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WO1999005768A1 - Procede et dispositif de charge d'une batterie rechargeable - Google Patents

Procede et dispositif de charge d'une batterie rechargeable Download PDF

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Publication number
WO1999005768A1
WO1999005768A1 PCT/DK1998/000329 DK9800329W WO9905768A1 WO 1999005768 A1 WO1999005768 A1 WO 1999005768A1 DK 9800329 W DK9800329 W DK 9800329W WO 9905768 A1 WO9905768 A1 WO 9905768A1
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WO
WIPO (PCT)
Prior art keywords
charging
battery
termination
charging process
parameter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/DK1998/000329
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English (en)
Inventor
Kim Rasmussen
Kim ØSTERGAARD
Kim Arthur Stück ANDERSEN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Chartec Laboratories AS
Original Assignee
Chartec Laboratories AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Chartec Laboratories AS filed Critical Chartec Laboratories AS
Priority to EP98934885A priority Critical patent/EP0998780A1/fr
Priority to JP2000504643A priority patent/JP2001511639A/ja
Priority to AU84339/98A priority patent/AU8433998A/en
Publication of WO1999005768A1 publication Critical patent/WO1999005768A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/007188—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters
    • H02J7/007192—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters in response to temperature
    • H02J7/007194—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters in response to temperature of the battery

