No matter how well you treat your laptop’s battery, it will eventually die. If you’re lucky, it will be time to replace your laptop by the time its battery dies. If you’re not, you’ll need to replace the battery.

Battery death can seem sudden, but it doesn’t have to. Windows will warn you when your battery reaches extremely low capacity levels, but you can also keep your own tabs on its capacity.

Windows Will Warn You

Windows doesn’t normally keep you up-to-date with your battery’s capacity level. As you use it and it weakens, you’ll just notice that your laptop doesn’t seem to last as long on battery.

Eventually, when your battery reaches a low enough capacity level, Windows will warn you. You’ll see a red X appear on the standard battery icon in your system tray and, when you click it, Windows will inform you that you should “consider replacing your battery.” Windows also says that your computer might shut down suddenly because there’s a problem with your battery — in other words, your battery can’t hold enough of a charge to power your laptop for long when it’s not connected to an outlet.

Note that this warning was added in Windows 7, so you won’t see it if you’re using Windows Vista or XP.

How to Check Your Laptop’s Battery Capacity

If you’re curious just how far your laptop’s battery capacity has declined, you can use a third-party tool to view it. NirSoft’s free BatteryInfoView does this well, displaying the battery’s approximate wear level, the capacity it was designed to have, and the capacity it currently has.

For example, in the below screenshot, we see that the battery was designed to hold 86,580 mWh of energy. However, the battery’s current capacity at full charge is only 61,261 mWh. In other words, the laptop’s battery only holds 70.8% of its original capacity when fully charged.

Some batteries may display more information, such as the number of charge and discharge cycles they’ve been through.

Calibrating Your Battery

RELATED: How to Calibrate Your Laptop's Battery for Accurate Battery Life Estimates

The information above may not be completely accurate if your battery requires calibration. For example, we had a battery that reported it was almost dead. Windows warned us that it was time to replace the battery and the battery appeared to be at 27.7% wear level according to its reported capacity.

After we calibrated the battery, Windows stopped warning us and the battery’s reported capacity went back up to 70.8%. The battery didn’t actually gain any additional charge, but the calibration helped the battery’s sensor actually detect how much capacity was in the battery. If Windows says it’s time to replace your battery, be sure to calibrate it first before checking its actual wear level. If you don’t, you may replace a battery that’s still in good enough shape. That would just be a waste of money.

Why Your Laptop’s Battery Capacity Declines

RELATED: Debunking Battery Life Myths for Mobile Phones, Tablets, and Laptops

Laptop batteries decline due to a number of factors. Heat, usage, age — all of these things are bad for batteries. Batteries will slowly die no matter what — even if you put your battery in a closet and never touched it, it would slowly lose capacity due to age. However, if you never use your battery — say you use your laptop at your desk most of the time and it gets rather hot, which is bad for the battery — removing the battery can certainly help prolong its life.

To make your laptop’s battery last longer, read our explanation of battery life myths and facts to know what works and what doesn’t.

Replacing Your Battery

If your laptop has a user-serviceable battery — that is, one you can remove on your own — you can replace your battery fairly easily. If your laptop doesn’t have a user-serviceable battery, you’ll need to contact the laptop’s manufacturer so they can crack your laptop open and change its battery for you.

Assuming you have a user-serviceable battery, you can order a replacement battery for your laptop model online. Don’t just head to eBay and buy the cheapest third-party batteries available — buy official batteries from a reputable company. Aftermarket batteries are often built on the cheap, with cut corners and insufficient testing. They can be dangerous — a cheap, counterfeit, and improperly designed battery could literally go up in flames.

There’s no point in obsessing over your battery’s capacity — it was designed to be used, after all — but it’s something to keep on eye on. If your capacity is dropping more quickly than you’d like, that may be a sign that you should be treating your battery better. Perhaps you’re exposing it to too much heat if you leave your battery in while playing demanding, strenuous PC games on your laptop.