I have an RC circuit where I measure the voltage across the capacitor over time with a voltmeter. For the supply voltage I am using a 5V phone charger.
I know what is supposed to happen, the voltage on the capacitor is going to increase rapidly in the beginning and will slow down as it charges until it reaches the supply voltage.
What I am measuring however is very different. The first couple of seconds the voltage increases, like it should, until 3.9V and then starts to drop while the capacitor is still supposed to be charging.
I'm very curious as to how this can be explained.
The capacitor's value is 150uF, the resistor is 20kOhm, the supply voltage is 5.22V measured with the voltmeter.