On my own phone there’s a function where it can stop charging at 95% to protect the battery health. Why can’t it do this at 99.99% and present it as 100%? It would be unnoticeable to users and would prevent the overcharge issue, right?
In: Technology
The issue doesn’t just happen at 100%, it just gets worse as it gets closer to 100%. So keeping something charged at a high percentage for a long time is harmful, not just 100%. So obviously 99% wouldn’t make too much of a difference.
They can and some do cut off when they’re close to full. It all depends on how sophisticated the charging system is, which roughly scales with the expense/complexity of the battery.
Running batteries way down to zero or all the way up to full is physically hard on the battery. For maximum life you want to charge up to no more than 80% or so, and not let it get down past 20% or so (depending on the battery details).
Smart charging systems know this and do it automatically (the laptop I’m typing this on holds at 80% all the time when plugged in, because I told it to). If I let it run up to 100% it would do so, then cut off the battery charging and could sit there plugged in at 100% indefinitely without battery damage.
Some car batteries have excess capacity above “100%” so they’ll say “100%” to you when they might only be at 80% of their physical capacity. That prolongs life and allows them some degradation over time without losing any range at “100%”. Some EVs with battery size options have only one physical battery, they’re just moving the 100% point in software.
At the other end of the spectrum, like cheap phones, they want to give you as much run time as they can so they run them up to 100% over and over and over, although even the most basic ones will usually have an overcharge controller that stops charging at 100% (overcharging a lithium-polymer battery, like you have in most phones, is very bad…like explode in fire bad).
The thing is, they already do.
What is being presented as 100% isn’t the full potential capacity of the battery. Going any further would be way more damaging and wouldn’t bring any real benefit.
The main issue is that *any* recharging is damaging and the higher you go the damage becomes exponential. So it becomes a tradeoff. Do you want the battery to last a long time until the next recharging or do you want the battery to have a long lifetime?
They do. The thing is, the battery percentage, and what is”full”, is arbitrary. What matters is the voltage the battery is being charged to. The higher the voltage, the harder it is on the battery. It’s completely up to the manufacturer what voltage they consider 100%.
With mobile devices, like phones and laptops, the batteries are pushed to the absolute limit to squeeze out every bit of battery life. These devices have been largely treated as disposable, and people didn’t care if they only lasted a few years.
Now, something like electric cars, battery longevity is extremely important. 100% on most electric cars is going to be a lower voltage than your phone.
It’s not over-charging that causes batteries to degrade, it’s just *being charged* that does it with the degradation being relative to how charged the battery is.
So 99% charged won’t really be any better, but say 90% will be that bit better for it.
Because of this the newer Android OS lets you set a max charge between 70-100%, I have my phone set to 90% so once it hits that it stops charging.
I’m using my old phone as a remote camera so because it’s always plugged in I have it limited to 70% to make becoming a spicy pillow less likely (I hope)
It’s not because of charging, it’s because of sitting at full. For example, for Teslas you can schedule your departure, and it will start charging to full just when it expects it to be complete by departure time. So it doesn’t sit all night on 100%, but when you get into car it just reaches it, so it doesn’t sit on it for too long. If you limit your max charge to like 80% or the best 50%, then you can be plugged indefinitely and everything runs on power from charger. So battery is only getting wear through time (aging) and holding charge (the farther from 50%, the worse it gets). As a customer, if you want, for most devices you can put a limit and that’s as far as you should think about it.
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