Micro Hybrid Systems are essentially first step towards the electrification of the powertrains. They are aimed at improving the fuel efficiency of the conventional gasoline and diesel power trains with conventional 12 V electrical system, and thus reduce the CO2 emissions as well. Various technologies like Engine Stop-Start, Intelligent Alternator Control, and Electrical Energy Management Systems are included in the bracket of micro hybrid systems.
These system functions demand a totally different approach for managing the SLI battery, which is a total departure from the conventional approach. Particularly, the Alternator Shutdown function of Intelligent Alternator Control maintains a calibrated average level of State of Charge, which is typically around 80%, to ensure that the battery can accept more current, during the energy recuperation, which indirectly improves fuel economy. However, continuous operation under partially discharged condition, results in the sulfation in the battery which is the main reason for the ageing of the battery. Symptoms of ageing include permanent loss of capacity, increase in internal resistance, etc.
This paper discusses a novel approach of ensuring the life of the battery in the altered operating conditions of a Micro Hybrid System. A Charge Refresh Cycle is implemented in the Battery Management System, which periodically performs a refresh charge on the battery to ensure that the battery is not affected due to partially discharged conditions, without having to disconnect the battery from the vehicle, and without the need of a visit to a service station. This is achieved by implementing a timer and an engine start counter, based on which the control signals for the refresh charge are triggered. The system not only ensures the performance of the battery, but also ensures the return of designed life of the battery. The function was validated under controlled conditions on several samples of batteries, and it was observed that the battery life is restored back to the designed life.