Fast battery charger for a device having a varying electrical load during recharging

• US 5,696,435 A
• Filed: 03/07/1995
• Issued: 12/09/1997
• Est. Priority Date: 06/07/1982
• Status: Expired due to Term

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Koenck, Steven E.
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US08/399,742
• Time in Patent Office: 1,008 Days
• Field of Search: 320/2, 320/5, 320/15, 320/22, 320/30, 320/39, 320/40, 320/56, 320/48, 320/21, 320/35
• US Class Current: 320/145
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G06F 1/263 Arrangements for using multiple switchable power supplies, e.g. battery and AC G06F1/30 takes precedence
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 50/213 adapted for cells having curved cross-section, e.g. round or elliptic H01M50/209, H01M50/216 take precedence
• CPC Class Codes: H01M 50/50 Current conducting connections for cells or batteries
• CPC Class Codes: H01M 6/5044 Cells or batteries structurally combined with cell condition indicating means
• CPC Class Codes: H01M 6/505 Cells combined with indicating means for external visualization of the condition, e.g. by change of colour or of light intensity
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00036 Charger exchanging data with battery
• CPC Class Codes: H02J 7/00038 using passive battery identification means, e.g. resistors or capacitors identification by mechanical connections H02J7/0045
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/0049 Detection of fully charged condition
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/0069 : Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/0071 : with a programmable schedule
• CPC Class Codes: H02J 7/00711 : with introduction of pulses during the charging process
• CPC Class Codes: H02J 7/00712 : the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: H02J 7/00714 : in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007194 : of the battery
• CPC Class Codes: H02J 9/061 : for DC powered loads
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries

Abstract

In an exemplary fast charging system, a hand-held computerized terminal with rechargeable batteries therein may be bodily inserted into a charger receptacle. The terminal may have volatile memory and other components requiring load current during charging. The system may automatically identify battery type and progressively increase charging current while monitoring for an increase in battery terminal voltage to ascertain the level of load current. The battery temperature may be brought into a relationship to surrounding temperature such that by applying a suitable overcharge current value and observing any resultant temperature increase, the level of remaining battery charge can be determined. For example, if the battery is found to be relatively fully discharged, a relatively high fast-charge rate may be safely applied while monitoring battery temperature. If the battery is initially relatively fully charged or reaches such a state during fast charge, the system may automatically switch to a lower sustainable overcharge rate selected according to battery type and temperature. A preferred system any automatically recharge the battery of a portable device according to an optimum schedule of essentially maximum safe charging rates as a function of battery temperature. The system may also convert a regulated charging current to a pulsed and modulated waveform to provide efficient net charging to the battery. The source of charging current can optionally be placed outside the terminal housing to eliminate any heat dissipation effects of the current source.

Claims

1. An apparatus for providing charging current to a rechargeable battery associated with a device which presents a varying load to the battery during recharging comprising:

connection means for electrically coupling a battery to a source of charging current, where the battery is connected to the device which presents a varying load and the charging current generally has a fixed DC amplitude;

pass means operatively positioned between the connection means and the battery for selectively passing the charging current to the battery to modify the charging current into a pulsed wave form, said pulsed wave form having a plurality of pulses with pulse widths which are dependent on a desired level of net charging current; and

so that pulsed current provides the desired level of net charging current to the battery over time while the battery is connected to the device which presents a varying load.

3. The apparatus of claim 1 wherein said charging current is a pulse width modulated signal.

4. The apparatus of claim 1 wherein said pass means is comprised of a switching device which is controlled by a modulated signal.

5. The apparatus of claim 1 wherein the desired net level of charging current is determined by the amount of charging current that is provided to the battery.

6. The apparatus of claim 1 further comprising a current sensor operatively coupled to the battery to sense the amount of charging current supplied to the battery, wherein the pulse widths are dependent upon a sensed charging current.

2. A method for providing charging current to a battery associated with a device presenting a varying load to the battery during charging comprising:

providing a regulated generally fixed amplitude charging current from a charging current source to the battery; and

pulsing the charging current through the battery so that the battery receives a net charging current over successive periods of time while the battery is connected to the device presenting a varying load to the battery, wherein duration of individual charging current pulses of the pulsed charging current depends on a desired net charging current.

7. The method of claim 2 further comprising the steps of:

sensing the charging current provided to the battery; and

controlling the pulsing of the charging current depending on the sensed charging current.

8. The method of claim 2 wherein the desired level of net charging current depends on the charging current supplied to the battery.

