Charging circuits for rechargeable batteries and cells

• US 5,204,611 A
• Filed: 05/02/1991
• Issued: 04/20/1993
• Est. Priority Date: 03/13/1991
• Status: Expired due to Term

• Current Assignee: Ecotality Incorporated (Blink Charging Co.)
• Original Assignee: Norvik Technologies Incorporated
• Inventors: Nor, Jiri K., Soltys, Josef V.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): DAVIDSON, BEN
• Application Number:
  US07/676,523
• Time in Patent Office: 719 Days
• Field of Search: 320/21, 320/20, 320/32, 320/39, 320/40, 320/35, 320/52, 320/23
• US Class Current: 320/145
• CPC Class Codes: B60L 2240/547 Voltage
• CPC Class Codes: B60L 2240/549 Current
• CPC Class Codes: B60L 53/11 DC charging controlled by the charging station, e.g. mode 4
• CPC Class Codes: B60L 53/14 Conductive energy transfer
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles
• CPC Class Codes: Y10S 320/13 Fault detection
• CPC Class Codes: Y10S 320/19 Charger status, e.g. voltmeter

Abstract

Circuits are provided whereby rechargeable batteries and cells are charged very fast by a controlled current, and substantially at a rate never exceeding the ability of the battery or cell to accept current--i.e., to convert electrical current to stored chemical energy. The resistance free terminal voltage of the battery or cell is detected during an interval when the charging current is interrupted, and compared against an independent reference voltage to control the charging current when a difference between the reference voltage and the sensed resistance free terminal voltage exists. The reference voltage may be altered at any instant in time, as a function of the ambient temperature, or the internal temperature or pressure of the battery, as a function of the charging current when it is within a predetermined range, or if a particular change in the value of the charging current occurs over a predetermined period of time. Charging characteristics may also be controlled and altered either through the passage of time or as a consequence of predetermined conditions occurring. The various provisions preclude thermal runaway for example, and assure very rapid and complete charging operations no matter what may be the condition of the battery--provided it is capable of accepting charge--and for various kinds of rechargeable batteries and cells including nickel cadmium, lead acid, and so on.

Claims

1. A circuit for charging rechargeable batteries and cells, comprising:

a source of electrical charging energy;

an output to which said electrical charging energy is delivered and across which a rechargeable battery or cell may be connected;

power controller means in series with said source, and arranged so that the rate of energy being delivered to a rechargeable battery or cell may be regulated as to its amount under the control of at least one sensing circuit and a control circuit;

a first sensing circuit means for detecting terminal voltage of said rechargeable battery or cell;

comparator means for comparing the detected terminal voltage with a reference voltage and for providing an output signal when a difference between said voltage exists;

means for providing a pulsed timing signal;

latching means having a control input and a signal input, said latching means being arranged to be controlled by said pulsed timing signal at its control input, and having the output of said comparator connected to its signal input;

the output of said latching means being connected to control means for controlling the amount of energy being delivered by said power controller in accordance with a predetermined relationship of said detected terminal voltage and said reference voltage as indicated by the presence or absence of an output signal from said latching means and as determined during a period of time when the flow of electrical charging current to said rechargeable battery or cell has been interrupted;

whereby the operation of said control means may be affected so as to control the operation of said power controller, and so as to thereby control the rate of the amount of charging energy being delivered to said output and thereby the value of the charging current;

said recharging circuit further comprising means to determine the value of the charging current being fed to said rechargeable battery or cell at any instant in time, and a network having an amplifier whose output is connected in a circuit whereby said reference voltage is algebraically affected by the output of said amplifier;

said amplifier being such as to have its output swing from its highest value to its lowest value when said charging current is within a predetermined range; and

means whereby said reference voltage may be altered at any instant in time, so as to thereby affect the output of said comparator means, wherein said reference voltage is altered as a consequence of the status of the rechargeable battery or cell connected across said output at the said any instant in time.

2. The recharging circuit of claim 1, further including a temperature sensitive device having an output which is a function of the temperature of the device and which changes in accordance with its temperature, which temperature is dependent upon the mounting of said temperature sensitive device;

and wherein said temperature sensitive device is connected in a circuit whereby said reference voltage is algebraically affected by the output of said temperature sensitive device of said when its temperature is within a predetermined temperature range.

3. The recharging circuit of claim 2, wherein said temperature sensitive device is chosen from a group consisting of thermistors, temperature sensitive resistors, two terminal temperature sensitive active devices, and multi-terminal temperature sensitive active devices.

