I am using this module for wireless charging, as a receiver, and i want to switch it on and off, because firstly it consumes about 5mA when idle and secondly i want to power it off when the battery is fully charged. So i decide to use this NPN transistor. I build the following schematic
in order to control the wireless charger receiver. The problem i am facing now is that the charging procedure takes much longer.
Any clue why is this happening? I dont think the the circuit is wrong, maybe a diode in Vbat in parallel with the collector pin, but i am not sure that this has anything to do with charging procedure.
I am using a lipo battery and i am starting charging at 3v and i should stop it around 4.1v. The capacity of the battery is 400mAh and the charger receives 300mA maximum. Therefore, when i am not using the transistor the charging procedure takes less than 50 minutes, but when i am using the transistor the charging procedure is about 6 hours(and i am guesing the battery is broken after that).
To control the transistor i am using and arduino uno gpio, therefore 5V/40mA maximum. During the charging procedure usinng the transistor the current floating from collector to emiter is only about 32.5, measured with a multimeter.
So, am i "opening" the transistor enough? I removed the base resistor and the I_CE current increased to 118.2mA and the charging procedure is more faster now. It's much better know, but still there is about 100mA kind of "lost".
Moreover, when base is set to low, there is a 15mA current floating from collector to emmiter.