The belt alternator starter found in some stop/start vehicles is made up of many components, including a battery pack and AC/DC motor. There also are electronics built into the system that send power from the generator to the vehicle’s conventional battery, and there’s an engine accessory drive.
Even though the technology has advanced, belt tension is still important. Stop/start magnifies that activity at every red light. Belt tension, to either extreme, causes several issues.
This video is sponsored by Litens.