It sometimes looks like that in the lab, but in real life it doesn't work. Here are two of the MANY situations that result in incredibly misleading voltage read

It sometimes looks like that in the lab, but in real life it doesn't work. Here are two of the MANY situations that result in incredibly misleading voltage readouts: My battery is 80% charged, and then I go outside where it is 10 degC colder. Suddenly my battery voltage drops by 200mV and my battery looks 20% charged My battery is 80% charged and then I start playing a video. The increased load drops the battery voltage and suddenly my battery looks 20% charged.