Apparatus for measuring internal resistance of wet cell storage batteries having non-removable cell caps

• US 5,047,722 A
• Filed: 04/17/1989
• Issued: 09/10/1991
• Est. Priority Date: 04/17/1989
• Status: Expired due to Term

• Current Assignee: Btech, Inc.
• Original Assignee: SSMC, Inc.
• Inventors: Wurst, John W., Garron, Stephen A., Dob, Allan M.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Mueller, Robert W.
• Application Number:
  US07/338,688
• Time in Patent Office: 876 Days
• Field of Search: 324/430, 324/434, 324/436, 324/427, 324/429, 340/636, 320/48
• US Class Current: 324/430
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

Apparatus for measuring the total internal resistance of a multicell battery having positive and negative terminals employs a first transistor device having an input and an output and having mutually exclusive conductive and non-conductive electric states. An arrangement of resistances is connected in series with the device to form a network. The network is connected between the positive and negative terminals. An operational amplifier has an output connected to the input of the device and first and second inputs. The first input is connected to the network at a point connected to both of the device and the arrangement. A square wave signal alternating between a positive voltage and ground on alternate half cycles is applied to the second input. The device is in the conductive state when the alternating voltage is positive and is in the non-conductive state when the alternating voltage is at ground. The network conducts no current when the device is in the non-conductive state and conducts a current of constant value when the device is in the conductive state. The voltage appearing between the terminals as a result of the current in the network is monotonically related to the internal resistance of the battery.

Claims

1. Apparatus for measuring the total internal resistance of a multicell battery having spaced apart positive and negative terminals comprising:

first transistor means having an input circuit and an output circuit and having mutually exclusive conductive and non-conductive electric states;

second resistance means connected in series with the output circuit of said first means to form a network, said network being connected between said positive and negative terminals;

an operational amplifier having an output circuit connected to the input circuit of the first means and first and second input circuits, the first input circuit of the amplifier being connected to said network at a point connected to both of the first and second means; and

third means including an oscillator to apply an alternating voltage to the second input circuit of the amplifier, the alternating voltage changing polarity on alternate half cycles, the first means being in the conductive state when the alternating voltage is of one polarity and being in the non-conductive state when the alternating voltage is of the other polarity, said network conducting no current when the first means is in the non-conductive state and conducting a current of constant value when the first means is in the conductive state, the voltage appearing between the positive and negative terminals as a result of the current flow in the network being monotonically related to the internal resistance of the battery.

2. Apparatus of claim 1 wherein said second means includes first and second resistances, and the output circuit of the first means includes first and second spaced apart leads, the first resistance being connected to the first lead, the second resistance being connected to the second lead.

3. Apparatus of claim 2 wherein the value of the first resistance is much larger than the value of the second resistance, the first input circuit of the amplifier being connected to the second lead.

4. Apparatus of claim 3 wherein said first means includes a drive transistor and a power transistor, the drive transistor having an input circuit defining the input circuit of the first means, the power transistor having an output defining the output circuit of the first means, the drive transistor having an output circuit, the power transistor having an input circuit, the output circuit of the drive transistor being connected to the input circuit of the power transistor.

5. Apparatus of claim 4 wherein the alternating voltage has the shape of a square wave.