Example implementations relate to a parallel backup power supply. For example, a parallel backup power supply system can include a plurality of backup power supply cells that support a plurality of loads. Each of the backup power supply cells can include a charging module to charge an associated backup power supply cell among the plurality of backup power supply cells and a cell controller. The cell controller is to can be configured to control the charging module and communicate with a management module. The parallel backup power supply system can also include the management module to activate each of the plurality of backup power supply cells to provide backup power in parallel to the plurality of loads as each of the plurality of backup power supply cells is fully charged.