Heavy Duty Truck and Bus Electrical Circuit Performance Requirement for 12/24-Volt Electric Starter Motors
The scope of this SAE Recommended Practice is to describe a design standard to define the maximum recommended voltage drop for starting motor main circuits, as well as control system circuits, for 12- through 24-V starter systems.
Rationale:This document is intended to give the industry a design standard to define the design of the electrical circuits used in conjunction with 12/24-V electric starting motors. The document will include all elements of the electric starter system main cranking and control circuits.This document is not intended to be updated or modified to include starter motors rated at voltages above the nominal 24 V electrical system. The starter is basically an electrical-to-mechanical power converter. If you double the available battery power in, you double the peak mechanical power out and double the heat losses. This means that we have to pay special attention to how battery power changes when we change the battery voltage and the effects it may have in overpowering the cranking system. A new stand-alone document will need to be created addressing electrical circuit performance for starter motor systems with ratings above the nominal 24-V system.