I know this probably has some simple explanation, but how does that juice-meter work on individual batteries (you know, the kind you have to press with your finger and thumb).
Does it have anything to do with the current running through one’s body (I doubt) or is it just some kind of thin strip, that when pressed hard enough - makes a closed circuit - and voila!
I’m too lazy to research this…
Basically, when you press on the two battery ends, you complete a circuit. The current from the batter goes through the strip on the battery, not through you. The more charged the batter, the more current that flows through the strip, and the hotter the strip gets. The strip is made of of a special material that changes color depending on the temperature. The final temperature of the strip determines how far up the strip it indicates. That’s why it takes a few seconds - it takes time to heat it.
Here’s a more detailed explanation of the same type of batter meter (but on the battery package, not the battery itself):
How do battery testers on battery packages work?
Arjuna34