Unfortunately, going back to point 1, and considering that 5% of 90 mAh is 4.5 mAh (assuming it still holds 90 mAh of charge over time it will be less, so adjust the figures downward correspondingly), a 10 ♚ drain would completely drain the battery after 450 hours, or about 19 days (less than 3 weeks).Īs a consequence of point 5, if you leave your iPad unattended for a few weeks, you may come back to a dead Pencil. A good design might have a leakage current budget of about 10 ♚. However, even in a low power mode, there is some current drain from the battery - unless you use a relay to cut power to the circuit, which Apple certainly didn't use in the Pencil.When the Pencil reaches a low battery state (say at 5%), I assume it enters a very low power mode, disconnecting from the iPad, to save battery (if it doesn't, and the user doesn't immediately start recharging the battery, it will be irrecoverably dead in a few hours as per point 3).
Most battery protection ICs include undervoltage protection and turn off the charge MOSFET in series with the battery when this condition is detected.
I don't care what Jony Ive says, it really needed an on-off switch. If, like me, you throw the iPad and the Pencil in a backpack which you take around with you all day, it's going to be waking up quite often, and draining the battery in the process. Its internal accelerometer senses when it's moved, and it pairs to the iPad.
about 9.5 months later, it had a battery failure and had to be replaced under warranty by Apple.
I own an iPad Pro 10.5" and a first-generation Apple Pencil for it.