Apple Working on Method to Extend Battery Life
With Apple coming out with devices that are both thinner in profile and more powerful, battery life is going to become even more of a concern than it is today. Apple's industrial design pretty much prohibits the idea of going with a larger battery, so the only option is to pack more power in a smaller space. This appears to be exactly the tack the company is taking, as a patent was revealed today
showing a new charging method that would increase the capacity of a lithium battery.
The patent, called "Increasing Energy Density in Rechargeable Lithium Battery Cells
," details how a battery's gravimetric and volumetric energy density would be improved using a multi-step constant-current constant-voltage (CC-CV) charging technique. CC-CV in general involves charging at a higher initial constant current until the battery is almost charged, then the charging at a constant voltage until the charge current drops and the battery is fully charged. This patent involves breaking that down into steps: first charging to 50% with constant current and following up with a period of constant voltage, repeating in smaller and smaller steps until the battery is charged. Using this technique, Apple claims they can produce batteries with larger charging elements - thereby increasing battery life - while keeping charge time the same.
CC-CV charging is not a new discovery, and one of the significant drawbacks with the technique is that it significant decreases battery life at lower temperature, with significant degradation at just 10° C or below. Also, leaving the battery attached to a traditional CC-CV charger can reduce the number of charge cycles through overvoltage. Apple's multi-step technique purports to avoid these obstacles by adjusting for either temperature or voltage using smart sensors.
Though the mere existence of a patent doesn't mean Apple is going to implement the technology any time soon, it's worth noting that this patent was applied for in August 2009. So it's entirely possible that work on this project has continued, with improvements to come in the near future with a new generation of devices.