A remaining charge capacity of a battery having an initial charge capacity is monitored. The battery powers a remote implantable medical device (IMD) that includes an active state, during which the remote IMD performs at least one function, and an inactive state, during which the remote IMD performs no functions. An active state charge consumption is computed based on stored parameters associated with an operational charge consumption for each function, and an inactive state charge consumption is computed based on a leakage current associated with the inactive state and a time the remote IMD is in the inactive state. The active state charge consumption and inactive state charge consumption are subtracted from the initial charge capacity to determine the remaining charge capacity.