ELECTRIFIED VEHICLE ROOF-MOUNTED BACKUP BATTERY

An electrified vehicle backup battery system includes a traction battery pack of an electrified vehicle, and a backup battery assembly that is removably mounted to the electrified vehicle. The backup battery assembly is configured to recharge the traction battery pack through a charge port of the electrified vehicle. A traction battery pack charging method includes recharging a traction battery pack of an electrified vehicle from a backup battery assembly that is mounted above a roof of the electrified vehicle.