Led Battery

I have a single LED, how can I activate a battery?

and what type of battery? can feed more than 1 LED-ie, a battery AA?

You can drive a single LED in a cell. Depending on the diode forward voltage ranging from 0.5V and more ... you may able to supply more a diode. The cell voltage is 1.5V AA. If your blood before is less than 0.75 volts, may be able to power 2 of them. That's all reached. He also wants to limit the current. Use a resistor in series with the diode. Otherwise, the diode in May explode! To find the current through the diode (I) I = (Včela - Vforward) / resistance. 10 mA to 20 mA is very well lit. If in doubt use a resistance of 220 ohms for a single diode. It is what we use only sure things work. I adjust it later!