From what i have read you will nee the new charger for the new battery.
"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."