Abstract: An emergency vehicle battery charging device is utilized to charge a depleted battery of a first vehicle from the engine system of a running second vehicle at a predetermined maximum charging current above that used for a trickle charge and below the typical starting current of either vehicle. The battery charging device includes a control housing having a first pair of cables extending therefrom which is rigidly connected to the battery terminals of one of the vehicles and a second pair of cables extending therefrom for being selectively connected to the battery terminals of the other of the vehicles. The cables include a current limiting device to prevent any exceeding of the predetermined maximum charging current which is preferably with in a range of about 40 to 60 amps. The control housing includes a polarity detecting device to verify the correct polarity of the connection of the terminals of the two batteries and to electrically disconnect the two batteries of there was an incorrect polarity.