Originally posted by AfterPentax But take care if you do so: the battery has an output of 7.2 volt and the adapter of 8.3. So there is some conversion needed.
For reference, the off-load output from my 'genuine' DLi109 'dummy' is 8.52v, which is remarkably similar to the off-load 8.33v from a fully-charged Pentax DLi109 battery.
This would suggest that at least a modicum of regulation is performed within the camera. However, disassembly of the 'dummy' battery does show there to be a modicum of circuitry within the unit, including a connection to the third (central) terminal. This corresponds to the "T" terminal on the original battery, there's no "D" terminal on the 'dummy', neither is there a corresponding contact in the K-70!
A guess would be that the "T" terminal is used to flag to the camera whether it's a battery or an adaptor that's fitted, possibly for power-saving purposes.
My only reservation about modifying a battery into a 'dummy', assuming a suitable 8.3v source was available, would be that it might not work at all if the third connector wasn't active ... a piece of adhesive tape to insulate the central terminal on a DLi90 battery could prove or disprove this. Ensure the tape is well fitted. You don't want it coming unstuck in the battery compartment!
Good luck!