9. The method of claim 2 further comprising the step of providing a switching device connected between the charging current source and the battery, wherein the pulsed charging current is pulsed by oscillating the switching device.

10. A circuit for providing charging current to a rechargeable battery associated with a device which presents

a varying load to the battery during recharging comprising:

a current source;

a current sensor operatively coupled to the battery for sensing the current through the battery and producing a control signal in response to the sensed current; and

a switching device connected between the current source and the battery, said switching device being operatively connected to said current sensor such that the control signal causes the switching device to repeatedly turn on and off to provide a pulsed charging current to the battery.

11. The circuit of claim 10 wherein said switching device comprises a transistor.

12. The apparatus of claim 10 wherein said control signal comprises a pulse width modulated signal.

13. A method of providing charging current to a rechargeable battery inside a housing of a device which presents a varying load to the battery during recharging, comprising the steps of:

connecting the device to a source of charging current located external to the housing of the device;

providing a control signal;

selectively passing the charging current from the source of charging current to the battery according to the control signal;

monitoring the amount of the charging current received by the battery and generating the control signal based on the amount of the charging current received by the battery; and

controlling the net amount of the charging current received by the battery for a given time by causing the control signal to increase and decrease the net amount of charging current passing through the pass means.

14. An apparatus for charging a battery contained within a housing of a device, where the battery is connected to a varying load and charging current for a given time is provided by a charging current source, said apparatus comprising:

a conductor for communicating the charging current from the charging current source to the battery;

a switching device positioned between the charging current source and the battery for converting the charging current from the charging current source into a pulsed current consisting of successive pulses having a duty cycle and a net value of charging current for a given time;

a sensor associated with the battery for sensing the net value of the charging current at the battery; and

a controller for receiving at the battery the net value of charging current for a given time, comparing it to a target net value, and adjusting operation of the switching device to vary the duty cycle of the pulsed current to maintain the target net value at the battery regardless of the varying load.

15. An apparatus for charging a battery contained within a housing of a device, where the battery is connected to a varying load and charging current for a given time is provided by a charging current source, said apparatus comprising:

a switching device positioned between the charging current source and the battery for converting the charging current from the charging current source into a pulsed current consisting of successive pulses having a duty cycle and a net value of charging current for a given time;

a sensor associated with the battery for sensing the net value of the charging current for a given time at the battery;

a controller for receiving the net value of charging current at the battery for a given time, comparing it to a target net value for and adjusting operation of the switching device to vary the duty cycle of the pulsed current to maintain the target net value at the battery regardless of the varying load; and

said charging current source comprising a current regulator to produce the charging current.

16. An apparatus for charging a battery pack for powering a device external to the battery pack, where the battery pack is connected to a varying load and charging current is provided by a charging current source external to the battery pack, said battery pack comprising:

a battery pack housing;

a battery disposed within the battery pack housing;

a switching device disposed within the battery pack housing and being operatively connected between the charging current source and the battery;

a processor disposed within the battery pack housing and being electrically connected to the switching device for providing a control signal to the switching device in order to control the net charging current supplied to the battery; and

a sensor operatively connected to the processor for sensing at least one operating parameter of the battery, wherein the net charging current supplied to the battery is controlled based on the sensed operating parameter of the battery.

17. An apparatus for charging a battery contained within a housing of an electronic device, where the battery is connected to a varying load and charging current is provided by a charging current source external to the housing of the electronic device, said apparatus comprising:

a switching device disposed within the housing of the electronic device and being operatively connected between the external charging current source and the battery;

a processor disposed within the housing of the electronic device and being electrically connected to the switching device for providing a control signal to the switching device in order to control the net charging current supplied to the battery; and

a sensor operatively connected to the processor for sensing at least one operating parameter of the battery, wherein the net charging current supplied to the battery is controlled based on the sensed operating parameter of the battery.

18. An apparatus for charging a battery contained within a housing of a device, where the battery is connected to a varying load and charging current for a given time is provided by a charging current source, said apparatus comprising:

a switching device positioned between the charging current source and the battery for converting the charging current from the charging current source into a converted charging current having a net value of charging current for a given time;

a sensing component operatively connected to the battery to receive current corresponding to the net value of the charging current received by the battery;

an amplifier connected to the sensing component for producing an amplified signal correlated to the net value of charging current to the battery; and

a controller for receiving the amplified signal and adjusting operation of the switching device to maintain a target net charging current at the battery regardless of the varying load.