

    Building Off-Grid in Terlingua, TX
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