As the industry strives to achieve improved fuel economy, stop-start systems for internal combustion engines are receiving additional focus. Studies and system proposals have been made for various electrical configurations ranging from 12 volts to 42 volts and higher [1, 2, 3]. Both cranking motor and belt alternator starter configurations have been proposed, with some concerns regarding the customer acceptance of the cranking motor solution [1] which were subsequently addressed [3]. Typically, 14 Volt Belt Alternator Starter (BAS) applications are limited to 1.6 liter gasoline (0.4 liter per cylinder) and 1.4 liter diesel (0.35 liter per cylinder) engines due to BAS torque output constraints. Some previous work extended this range to 0.7 liter per cylinder by utilizing a boosted supply voltage and auxiliary energy storage device [1]. This paper details a 2.4 liter 4 cylinder GDI (0.6 liter per cylinder) application of a non-boosted 14 V BAS system with integrated battery state of health monitoring.
A key enabler for the application is a high (3.24:1) pulley ratio which reduced cranking current by 43%. The lower cranking speed did not result in longer start times as a fast-start algorithm allowing fuel injection and spark on first partial compression stroke was employed which actually reduced start time by 22%. Functionality was further improved by using the higher rotation speed of the alternator together with battery state of health monitoring for improved battery recharging and efficient energy recovery.
