A laptop computer comes with two power sources. It can use power from the wall, just like a desktop computer. It can also run off battery power. Managing the two isn’t a problem, though it does raise some interesting issues.

Here are my laptop battery tips, which can also be found in my book Laptops For Dummies:

I leave my laptop plugged in all the time. Does it run off the battery or wall power?

A laptop that’s plugged in runs off wall power. The battery is still maintained at a full charge, so as it drains, it will be charged. Laptops are not powered from the battery unless they’re unplugged.

Can I take the battery out of my laptop and still use the laptop?

Yes, and most laptops work fine like that. Some will not work, and with some laptops you cannot remove the battery. The only way to find out is to try.

What do I do with the battery when I take it out of the laptop?

Store the battery in a cool, dry place in a non-conducting container, like a cardboard box.

I took the battery out of my laptop and now the laptop doesn’t work.

Put the battery back into the laptop. Again, some laptops don’t work when you remove their battery.

Can I use the battery later?

Sure, but the battery will drain over time. It will need to be recharged, which takes place after you insert it back into your laptop.

If I leave the battery in the laptop, will it drain when I’m on AC power?

Yes. Batteries drain over time. The laptop’s power management system detects that and automatically recharges the battery as it drains.

Is that draining and recharging of the battery harmful?

Not really. Again, if you don’t plan on using the battery in the laptop, take it out. But keep in mind that you can prolong the battery’s life by adjusting how it’s managed in a laptop that’s plugged in all the time.

For example, it’s possible to set the recharge level for the battery at 90 percent or even 80 percent. That way, when you leave the battery in a plugged-in laptop, the power management system won’t recharge the battery until it drains to 90 or 80 precent of capacity. By doing so, you can prolong the battery’s life. But keep in mind that not every laptop has the controls to let you reset the battery’s recharge level.

How can I best preserve the laptop’s battery?

Simple: Don’t use it. But seriously, laptops are designed to be used on battery power. As long as you use good power management (described in Laptops For Dummies), the battery will last as long as the laptop itself.

How long is that?

Laptops should last about 4 or 5 years, which is about how long their battery should last. After that, if the battery dies, you can buy a replacement. (They’re not cheap.) My advice, however, is simply to get a new laptop, which comes with a new battery, and is probably a better deal for the long haul.