Intel recommends standardization for ultrabook batteries
 

At the Intel Developer Forum in Beijing, China, Intel is advocating a standardized battery design for ultrabooks. Although the firm concedes that high-end ultrabook chassis may require custom batteries for "industrial design reasons," it argues that standardization would allow mainstream ultrabooks to hit lower price points. Savings of 5-10% are quoted in the presentation slides posted by Liliputing. Standardization would also make it easier for notebook makers to source batteries, the slides contend.

http://techreport.com/discussions.x/22795