be installed in a vehicle and while utilizing a portion of this vehicle 39 s electrical system can be used to charge another vehicle 39 s battery or batteries this battery charger has a polarity sensor and when properly connected to an external battery will automatically switch away from charging the internal battery to charging the external battery or batteries and when dis connected from the external battery or batteries will automatically switch back to charging the internal battery thus making it an automatic vehicle to vehicle battery charger application_number US 32192081 A description my invention is an apparatus for charging batteries referred to throughout the embodiment as vehicular battery charger battery charger or simply charger in order to help simplify the explaining as well as the understanding of this battery charger 39 s electrical circuit i have broken it into eleven categories 1 means for installation as well as means for connecting to the battery charger 39 s output power the receptacle 5 is a permanent part of the battery charger offering a convenient means of connecting to the battery charger 39 s output power on external the jumper cable 2 3 and 4 can be made into any length desirable 12 gauge or heavier automotive wire is recommended with the jumber cable line 2 line 3 and line 4 hooked up to the external battery 1 and to the receptacle 5 voltage goes from the battery 1 through line 3 in series through the receptacle 5 and on in series through the diode 6 and from the diode 6 a portion of the voltage goes.