Definitions

  • the present invention relates to a method and an apparatus for charging a rechargeable battery. More particularly, the present invention is directed to the control of the termination of the charging process.
  • NiCd Nickel -Cadmium
  • NiMH Nickel-Metal- Hydride
  • a typical method of detecting this event is to measure the increase in battery temperature as a function of time in order to detect when the battery tempera- ture rate of change ( ⁇ T/ ⁇ t) reaches a predetermined high limit, see for example the patent specifications US 3,852,652, US 5,329,219 and US 5,550,453.
  • a common drawback of the above mentioned known charging processes is the use of a predetermined reference value to be reached for the measured battery temperature rate of change when terminating the charging process.
  • a reference value should be chosen as a function of the battery technology, the manufacturer of the battery, the number of cells within the battery and the size of the battery cells.
  • the optimal reference value will change as a function of battery use and degradation.
  • the use of a predetermined reference value which is constant throughout the battery life might result in undercharge of the battery leading to a poor battery capacity or overcharge of the battery leading to a decreased battery lifetime. Therefore, the need exists for a battery charging method and apparatus allowing a charging reference value to be determined during the charging process as a function of the measured battery temperature rate of change.
  • the present invention provides a method where termination of the charging process can be controlled in an optimum way by using a reference value which is determined during the charging process based on determined values of the rate of change of battery temperature, whereby a change in the reference value, for example as a function of battery life, is taken into account .
  • a method of charging a rechargeable battery comprising: connecting an electrical power source to the terminals of the battery and supplying a charging current to the battery, determining values of the rate of change of battery temperature during at least part of the process of charging the battery, determining and storing a reference value based on the obtained values of the rate of change of battery temperature, comparing values of the rate of change of battery temperature with the stored reference value or a function thereof, and controlling termination of the charging process based on said comparison.
  • the temperature When monitoring battery temperature during a charging process the temperature will increase when the battery approaches the fully charged state.
  • a threshold value for the battery temperature rate of change and having termination of the charging process based on such a threshold value.
  • this threshold value it is preferred to determine the threshold value based on the determined reference value.
  • termination of the charging process may be initiated at the point in time at which the determined value of the rate of change of battery temperature exceeds the stored reference value by a predetermined amount.
  • the determined and stored reference value represents a minimum of the obtained values of the rate of change of battery temperature.
  • the threshold value may be calculated by adding a predetermined maximum allowed change in the rate of change of battery temperature to the obtained reference value.
  • a predetermined maximum allowed change may be in the range of 0,25-2°C/min. and preferably about 0,5°C/min.
  • the optimal value will vary for different battery capacities and different battery technologies.
  • termination of the charging process comprises reducing the charging current. This reduction may be abrupt by turning the power supply off, but the termination of the charging process may alternatively comprise a final charging period, during which period the battery may be charged with a reduced current until the charging process is finally stopped.
  • the duration of the final charging period may be determined as a function of the total charging time passed at the point in time at which termination of the charging process is initiated.
  • the length of the final charging period may be in the range of 5-50%, preferably around 25%, of the total charging time lapsed up to the point in time at which termination of the charging process is initiated.
  • the final charging period need not be a function of the charging time but may have a predetermined duration.
  • the charging process may be controlled so as to reduce battery terminal voltage by at least a predetermined amount during initiation of the final charging period for avoiding overcharging.
  • the battery terminal voltage may be reduced at least 100 mV, preferably at least 200 mV, at the initiation of the final charging period, with the battery terminal voltage preferably not being increased during this final period.
  • the battery terminal voltage may also be reduced as a function of the number of cells within the battery. Such a reduction may be in the range of 10-lOOmV per cell, preferably in the range of 20-70mV per cell, and even more preferred about 40mV per cell.
  • the charging power may be reduced by controlling the charging process so that the battery terminal voltage is not allowed to increase during the final charging period, for example by keeping the voltage constant during this final charging period.
  • the determined rate of change of battery temperature during upstart of the charging process may vary as a function of the initial battery temperature.
  • a high value of the rate of change of battery temperature can be observed during upstart of the charging process until the battery has reached the ambient temperature. It is therefore a goal to avoid the influence of such an initial high rate of change of battery temperature.
  • control of the termination of the charging process is based on values of the rate of change of battery temperature being determined after a predetermined time period has lapsed or after a point in time at which point in time the value of a characteristic start-up charging parameter measured during an initial stage of the charging process has reached a predetermined value.
  • the characteristic start-up charging parameter is the battery terminal voltage, which may be measured as an open circuit voltage.
  • the capacity of the battery may decrease due to self discharging.
  • self discharge may vary for different batteries and for different technologies.
  • self discharging might be a problem, it is preferred that the state of charge of the battery is maintained after termination of the charging process by means of a pulsating trickle-charge current, or by means of a low maintenance current .
