Battery pack

A battery pack comprising:

• a non-aqueous electrolyte secondary battery comprising an electrode assembly, a lithium-ion conductive non-aqueous electrolyte, and a battery case for housing the electrode assembly and the non-aqueous electrolyte, the electrode assembly comprising a positive electrode including a positive electrode active material capable of absorbing and desorbing lithium, a negative electrode including an alloyable active material, and an insulating layer interposed between the positive electrode and the negative electrode;
• thickness detection means for detecting the thickness of the electrode assembly;
• cycle number detection means for detecting the number of charge and discharge cycles of the non-aqueous electrolyte secondary battery;
• and
• determination means for determining the replacement time of the non-aqueous electrolyte secondary battery or the presence or absence of cycle deterioration of the non-aqueous electrolyte secondary battery according to a detection result by the thickness detection means and a detection result by the cycle number detection means.