Battery Indicator Light Behavior

A reader question prompted today's post and digging into the answer brought me further into the fascinating world that our usability team inhabits. Reader Alex wanted to ask about the behavior of the battery LED lights on his ThinkPad T60.

As he writes, the battery LED behaves as such:

  • Charging -> Green, intermittent blinking ( etc etc)
  • Charged, and still Plugged in -> Green, constant on
  • Running on battery -> Green, constant on
  • Running on battery, low -> Orange, constant on
  • Running on battery, very low -> Orange, steadily blinking

He was okay with most of it, but he wondered why the first category (charging) didn't behave more like this:  Charging -> Orange, constant on or Green but steadily blinking (similar to the turn signal on a car). His reasoning was that it would be more consistent with how other battery devices operate and perhaps be more intuitive. When we went to our latest generation of products, would you believe our usability team actually studied this very topic in minute detail?  With previous generation ThinkPad designs (pre-anything with a "60" in its name), the light's behavior was not well understood by most customers.  The color amber and the blink rate were used incorrectly based on standard usability principles.  Most significantly, the LED behaved differently in different circumstances.  The team determined it was a mess. With the current generation, the team wanted to address all of these issues and make it so that even if the system was not powered up, a user could look at the battery indicators and accurately determine battery status.  As a result, this is what they came up with:

When your system is plugged into the wall and charging, the light changes status as the battery moves through charge states.  When battery level is critically low (below 5%), it uses amber and blinks rather rapidly.  As the battery moves from 5 - 20% charged, the light becomes steady with an occasional blink.  Greater than 20% charged, it changes to green, but maintains an occasional blink.  Above 80% charged, it becomes solid on all of the time. (More specifics are available on the chart above). Discharging is a bit different.  From 100 - 80%, the light will stay a solid green.  From 20 - 5%, it will change to solid amber to indicate that the battery is nearing time to be charged.  Below 5%, it will start blinking amber to show that battery level is critical. When we did have blinking, our team wanted it to be subtle to avoid the "bling" effect where it would be gaudy and annoying.  The only exception is when the battery is critical -- in which case subtlety is definitely not what you want. I hope this gives you a new appreciation of some of the things our design and usability teams think about.  While these sorts of things are subtle to many, they are part of the ownership experience of using a ThinkPad.