The source of the confusion stems from how Apple manages the charging process from the point when a battery is very nearly charged until a user unplugs the device.
So here’s how things work: Apple does, in fact, display the iPad (and iPhone and iPod Touch) as 100 percent charged just before a device reaches a completely charged state. At that point, it will continue charging to 100 percent, then discharge a bit and charge back up to 100 percent, repeating that process until the device is unplugged.
Doing so allows devices to maintain an optimum charge, Apple VP Michael Tchao told AllThingsD today.
“That circuitry is designed so you can keep your device plugged in as long as you would like,” Tchao said. “It’s a great feature that’s always been in iOS.”
It appears to have gone largely unnoticed until this latest generation iPad, when DisplayMate analyst Ray Soneira noted that his testing showed the iPad not fully charged when it displayed 100 percent.
No matter where in that cycle a battery is, Tchao said, owners of the new iPad can expect the 10 hours of battery life that Apple has promised.
The decision not to keep changing the battery status was designed so as not to distract or confuse users.
Battery life has, of course, become a critical issue for device makers and consumers alike.
Chips, screens and other components continue to increase in sophistication at a rapid rate, while battery life has improved only incrementally.
The new iPad, for example, has a screen that displays far more information and requires additional graphics horsepower, yet offers similar battery life to its predecessor. In order to make this happen, Apple has put a significantly larger battery in the new tablet, likely accounting for the device’s slightly thicker body.
It would make sense then that users would find it takes longer to fully charge the device than its predecessor.
Further confusion often comes in for longtime gadget owners who can remember the days of nickel cadmium (NiCad) batteries, which had a so-called “memory effect,” requiring users to fully discharge the battery each time in order to keep getting maximum battery life.
Newer batteries, which use lithium-ion and other compounds, don’t have this issue. However, they do have a limited lifespan and lose capacity over time.
Yankee Group analyst Carl Howe said battery charging has become a complex art and science.
“What’s really subtle is that consumers think they understand that 100% means ‘full’,” Howe said. “That might have been the case with older batteries, but today’s batteries have microprocessors managing their charging. So 100% is whatever that microprocessor says it is — it’s not any absolute measurement of ion concentration or anything.”
Howe says consumers are probably best off just leaving it to the device to handle things.
“We don’t have to understand their engineering to use them,” Howe said. “However, we shouldn’t apply our prejudices formed (both good and bad) from older generations of battery technology to today’s systems either. If it says it’s charged, consumers should assume it is, and not worry about whether the charger is drawing current.”
So there you have it — more than you ever wanted to know about battery life. Now if only someone would just hurry up with batteries that last longer.