Laptop batteries are rated by, Voltage (V) and Milliamp-hours (mAh)Voltage is the rate at which energy is drawn from the battery and Milliamp-hours Represents the capacity of the batteryThe Milliamp-hour rating Corresponds to the run time of the batteryA battery with a high Milliamp-hour rating has a relatively longer run time than a battery with a Low Milliamp-hour rating.

Batteries with different Milliamp-hours can be used on the same laptop provided the voltage rating is the sameThe voltage rating has to match that of the original battery or as recommended by the computer manualUsing a battery with a different voltage setting can seriously damage the laptopThe power ratings of most compatible/replacment batteries are higher than the original manufacturers' batteriesThis will not damage your laptop, in fact, it simply means that these batteries in many cases last longer than original manufacturers' batteriesAsk the experts like
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The run time of a laptop battery will vary on individual notebook computers, based on the applications being used (i.ehigh graphics, games), the number of times something is saved or retrieved from the hard drive and/or CD Rom drive, the memory of notebook, and chemistry and capacity of the batteryA ‘realistic' average run-time for a battery is 1.5 to 3 hoursUsing devices like a wireless adapter on the laptop also drains the battery considerably.

The life of a battery under normal use is around 500 to 900 charge-discharge cyclesThis is about one and a half to three years of battery life for the average userAs the rechargeable battery begins to fail, the running time of the battery begins to decline.