What is the Average Life of a Laptop Battery?

If we are talking time between charges, that will range between 90 minutes and 8-1/2 hours, depending on the laptop and the battery, assuming a battery pack in good condition.

If we are talking how long it will last before needing to buy a new one, that depends a lot on temperature and whether you store it fully charged or partially discharged when not in use.
Under normal conditions, 2-3 years.
Under heavy use in high temperatures, closer to six months.

Depending on battery cells, 4/6/9/8/12, genarally 3 hours also. You may get 2 hours watching dvd for play high quality 3d games.
Source: http://www.battery4us.com

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Nowadays most laptop has a battery life of about 6 hours. Old ones bought in the 2000~2004 last for about 2 hours. Check some equipment at techrentals.com.au that can be helpful to your laptop's battery.

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A laptop battery commonly has 300-400 charge/discharge cycle,after that,the battery will be dead and you should get a new one to replace the old battery.Hope this could help you.
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