  • the first aspect of the present invention also provides an apparatus for charging a rechargeable battery, said apparatus comprising: means for connecting the battery terminals to an electrical power source for the supply of a charging current to the battery, said battery having a battery terminal voltage and a temperature, means for measuring the rate of change of the battery temperature during at least part of the process of charging the battery, means for determining and storing a charging reference value based on measurement values of the rate of change of battery temperature, means for comparing measurement values of the rate of change of battery temperature with the stored reference value or a function thereof, and means for controlling termination of the charging process in response to such a comparison.
  • the termination control means may be adapted to initiate termination of the charging process at the point in time at which the determined value of the rate of change of battery temperature reaches a threshold value which exceeds the stored reference value by a predetermined amount.
  • the comparing means may be adapted to determine such a threshold value by adding a predetermined maximum allowed change in the rate of change of battery temperature to the obtained reference value.
  • the means for determining and storing the reference value is adapted to determine and store a minimum of the obtained values of the rate of change of battery temperature.
  • the termination control means is adapted to reduce the charging current during the process of termination.
  • the termination means may be adapted to determine a final charging period, and preferably being adapted to determine the duration of such final charging period as a function of the total charging time passed at the point in time at which termination of the charging process is initiated.
  • the termination control means is adapted to reduce battery terminal voltage by at least a prede- termined amount during the final charging period for avoiding overcharging.
  • the termination control means is adapted to perform such reduction at the initial stage of the final charging period.
  • this apparatus comprises means for measuring a characteristic start-up charging parameter, and that the termination control means is adapted to control termination of the charging process based on values of the rate of change of battery temperature being determined after a prede- termined time period has lapsed or after a point in time at which point in time the value of the characteristic start-up charging parameter measured during an initial stage of the charging process has reached a predetermined value.
  • the characteristic start-up charging parameter may be the battery terminal voltage, and it is preferred that the means for measuring the start-up charging parameter is adapted to measure the battery terminal voltage as an open circuit voltage.
  • the apparatus further is provided with means for maintaining the state of charge of the battery after termination of the charging process.
  • Such maintaining means may provide a pulsating trickle-charge current, or a low maintenance current .
  • a method of charging a rechargeable battery comprising: connecting an electrical power source to the terminals of the battery and supplying a charging current to the battery, determining values of a first characteristic charging parameter during at least part of the charging process, and controlling termination of the charging process based on values of the first parameter being determined after a point in time at which point in time a second characteristic charging parameter measured during an initial stage of the charging process has reached a predetermined value or fulfills a predetermined criteria.
  • the first characteristic charging parameter may be any battery parameter which is suitable for the control of the charging process such as battery terminal voltage, charging current, battery temperature, the rate of change of any of these parameters or any combination of these parameters and/or their rate of change.
  • the first characteristic charging parameter is the rate of change of battery temperature calculated from measured values of the battery temperature.
  • the second characteristic charging parameter may also be selected from any of the above mentioned first characteristic charging parameters with the exception that it should not be the same parameter as the one chosen as the first characteristic parameter. However, it is preferred that the second characteristic charging parameter is the battery voltage.
  • the obtained values of the first parameter are compared with a stored reference value or a function thereof, and the termina- tion of the charging process is based on said comparison.
  • the termination of the charging process is initiated when the measured values of the first charging parameter reaches a threshold value being a function of the stored refe- rence value.
  • termination of the charging process may be initiated at the point in time at which the obtained value of the first parameter exceeds the stored reference value by a predetermined amount .
  • the stored reference value is determined during the charging process based on obtained values of the first parameter.
  • the reference value may be determined as a maximum of the obtained values, but it is preferred that the reference value represents a minimum value of the obtained first parameter values.
  • the termination comprises a final charging period, and it is preferred that the length of the final charging period is determined as a function of the total charging time passed at the point in time at which termination of the charging process is initiated. Furthermore, it is preferred that termination of the charging process comprises reducing the charging current or charging with a reduced current during the final charging period.
  • an apparatus for charging a rechargeable battery comprising: means for connecting the battery terminals to an electrical power source for the supply of a charging current to the battery, said battery having a battery terminal voltage and a temperature, means for determining values of a first characteristic charging parameter during at least part of the charging process, means for determining a second characteristic charging parameter during an initial stage of the charging process, and means for controlling termination of the charging process.
  • the termination control means is adapted to control the termination process based on values of the first parameter being determined after a point in time at which point in time the second characteristic charging parameter has reached a predetermined value or fulfills a predetermined criteria.
