privatebydesign said:
There is a new charger, it will charge the new and the old batteries. The old charger will charge the new batteries but not to their max potential.
So all batteries can be used in all cameras, all chargers can charge all batteries. You only get the best out of the new camera and batteries if you use the new charger.
The LP-E4 was for the 1D MkIII, 1DS MkIII and 1D MkIV, the LP-E4N was basically the same (backward and forward compatibility) and was changed because of newer Japanese Li-Ion battery regulations.
This seems to conflict with the Chuck Westfall interview. The old charger will not charge the new batteries. I suspect there is a physical key that blocks them?
"AH: What are the specifications of the new batter pack? Is the camera compatible with the older LP-EN4?
The new LP-E19 battery pack is a 2700 mAH device running at 10.8 volts. In addition to the LP-E19, the EOS-1D X is also compatible with existing Canon LP-E4N and LP-E4 battery packs; However, maximum continuous shooting speeds are reduced to 12 fps through the viewfinder and 14 fps with the mirror locked up when using the older batteries (versus 14 fps and 16 fps respectively using the LP-E19). Users can charge LPE-4, LP-E4N and LP-E19 battery packs on the new Battery Charger LC-E19. However, LP-E19 battery packs cannot be charged on Battery Charger LC-E4 or LC-E4N."