4. The recharging circuit of claim 1, further including a resistor within a battery having a number of cells being charged, which resistor has a value which is a function of the number of cells in said battery.

5. The recharging circuit of claim 1, wherein said power controller is chosen from a group consisting of silicon controlled rectifiers, linear regulators, switching regulators, and magnetic regulators.

6. The recharging circuit of claim 1, wherein pressure sensing means are provided for sensing internal pressure of said rechargeable battery or cell being charged, and wherein means are provided whereby said reference voltage is affected by the output of said pressure sensing means;

whereby the operation of said recharging circuit and the delivery of charging current to said output may be controlled by the status of the internal pressure of said rechargeable battery or cell being charged.

7. A circuit for charging rechargeable batteries and cells, comprising:

a source of electrical charging energy;

an output to which said electrical charging energy is delivered and across which a rechargeable battery or cell may be connected;

a switching inverter device in series with said source, and arranged so that the rate of energy being delivered to a rechargeable battery or cell may be regulated as to its amount by switching from the conducting and non-conducting states of said switching inverter device under the control of at least one sensing circuit and a control circuit;

a first sensing circuit means for detecting terminal voltage of said rechargeable battery or cell;

comparator means for comparing the detected terminal voltage with a reference voltage and for providing an output signal when a difference between said voltages exists;

means for providing a pulsed timing signal;

latching means having a control input and a signal input, said latching means being arranged to be controlled by said pulsed timing signal at its control input, and having the output of said comparator connected to its signal input;

the output of said latching means being connected to control means for controlling the switching of said switching inverter in accordance with a predetermined relationship of said detected terminal voltage and said reference voltage as indicated by the presence or absence of an output signal from said latching means and as determined during a period of time when the flow of electrical charging current to said rechargeable battery or cell has been interrupted;

whereby the operation of said control means may be affected as to the duration of each switching sequence of said switching inverter from one of its conducting and non-conducting states to the other of said states, so as to thereby control the rate of the amount of charging energy being delivered to said output and thereby the value of the charging current;

said recharging circuit further comprising means to determine the value of the charging current being fed to said rechargeable battery or cell at any instant in time, and a network having an amplifier whose output is connected in a circuit whereby said reference voltage is algebraically affected by the output of said amplifier;

said amplifier being such as to have its output swing from its highest value to its lowest value when said charging current is within a predetermined range; and

means whereby said reference voltage may be altered at any instant in time, so as to thereby affect the output of said comparator means, wherein said reference voltage is altered as a consequence of the status of the rechargeable battery or cell connected across said output at the said any instant in time.

8. The recharging circuit of claim 7, further including temperature sensitive device having an output which is a function of the temperature of the device and which changes in accordance with its temperature, which temperature is dependent upon the manner in which said temperature sensitive device is mounted in said circuit;

and wherein said temperature sensitive device is connected in a circuit whereby said reference voltage is algebraically affected by the output of said temperature sensitive device when its temperature is within a predetermined temperature range.

9. The recharging circuit of claim 8, wherein said temperature sensitive device is mounted in such a manner that its temperature is affected by ambient temperature where said recharging circuit or said rechargeable battery or cell is placed.

10. The recharging circuit of claim 8, wherein said temperature sensitive device is mounted in such a manner that its temperature is affected by the internal temperature of said rechargeable battery or cell.

11. The recharging circuit of claim 9, wherein said temperature sensitive device is chosen from a group consisting of thermistors, temperature sensitive resistors, two terminal temperature sensitive active devices, and multi-terminal temperature sensitive active devices.

12. The recharging circuit of claim 10, wherein said temperature sensitive device is chosen from a group consisting of thermistors, temperature sensitive resistors, two terminal temperature sensitive active devices, and multi-terminal temperature sensitive active devices.

13. The recharging circuit of claim 8, wherein means are provided to detect whether said temperature sensitive device is present or absent, and to emit a signal indicative of the fact that said temperature sensitive device is absent, and wherein said signal also functions to cause cessation of said delivery of said electrical charging energy to said output.

14. The recharging circuit of claim 13, wherein said signal which is indicative of the fact that said temperature sensitive device is absent also functions to render said latching means in a condition that no control output is emitted therefrom.

15. The recharging circuit of claim 7, wherein the value of the output of said amplifier is a function of said charging current when said charging current is within said predetermined range.

16. The recharging circuit of claim 7, wherein said source of electrical energy is a direct current source.

17. The recharging circuit of claim 7, wherein said source of electrical energy is a rectified alternating current source.

