Hi SV,
Been a long time to find this key
navigate to
HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Symantec Endpoint Protection\AV\AdministratorOnly\General
on the right hand side you will find a key called
SSPowerMgmt
meaning Schedule scan power management :)
if its 1 its enabled ( Delay scan running on batteries is enabled)
if its 0 its disabled(Delay scan running on batteries is disabled)