Eli5: Why do charged electronics (Game controllers, eReaders,) lose their charge when they’re not being used?


Eli5: Why do charged electronics (Game controllers, eReaders,) lose their charge when they’re not being used?

In: 1469


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.