noted that a contactor 68 may be electrically coupled between 36 volt battery 64 and dc to dc converter 60 to provide electrical isolation between the 36 volt battery and the rest of the vehicle battery control module 57 is coupled to contactor 68 to control the opening and closing of contactor 68 system controller 54 is also coupled to an indicator 80 indicator 80 may comprise an audible indicator a visual indicator or a combination of the two one example of an indicator is an lcd display that can display various messages and actions for the vehicle operator to perform instrument panel reminder lights or chimes may also be used to generate messages a 12 volt source 65 such as a 12 volt battery from another vehicle battery charger or generator is shown electrically coupled to 12 volt battery 66 referring now to fig2 a method for charging a 12 volt battery when the 42 volt battery is charged is illustrated in step 100 if the 12 volt battery is not dead and the 42 volt battery is not charged the system starts again in step 100 in step 100 if the 12 volt battery is not charged and the 42 volt battery is charged step 102 is executed in step 102 the 12 volt battery is charged in a conventional manner that is jumper cables may be connected from a 12 volt source such as another charged battery typically when charging a 12 volt battery the positive terminal of the charged battery is connected to the positive terminal of the dead battery while the negative terminal of the charged battery is coupled to chassis ground in the vehicle with the dead battery the negative battery terminals may also be coupled together in step 104 the charge of.