What effect do small discharges have on a notebook battery?

Say you have your laptop on battery and use 10-20 percent of the battery before plugging it in again. What kind of effect do these small discharges have on the life of the battery, number of good charge cycles, etc?

 

Batteries have a set number of charge/discharge cycles. If you choose to charge when it is at 80-90% remaining you are simply using one of those cycles (for possibly, no reason).

If I know that I will only need a few minutes of computer time and the battery is fully charged, I remove it, use the system and put the battery back in when I am done and have unplugged from the wall.

I always try to fully use the battery (to ~5% remaining) before I fully charge it.

(Fully charging it also means not removing the plug when the green light first comes on - it is about 90 minutes afterwards - when the battery is at room temperature again and not 'hot').

 

in my personal opinion, these things make a very small difference, so changing your plugging/unplugging habits won't make a significant difference in the life time of your battery...

but I could be wrong...

 

Not much. A charge cycle is defined as the combination of a complete discharge and charging to 100%. Partial discharges add up to a cycle roughly linearly. That is, if you regularly use 20% (depleting the battery to 80%) and then charge it back up to 100%, it would take you about 5 iterations of this pattern to spend 1 cycle. This is not exact because there are some non-linear factors involved, but never mind; it's close enough. Apple has a pretty decent explanation of this for lithium-ion batteries.

 

Althernai,

A charge cycle may be defined as you state, by my experience shows that by doing so you will definitely be in the lower range of the 500-1000 charge cycles a manufacturer claims.

Essentially, it works out that any time you charge is a charge cycle - although not strictly as linear as that. And certainly not as linear as Apple claims in your link, either.

 

Usually, the battery cycle out run the usefulness of a notebook(and if it doesn't just get a replacement which is quite cheap nowadays unlike the early days) so I would just say forget about it and use it in the way that feels most natural.

 

I'm not going to alter my usage pattern to anything inconvenient to preserve my battery. When it wears out I'll spend the $50 on a new one.