A second, or spare, battery can extend the battery life of your laptop. When your primary battery becomes discharged, insert your spare battery to keep using your laptop.
One option you probably ignored when you bought your laptop was getting a spare battery. This item is a must for someone who is seriously on the road or in a remote location, where a long time is spent away from the power socket. Before you use a spare battery, ensure that it’s fully charged.
If your laptop has some type of quick-swapping ability, when the power gets low, you can just eject your laptop’s original, spent battery and quickly insert the spare battery. But be sure that your laptop can survive such a transplant before you attempt it! Perform a test swap in a noncritical situation, just to be sure.
If your laptop doesn’t have the ability to hot-swap batteries, just turn off (or hibernate) the laptop when the original battery is nearly spent. Remove the old battery, insert the fresh one, and then turn the laptop on again. Keep the following points in mind:
If you plan on pulling this trick often, get a laptop that supports hot-swapping batteries in the first place.
Label the batteries with a Sharpie so that you don’t get the two (or more) batteries confused and accidentally insert a dead battery.
Be wary of generic batteries! Always try to get a manufacturer’s (or manufacturer-approved) battery for your laptop. Get anything less, and you run the risk of setting your laptop ablaze!