Eli5: How does a power bank charge a device until it dies, wouldn’t equilibrium be reached?
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So someone explain this to me, I have a power bank that will lose charge if accidentally left on. So tell me, if it’s not plugged into any device, where does the power go?
It’s like pouring into a glass from a kettle. If you just connected them it would just reach an equilibrium but instead you raise the kettle as you pour and thus are able to pour everything save the last few drops.
The power bank contains a circuit that always keeps it’s voltage higher than the device you are charging, resulting in a similar effect.
There are road signs in the power bank that tell the power which way to flow. Into the bank from this port, out of the bank thru this other port.
Imagine you fill a bucket with water from another bucket.
The bucket below does not care how much is in the one you are pouring from.
Equilibrium states are only reached if the device can also charge back the power bank. This is however not the case here.
If we think of voltage as height for potential energy we can use a crude analogy. Something cannot travel higher than it’s initial height on a pendulum or slope or if you bounce it off the ground. However, if you split up two bits of mass from the same height you can make one of them go higher while the other doesn’t bounce as much. The typical backyard experiment for this is dropping a tennis ball and basketball next to each other, you see they can’t return to the original height. If you drop the tennis ball place directly on top of the basketball, it will bounce to a much higher elevation. A boost convertor sort of does this with capacitors, and inductor, a diode, and a transistor. It “bounces” a little bit of electricity off of another bit to boost the voltage of some of the current, while having some loss to the remaining electricity.
If you get the water analogy of electricity the boost convertor is basically a hydraulic ram.
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