Nowadays a lot of notebook users handle their notebooks like a desktop computer. This means, mostly the device is located on one place and it is always connected with the power supply. But this is not really good for the lifespan of the battery. The manufacturers of the mostly used lithium ion batteries guarantee about 500-1000 load cycles. These load cycles doesn't only contain charging of drained batteries but also these of only partly discharged ones. For example, the self-discharge with a cut-off power supply causes a discharge and when turning on the notebook again it takes a complete load cycle to charge the battery again.
Li ion laptop battery" by Kristoferb.
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