Calibrate Laptop Battery

Do I Need to Calibrate My Laptop Battery?

Laptop battery life is important to us road warriors. Can we squeeze in one more hour of work; finish watching this movie; complete a Skype phone call with a client; or receive that long-awaited email before we run out of juice? Most of us depend upon a battery life meter, either the one built into your laptop or an app that comes with a specific make and model of laptop. But those meters can mislead you.

"Calibration" in this context means ensuring that the software power meter accurately measures the amount of power remaining in the battery. Here's how the power meter gets out of synch with the battery over time:

The meter you see on your screen is a software app's representation of battery power level measurements taken by a specialized chip built into your computer. The chip measures the percentage of "fully charged" power remaining in the battery; assumes that "fully charged" means the rated capacity of the battery; and multiplies "percentage remaining" times "rated capacity" to come up with an estimate of how much power remains. But this simple math does not work in the real world.

Most users recharge laptop batteries too little and too soon. They plug into an electrical outlet whenever one is available, even if the battery is still half-full or better. Then they unplug from the outlet before the battery is fully recharged. This "short cycling" does two undesirable things.

Recharging too soon can shorten the lifespan of a battery; it is designed to be recharged only so many times before being replaced. Recharging too soon means you are wasting part of a recharge cycle, and those cycles are not unlimited.

Unplugging from the electrical outlet before the battery is fully recharged may result in the battery "remembering" as its full charge a lower capacity than its rated fully-charged capacity. The battery stops recharging at that lower level.

The power measurement chip reports that the battery has more power than it truly does. Result: your battery dies before you expect it! It's as if your car's gas gauge reported 10 gallons when, in fact, only 5 gallons remained in the tank.

Some gas gauges translate gallons into miles remaining, and most laptop power meters translate watts into hours and minutes remaining. Time can seem to leap ahead when your power meter is not properly calibrated to your battery.

How to Calibrate Your Laptop Battery

Calibrating a laptop battery puts the power meter back into sync with the battery's actual "fully charged" state. It also helps the battery regain part of the power capacity it lost due to short-cycling, extending battery time. Most people should calibrate laptop batteries about once every two to three months. Here's how to calibrate your battery:

1. Plug the computer into an electrical outlet and let the battery charge fully.
2. Unplug the computer and use it normally until the battery is so drained that it goes into sleep mode automatically. (The battery really has a small reserve left, but if that is used up then data will be lost because the computer will shut down completely.)
3. Repeat Step 1: Fully recharge the battery.

This process should also work for iPods, iPhones and other portable devices which have a battery life indicator on the screeen. Running the battery through this charge/discharge/recharge cycle should calibrate the battery and get it back in sync with the power meter display on your device.

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