New Controller, new voltage readings?

bmet
bmet Solar Expert Posts: 630 ✭✭
in Solar Beginners Corner #1
When I was connected to my old HQRP controller the voltage across the + and - terminals coming from the panel was usually in the 20.5 range. Now that I've connected over to the SunSaver the voltage is never above 19.1 . Is this value Vmp or Voc, and why would it be different? Thank you.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: New Controller, new voltage readings?

    With a load on the charge controller you'd be measuring something near Vmp. With no load you'd be measuring something near Voc. The "near" factor is due to the consumption of the charge controller itself. A typical "12 Volt" panel's Vmp is 17.5. Different controllers will 'load' the panels differently, according to what's going on inside them.

    In practical terms, what matters with a charge controller is the V and A out, not what's going in. The important input factors are that Voc doesn't exceed the controller's max and that there isn't too much extra Wattage so that money is wasted on panels whose power you won't be making use of.
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #3
    Re: New Controller, new voltage readings?

    Thank you for that explanation. Tomorrow I am returning to the site to readjust the angle for the Summer, and we'll see what the number is. The initial measurement of 19.1 VDC was constant from installation(2:30 ish) to about 5pm. The documentation states that removing the jumper (for lead acid battery) is supposed to set 14.4 volts, but I never metered more than 14.1 across the SunSaver's solar terminal. I'm going to connect a different battery tomorrow at mid-day, and measure what the output is.

    Thank you.
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