You might have heard about a mini-controversy surrounding the battery on Apple's new iPad. It turns out that when it reads 100 percent, the battery may or may not be at full capacity.
Is it a big deal?
It's not, it turns out. Let me explain.
Raymond Soneira, a respected expert in display technology, told me he became aware of the quirk when charging his Apple iPad to test the screen. He used a secondary device to indicate when the iPad was still accepting a charge. Soneira said after the on-screen battery indicator read 100 percent, it took another 2 hours and 10 minutes for the iPad to stop charging completely.
This would be an obvious problem if the new iPad were behaving in a way that's different from other Apple products like it, or from other electronics products out there. It would also be worrisome if the iPad didn't live up to Apple's marketing claim of 10 hours of battery life when the indicator reads 100 percent.
But none of that is the case here. To assess how big a deal this is, I talked to Carl Howe, a Yankee Group analyst who's an expert in batteries; and to a few other people who are familiar with Apple's engineering. Here's what I learned:
- The new iPad's charging system works the same as other iOS devices.
- iOS devices are designed to show 100 percent charge when they are near full.
- If Apple were to let the battery charge all the way and let power trickle into it from there, it could harm the longevity of the battery. So if you leave a device plugged into the charger, it will charge all the way, then allow some power to discharge, then charge more — what's sometimes called "letting the battery cycle."
- Part of the reason why iOS devices show 100 percent a bit early? It might be odd to see a plugged-in device go from 100 percent to 98 percent and back up, as the battery cycles.
Howe told me that across many types of electronics, "100 percent is whatever the computer says it is." In other words, different companies have different ways of determining what's really a full charge.
It's not an exact science, because "lithium ion batteries are really complex devices," Howe said. "If you mistreat them, they do bad things." Depending on the type of device the battery is in, it needs to be managed differently. So companies work up unique formulas to get the most out of their batteries.
Based on my experience reviewing products, it comes down to this: As long as the new iPad delivers the battery performance Apple promises — 10 hours on a 100 percent charge — consumers probably won't have a problem with it.