A polymer battery pack assembly comprising a mounting frame having a first cavity defining a first mounting location and a second cavity defining a second mounting location, the first and second cavities being separated from each other; a top case mounted on the second mounting location, the top case having a third cavity defining a third mounting location; a lithium polymer battery cell mounted within the first mounting location, the battery cell having a positive tap and a negative tap extending beyond the first cavity towards the second mounting location; and a protection circuit module mounted in the third mounting location, the protection circuit module being electrically connected to the positive tap and the negative tap when the top case is mounted to the mounting frame such that the protection circuit module fits into said second cavity.