Lithium battery pack protection device and lithium battery pack

The utility model discloses a lithium battery pack protection device and a lithium battery pack. The lithium battery pack protection device comprises a lower shell, an upper shell and a fastening piece, wherein the periphery of the upper end of the lower shell is provided with an extending edge which extends outwards, and the extending edge has a multi-step projection; the lower end of the upper shell is provided with the extending edge and a groove which are matched with the extending edge and the projection of the upper end of the lower shell; and the fastening piece connects the upper shell with the lower shell. After adopting the technical scheme, the water inlet path of the shell can be increased due to the mutually-matched extending edges of the upper and the lower shells, the contact area of the two extending edges is large, the fastening piece is used for increasing the pressure of the two extending edges to left a clearance seal therebetween, so water can be prevented from entering the shell. When ra