Why does a laptop say it’s at 6-8% charge, and then it dies, but when it’s at a higher charge, going from 60% to 59% takes a while?
In: Technology
Probably bad algorithm to estimate battery life. Batteries tend to discharge in non-linear fashion, but it’s easier to estimate battery life linearly.
Not sure if this is the correct answer but I heard batteries take longer to charge the more juice they have. It’s like stacking bricks, at a certain height.. it takes more time and energy to stack it there. So maybe the same goes for how the power is used and the last 10% deplete faster.
Weird how it feels like the opposite with most cell phones (that I’ve owned). I’ll start using my phone at 5% just to kill it and be scrolling for a couple hours
It is an estimate and as batteries get older/weaker anything below 10% should be considered 1% unless you enjoy living on the edge.
Because it’s an estimation. The computer doesn’t actually know how much charge is left. Batteries are direct current, that means as the battery discharges the output voltage changes. Through battery testing they’re able to determine a reproducible voltage curve. Then they assign percentage of charge to voltage. By measuring the voltage the computer can estimate the amount of charge left.
As the battery ages the chemistry changes making the voltage curve not as predictable as programmed. That’s why the battery will die at 6%. Then when you plug it in it says 0%.
Voltage curve:
https://images.app.goo.gl/aws4HdaGGfThUhYBA
In the image it starts at 1.5 V then gradually decreases to 1 V then suddenly goes to zero.
When rechargeable batteries age the sudden drop in voltage drifts to the left due to changes in the battery chemistry. So instead of suddenly dropping to zero at one volt it’ll do it at 1.2 volts. The computer thinks 1.2 V is 6%, so it says 6% battery life left. Then the sudden drop occurs and the battery dies.
You probably have your laptop configured to begin shutting down when it has some power left over (perhaps 5%), to avoid it losing power while doing something important. It shuts down when it’s hit that preset limit, not when it absolutely can’t run any more.
Most laptops shut down long before they reach an empty battery, mostly to preserve your work and system when the battery is low.
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