Use LED lights and cell phone batteries to make flashlights?
The current of a single LED lamp is about 10mA, the battery voltage, the rated voltage of the -LED lamp) and the /10mA= current limiting resistor. If there is no resistance current limit, constant current source circuit can be used. However, constant current source is not only economical, but also more complicated.
It depends on what LED is, if strawhat micro light LED, it depends on a few LED lights, and then the calculation, if the power of LED 3-5W, it can also direct drive in general, but for security reasons, can add a constant current voltage stabilizing circuit.
LED lamp is much power, mobile phone battery is a large capacity, if more than LED rated current to a current limiting resistor
