If you have an option in the BIOS or drivers to set the battery charging threshhold to stop charging at 80% or possibly even lower (I believe Lithium Ion/Polymer cells are happiest at around 40-60% state of charge, which is why they are usually shipped that way). Sometimes this feature exists, but only vaguely described as “battery life optimization” or some similar wankery that they never properly explain.

You can also just remove the battery entirely if it will be always plugged in, but setting it to a low/modest maximum charge gives you a nice, reliable, built-in UPS in case of power interruptions.