how is battery cycles calculated?

[skanky]

say i have a 48wh battery, does it count 1 cycle as:

1) when im on battery and it uses 48wh no matter if i charge it at 90% or 30%, it just counts 48wh and increments the charge cycle by 1

or

2) increase by 1 everytime you plug it into the mains?

thanks.

[lfeagan]

I would think there are two ways to determine if the cycle count needs to be incremented:

1) When the battery goes below some threshold, such as 30% charge, and is then recharged. Of course, in terms of computing this, we would only need to keep track of when it goes below a certain threshold as the recharging of it is implicit for it to have that change from above to below 30%.

2) When some comination of the sum of the the differences between each charge/discharge session exceeds a total of 70% or some number like that.

And, perhaps a third method which just pays attention to the total number of times you start a charge and then discharge, regardless of percent. This would be because any charge/discharge affects the cell chemistry.

[pramit]

I found Apple's site to be pretty insightful on Li-Ion batteries and charge cycles.

http://www.apple.com/batteries/

Enjoy!