We all know that devices can have their batteries weaken over time if you leave them charging for too long. Why does that happen and why can’t our devices just stop taking in power / cut off right when it’s full?

Question

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

Answer 1

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.