ELECTRIC BATTERY CHARGER

• US 3,809,993 A
• Filed: 12/13/1972
• Issued: 05/07/1974
• Est. Priority Date: 12/17/1971
• Status: Expired due to Term

• Current Assignee: Frederick Charles Wheeler
• Original Assignee: Frederick Charles Wheeler
• Inventors: Wheeler, Frederick Charles
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US05/314,773
• Time in Patent Office: 510 Days
• Field of Search: 320/2,25,26,35,36,39,40
• US Class Current: 320/154
• CPC Class Codes: H02J 7/0034 using reverse polarity correcting or protecting circuits mechanical means of polarity protection H02J7/0045
• CPC Class Codes: Y10S 320/15 Polarity control

Abstract

A battery charger incorporating an electric current heated thermo-operated switch which prevents the passage of charging current to a bettery connected to the charger the wrong way round, and acts to disconnect a battery intermittently when fully charged, when connected to right way round.

Claims

1. A battery charger comprising a source of unidirectional charging current, a first battery connecting terminal for connection of the charger to one terminal of a battery to be charged;

a second battery connecting terminal for connection of the charger to the other terminal of the battery to be charged;

a first circuit including in series said first battery connecting terminal, an electric current heated thermo-operated two-way switch, a diode, a current limiting device, and said second battery connecting terminal;

a second circuit including an electrical connection between said first battery connecting terminal and one side of said source of charging current and in which said two-way switch is included, said second circuit also including an electrical connection between the other side of said source of charging current and said second battery connecting terminal independent of said two-way switch;

said two-way switch being operable such that when cold, said two-way switch completes said first circuit and when hot opens said first circuit and closes said second circuit, said diode being connected such way round as to prevent operation of said two-way switch when a battery is connected to the battery connecting terminals the wrong way.

2. A battery charger as claimed in claim 1 in which the thermo-operated switch is a bi-metallic switch heated by a current passing through the switch, said switch being operable to open said second circuit when the current which passes is that when the battery is fully charged.

3. A battery charger as claimed in claim 1 in which there is provided more than one path for the simultaneous paSsage of charging current between said one side of said source of charging current and said first battery connecting terminal, one of which is of substantially greater resistance than the other path, said path of substantially greater resistance constituting said second circuit, whereby the thermo-operated switch in said path of substantially greater resistance is influenced by and passes only a portion of the total charging current.

4. A battery charger as claimed in claim 3 in which there are two paths and there is provided a relay having an energising coil, said energising coil being connected to the path of substantially greater resistance, while the contacts of the relay are connected in the path of lower resistance.

5. A battery charger as claimed in claim 4 in which a resistor is connected in each of the two paths the values of which are so chosen that the charging current flowing by way of the coil is substantially less than that flowing by way of the contacts.

6. A battery charger as claimed in claim 5 in which there is provided a thermally operated switch across the resistor in the path including the coil, which is normally closed, and which opens due to rise in temperature of the coil above a predetermined value.

7. A battery charger as claimed in claim 3 in which there are provided two paths for the simultaneous passage of charging current, a plurality of resistors, a further electric current heated thermo-operated switch acting as a two-way switch, which when cold connects the source of charging current with said second circuit by way of one of said resistors and when hot connects the source of charging current to said first battery terminal by way of said resistor to establish the path of relatively low resistance, while the path of relatively high resistance is by way of another resistor between said source of charging current and the first mentioned thermo-operated switch in said second circuit.

8. A battery charger as claimed in claim 7 in which the path of higher resistance is more than four times the resistance of the path of lower resistance.

9. A battery charger as claimed in claim 4 in which the path of higher resistance is more than four times the resistance of the path of lower resistance.

10. A battery charger as claimed in claim 1 provided with a warning light connected across the contacts of the thermo-operated switch which are closed when the switch is cold and which is illuminated when the switch is hot to indicate that the battery is connected the correct way round and is being charged.

11. A battery charger as claimed in claim 1 provided with a warning light and a diode which are connected in series across the battery connecting terminals to indicate when the battery is connected the wrong way round.

12. A battery charger as claimed in claim 1 in which said thermo-operated switch includes a movable member, and an overload cut-out in series with said movable member.