-- Question for battery and electric gurus! ---

[basslover911]

It might be very simple, but...

Can I charge a li-ion battery (3.6V) or nimh battery with a voltage of less than what the battery puts out? IE maybe 1 volt or so?

It would probably take a lot longer, but is it possible?

[jamesqf]

No. Think of voltage as analogous to pressure. If you're pumping up a tire, the pump pressure has to be higher than the pressure inside the tire, otherwise the air comes out, no?

What are you planning to charge it with, a solar panel or something like that, that has a variable voltage? Then you put a diode in the circuit, so the current only flows when the panel's outputting a higher voltage than the battery.

[basslover911]

^Ok along those lines I was thinking.

I was trying to power a single LED with a 2x2" solar panel but they seem to only output .5V

[jamesqf]

You could stop by say Home Depot and buy one of the solar powered yard lights. I have a couple (won them as a door prize), but have never taken them apart to look at the electronics. Just assumed the panel was built to output higher than battery voltage in the sunlight.

[Daox]

You can use a lower voltage to charge a battery of a higher voltage, but you need a DC to DC converter to boost the lower voltage up. As you increase the voltage, you'll have less amperage, plus you take an efficiency loss at the dc to dc converter... But, you can do it.

[basslover911]

^Ohhh okay okay.

I think the simplest route would probably be a simple outdoor light though (and probably cheaper too ! )

Thank you guys so much! (hopefully this thread could someday answer others questions about the same thing )