Topic: ...." I Know Nothing "...

[moehoward4]

I got some 3 volt solar panels from eBay that actually put out about 3.6 volts in full sun. What do I need to do to knock the 3.6 DOWN to 3 volts? Specifics please as like the topic says, " I Know Nothing " about electronics.  Thanks

[nincehelser]

I got some 3 volt solar panels from eBay that actually put out about 3.6 volts in full sun. What do I need to do to knock the 3.6 DOWN to 3 volts? Specifics please as like the topic says, " I Know Nothing " about electronics.  Thanks

Unfortunately the answer isn't so simple.

If you measured the voltage "open circuit", 3.6V may be normal, but when you actually hook it up, the provided voltage will probably drop down closer to 3V. 

If you actually need to regulate the voltage, you use, oddly enough, a "voltage regulator".  The issue here is that voltage regulators aren't always very efficient, which can be a big issue working with solar panels.

[moehoward4]

I hadn't thought of that, so I guess I'll have to set something up to see what they actually put out.....Thanks

[92merc]

[nincehelser]

I hadn't thought of that, so I guess I'll have to set something up to see what they actually put out.....Thanks

Another thing to keep in mind is that solar panels aren't modeled well as an ideal voltage source.   They're better modeled as a current source.

I say this because most people are familiar with voltages sources (e.g. batteries) but not so familiar with current sources.  In other words, if you try to think of a solar cell as being like a battery, it can really mislead you.

[pfletch101]

Why do you need 3V (rather than a voltage which is only 20% higher), and, if you really do need 3V, how precisely controlled does it need to be? Bear in mind that your solar cells are likely to spend much of their time in less than full sun, so low voltage is more likely to be an issue than high unless your power requirements are substantially less than their maximum power rating. As nincehelser implies, the voltage and current sourced by a solar panel at any level of illumination are interrelated - it will happily drive current through a short circuit across its terminals, but the voltage across them will be zero under those circumstances.

[DanS]

I got some 3 volt solar panels from eBay that actually put out about 3.6 volts in full sun. What do I need to do to knock the 3.6 DOWN to 3 volts? Specifics please as like the topic says, " I Know Nothing " about electronics.  Thanks

Another option would be to try inserting a common !N4000 series (4001/4007) diode inline. This will drop the voltage around the amount you need. But like mentioned earlier, when you don't have full sun you may be too low. A safe thing to try though because at the highest voltage you will be near 3 volts.