A battery cell assembly includes a thin sensor assembly having a plastic sheet, first, second, third, and fourth conductive pads, first and second resistive traces, a sensing circuit, a microprocessor, and an electrical connector. The plastic sheet has a first side and a second side. The plastic sheet further having first and second sheet portions, a first connecting portion, and first, second, and third tabs. The first connecting portion is coupled to and between the first and second sheet portions. The first and second resistive traces are disposed directly on and coupled to the first and second sheet portions, respectively. The first and second conductive pads are disposed directly on and coupled to the first and second tabs, respectively, on the first side.