Hewlett-Packard on Monday started offering as an accessory to its consumer laptops batteries that can hold their capacity for the lifetime of the computer.

HP is offering batteries based on Boston-Power's Sonata lithium-ion technology for 18 existing laptop models, representing about 70% of HP's consumer notebook portfolio. The batteries, which cost $150, will be available under HP's Enviro brand.

Boston-Power claims its batteries won't give up their capacity for three years, which is threefold the time for most other laptop batteries. In addition, the company claims the devices can recharge faster, reaching 80% of capacity in 30 minutes.

HP is offering a three-year warranty with the Enviro batteries, which amounts to the life of the laptop and about three times the warranty offered on most other batteries. HP is the only manufacturer to offer such a long-term warranty on a consumer laptop battery, according to Boston-Power.

HP plans to offer this month Boston-Power batteries as a point-of-sale option for consumers buying laptops through HP's Web site. People who have already bought HP Pavilion, HDX, Compaq Presario, and G series laptops can buy Enviro batteries as of Monday through HP as an accessory. A complete list of compatible individual laptop models is available on HP's site.

"HP's endorsement of Sonata is a great step forward in popularizing this battery technology," Christina Lampe-Onnerud, Boston-Power founder and chief executive, said in a statement.

HP has worked with Boston-Power for three years to bring Sonata to HP consumer laptops. Landing the world's largest computer maker as its first customer in the mobile PC market is a major boost for Boston-Power, which was founded in 2005. Headquartered in Westborough, Mass., the company has more than 40 patents filed and has received venture funding from Oak Investment Partners, Venrock, GGV Capital, and Gabriel Venture Partners.

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