18. The recharging circuit of claim 7, wherein said pulsed timing signal is generated by a timer circuit within said recharging circuit.

19. The recharging circuit of claim 18, wherein said pulsed timing signal is triggered by an alternating current source.

20. The recharging circuit of claim 7, wherein said latching means has an output which is complementary to said output connected to said control means, said complementary signal being arranged to provide a further signal confirming that said electrical charging energy is being delivered to said output.

21. The recharging circuit of claim 7, further including a resistor within a battery having a number of cells being charged, which resistor has a value which is a function of the number of cells in said battery.

22. The recharging circuit of claim 7, wherein pressure sensing means are provided for sensing internal pressure of said rechargeable battery or cell being charged, and wherein means are provided whereby said reference voltage is affected by the output of said pressure sensing means;

whereby the operation of said recharging circuit and the delivery of charging current to said output may be controlled by the status of the internal pressure of said rechargeable battery or cell being charged.

23. A circuit for charging rechargeable batteries and cells, comprising:

a source of electrical charging energy;

an output to which said electrical charging energy is delivered and across which a rechargeable battery or cell may be connected;

a switching inverter device in series with said source, and arranged so that the rate of energy being delivered to a rechargeable battery or cell may be regulated as to its amount by switching from the conducting and non-conducting states of said switching inverter device under the control of at least one sensing circuit and a control circuit;

a first sensing circuit means for detecting terminal voltage of said rechargeable battery or cell;

comparator means for comparing the detected terminal voltage with a reference voltage and for providing an output signal when a difference between said voltages exists;

means for providing a pulsed timing signal;

latching means having a control input and a signal input, said latching means being arranged to be controlled by said pulsed timing signal at its control input, and having the output of said comparator connected to its signal input;

the output of said latching means being connected to control means for controlling the switching of said switching inverter in accordance with a predetermined relationship of said detected terminal voltage and said reference voltage as indicated by the presence or absence of an output signal from said latching means and as determined during a period of time when the flow of electrical charging current to said rechargeable battery or cell has been interrupted;

whereby the operation of said control means may be affected as to the duration of each switching sequence of said switching inverter from one of its conducting and non-conducting states to the other of said states, so as to thereby control the rate of the amount of charging energy being delivered to said output and thereby the value of the charging current;

said recharging circuit further comprising means to determine the value of the charging current being fed to said rechargeable battery or cell at any instant in time, and a network having an amplifier whose output is connected in a circuit whereby said reference voltage is algebraically affected by the output of said amplifier;

said amplifier being such as to have its output swing from its highest value to its lowest value when said charging current is within a predetermined range; and

means whereby the value of said detected terminal voltage as it is fed to said comparator means for comparison with said reference voltage may be altered as a consequence of the status of the rechargeable battery or cell connected across said output at any instant in time.

24. The recharging circuit of claim 23, further including a temperature sensitive device having an output which is a function of the temperature of the device and which changes in accordance with its temperature, which temperature is dependent upon the mounting of said temperature sensitive device;

and wherein said temperature sensitive device is connected in a circuit whereby said detected terminal voltage is algebraically affected by the output of said temperature sensitive device when its temperature is within a predetermined temperature range.

25. The recharging circuit of claim 24, wherein said temperature sensitive device is chosen from a group consisting of thermistors, temperature sensitive resistors, two terminal temperature sensitive active devices, and multi-terminal temperature sensitive active devices.

26. The recharging circuit of claim 23, further including a resistor within a battery having a number of cells being charged, which resistor has a value which is a function of the number of cells in said battery.

27. The recharging circuit of claim 23, wherein pressure sensing means are provided for sensing a internal pressure of said rechargeable battery or cell being charged, and wherein means are provided whereby said reference voltage is affected by the output of said pressure sensing means;

whereby the operation of said recharging circuit and the delivery of charging current to said output may be controlled by the status of the internal pressure of said rechargeable battery or cell being charged.

