I have a very small project which requires a typical 9v battery for mobile use. But to keep from having to replace the battery I would like to put in a rechargable 9v battery and use a 9v output from a dc power plug to charge it. I have charged batteries with solar panels before and all that is needed is the diode on posotive. But is this the same for what I am wanting? Will the battery not have enough resistance to keep a safe low amperage? or will the battery consume only what it needs? or must a resistor be put in series with the diode?