Your PC shouldn't be drawing ANY power when hibernating. The PC writes all the contents fo RAM to a file on the hard drive and shuts off.
Are you possibly referring to standby mode? That's where the PC writes system state to RAM. That will draw power, as the PC requires the RAM to be powered to maintain the system state.
Where is it drawing the voltage? Is that between the PSU and the battery or between the PC and the PSU? Also, is it on the ACC line or on the 12v hot?