  • the means for determining the first characteristic parameter is adapted to determine the rate of change of battery temperature, and it is preferred that the means for determining the second characteristic parameter is adapted to determine the battery voltage.
  • the voltage is determined as an open circuit voltage.
  • the apparatus comprises means for storing a reference value and means for comparing determined values of the first parameter with the stored reference value or a function thereof, and that the termination control means is adapted to terminate the charging process based on this comparison.
  • the apparatus further comprises means for determining the reference value, said reference value determining means being adapted to determine the reference value during the charging process based on obtained values of the first parameter.
  • the reference value determining means is adapted to determine a minimum value of the obtained first parameter values.
  • the reference value determining means may alternatively be adapted to determine a maximum value of the obtained first parameter values.
  • the termination control means is adapted to initiate termina- tion of the charging process at the point in time at which the determined value of the first parameter exceeds the stored reference value by a predetermined amount .
  • the termination control means is adapted to determine a final charging period, and that the duration of this final charging period preferably is determined as a function of the total charging time passed at the point in time at which termination of the charging process is initiated. During such final charging period it is preferred that the termination control means is adapted to reduce the charging current.
  • the termination control means may alternatively be adapted to terminate the charging process abruptly without any final charging period.
  • the apparatus according to the second aspect of the invention further is provided with means for maintaining the state of charge of the battery after termination of the charging process.
  • Such maintaining means may provide a pulsating trickle-charge current, or a low maintenance current.
  • Fig. 1 is a schematic diagram of a battery charging apparatus according to an embodiment of the present invention
  • Fig. 2 is a flow diagram illustrating the operation of an exemplary embodiment of the invention
  • Fig. 3 illustrates a charging process according to the present invention
  • Fig. 4 illustrates a charging process similar to the process of Fig. 3 but with the battery having a higher initial temperature
  • Fig. 5 shows the charging curves for the battery of Fig. 3 when the battery is holding 90% of its capacity at the start of the charging process
  • Fig. 6 illustrates a charging process according to the present invention with a low initial battery temperature and a high ambient charging temperature.
  • Fig. 1 shows a battery pack 10 which is to be charged by a battery charger apparatus 20.
  • the battery pack 10 comprises a number of series connected individual battery cells 11, a battery temperature sensing thermistor 12 (NTC thermistor) , a battery type resistor 13 and battery pack output terminals 14, 15, 16, 17.
  • Battery output voltage is provided across terminals 14 and 17, and the charging current supplied to the battery is sensed by a sense resistor 23 connected to the battery terminal 17 and ground.
  • the thermistor 12 has current supplied through a pull-up resistor 21 and senses battery temperature and provides a related output at the terminal 16.
  • the type resistor 13 has current supplied through pull-up resistor 22 and provides a battery type related voltage at the terminal 15.
  • the battery charger 20 comprises a power supply 24, a micro controller 25, and a signal conditioning circuitry 26.
  • the power supply 24, which preferably is a switch mode power supply, has a power input 27 which is supplied with a DC voltage, preferably in the range of 12-15 Volts DC.
  • the power supply has an output terminal 28 which provides the charging power to the battery terminal 14, preferably through a switch 29.
  • the charg- ing output 28 of the power supply 24 is controlled from a control output 30 of the micro controller 25.
  • the control output 30 is preferably a PWM (pulse width modulated) signal, which may be fed to a filter for converting the PWM signal to a variable analogue voltage, which is then used for the control of the power supply 24.
  • the micro controller 25 controls the power output to the battery 10 and terminal 28 by controlling the duration of on- and off-periods of the PWM signal.
  • the signal conditioning circuitry 26 converts the voltage input signals representing the battery terminal voltage, the battery type, the battery temperature, and the charging current, to voltage output signals being suitable as input signals for analogue to digital, A/D, converter inputs 32 of the micro controller 25.
  • the current sense resistor 23 has a very low value which may be around 0,1 ⁇ , and the conditioning circuitry 26 may then comprise an operational amplifier in order to provide a suitable output.
  • the supply voltage for the micro controller 25 is preferably around 5 Volts, and since the battery terminal voltage may exceed 5 Volts, the conditioning circuitry may also comprise a voltage divider for providing a suitable output signal for the battery terminal voltage.
  • the micro controller 25 comprises a switch control output 31 for switching the switch 29 on and off.
  • the switch 29 may be turned off at short time intervals during the charging process in order to measure an open circuit voltage of the battery, thereby avoiding the voltage drop from the internal loss resistance when measuring the battery terminal volt- age .
  • the micro controller 25 which for example may be an COP 8ACC from National Semiconductor, is programmed to implement battery charging in accordance with the present invention.
  • the micro controller 25 controls the power delivered from the power supply 24 to the battery 10 based upon the input signals from the conditioning circuitry 26, which input signals represent the battery type and the battery charging parameters: battery terminal voltage, battery temperature and charging current.
  • Step 40 is indicative of connection of the battery pack 10 to the charger 20 and initialising the micro controller 25.
  • the micro controller 25 reads the value of the battery type voltage, and this value is used as a reference for addressing battery specific predetermined charg- ing parameters stored in the micro controller 25.
