Yes, the LP-E4 battery (for the 1DIV, 1DsIII, maybe others) works fine in the 1D X.
There's a 'minor' issue with the respective chargers, though - the old charger (that came with the 1DIV) can only charge the new battery (LP-E4N for the 1D X) to about 90% capacity.
1 day shoot maybe 50 - 100 frames goto use it ill get about 40 - 60 more frames boom not working battery flashing, my 7D you had forever even on flashing last bar.
LP-E4 and LP-E4N are interchangeable. Also noticed recently some improper discharge, but camera had not been used in two weeks and it has been freezing cold over here.
1 day shoot maybe 50 - 100 frames goto use it ill get about 40 - 60 more frames boom not working battery flashing, my 7D you had forever even on flashing last bar.
I'd contact Canon Support. I can shoot a couple of hundred shots, let it sit for a week, shoot another hundred shots, and still have three bars on the battery indicator.
1 day shoot maybe 50 - 100 frames goto use it ill get about 40 - 60 more frames boom not working battery flashing, my 7D you had forever even on flashing last bar.
I'd contact Canon Support. I can shoot a couple of hundred shots, let it sit for a week, shoot another hundred shots, and still have three bars on the battery indicator.