System and method of controlling operation of a device having multiple rechargeable packs configured to store energy. The multiple rechargeable packs include at least one primary pack characterized by a first capacity and at least one auxiliary pack characterized by a second capacity, the first capacity being greater than the second capacity. A controller is configured to selectively command one or more of the multiple rechargeable packs to begin at least one of discharging and charging. When an estimated end of trip time is less than or equal to a discharging time of the at least one auxiliary pack, the discharging of the at least one auxiliary pack is begun. When the estimated end of trip time is greater than the discharging time, the discharging is delayed until the respective state of charge of the at least one primary pack reaches a first threshold.