Battery Charging Question

Hi everyone, I have a question about battery charging and yes I have read the battery guide already available on the site and found it extremely helpful, but it doesn't answer my question.

I'm a university student so I'm on the go around campus all the time, my question if whether i have to charge the Li-ion battery in my laptop to 100% each time? say it drops to 20% battery power left, which is when i usually would start charging it, but I have 30min till class so i only charge it to 80%, then i use it down to 20% again during class, come out and charge it up to full or part way again, say to 90%.

Is this type of charging going to weaken the battery? Especially if I perform this kind of charging say once or twice a week? I read somewhere to only charge these things when they need it and to avoid excessive charging as it weakens the cells.

Thanks in advance for your time guys,

- kyo

 

No. Lithium-Ion batteries are not subject to memory, so it does not matter how high you charge it each time. The issue you are referring to is charge/discharge cycles, which is a basically just a measure of how much energy you've put through (and pulled out) of the battery, and that will not change no matter where you charge the battery to. For example, starting with a full battery:

You use the battery to 50%, charge to 100%, and then use the battery to 50%, and charge back to 100% again.

That would count as one full charge/discharge cycle.

You use the battery to 25%, charge up to 100%, and then use the battery to 75%, and charge back to 100% again.

That is also one full charge/discharge cycle.

You go from 100% to 75% 4 times, charging back up to 100% each time.

That is also one full charge/discharge cycle.

Now, there are some other variables involved, but in general, as long as you're not discharging below an unsafe minimum, the amount you charge to each time should not greatly affect battery life, as long as you're using the battery. Now battery storage, that's an entirely separate issue entirely...

 

And on the other end of the spectrum, to avoid shortening your battery's life, don't forget that it's important not to let the battery discharge to much beyond 10%.