Because we use batteries in Laptop and Notebook computers as well as mobile phones we technology users really cannot use primary batteries (Use up and discard) and similarly Lead acid batteries won't do either. We have to have sealed units that are relatively light and will recharge multiple times before degenerating and no longer holding a useful charge for long enough to be an effective souce of power when there is no plug in power.
When Laptops and notebook computers were in their infancy many used rechargeable NiCad batteries which had to be properly managed. If the battery was put back on charge before being completely drained they developed a 'Memory' which meant that the battery would stop charging before being completely full thus effectively cutting the effective life of the cell. This managing process was called stroking the battery.
This often became so bad that unless the user was careful their battery was useless after only a few months. Modern Lithium Ion Batteries used in modern laptops are much improved and now no longer need the stroking as they no longer develop memories.
Currently the useful life of a normal sized battery in a laptop running a Internet browser, an Email program and a spreadsheet and word processing software, would start out new at between 90 minutes and 2 hours. This would steadily regress over a period of 18 months or so and at that stage the useful life would appear to have deteriorated by 50% (If in use daily).
Thereafter the deterioration is likely to be fairly rapid and within 2 years or so a frequently used laptop would find its battery life severely shortened and the need to be constantly plugged into a wall socket when in use almost constant.
A Laptop Battery therefore is likely to be in need of replacement within 2 years. The original manufacturer will sell you a new battery through one of their main dealers with joy and at an exorbitant price. The price of a replacement Notebook Battery seems to have nothing to do with the actual cost of manufacturing but rather to do with the OEM name.
But there is a replacement battery for just about any brand of computer to be found at the Laptop battery link. So if you are needing a notebook battery for a Acer, Advent, Apple, BenQ or Dell or any of the others like the HP or Fujitsu Siemens or the Sony there is a Laptop Battery available for you at the Notebook Battery link.
These are replacement batteries and are compatible and will extend the useful battery life of your Laptop for the same length of time as the old one. The batteries while not being OEM are fully compatible and will not void your computers Warranty. And the prices are well below the cost of new OEM costs.