  • These predetermined parameters may represent a maximum charging current, Imax; an initial value for an end time period, End_Time, which initial value defines a safety time at which the charging process will be stopped unless a new value of End_Time is determined and stored during the charging process; a maximum change in the rate of change of battery temperature, ⁇ T/ ⁇ t_add, which defines a maximum allowed change in the rate of change of battery temperature compared to a determined minimum value of the battery temperature rate of change, Min_ ⁇ T/ ⁇ t, which minimum value is a variable determined during the charging process; an initial value for Min_ ⁇ T/ ⁇ t, which initial value preferably is set at a large value; an initial voltage limit, VoltLimit, which defines a minimum limit that the measured battery voltage should reach before updating the predetermined initial value of Min_ ⁇ T/ ⁇ t; an initial time period, TimeLimit, defining a time period which shall expire before updating the predetermined initial value of Min_ ⁇ T/ ⁇ t.
  • the value of VoltLimit will typical be 1,4 Volts per battery cell, while the value of TimeLimit will typical be 5 minutes for NiCd or NiMH batteries. If the measured battery voltage reaches VoltLimit before TimeLimit has expired, then updating of the predetermined initial value of Min_ ⁇ T/ ⁇ t will start at the point in time when VoltLimit has been reached, otherwise updating of the predetermined initial value of Min_ ⁇ T/ ⁇ t will start when the TimeLimit period has expired.
  • the charging process is started at process step 41.
  • the charging process is controlled based on measured values of the open circuit battery voltage, Vopen, the charging current, Char, and the battery temperature, Tbat. From the values of Tbat, values of the battery temperature rate of change ⁇ T/ ⁇ t are calculated.
  • Ichar the charging current Ichar until the predetermined Imax has been reached.
  • a second charging stage is entered, in which the output of the power supply is preferably controlled so as to charge at a constant charging current, i.e. the output of the power supply is controlled so that Ichar is close to Imax.
  • the value of Imax is chosen to be within the range of 0,5-1,5 A for NiCd and NiMH batteries.
  • decision step 42 it is determined if the charging time has reached the stored value of TimeLimit and if ⁇ T/ ⁇ t is smaller than the stored value of Min_ ⁇ T/ ⁇ t . If so, then at process step 43, the stored value of Min_ ⁇ T/ ⁇ t is replaced with the measured value of ⁇ T/ ⁇ t, from where the process passes on to decision step 44. If the requirements at step 42 are not fulfilled, then the process passes on directly to decision step 44, where it is determined if the measured open circuit voltage Vopen has reached the stored value VoltLimit. If no, then the process passes on to decision step 49, where it is determined if the charging time has reached the stored value of End_Time.
  • the process returns to process step 41 for further charging. If End_Time has been reached, then the normal charging process is stopped and the charging current is reduced to a low maintenance or trickle charging current at process step 50 in order to maintain the charging status of the battery.
  • the maintenance or trickle charge current is preferably set in the range of 0,05-0,lC, where 1C is equivalent to a charging current used to fully charge the battery in one hour.
  • step 44 to 49 and then to 50 is not the route of a normal charging process.
  • the battery to be charged might be a defect battery or there might be a bad connection to the battery terminals, leading to the result that measured battery voltage will not reach the stored VoltLimit value within the initial safety value of End_Time.
  • the charger will automatically terminate the charging process at expiration of the initial End_Time period.
  • the process passes on to decision step 45, where it is determined if the measured value of ⁇ T/ ⁇ t is smaller than the stored value of Min_ ⁇ T/ ⁇ t. If so, then at process step 46, the stored value of Min_ ⁇ T/ ⁇ t is replaced with the measured value of ⁇ T/ ⁇ t, from where the process passes on to decision step 47. If the requirement at step 45 is not fulfilled, then the pro- cess passes on directly to decision step 47, where it is determined if the measured value of ⁇ T/ ⁇ t is larger than the combined value of the presently stored minimum value added to the predetermined maximum allowed value of the change in ⁇ T/ ⁇ t, i.e. if the measured value of ⁇ T/ ⁇ t has reached Min_ ⁇ T/ ⁇ t plus ⁇ T/ ⁇ t_add.
  • step 47 If the answer to the decision at step 47 is no, then the charging process has not yet reached the normal stage of termination and the process passes on to decision step 49 , from where the charging process proceeds or stops as described above.
  • step 48 a maximum allowed battery voltage, MaxVolt, is defined as fl (Voltage).
  • fl Voltage
  • step 48 a third stage of the charging process is entered where the remaining part of the charging process is controlled so that the measured battery voltage does not exceed MaxVolt.
  • the value of MaxVolt is not a predetermined value but a function of the measured battery voltage V ( ⁇ T/ ⁇ t) at the point in time where ⁇ T/ ⁇ t has reached Min_ ⁇ T/ ⁇ t plus ⁇ T/ ⁇ t_add.
  • fl Voltage
  • kl x V ( ⁇ T/ ⁇ t) - k2) the constant kl may be set to 1 and the k2 may be chosen in the range of O-lOOmV, preferably about 40mV, per battery cell.
  • MaxVolt the value of MaxVolt may preferably be set to V ( ⁇ T/ ⁇ t) - 160mV.
  • the constant k2 may alternative- ly be set to zero, which for example may work for NiCd batteries. However, it is also preferred to have k2 in the range of 50mV for NiCd batteries.
  • the stored initial value of End_Time is replaced with a new End_Time value being a function of the total charging time f2 (Time) at the point in time, t ( ⁇ T/ ⁇ t), where ⁇ T/ ⁇ t has reached Min_ ⁇ T/ ⁇ t plus ⁇ T/ ⁇ t_add.
  • the new value of End Time is defined as (k3 x T8 t ( ⁇ T/ ⁇ t) + k4) , where the constant k3 may be set to about 1,25 and k4 may be set to zero.
  • k3 can also be chosen in the range of 1-2, and k4 may represent a fixed time period in the range of 0-20 minutes.
  • process step 48 it is determined how the charging process is to be terminated, i. e. a final charging period and the maximum battery voltage is determined.
  • the measured battery temperature is compensated for variations due to a change in the battery temperature.
  • Using a maximum allowed voltage results in a decrease in the charging current during the final charging period.
  • the termination of the charging process is illustrated by the loop comprising process step 51 and decision step 52.