28. A circuit for charging rechargeable batteries and cells, comprising:

a source of electrical charging energy;

an output to which said electrical charging energy is delivered and across which a rechargeable battery or cell may be connected;

power controller means in series with said source, and arranged so that the rate of energy being delivered to a rechargeable battery or cell may be regulated as to its amount under the control of at least one sensing circuit and a control circuit;

a first sensing circuit means for detecting terminal voltage of said rechargeable battery or cell;

comparator means for comparing the detected terminal voltage with a reference voltage and for providing an output signal when a difference between said voltages exists;

means for providing a pulsed timing signal;

latching means having a control input and a signal input, said latching means being arranged to be controlled by said pulsed timing signal at its control input, and having the output of said comparator connected to its signal input;

the output of said latching means being connected to control means for controlling the amount of energy being delivered by said power controller in accordance with a predetermined relationship of said detected terminal voltage and said reference voltage as indicated by the presence or absence of an output signal from said latching means and as determined during a period of time when the flow of electrical charging current to said rechargeable battery or cell has been interrupted;

whereby the operation of said control means may be affected so as to control the operation of said power controller, and so as to thereby control the rate of the amount of charging energy being delivered to said output and thereby the value of the charging current;

said recharging circuit further comprising means to determine the value of the charging current being fed to said rechargeable battery or cell at any instant in time, and a network having an amplifier whose output is connected in a circuit whereby said reference voltage is algebraically affected by the output of said amplifier;

said amplifier being such as to have its output swing from its highest value to its lowest value when said charging current is within a predetermined range; and

means whereby the value of said detected terminal voltage as it is fed to said comparator means for comparison with said reference voltage may be altered as a consequence of the status of the rechargeable battery or cell connected across said output at any instant in time.

29. The recharging circuit of claim 28, further including a temperature sensitive device having an output which is a function of the temperature of the device and which changes in accordance with its temperature, which temperature is dependent upon the mounting of said temperature sensitive device;

and wherein said temperature sensitive device is connected in a circuit whereby said detected terminal voltage is algebraically affected by the output of said temperature sensitive device when its temperature is within a predetermined temperature range.

30. The recharging circuit of claim 29, wherein said temperature sensitive device is chosen from a group consisting of thermistors, temperature sensitive resistors, two terminal temperature sensitive active devices, and multi-terminal temperature sensitive active devices.

31. The recharging circuit of claim 28, further including a resistor within a battery having a number of cells being charged, which resistor has a value which is a function of the number of cells in said battery.

32. The recharging circuit of claim 28, wherein said power controller is chosen from a group consisting of silicon controlled rectifiers, linear regulators, switching regulators, and magnetic regulators.

33. The recharging circuit of claim 28, wherein pressure sensing means are provided for sensing internal pressure of said rechargeable battery or cell being charged, and wherein means are provided whereby said reference voltage is affected by the output of said pressure sensing means;

whereby the operation of said recharging circuit and the delivery of charging current to said output may be controlled by the status of the internal pressure of said rechargeable battery or cell being charged.

34. A method of recharging rechargeable batteries and cells, comprising the steps of:

(a) providing an electrical charging current from a source thereof to an output across which a rechargeable battery or cell may be connected;

(b) periodically interrupting the flow of electrical charging current to said output and determining the resistance free terminal voltage of the rechargeable battery or cell being recharged during the interval when said flow of electrical charging current has been interrupted, and comparing the sensed resistance free voltage with a reference voltage independent of the rechargeable battery or cell being recharged;

(c) wherein for a first fixed and predetermined period of time, said electrical charging current is delivered to said output at the lesser of either a predetermined maximum current value or a current which said rechargeable battery or cell can accept without any substantial rise in its internal temperature;

whereby when said rechargeable battery or cell can accept a charging current which is greater than said predetermined maximum current value, said electrical charging current is delivered to said output at a constant value equal to said maximum current value;

and wherein, following said first fixed period of time said electrical charging current continues to be delivered to said output at said maximum value for a second variable time period which exists for so long as said sensed resistance free voltage of the rechargeable battery or cell being recharged is less than said independent reference voltage, whereby said second variable time period is terminated at the first instance when said sensed resistance free voltage reaches the same value as said independent reference voltage, and said electrical charging current is permitted to reduce in such a manner that the sensed resistance free voltage and said independent reference voltage remain at the same value;

(d) operating a timer from the beginning of the charge cycle so that, following a third predetermined period of time from the beginning of the charge cycle, the electrical charging current is reduced to a predetermined value of from zero to a predetermined low charging current in the event that the charge current is still at said maximum value; and

(e) operating a timer from the beginning of the charge cycle so that at the end of a fourth predetermined period of time which follows the instant when the electrical charging current begins to be reduced, the electrical charging current is forceably altered to a predetermined value of from zero to a predetermined low charging current which is below said predetermined maximum current value.

