Your iPad battery may last longer if you don't charge it fully

What we hadn't taken into account was the lifespan of the typical lithium-ion battery. You see, there is a tradeoff to be made between how full of a charge you keep per cycle with the overall lifespan of your battery. Batteries can't last forever, and eventually lose their ability to retain a charge. It turns out that charging your battery longer can speed up the degradation process that will forever kill your battery. Battery University found the difference in how fast your battery will degrade based on charging it to certain levels. 

Given that we've seen data saying the new iPad has a temperature of around 86F (30C) when charging, the difference between charging the battery fully and to just 60% is pretty substantial at that temperature. If you keep the battery around a 40% charge, your battery will only degrade 4% over the span of a year, but if you fully charge your battery, you could lose as much as 20% in the same period. 

It's possible that Apple factored in all of this and has set the battery meter to give a false reading in order to provide longer battery lifetimes, but there's no way to confirm that. Either way, maybe it isn't good to leave your iPad charging too long. 

source: Battery University via Mashable