  • the charging process is continued as described above until the total charging time reaches the stored value of End_Time in step 52, at which point in time the charging process is stopped and the charging current is reduced to a low maintenance or trickle charging current at process step 50 in order to maintain the charging status of the battery.
  • the measured battery voltage is the open circuit battery voltage, Vopen. This is indicated in Table I, where fl (Voltage) is given as Fl (Vopen) . However, it should be understood that the principles of the present invention may also be applied when the measured battery terminal voltage is the terminal voltage during charging.
  • Fig. 3 shows the charging curves for a charging process controlled as described above with reference to the flow diagram of Fig. 2.
  • the battery of Fig. 3 is fully discharged before the charging process is started and the battery is charged at room temperature with an initial battery temperature around 23 °C .
  • the thick solid line waveform represents the measured open circuit battery voltage
  • the dashed waveform represents the measured charging current
  • the thin solid line waveform represents the measured battery temperature.
  • the battery of Fig. 3 is a 1600 mAh NiMH battery with 6 cells.
  • Imax is set to 900 mA
  • the initial End_Time value is set to 160 min.
  • the initial value of Min_ ⁇ T/ ⁇ t is set to a high value of 10°C/min., thereby disabling the effect of the rate of temperature change during the upstart of the charging process
  • the value of ⁇ T/ ⁇ t_add is set to 0,5°C/min.
  • the value TimeLimit is set to 5 min.
  • the value of VoltLimit is set to 8,25 Volt.
  • the function for MaxVolt is set to V ( ⁇ T/ ⁇ t) - 240 mV
  • the function for End_Time is set to 1,25 x t ( ⁇ T/ ⁇ t).
  • ⁇ T/ ⁇ t_add the optimal value of ⁇ T/ ⁇ t_add will vary as a function of battery capacity and the maximum charging current.
  • the value of ⁇ T/ ⁇ t_add should be larger both for a smaller nominal battery capacity and for a higher charging current .
  • the temperature is measured using a 10 bit AD converter resulting in a resolution in ⁇ T of about 0,1°C.
  • the measured open circuit voltage Vopen is compensated for changes due to battery temperature variation when compared to the stored value of VoltLimit. Such a compensation might be 20 mV/°C subtracted from the measured values of Vopen for temperatures below 35°C, when comparing Vopen to VoltLimit.
  • the first stage of charging is rather short and the charging current reaches Imax within a short time period.
  • the current is controlled to be approximately Imax and during the third stage of charging equivalent to the final charging period, the charging current is decreased.
  • Fig. 4 shows the charging curves corresponding to the curves of Fig. 3 for another sample of a 1600 mAh NiMH battery with 6 cells.
  • the predetermined charging parameters and functions are the same as for the charging process of Fig. 3.
  • the battery of Fig. 4 is charged at the same room temperature of about 23 °C as the battery of Fig. 3, but the battery of Fig. 4 has been stored at a higher temperature before being charged resulting in an initial battery temperature around 27°C.
  • the temperature rate of change ⁇ T/ ⁇ t will be smaller for the charging curves of Fig. 4 than for the curves of Fig. 3.
  • the ⁇ T/ ⁇ t termination value need to be smaller for the charging process of Fig. 4 when compared to the charging process of Fig. 3 in order to avoid overcharge of the battery.
  • the charging process should be controlled so as to avoid termination based on an initial high value of ⁇ T/ ⁇ t. This might be done in a simple way by having a TimeLimit set at a high value, for example 15 min.
  • Fig. 5 shows the charging curves for the battery of Fig. 3 when the battery is holding 90% of its capacity at the start of the charging process.
  • the battery voltage reaches VoltLimit within 4 min. from start of the charging process compared to the 35 min. of the fully discharged battery of Fig. 3.
  • the use of the parameter VoltLimit to determine, when the values of ⁇ T/ ⁇ t can be used to control termination of the charging process brings a charging solution which avoids overcharging of almost fully charged batteries.
  • Fig. 6 also illustrates a charging process for the battery of Fig. 3.
  • the battery is holding about 50% of its capacity at the start of the charging process.
  • the initial battery temperature is very low, about -7°C, whereas the ambient charging temperature is high, about 35°C.
  • the battery is charged with a low maintenance current until the battery temperature reaches 5°C, from which point in time a normal charging process is started. From Fig. 6 it is seen that the normal charging process is initiated around Time equal to 9 min. and correspondingly TimeLimit is reached at Time equal to 14 min., when the initial value for TimeLimit is set to 5 min.
  • Vopen Due to the temperature compensation and the low battery temperature, the measured values of Vopen have to reach a relatively high value before reaching the corresponding VoltLimit value.
  • the value of Min_ ⁇ T/ ⁇ t is not updated before Time equals 14 min. , but only the reference values stored after Time equal to 27 min. is used for the termination process. Since the value of ⁇ T/ ⁇ t decreases through the charging process until the almost fully charged state is reached, new reference values are stored until this almost fully charged state is reached. Thus, the value of ⁇ T/ ⁇ t does not have to reach a very high value in order to start the termination process, thereby avoiding overcharge of the battery. What has been described with reference to the present embodiments illustrates how a reference value is used for the rate of change of battery temperature, which reference value is determined and stored during the charging process .
  • the obtained reference value is used when determining a threshold value for control of termination of the charging process, whereby this embodiment of the present invention implements adaptive battery charging. This allows the present embodiments to account for changes or differences in the threshold value of the battery temperature rate of change due to aging or manufacturing tolerances. Furthermore, it allows the present embodiments to account for variations in the threshold value due to differences in ambient temperatures .
  • the above described embodiments for a charging process also bring a solution which accounts for differences in the initial battery temperature, whereby a premature termination of the charging process due to a high initial temperature rate of change is avoided.
  • NiMH Nickel Metal Hydride
  • Lithium batteries Lithium batteries

