24-05-2016, 04:04 PM
I just looked at that solar panel.
Its 10 watts PEAK.
And by my calculations more like about 8 odd watts.
Look at the photo of the back of it, output voltage 17.4 volts and current 0.47 amps, gives around 8.2 watts in full midday summer sunlight.
The 21 odd volts is unloaded IE no current being drawn. Maximum power output point is the 17 odd volts.
Drop that by around a third for average output over a day.
Those little switching converters are around 90 odd percent efficient so 8.2 watts in looses 10 percent being converted to 5 volts out so you'd get 7.4 odd watts or about 1.5 amps out at 5 volts.
I'd get at least a 40 watt panel if you want to draw 2 odd amps out with a switching converter.
The little ua / lm 7805 have really poor efficiency at those currents and voltages, basically the difference in input voltage, up to 21 odd volts in this case, and output voltage, 5 volts, is WASTED as HEAT and you get NO extra current output from that which you put in, IE 0.47 amps in this case.
My thoughts anyway
Its 10 watts PEAK.
And by my calculations more like about 8 odd watts.
Look at the photo of the back of it, output voltage 17.4 volts and current 0.47 amps, gives around 8.2 watts in full midday summer sunlight.
The 21 odd volts is unloaded IE no current being drawn. Maximum power output point is the 17 odd volts.
Drop that by around a third for average output over a day.
Those little switching converters are around 90 odd percent efficient so 8.2 watts in looses 10 percent being converted to 5 volts out so you'd get 7.4 odd watts or about 1.5 amps out at 5 volts.
I'd get at least a 40 watt panel if you want to draw 2 odd amps out with a switching converter.
The little ua / lm 7805 have really poor efficiency at those currents and voltages, basically the difference in input voltage, up to 21 odd volts in this case, and output voltage, 5 volts, is WASTED as HEAT and you get NO extra current output from that which you put in, IE 0.47 amps in this case.
My thoughts anyway
"If a clutered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign." Albert Einstein
Well, I have the cluttered desk, I guess that's a start!
Well, I have the cluttered desk, I guess that's a start!