I own one for one of my cameras. It is the camera manufacturers model and cost a fortune! About what you said you didn't want to know, but others might. My Pentax Battery Grip for my K-20D only uses the same Lithium Ion Battery as the Camera, so no AA advantage there. And I am sure that would be the same for my K-5 if I had a grip for it. Only my old K-100D that was purchased after the K-20D for conversion to IR use does in theory use AA Batteries among others but in practice the camera only functions properly with non-rechargeable Li Ion batteries.
Adapter battery for nikon has 3 contacts with different spacing and it was necessary to revise the distance as a Pentax Battery Grip and body and the external power adapter
Pentax K20D like new. Used for a year, very well look after. Also original Pentax battery grip and 3 batteries (2 original Pentax and one different made)
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