Micro power battery state-of-charge monitor

This paper presents the design and implementation of a micro power battery state of charge monitor. The novelty of this design lies in the extreme low power consumption and accurate prediction of the battery reserve time. The average current drawn is successfully limited to 60 muA, which is significantly smaller than those in currently available devices. The proposed design predicts the reserved battery charge with an accuracy of 5% under different discharge conditions. The automated learning scheme using software is utilized. Protection of the battery against excessive current drain and usage outside the specified temperature range is incorporated. This paper details the proposed technique adopted for power reduction. The battery temperature and current sensing circuits are normally in power down mode, they go into active mode for the microcontroller to take measurements. An ON/OFF ratio of 1:153 is achieved which results in power reduction by a factor of 59.30. The average current requirement of the proposed design is reduced from 3302.79 muA to 55.69 muA with the adoption of power reduction approach. The proposed design has been tested on a NiMH, NiCd and Li-Ion battery packs and the experimental results confirm the utility of the proposed design .