Electrochemical behaviors of 2.5V Li[Li1/3Ti5/3]O4 (LTO)/Li[Li0.1Al0.1Mn1.8]O4 (LAMO) cells for the first-generation 12V lead-free battery were examined at −10, 25, and 55°C. The LTO/LAMO cells showed the same rechargeable capacity in temperature ranging from −10 to 55°C when the cells were examined at 0.5mAcm−2 in cell potential ranging from 0 to 3.0V. Capacity fading after 250 cycles was negligibly small at −10°C. Rechargeable capacities, however, faded 5% at 25°C and 15% at 55°C after 250 cycles. In the discharged LTO/LAMO cell after 250 cycles at 55°C, the state of charge (SOC) of the positive electrode was 16% while SOC of the negative electrode was 0%, indicated that the capacity fading was due to an imbalance in SOC between the positive and negative electrodes. To understand the progress of an imbalance in SOC, the LTO/LAMO cell with a lithium auxiliary electrode was fabricated and examined at 55°C for 400 cycles, and the possible origin of capacity fading was discussed.