Eli5: Why do charged electronics (Game controllers, eReaders,) lose their charge when they’re not being used?
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I do not know if this explains for *all* electronics discharge, but just last year a team of Canadians found [why many batteries may be self-discharging](https://www.cbc.ca/news/canada/nova-scotia/battery-power-laptop-phone-research-dalhousie-university-1.6724175).
It turns out that batteries have been frequently constructed using tape that’s made with polyethylene terephthalate (PET) plastic. This plastic degrades over time (and with heat) releasing a molecule that ends up shuttling electrons between the positive and negative electrodes, thereby discharging them!
This issue can be resolved by switching to a slightly more expensive, but also more stable, plastic used in the tape.
From the article:
> “A lot of the companies made clear that this is very relevant to them,” Metzger said. “They want to make changes to these components in their battery cells because, of course, they want to avoid self-discharge.”
Starting this year we just might find that the problem of self-discharging batteries (from newly produced batteries) has greatly improved.
Store your batteries (or devices with non-removable batteries) at nominal voltage. So e.g. 3.7 Volt for one lithium-ion cell.
All batteries are releasing electricity from a chemical reaction. While drawing power from the battery can make the reaction go faster, it cannot be made to stop completely. Also, for most charged electronics “off” isn’t off, it’s just a low-power standby setting waiting for them to be switched back “on”.
Batteries self discharge, the decay of charge can be explained by the same thing that makes ice melt and coffee get cold. Mantaining an electric charge and all of those teeny particles excited requires energy, and that energy dissipates in the form of heat in minuscule quantities, it is harder for the battery to be charged than it is for it to not be charged, thus it will eventually lose all charge. Using them will only accelerate this process.
I just want to add, it’s not entirely true that batteries *just* self discharge.
Cheap batteries self discharge, because in a battery there is a + side and the – side, but internally, those two are back to back, very very close, and when using lower quality chemical “ingredients”, that barrier lets some electricity through, directly, inside the battery itself. That acts as a very small short circuit and turns that wasted energy into heat, but so slowly that the heat is barely detectable.
Good quality batteries have this problem reduced almost to zero, and can keep the charge for many years.
On top of that, cost optimized electronics without a physical off switch, tend to not exactly go fully off, and the battery is constantly powering some things needlessly, because “electronic” switches are not ideal, and the cheaper you go, the more electricity they let through when off. That off “leak” is not enough to power things like display or a wireless chip or the cpu, so it just lingers around the circuits and gets turned into very small amounts of heat.
I have a Nintendo 2ds I bought because i always wanted a gameboy as a kid, but being an adult i just use it like once a year or less, when i have a particularly bad day. After something like a year without charge it can still give couple of hours of play.
Ok, so something often not thought about is that the battery is still supplying energy. A very small amount of power is still flowing in the device, which is an unavoidable part of physics. So, the battery will drain very slowly as a result.
Wow, even our gadgets need a break to recharge themselves! They’re just like us, but with better battery management.
Batteries are made up of two or more materials. When we store electrical power in batteries, we basically use an electrical voltage to “push” electrons from one half of the battery to the other, changing the materials/chemicals inside a little to force them to have more or fewer electrons than their default/natural state
Essentially we take an electron from one chemical (forcing it to have one fewer electron than it wants), and give it to the other (forcing it to hold an extra one). When we connect a circuit, they try to go back the other way to their more natural state, pushing electrons along the wire to create a new voltage we can use
Unfortunately we can’t perfectly insulate either chemical from contact with the other or the outside world, so over time electrons will slowly “leak” back to where they “want” to be, losing the charge because the electron imbalance we forced to be there is reduced
It’s a bit like pumping water up to a tank so that later you can release the water through a turbine to make electricity…. over time a bit of water will leak through the valves or evaporate, reducing the amount of stored energy
Two reasons for the most part:
1. Unless the device has a mechanical switch that physically removes power from the electronics, the odds are that the electronics aren’t truly ‘off’. They are probably running at a relatively low frequency (32kHz) looking for an interrupt (e.g. a button press, or a cord/signal connection) to wake them up, monitoring the battery, etc.
2. Again, unless power is physically disconnected from the electronics, solid state circuits ‘leak’ (if you Google up a microcontroller data sheet, look for ‘leakage current’). So, even if the device isn’t running in some standby mode pretending to be off, there will still be some power draw.
That said, #1 is the overwhelming reason for the battery discharge.
Who knew, even our gadgets need some ‘me time’ to recharge themselves! Guess we all have something in common!
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