Eli5: Why do charged electronics (Game controllers, eReaders,) lose their charge when they’re not being used?
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They are really not turned off completely. Most go into a low power mode. This is usually to maintain the wireless connection, so that they do have to restart the initial setup. Imagine your phone turned off every time you locked your screen and you have to wait for it to ‘boot up’.
The battery in itself can’t hold the same level of power forever, the potential energy to drive the current trickles down. It’s like a leaky water bottle, it will slowly discharge even when not in use.
Batteries are in general, Capacitors, they store a charge, but the charge dissipates over time.
Two things factor into this. All batteries have what’s called a self discharge rate, which is where energy is lost over time because even when not being used the chemical reaction that makes power is still slowly happening. How fast this happens depends on what chemistry the battery uses.
The other (larger) factor for electronics is that even when they are “off” they are still running a program to watch things like power button presses. Running this program uses power and slowly drains the battery.
Edit: 3rd factor I forgot about for some battery types (li-ion and similar) they have built in battery management system electronics (BMS). These use a small amount of power and monitor the health of the battery, making sure it is not discharged too low or charged too high.
In a broader sense, they lose charges because of entropy. Entropy is universal, eternal, and will literally be the end of the universe. The sun is low entropy, and moving towards high entropy as it will die. In this specific case, high entropy means a higher portion of its energy (potential, kynitic, etc) is unavailable for work.
Your battery is in a low entropy state if it’s charged, and laws of thermodynamics tells us that any state of low entropy will tend to go to go higher or go the same from any spontaneous action. We create insulation between cells to prevent this, but nothing is perfect and nothing beats entropy in the end.
Easy, some use bad designs where they still use a very small amount of power even when you think they are off.
To make matters worse, all current rechargeable battery chemistry loose charge over time.
Many have mentioned the self discharge rate, but a bigger thing is the fact that we as a society chose buttons over switches for powering on and off.
A switch used to cut a circuit off, so the battery wasn’t slowly flowing power through a circuit while it was off. With buttons that turn things on the battery is always in a completed circuit waiting for the devices computer to sense the button press and turn on. Not only does the a completed circuit kill batteries faster (9 volts in flashlights), the computer itself requires a small amount of power to be ready to respond to the button.
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Batteries over time lose thier charge. It’s slow and unnoticeable with new batteries, but older batteries will do it faster. Plus wireless controllers constantly talk to the console if you have them on, even if you are not using them. This will drain the battery. Turn them off if you are not using them.
Because batteries are not magic.
It’s a chemical reaction that cannot be stopped even when they’re not being used.
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