I purchased voltage regulator SKU 180057. Im using this on my RV batteries. I charge my batteries with a solar cell rated for max output of 24 volts and 1.5 amps. Today I read 21.1 volts coming from solar cell. My batteries read 12.83 volts while not connected to anything.  I connected the solar cell to the regulator (but not to batteries) and it read input of 20.3 volts and i set output to 13.1 volts. Then I connected the regulator to the battery and the readings on the regulator say input is 13.5 volts and output is 12.5 volts. I understand there has to be 2 volt difference for regulator to operate. Does this sound like it is not operating properly?