A recent report claims that the third-generation iPad continues to draw a significant amount of wattage after displaying a “100%” battery level. The device actually finishes its charging cycle roughly two hours after “prematurely reporting” a full charge. The report comes from a follow-up test by DisplayMate President Dr. Raymond Soneira.
The findings have not been corroborated and therefore may not reflect all third-generation iPads. It seems that the problem is not hardware related and has to do with the devices programmed charge rate. Soneira found that the iPad continued to draw 10 watts of electricity for two hours after indicating 100% charge, then began to reduce power for an additional ten minutes until a decline in power draw signaled the end of the charging cycle. The following explanation was offered by Soneira:
The charge indicator on all mobile devices is based on a mathematical model of the charge rates, discharge rates, and recent discharge history of the battery. It uses this information to estimate how much running time is left. It's actually rather difficult to do because most batteries degrade slowly as they discharge and then tend to surprise with a precipitous decline near the end.
Apple boasts that despite the new iPad’s power hungry components, the third-generation iPad’s battery life is similar to that of the iPad 2. The claims were based on a fully charged unit and the newly-discovered indicator issue can confuse customers into thinking their device isn’t performing up to advertised standards.
Apple launched the latest iPad on March 16 and announced on Monday that unit sales reached 3 million over the launch weekend. The Cupertino California company continues its fastest international iPad rollout ever as the tablets went on sale in an additional 25 countries and territories.