Electronic fuel gauges in battery packs may not be where you expect it!
As far as you may know, many laptop, notebook and even netbook battery packs (especially lithium ion) have an electronic fuel gauge inside them.
This means that when charged up, the battery pack can be quickly swapped without having to recalibrate the electronic fuel gauge inside them.
But this is not so with the Asus Eee PC (and possibly others), which has the electronic fuel gauge inside the Eee PC itself and not the battery pack.
I had to advise a client when swapping battery packs in such a unit to leave the unit turned off while being plugged in for up to about 72 hours to recalibrate the electronic fuel gauge.
This means that when charged up, the battery pack can be quickly swapped without having to recalibrate the electronic fuel gauge inside them.
But this is not so with the Asus Eee PC (and possibly others), which has the electronic fuel gauge inside the Eee PC itself and not the battery pack.
I had to advise a client when swapping battery packs in such a unit to leave the unit turned off while being plugged in for up to about 72 hours to recalibrate the electronic fuel gauge.