WHAT’S THIS FUSS ABOUT CHARGING?

Charging your mobile device’s battery was pretty much a non-issue for many years…customers seldom complained; manufacturers did not see charging as a limitation; and charging, well, was really not a problem.

That began to change in the past year or two. Several factors are converging to elevate battery charging to a whole new level of importance and complexity. So what are these factors:

1. The rise in battery capacity has made charging painfully slow. Early cell phones and smartphones had batteries that lasted days, but the newest smartphones now sport large capacity batteries (up to 3,200 mAh) and are charging using the same 5-Watt AC wall adapter that shipped with the smaller smartphones 5 years ago. The result: It takes hours to charge the newest smartphones. In technical terms, this is called the C-rate. A 3,200 mAh packs 12.2 Watt-hours of stored electrical energy. Dividing the power of the AC adapter by the energy of the battery gives the charging C-rate, in this case, 5 divided by 12.2 equals 0.4C, which equates to 3 hours or more of charge time. In contrast, batteries from earlier generations of mobile devices charged at twice that rate, somewhere near 0.7C. So there has been a drive in the industry to increase the power of AC wall adapters and increase charging rates.
2. The rise of energy density makes charging more complex: As I mentioned in a previous post,  increasing charge rates at these higher energy densities have a serious impact on cycle life, effectively reducing the battery warranty. In other words, the simple charging methodologies of earlier generations of mobile devices are not applicable to charging the newest generation of smartphone batteries. Therefore, charging newer mobile devices at higher charge rates (in order to reduce charge times) now involves newer designs and methodologies for charging — otherwise, you can charge fast, but your battery will not last! That is not an acceptable compromise.
3. Consumers asking for super fast charging: End users and consumers are now beginning to realize that if batteries cannot have battery capacities that can last several days, if not weeks, then they should have the ability to charge their batteries at blazing fast speeds; certainly faster than 30 minutes, and possibly 15 minutes if possible. These kinds of charge times are equivalent to charge rates in the range of 1.5C to 3.0C, in other words, about 4 to 10X faster than presently shipping in smartphones. Naturally, at these super fast charge rates, the design of the entire battery charging circuitry and methodologies need to be conceived from scratch to allow for the extra charging power and to deliver sufficient battery cycle life (and battery warranty).

Handset manufacturers are beginning to recognize these factors and why fast charging should become an important part of the mobile experience. It is a major transformation for them — new designs for their charging platforms are required and that is not trivial. But that train has left the station, and handset makers who are not taking action will miss the boat. The first shot across the bow came from a small but promising handset maker in China called Oppo. They released in early 2014 the first smartphone that is capable of charging at 1.5C. Expect to see more mobile device makers to follow suit.

In future posts, I will talk more about the metrics of fast charging, especially as mobile handset makers will begin to make claims about charge times that may be confusing.