AUTOMATIC BATTERY CHARGER

• US 3,781,631 A
• Filed: 02/11/1972
• Issued: 12/25/1973
• Est. Priority Date: 02/11/1972
• Status: Expired due to Term

• Current Assignee: Heath Company
• Original Assignee: Lawrence L. Grover, Ronald C. Nelson
• Inventors: Nelson, Ronald C., Grover, Lawrence L.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/225,457
• Time in Patent Office: 683 Days
• Field of Search: 320/23,25,26,39,40,DIG.1,DIG.2 317/9,33 323/22SC
• US Class Current: 320/139
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/0034 using reverse polarity correcting or protecting circuits mechanical means of polarity protection H02J7/0045
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y10S 320/13 Fault detection
• CPC Class Codes: Y10S 320/15 Polarity control

Abstract

A completely automatic battery charger requiring no internal or external adjustments to automatically charge a battery of a predetermined voltage. Current from a power supply is conducted to a properly connected battery by an SCR which is gated on during each proper polarity pulse of the cycle by a gate circuit. The gate circuit is rendered conducting only when a battery of the proper terminal voltage is properly connected to the terminals of the battery charger. Disabling circuits prevent the gate circuit from triggering the SCR under all adverse conditions including reverse connecting a battery to the charger terminals, short circuiting the charger terminals together, or connecting an undervoltage or overvoltage battery to the charger terminals. An overcharge protection circuit disables the SCR gate circuit when the battery terminal voltage reaches a predetermined value. The gate circuit is effective to gate the SCR either fully on or not provide any gate signal at all. Hence, strong pulses are provided to the battery whenever the charger is charging, and correspondingly, no polarization of the battery occurs even when the charger is left connected to the battery for weeks or months.

Claims

1. A fully automatic high efficiency battery charger particularly characterized by the absence of current limiting resistors in a main charging circuit of the charger comprising, in combination a main charging circuit comprising power supply means for providing a source of charging voltage pulses, first and second output terminals for connecting the charger to a battery to be charged, first and second leads connecting the power supply to the respective output terminals, a controllable conduction device in the form of a thyristor having an anode, a cathode, and a control electrode, with the anode and cathode connected in series in one of the leads whereby there is a series circuit including the frist output terminal, the thyristor, the power supply, and the second lead and terminal, the series circuit of first lead, thyristor, and power supply, forming a high efficiency charging circuit path particularly characterized by teh absence of current limiting resistors;

first control means for selectively rendering the controllable conduction device conducting in response to pulses of only one polarity from the source of charging voltage;

second control means for automatically controlling the first control means to prevent conduction of the controllable conduction device in response to pulses from the source of charging voltage of said only one polarity in response to a battery connected to the terminals and having a terminal voltage above a preselected maximum value, the second control means being further effective to automatically render the controllable conduction device conducting in response to pulses of said only one polarity after a drop in terminal voltage of the battery to a level below the preselected maximum value;

third control means for controlling the first control means to prevent conduction of the controllable conduction device in response to pulses from the source of charging voltage of said only one polarity, except when a battery having a terminal volage above a preselected minimum value is connected to the output terminals with proper polarity, said third control means comprising second power supply means, voltage divider means having a junction and connected between one of said terminals and said second power supply means, said second power supply means providing an opposing polarity voltage of a polarity opposing the voltage on said one of said terminals when a battery is properly connected to said terminals, whereby said junction is at a predetermined level and polarity when a battery is properly connected to the terminals, and solid state switch means for preventing conduction of said first control means unless the voltage at said junction is of a predetermined polarity relative to the polarity of said one terminal;

whereby, the output terminals receive current from the power source, via the controllable conduction device only when a battery having a terminal voltage within a preselected range is properly connected to the terminals, the charger is effective to recharge the battery whenever the terminal voltage of the battery drops to within the preselected range, and the terminals can be short circuited together, and can also be reverse polarity connected to the battery without damage to either the battery or the battery charger.

2. A battery charger according to claim 1 wherein said second power supply means supplies a direct current of said opposing polarity and includes a diode connected to said power supply, and filter means connected between the diode and the power supply to provide a direct current of said opposing polarity.