I thought I knew the answer to this but a colleague has just sown the seeds of doubt in my mind. Best way to treat a laptop battery for long lifetime? Whenever possible charge fully then discharge fully (might not be completely necessary with Li-Ion but can't harm). When it has fully charged on my desk should I unplug and let the battery discharge as I use or is it ok to just leave it plugged in? My colleague says I should unplug. I think there's logic in the laptop/battery that prevents damage when it's reached the fully charged state. Who's right?