My portable solar panel gives out 18-20 volts instead of the 12-14 that it is supposed to. I know that if I put a resistor in line (series) that it will bring the voltage down so my voltage regulator likes it better. What specs on the resistor do I need? I know P=IE and E=IR, but it has been 20 years since my electronics classes, and I also need to know the size of the resistor as well as the Ohms rating. Can anyone help?
I use this panel to charge 12volt lead gel cel and lead acid marine deep-discharge batteries. The gel cells range from 5Ah to 12Ah and the marine batteries are more along the lines of 60Ah. The voltage regulator is designed for use with solar panels so that batteries don’t get fried. It makes sure that a stable current is sent to the batteries and as they reach full, it switches to a trickle charge. When the sun goes down it has a built in diode to prevent battery discharge. It was flashing rather than the normal solid light, so I pulled out a multimeter and pegged the dial…switched to 50 volt range and it told me it was at 19 or 20 volts. First I put a 12 volt (10 watt) light in parallel with the regulator and it brought the voltage down to about 14. I randomly grabbed a scrap resistor out of my junk drawer (1/2 watt I think) and put it in series with the regulator(input). The light changed to solid, not blinking, but how much efficiency am I losing if I overresist? L.A. sunlight.
The regulator is a marine battery device for use on boats. This is its intended purpose. The regulator is not the problem… with no other devices attached, the panel is putting out close to 20 volts at around an amp. I’m not complaining about the great output, I just want to make sure I don’t blow anything up. It is rated as a 14 volt, 750mA device, but it is putting out 20ish at closer to 1 Amp.
This solar panel is from Ramsey Electronics website, where you can see it and see the specs.
