Accurate charge-control and state-of-charge monitoring of lead-acid batteries is an ever-increasing necessity in an industry that demands low-maintenance costs and highly available systems. If the batteries are charged by photovoltaic panels and are installed in remote sites (e.g. Oil sea-platforms, highway emergency bays, autonomous communications systems) and exposed to aggressive environmental conditions (e.g. Extreme temperature, high humidity), the problem of extending the batteries’ useful life becomes a challenge. Most charging algorithms do not perform well when photovoltaic panels are the sole source of energy because energy availability is not guaranteed. A charge algorithm that maximizes the use of energy generated by the panel during daylight hours is needed. This paper presents a microcontroller-based charge-controller suitable for photovoltaic applications. The controller performs temperature compensation on the charge algorithm. It also stores those parameters that provide an indication on batteries’ state-of-charge and state-of-health: Panel voltage, battery’s voltage and current, current demanded by a load and room temperature. The controller has serial communication capabilities that make possible the connection to a personal computer or central station. By using a local industrial network or radio links, multiple controllers can be monitored by a central station running a battery management program. The information collected by all the controllers in the system is analyzed to determine the state-of-charge of individual batteries and, if required, command the appropriate controller to perform special procedures like, for example, thorough diagnostics or equalization. Preliminary field-test results of a controller installed in a high-way emergency bay are presented in this paper. It is shown that protection against deep discharges is achieved, which contributes to extend the battery useful life.

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