Tempering curve
The start-up curve is the time course of the on- board electrical system voltage of a motor vehicle standardized in accordance with DIN 40839 , which occurs around the start-up area of the internal combustion engine . The curve is essentially determined by the internal resistance of the starter battery and the current consumption of the starter .
The curve is characterized by four main phases:
- constant battery voltage before starting (nominal voltage of the vehicle electrical system)
- strong voltage drop at the moment the starter is switched on, highest current consumption due to stationary starter (in vehicles with internal combustion engines usually a series motor )
- Revving up the starter and combustion engine, decreasing power consumption and thus increasing voltage
- Running engine, alternator supplies electricity and keeps the on-board network at nominal voltage again, starter is switched off and disengages automatically
Among other things, the start-up curve is used to test control units in the vehicle, which must also function reliably at the starting moment with the reduced voltage without misfires.