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Automotive start, light, ignition (SLI) lead acid batteries used in tanks are prone to capacity loss due to low temperatures, self-discharge, sulfation and shorting of plates. Monitoring and charge control of these batteries can be improved by using the concept of a smart battery system (SBS). In a SBS, battery data from sensors embedded in the battery package are acquired by a smart battery controller which processes this data, and transmits charge control information, to a central processor for effecting control actions over a controller area network (CAN) bus. Smart battery circuitry has been designed, developed and implemented to monitor the SOC of a 12V automotive lead acid battery used in tanks. The hardware comprises ac impedance measuring hardware interfaced to a Motorola 68HC12 microcontroller with a built-in CAN controller interface. The SOC estimation algorithms are based on a fuzzy logic model that is directly implemented into the Motorola 68HC12 microcontroller.

MEMS (Microelectromechanical Systems), as a technology, represents a new paradigm for integration of computational functions with elements that interact with the physical world. By combining mechanical moving parts with more traditional integrated circuits, new capabilities exist for sensing/actuating systems not previously possible. In developing MEMS, fundamental issues of packaging and fabrication have required considerable attention. An analogous group of technologies are emerging which combine chemically reacting elements with computational functions. These might be referred to as Microelectrochemical Systems. Examples include chemical sensors and actuators, as well as on-board chemical sources of energy, such as microscopic batteries, fuel cells, energy harvesters. The merger of chemical systems and computational capabilities requires us to address a host of issues such as packaging and fabrication, as was (and is) needed with MEMS.

Efficient, small, and reliable dc-dc power converters with high power density are highly desirable in applications such as aerospace and electric vehicles, where battery storage is limited. Bidirectional full-bridge (FB) dc-dc converters are very popular in medium and high-power applications requiring regenerative capabilities. Full-bridge topology has several advantages such as: Inherent galvanic isolation between input and output as well as high conversion ratio due to the transformer with a turns ratio n. Reduction in passive component sizes due to the increase in inductor current frequency to twice the switching frequency. Reduced voltage stresses on the low-voltage side switches and current stresses on the high-voltage side switches. However, due to the high number of switches, device losses increase.

Battery state of charge meters based on combining fuzzy logic analysis and either Coulomb counting or battery impedance measurements have been designed, fabricated and tested. The Coulomb counting meters have been implemented in digital hardware using Motorola 68HC11 and 68HC12 microcontrollers and in field programmable gate arrays. The impedance meter has been prototyped in analog hardware using discrete components. In this paper, we present the hardware/software designs for these meters and some test results on primary Li/SO2 cells.