Your system may be able to recover most of the energy draw from the battery but (if I understand you right) that is because the energy drawn from the battery does no work, and you are just drawing power from the battery and sticking it back in, experiencing losses along the way. So these losses, along with no other work being done, make a system with an efficiency of 0%.
Or are you just trying to draw power from the battery for nothing and sticking it back in the battery (minus the losses)? Because just connecting a battery to a capacitor will do that too and have less losses since the battery takes longer to actually empty (actually a battery just sitting there would be best).
Because energy used to perform work and those attributed to losses cannot be recovered and restored back to the system. THe only way you can recover most of the energy is if it was extracted from the source for no reason (ie. not used for work or anything really) and restored back into the source or stored somewhere else, minus losses.
THere are systems like motor drivers where the due to the way the motor is, energy is stored in it's winding inductance as it dissipates other energy input as work, and when you denergize the motor you can recapture this unused energy from the winding inductance to increase efficiency, but it's more of a side-effect and we have to make the most of it. Preferably the inductance would store no energy.