35. The method of claim 34, wherein the rechargeable battery or cell being recharged is constantly monitored to determine if the cell or at least one cell in the battery being recharged is faulty;

and

wherein in the event of a faulty cell being detected, the electrical charging current is instantaneously discontinued and an alarm signal to that effect is given.

36. The method of claim 35, wherein the continual testing for a faulty cell is inhibited for a first predetermined period of time which is shorter than said first fixed period of time during which said charging current is delivered to said output at its maximum value.

37. The method of claim 34, wherein, for nickel cadmium batteries and cells having capacities in the range of 500 mAh to 1200 mAh, and with a maximum value of electrical charging current being in the order of 7.5 amperes and the resistance free charging voltage being in the range of 1.5 volts per cell, said second variable time period for cells in good condition terminates in about no more than about 8 or 10 minutes from the beginning of the charging cycle;

and

for nickel cadmium cells or batteries having capacities in the range of 1800 mAh to 2500 mAh and similar charging current and charging voltage values, said second variable period of time terminates in no more than about 15 or 20 minutes from the beginning of the charging cycle.

38. The method of claim 34, wherein step (e) is carried out to forceably reduce the electrical charging current to a trickle current.

39. The method of claim 34, wherein step (e) is carried out to alter said charging current to a predetermined finishing charge current value of between about 0.5 C and 3 C;

and terminating said finishing charge current at the first instance where either a fifth predetermined period of time measured from the beginning of the charge cycle expires, or the sensed resistance free voltage of the rechargeable battery or cell being charged has increased above the value of said independent reference voltage by a predetermined amount.

40. A method of recharging rechargeable batteries and cells, comprising the steps of:

(a) providing an electrical charging current from a source thereof to an output across which a rechargeable battery or cell may be connected;

(b) periodically interrupting the flow of electrical charging current to said output and determining the resistance free terminal voltage of the rechargeable battery or cell being recharged during the interval when said flow of electrical charging current has been interrupted, and comparing the sensed resistance free voltage with a reference voltage independent of the rechargeable battery or cell being recharged;

(c) wherein for a first fixed and predetermined period of time, said electrical charging current is delivered to said output at the lesser of either a predetermined maximum current value or a current which said rechargeable battery or cell can accept without any substantial rise in its internal temperature;

whereby when said rechargeable battery or cell can accept a charging current which is greater than said predetermined maximum current value, said electrical charging current is delivered to said output at a constant value equal to said maximum current value;

and wherein, following said first fixed period of time said electrical charging current continues to be delivered to said output at said maximum value for a second variable time period which exists for so long as said sensed resistance free voltage of the rechargeable battery or cell being recharged is less than said independent reference voltage, whereby said second variable time period is terminated at the first instance when said sensed resistance free voltage reaches the same value as said independent reference voltage, and said electrical charging current is permitted to reduce in such a manner that the sensed resistance free voltage and said independent reference voltage remain substantially at the same value;

(d) constantly sampling said electrical charging current on a periodic basis during the period of time which follows said second variable time period and while said electrical charging current is permitted to reduce, and comparing the value of said electrical charging current at each sampling instant with the value of said electrical charging current at at least the prior sampling instant thereof; and

when any increase of said electrical charging current is sensed, operating a control circuit means so as to force said electrical charging current to continue to reduce.

41. The method of claim 40, wherein said electrical charging current is reduced in a controlled manner to a predetermined value of from zero to a predetermined low charging current which is below said predetermined maximum current value.

42. The method of claim 40, wherein, upon a decrease of current of at least a predetermined amount within a predetermined period of time being sensed, control circuit means are operated to force said electrical charging current to assume a different charge of value over a further predetermined period of time.

43. The method of claim 41, wherein said charging current is reduced to a predetermined finishing charge current value of between about 0.5 C and 3 C, instituting a further charge period of constant current charging at said predetermined finishing charge current value;

and terminating said finishing charge current at the first instance where any one of a group of criteria is reached, said group of criteria consisting of;

(i) when a further predetermined period of time measured from the beginning of the charge cycle expires;

(ii) the sensed resistance free voltage of the rechargeable battery or cell being charged has increased above the value of said independent reference voltage by a predetermined amount;

(iii) the sensed resistance free voltage of the rechargeable battery or cell being charged ceases to rise and begins to decrease; and

(iv) the sensed resistance free voltage of the rechargeable battery or cell being charged ceases to rise and remains constant.

