Battery disconnect sensing circuit for battery charging systems

A battery disconnect sensing circuit for battery charging systems comprising first and second voltage dividers connected in parallel and adapted to be connected across the voltage output of a battery charging system, said first voltage divider having a first output terminal and said second voltage divider having a second output terminal in which, under steady state or gradually changing voltage conditions supplied to said voltage dividers, the voltage value at said first terminal is greater than that at said second terminal, voltage comparator means connected to said first and second terminals for producing a control signal in response to a voltage value at said second terminal signal exceeding that at said first terminal, and circuit means connected to said terminals for causing the voltage value at said second terminal to momentarily exceed that at said first terminal in response to a rapid increase in voltage value supplied to said voltage dividers.

In a battery charging system including a source of charging current whose voltage output is controlled at a predetermined value when connected to a battery and increases to a higher value when disconnected from said battery, and controller means connected with said source to activate the battery charging system automatically in response to electrical connection thereof to said battery, the improvement which comprises:

• means for momentarily effecting reversal of the higher voltage value, and battery disconnect sensing means connected said charging source and to said controller means for sensing said reversed higher voltage upon disconnection of said battery charger system from said battery and for responding thereto by automatically deactivating said battery charging system.