Lithium battery pack

A lithium battery pack, comprising:na battery set composed of two or more lithium battery cells connected in series;a first protection circuit including a first voltage detect part for detecting voltages of a first stage of the battery set having two or more battery cells of the battery set, and a first signal output part for issuing an output signal when a detect voltage of the two or more battery cells of the first stage detected by the first voltage detect part goes below a given over-discharge judgment voltage value;a second protection circuit including a second voltage detect part for detecting voltages of a second stage of the battery set, different from the first stage, having two or more battery cells, other than the two or more battery cells of the first stage, of the battery set, and a second signal output part for issuing an output signal when a detect voltage of the two or more battery cells of the second stage detected by the second voltage detect part goes below a given over-discharge judgment voltage value; anddead time means connected between the second signal output part of the second protection circuit for issuing an output not responding to a variation in an input signal occurring within a given time.

A power tool, comprising:na battery set including two or more lithium battery cells connected in series;a first protection circuit for detecting cell voltage(s) of a first stage of the battery set having two or more lithium battery cells of the battery set and, when the thus detected voltage of the two or more battery cells of the first stage goes below a given over-discharge judgment voltage value, for issuing an output signal;a second protection circuit for detecting cell voltage(s) of a second stage of the battery set, different from the first stage, having two or more lithium battery cells, other than the two or more lithium battery cells of the first stage, of the battery set and, when the thus detected voltage of the two or more battery cells of the second stage goes below a given over-discharge judgment voltage value, for issuing an output signal;switch means connected to the current path of the battery set such that it can be turned on or off according to the outputs of the first and second protection circuits;dead time means connected between the second protection circuit and the switch means for issuing an output not responding to a variation in an input signal within a given time; anda motor to which a voltage from the battery set can be supplied through the switch means.