When jump starting a car is it better to rev the engine?
You’ll want the donor car running at 1500-2000 rpm while attempting to start the car with a dead battery. This keeps the alternator rpm in a range where it can supply the necessary amperage without maxing out the windings. If the battery is completely dead, let the donor car charge it at the above rpm for a couple minutes before trying to start it, and be sure to run the jumped car for a while at engine speeds greater than idle to charge the battery. Make sure to check both batteries for proper electrolyte level before starting. An internal arc in a battery with low electrolyte can result in a hydrogen explosion.
