GB2175404A - Battery tester - Google Patents

Abstract

A device for testing the condition of heavy-duty batteries includes a pair of probes (10) interconnected by a resistance winding strip (13) to provide a discharge path when the probes are placed across the respective battery terminals. The discharge circuit is completed by depressing the probe plunger (18) against the bias of a spring (19) to close the electrical contacts (20,21). Any sparking which occurs when the contact is made or broken takes place within the plunger housing (16), and is therefore harmless. <IMAGE>

Description

SPECIFICATION Battery tester This invention relates to a device for testing the condition of heavy duty batteries, such as 12 volt car batteries.

One such device is disclosed in our U.K.

Patent 872 069. In this known device, a resistance winding is connected between a pair of conductive probes having insulated handles, the resistance providing a discharge path when the probes are placed across the respective terminals of the battery. The resistance wire also serves to mechanically connect the two probes and to maintain them spaced apart from one another. A voltmeter is connected across the probes to indicate the voltage during a discharge, the behaviour of the needle of the meter providing information regarding the condition of the battery.

The discharge current is normally around 250 amps. Accordingly, if the battery being tested has been charged overnight and a layer of hydrogen has formed across the top of the battery, there is a risk that the gas could be ignited by a spark produced when the probes contact the battery terminals. The resulting explosion is likely to destroy the battery and cause possible injury.

In accordance with the present invention there is provided a device for testing the condition of heavy duty batteries, the device including a pair of probes for placing across the respective battery terminals, the probes being connected to one another by a resistance winding providing a discharge path for the battery, and at least one of the probes including a circuit breaker having electrical contacts substantially enclosed within a housing. By delaying the closing of the circuit breaker until after the probes have been placed across the terminals, the risk of sparking at the terminals is eliminated. Any sparking which does occur takes place within the enclosed housing and is therefore harmless.

The or each probe preferably includes a first component which initially contacts the respective battery terminal, and a second component movable relative to the first component against a resilient bias. The circuit breaker is then closed in response to a predetermined movement of the second component against the resilient bias.

By way of example only, an embodiment of the invention is illustrated in the accompanying drawings in which: Figure 1 is an end elevation of a battery tester embodying the invention; and Figure 2 is a side elevation of the tester including a half section on line A-A in Fig. 1.

Referring to these Figures, the battery tester includes a pair of probes 10 having insulated handles 11 and conductive stems 12. A copper/nickel resistance winding strip 13 is connected between the two stems 1 2a and 12b, the strip 13 being wound in concertina fashion around fastening members 25 extending between side cheeks 26. The winding 13 provides a discharge path for the battery current when the probes 10 are placed across the battery terminals. The winding 13 also serves as a spring-loaded mechanical connection between the probes 10, allowing the probes to flex toward or away from one another to accommodate variable spacing between the terminals of the battery being tested. The side cheeks 26 serve as heat shields for the resistance winding 13, and are interconnected by cap screws 27 and nuts 28.

A cable 14 has one end connected to the stem 1 2b and its other end connected to a voltmeter assembly 15 connected to the stem 1 2a such that the meter is connected across the winding 13.

Each probe stem 12 incorporates a plunger assembly including a plunger housing 16 screwed on to the threaded end of the stem 12 against a lock nut 17. A plunger 18 is slidably received in an end cap 24 which screws into the base of the housing 16 against a washer 28, the plunger being retained in the housing by a dowel 23 passing through a hole 29 and resting on the washer 28. A spring 19 bearing against the dowel 23 normally holds the plunger contact 20 away from the end contact 21 of the stem 12a.

In use, with the tip 27 of each plunger 18 engaging a respective battery terminal, the plunger housing 16 and associated end cap 24 are pushed down by the stem 12 against the bias of the spring 19 until there is contact between the contact 21 and the contact 20.

Any sparking which occurs when the contact is made or broken takes place within the plunger housing and is therefore harmless.

1. A device for testing the condition of heavy-duty batteries, the device comprising a pair of probes for placing across the respective battery terminals, the probes when placed across the terminals forming part of a discharge circuit for the battery, the circuit further including a pair of normally open electrical contacts substantially enclosed within a housing, and means for engaging the contacts to complete the circuit after the probes have been placed across the terminals.

2. A device according to claim 1 in which the contacts are engaged in response to relative movement between first and second components of one of the probes.

