Abstract: A fault-tolerant battery set and a start-up battery module are described. The fault-tolerant battery set includes a main battery module, a battery monitoring unit, a control switch unit, and a back-up battery module. The main battery module includes a battery unit and a battery monitoring circuit. When the battery unit fails, the control switch unit conducts a power supply connection path according to a failure signal sent from the battery monitoring circuit, so as to replace the failed main battery module with a back-up power provided by the back-up battery module through the power supply connection path.

Abstract: A composite battery set of a power tool, comprising a battery, a non-polarity ultracapacitor, a switch, a motor, etc. The ultracapacitor is a non-polarity ultracapacitor, and the power released by the fully charged battery at a high discharge rate is utilized to drive a motor. As such, a switch is used to switch and connect the non-polarity ultracapacitor to the different polarities of the motor, thus achieving the switching of the rotation directions of the motor.