44. A method of recharging rechargeable batteries and cells, comprising the steps of:

(a) providing an electrical charging current from a source thereof to an output across which a rechargeable battery or cell may be connected;

(b) periodically interrupting the flow of electrical charging current to said output and determining the resistance free terminal voltage of the rechargeable battery or cell being recharged during the interval when said flow of electrical charging current has been interrupted, and comparing the sensed resistance free voltage with a reference voltage independent of the rechargeable battery or cell being recharged;

(c) wherein for a first fixed and predetermined period of time, said electrical charging current is delivered to said output at the lesser of either a predetermined maximum current value or a current which said rechargeable battery or cell can accept without any substantial rise in its internal temperature;

whereby when said rechargeable battery or cell can accept a charging current which is greater than said predetermined maximum current value, said electrical charging current is delivered to said output at a constant value equal to said maximum current value;

and wherein, following said first fixed period of time said electrical charging current continues to be delivered to said output at said maximum value for a second variable time period which exists for so long as said sensed resistance free voltage of the rechargeable battery or cell being recharged is less than said independent reference voltage, whereby said second variable time period is terminated at the first instance when said sensed resistance free voltage reaches the same value as said independent reference voltage, and said electrical charging current is permitted to reduce in such a manner that the sensed resistance free voltage and said independent reference voltage remain at the same value; and

(d) sensing said charging current as it is reducing, and when said charging current reaches a predetermined finishing charge current value of between about 0.5 C and 3 C, instituting a further charge period of constant current charging at said predetermined finishing charge current value; and

terminating said finishing charge current at the first instance where any one of a group of criteria is reached, said group of criteria consisting of;

(i) when a further predetermined period of time measured from the beginning of the charge cycle expires;

(ii) the sensed resistance free voltage of the rechargeable battery or cell being charged has increased above the value of said independent reference voltage by a predetermined amount;

(iii) the sensed resistance free voltage of the rechargeable battery or cell being charged cease to rise and begins to decrease; and

(iv) the sensed resistance free voltage of the rechargeable battery or cell being charged ceases to rise and remains constant.

45. A method of recharging rechargeable batteries and cells, comprising the steps of:

(a) providing an electrical charging current from a source thereof to an output across which a rechargeable battery or cell may be connected;

(b) periodically interrupting the flow of electrical charging current to said output and determining the resistance free terminal voltage of the rechargeable battery or cell being recharged during the interval when said flow of electrical charging current has been interrupted, and comparing the sensed resistance free voltage with a reference voltage independent of the rechargeable battery or cell being recharged;

(c) wherein for a first fixed and predetermined period of time, said electrical charging current is delivered to said output at the lesser of either a predetermined maximum current value or a current which said rechargeable battery or cell can accept without any substantial rise in its internal temperature;

whereby when said rechargeable battery or cell can accept a charging current which is greater than said predetermined maximum current value, said electrical charging current is delivered to said output at a constant value equal to said maximum current value;

and wherein, following said first fixed period of time said electrical charging current continues to be delivered to said output at said maximum value for a second variable time period which exists for so long as said sensed resistance free voltage of the rechargeable battery or cell being recharged is less than said independent reference voltage, whereby said second variable time period is terminated at the first instance when said sensed resistance free voltage reaches the same value as said independent reference voltage, and said electrical charging current is permitted to reduce in such a manner that the sensed resistance free voltage and said independent reference voltage remain substantially at the same value; and

(d) sensing at least one of the internal temperature of the rechargeable battery or cell being recharged and the internal pressure of the rechargeable battery or cell being recharged during the period of time which follows said second variable time period and while said electrical charging current is permitted to reduce; and

when a chosen one of the criteria taken from a group consisting of a predetermined temperature rise, a predetermined absolute internal temperature, a predetermined internal pressure rise, and a predetermined absolute internal pressure of said rechargeable battery or cell being charged is reached, terminating the flow of said electrical charging current to said rechargeable battery or cell being recharged.

46. The method of claim 45, wherein the internal temperature of the rechargeable battery or cell being charged is sensed, and the flow of said electrical charging current is terminated when a predetermined absolute temperature or a predetermined temperature rise is reached.

47. The method of claim 45, wherein the internal pressure of the rechargeable battery or cell being charged is sensed, and the flow of said electrical charging current is terminated when a predetermined absolute pressure or a predetermined pressure rise is reached.

48. The method of claim 45, wherein each of the internal temperature and internal pressure of the rechargeable battery or cell being charged is sensed, and the flow of said electrical charging current is terminated when any of a predetermined absolute temperature, a predetermined temperature rise, a predetermined absolute pressure, or a predetermined pressure rise, is reached.