I'm designing a small battery powered system, actually I'm battery powering a module which already has all the switching regulators it needs. This provides me with a wide input range of 5-10V. I was thinking of connecting the batteries directly to the module instead of using a regulator because I don't want to pay an efficiency penalty, especially in low power mode. I was worried about inrush current though when the batteries are first turned on. I know the internal resistance of the batteries should limit it some but should I add some kind of current limiting or soft-start circuit to protect the batteries from damage or overheating?
That'd be easy to do with a regulator, not sure what I'd use without one. Maybe a high side switch with some time based control. Should I even be concerned about this? Target batteries are LiOn that won't be recharged in the device itself.