What is Undervoltage?
UNDERVOLTAGE: A sudden dip in voltage caused by engine starting or other heavy loads. This is one of the primary causes of memory loss in GPS navigation systems and crashes in mobile computer systems.
Cranking voltage with a fully charged battery can drop to 6 volts during the initial engagement of the starter motor.
With the engine OFF, battery voltages can be expected to drop to 10 Volts in a 12V system, or 20 Volts in a 24/28 volt system under normal use. Frequent events, like a fuse blowing on a lighting system, will drop system voltages below this for a few seconds before the fuse or circuit breaker opens.