The practice of increasing the engine speed of the donor vehicle during a jump start procedure is a common one. The intention behind this action is to provide a higher voltage output from the alternator, potentially delivering a stronger and faster charge to the depleted battery in the recipient vehicle. This involves pressing the accelerator pedal of the running vehicle to elevate the RPMs beyond the standard idle speed.
The perceived benefit stems from the understanding of how an alternator functions. Alternators produce more current at higher rotational speeds. Historically, this was considered a crucial step because older alternators were less efficient at lower speeds. Increasing the engine speed was thought to overcome this limitation and provide a more substantial current flow to the vehicle with the dead battery, thereby facilitating a quicker start. However, modern vehicle electrical systems are generally designed to provide sufficient amperage at idle.
