Will a 4.5 volt charger burn up a 3.7 volt cell phone battery? If so, what resistor would I need to kill .8 V?

Question

I'm building a solar charger for my phone. Should I bother to drop the voltage to the exact number listed on the battery. The panel puts out 4.5 V, and the battery takes 3.7 V. Will this hurt my phone? If so, would someone please tell me which resistor I need. (also, if you could supply an equation or formula to find out how many ohms i would need to drop voltage by a fixed amount.) Thank you for sharing your knowledge.

Answer 1

Dont use resistors, try using a Zenor Diode.  The diode will kill .6 volts.  As for resistors, you want a resistor to slow down current.  It is current that will kill a drained battery while voltage kills a full batt.  You will need to rectify the panel so that the full battery doesn't unload into the panel during off peak hours.  The diode, a one way current valve, requires .6 volts to overcome the pn junction.