iPad 3 backlight said to be using 7W at max brightness
When the iPad first came out, people went something along the lines of “wee” while we went something along the “this 42.5Wh battery is going to cause issues”. Then people caught on to the bigger battery and claimed it was due to the LTE radio, while I was running around places like Twitter trying to point out that if the LTE radio is responsible for no gain in battery life with a 70% gain in battery capacity, then the WiFi version of the iPad – and the LTE version with LTE turned off – should have 17 hours of battery life. Now it’s become common knowledge that the iPad has battery issues, and there are even some that say the iPad 3 software is designed to show 100% battery status before it’s fully charged, giving the beneficial (for Apple) illusion of a faster charge time.
As for what’s causing the iPad 3 to use so much power, DisplayMate has an answer to that. The ridiculous PPI on the iPad 3 means more display components are in the way of the backlight lighting through, meaning you need more LEDs to actually light up the screen to the same user-end brightness. LEDs use power, a lot of power actually, enough so that the estimated backlight power consumption has increased from 2.8 watts to 7 watts. In essence, if you turn the brightness on the new iPad to max, you essentially have a 9.7-inch 7 watt flashlight. Common math means that running a 7 watt light off a 42.5 watt hour battery will see it run out of power around the 6 hour mark, and DisplayMate’s tests show 5.8 hours. That is naturally going to be lower if you start using all the other components, like wireless radios and processing power, since the backlight isn’t the only thing that uses power.
Do note that this is at the highest brightness, which few people run the device at – but it does mean higher power consumption overall. The 10 hour battery life that Apple claims is still possible, but definitely not at the highest brightness – which is true for the iPad 2 as well, just to a lesser degree. At the same time, more pixels need power, more processing power is needed to push out graphics (and hence more power consumption there), and so on, all adding up to explain a battery that looks like it has escaped from a laptop.[DisplayMate]