Dr. Raymond Soneira of DisplayMate Technologies first because he believed that it wrongfully indicated its battery was 100 percent charged when in fact it was closer to 90 percent full. He wrote that if you unplugged your charging iPad at the first moment the battery meter ticked over to 100 percent, "you get 1.2 hours less running time."

But worse still, Soneira further alleged that Apple says leaving your iPad plugged in for long--when you wanted to, say, top off the battery--could "harm the longevity of the battery."

It's unclear where Soneira's Apple-attributed quote about overcharging the battery harming its longevity comes from. has found no statements from Apple to any press organization on the subject, and the company declined to comment for this story. All references to such a claim seem to trace back to Soneira's report, or CNBC's coverage of same. And Apple's own guide about

Carl Howe, the vice president for data sciences research for mobile-focused market research company The Yankee Group, told that "There is no damage caused [to the iPad's battery] by leaving it plugged in. ... There's a charging circuit that makes sure that doesn't happen." To describe how the charging circuit works, Howe compared it to how you'd use a pitcher to fill a glass of water: "You don't pour water in at full speed until the water flops over; the way you do it is you pour in the water until you get within five or ten percent of the top, and then you slow down--and make sure you put in the least amount you can to keep it from overflowing. That's the way the charging circuit works."

That charging slowdown is referred to as trickle-charge mode--"it's like trickling in the water from the pitcher, to make sure you don't go over the lip of the battery," Howe explained. In fact, that trickle charge mode explains Soneira's other concern regarding how full the battery is when the new iPad first reads 100 percent. Howe agrees that, at that point, the battery can indeed get fuller, but says that's not a problem. "The capacity that [Apple is] advertising is based on when the iPad first says 100 percent--everything you get over and beyond that at the trickle charge stage is just kind of gravy."