3. A device according to claim 2 further comprising a second pair of normally open electrical contacts substantially enclosed within a housing, the second pair of contacts being engaged in response to relative movement between first and second components of the other probe.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Battery tester This invention relates to a device for testing the condition of heavy duty batteries, such as 12 volt car batteries. One such device is disclosed in our U.K. Patent 872 069. In this known device, a resistance winding is connected between a pair of conductive probes having insulated handles, the resistance providing a discharge path when the probes are placed across the respective terminals of the battery. The resistance wire also serves to mechanically connect the two probes and to maintain them spaced apart from one another. A voltmeter is connected across the probes to indicate the voltage during a discharge, the behaviour of the needle of the meter providing information regarding the condition of the battery. The discharge current is normally around 250 amps. Accordingly, if the battery being tested has been charged overnight and a layer of hydrogen has formed across the top of the battery, there is a risk that the gas could be ignited by a spark produced when the probes contact the battery terminals. The resulting explosion is likely to destroy the battery and cause possible injury. In accordance with the present invention there is provided a device for testing the condition of heavy duty batteries, the device including a pair of probes for placing across the respective battery terminals, the probes being connected to one another by a resistance winding providing a discharge path for the battery, and at least one of the probes including a circuit breaker having electrical contacts substantially enclosed within a housing. By delaying the closing of the circuit breaker until after the probes have been placed across the terminals, the risk of sparking at the terminals is eliminated. Any sparking which does occur takes place within the enclosed housing and is therefore harmless. The or each probe preferably includes a first component which initially contacts the respective battery terminal, and a second component movable relative to the first component against a resilient bias. The circuit breaker is then closed in response to a predetermined movement of the second component against the resilient bias. By way of example only, an embodiment of the invention is illustrated in the accompanying drawings in which: Figure 1 is an end elevation of a battery tester embodying the invention; and Figure 2 is a side elevation of the tester including a half section on line A-A in Fig. 1. Referring to these Figures, the battery tester includes a pair of probes 10 having insulated handles 11 and conductive stems 12. A copper/nickel resistance winding strip 13 is connected between the two stems 1 2a and 12b, the strip 13 being wound in concertina fashion around fastening members 25 extending between side cheeks 26. The winding 13 provides a discharge path for the battery current when the probes 10 are placed across the battery terminals. The winding 13 also serves as a spring-loaded mechanical connection between the probes 10, allowing the probes to flex toward or away from one another to accommodate variable spacing between the terminals of the battery being tested. The side cheeks 26 serve as heat shields for the resistance winding 13, and are interconnected by cap screws 27 and nuts 28. A cable 14 has one end connected to the stem 1 2b and its other end connected to a voltmeter assembly 15 connected to the stem 1 2a such that the meter is connected across the winding 13. Each probe stem 12 incorporates a plunger assembly including a plunger housing 16 screwed on to the threaded end of the stem 12 against a lock nut 17. A plunger 18 is slidably received in an end cap 24 which screws into the base of the housing 16 against a washer 28, the plunger being retained in the housing by a dowel 23 passing through a hole 29 and resting on the washer 28. A spring 19 bearing against the dowel 23 normally holds the plunger contact 20 away from the end contact 21 of the stem 12a. In use, with the tip 27 of each plunger 18 engaging a respective battery terminal, the plunger housing 16 and associated end cap 24 are pushed down by the stem 12 against the bias of the spring 19 until there is contact between the contact 21 and the contact 20. Any sparking which occurs when the contact is made or broken takes place within the plunger housing and is therefore harmless. CLAIMS

1. A device for testing the condition of heavy-duty batteries, the device comprising a pair of probes for placing across the respective battery terminals, the probes when placed across the terminals forming part of a discharge circuit for the battery, the circuit further including a pair of normally open electrical contacts substantially enclosed within a housing, and means for engaging the contacts to complete the circuit after the probes have been placed across the terminals.

2. A device according to claim 1 in which the contacts are engaged in response to relative movement between first and second components of one of the probes.

3. A device according to claim 2 further comprising a second pair of normally open electrical contacts substantially enclosed within a housing, the second pair of contacts being engaged in response to relative movement between first and second components of the other probe.

4. A device according to claim 2 in which the relative movement is against a resilient bias.

5. A device according to any one of the preceeding claims in which the probes are mechanically connected to one another by an electrical resistance forming part of the discharge circuit.

6. A device substantially as herein described with reference to the accompanying drawings.