Laptop Battery Power Ratings and Power Consumption 101  

Power Rating Terms

Every laptop battery is given a power rating in order to show you, the consumer, about how long your battery should last before it needs to be recharged. These electrical specifications are given using volts (V) and milliAmps (mAh). For example, you may see your battery is given a rating of: 10.8V, 4000mAh.

Volts and milliAmp hours are used because they measure the amount of energy used by a laptop battery. A volt (V) is a measurement used for the amount of pressure the positive and negative electrodes produce in a battery during the process of discharging energy. Amps (A) measure the amount of resistance the energy in your battery produces in order to power a laptop.

Think of volts and amps in terms of a shower. When a shower is turned on half way, the water that goes through the pipe produces a certain amount of pressure. When you turn it on to its full amount, the water produces more pressure in the pipe. This pressure, or power, is similar to the volts a battery uses. If a laptop is running simple programs, little power is needed to discharge energy into a laptop. However, if a laptop is running a DVD movie or other high energy consumption applications, more power will be needed to discharge the necessary amount of energy to run the DVD movie.

You may also notice that increasing the size of the pipe and shower head without having to open the faucet all the way will produce similar results. This is an example of the amount of resistance in the flow of energy. Measuring this resistance is measured in terms of amps. In terms of a battery, the amount of resistance is dependant on the size of the battery and the amount of energy inside.

Battery life: A Few Things to Consider

Laptop ratings are given in terms of amp hours (Ah). Amp hours measure the length of time a battery will discharge energy before it needs charging. In order to adequately measure battery life, manufacturers use milliAmp hours (mAh). This means that every 1000mAh is equal to 1Ah. What does this mean for your new battery? If your original battery is measured at 2500mAh and your replacement battery is measured at 5000mAh, then your battery run time will double.

Keep in mind that technology constantly changes. Your old battery may be rated at a lower run time than a newer one because of technological advancements that have produced longer lasting batteries.

Additionally, your battery's run time depends on the programs you use. Some programs require more energy to run than others. Examples are: the screen (particularly if set at the brigh test setting), hard drives, CD and DVD drives, and wireless network cards. Unfortunately, there is no definite answer to the question, how long exactly will my laptop battery last? The key factor is how and what you use your laptop for.

One way of conserving power is to go to your Power Management settings icon in the Control Panel. You can shut off settings or programs you do not use. Also consider dimming your screen and shutting off your wireless card when you don't need it.