Originally Posted by austin420
i think the touchstone and aftermarket battery cover cost at least 70 dollars alone.
The technology behind it is dead simple though. It would be trivial to introduce something like this built into a battery pack. IIRC, the voltage on the receiving coil is Vr = Vs * (Cs / Cr), where Vr is the voltage on the receiving coil, Vs is the voltage on the sending coil (the touchstone base) and Cs and Cr are the number of loops in the source and receiving coils.
Therefore it would be easy to make a coil that grabbed 3.6V from the 5V touchstone and fed it directly into the battery. The only problem is that the coil plus voltage protection circuitry inside of the battery would reduce the amount of space that you could actually use for the battery. Considering how small batteries in cell phones already are, even making them a sliver thinner to fit the coil inside of the battery pack would mean a drastic drop in battery capacity.
To the OP: did you have to break any stickers to pull the circuit board out?