A system for controlling charging of a battery in a hybrid-electric vehicle. The system is configured to estimate a total vehicle power requirement and an available internal combustion engine power provided by the engine in each gear of a transmission system of the vehicle. The system may then determine a highest gear of the transmission system that has an estimated available power at least equal to the estimated total vehicle power requirement. The system may then, responsive to a state of charge of the battery falling below a predetermined low-charge threshold, and if the transmission system is not currently in the highest gear that has an estimated available power at least equal to the estimated total power requirement, control operation of the vehicle to shift the transmission system to the highest gear that has an estimated available power at least equal to the estimated total power requirement.