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  • Secondary Cells (AREA)

Abstract

L'invention concerne un procédé et un dispositif de charge d'une batterie. Pendant au moins une partie du processus de charge, on détermine, d'une part, le taux de variation de température de la batterie, et d'autre part, une valeur de référence établie à partir des valeurs obtenues du taux de variation de température de la batterie, on compare cette valeur de référence à d'autres valeurs déterminées du taux de variation de température de la batterie, ce qui permet, sur la base de cette comparaison, de commander la fin du processus de charge. La valeur de référence peut être déterminée en tant que valeur minimale des valeurs obtenues du taux de variation de température de la batterie, la fin du processus de charge pouvant débuter lorsque le taux de variation de la température de la batterie dépasse d'une quantité déterminée la valeur de référence.
PCT/DK1998/000329 1997-07-21 1998-07-14 Procede et dispositif de charge d'une batterie rechargeable Ceased WO1999005768A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP98934885A EP0998780A1 (fr) 1997-07-21 1998-07-14 Procede et dispositif de charge d'une batterie rechargeable
JP2000504643A JP2001511639A (ja) 1997-07-21 1998-07-14 再充電可能バッテリーの充電方法と装置
AU84339/98A AU8433998A (en) 1997-07-21 1998-07-14 Method and apparatus for charging a rechargeable battery

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK0884/97 1997-07-21
DK88497 1997-07-21

Publications (1)

Publication Number Publication Date
WO1999005768A1 true WO1999005768A1 (fr) 1999-02-04

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK1998/000329 Ceased WO1999005768A1 (fr) 1997-07-21 1998-07-14 Procede et dispositif de charge d'une batterie rechargeable

Country Status (4)

Country Link
EP (1) EP0998780A1 (fr)
JP (1) JP2001511639A (fr)
AU (1) AU8433998A (fr)
WO (1) WO1999005768A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1345304A4 (fr) * 2000-11-24 2006-02-01 Tokyo R & D Kk Systeme de charge de bloc-batterie
CN102024997A (zh) * 2009-09-10 2011-04-20 富港电子（东莞）有限公司 电子装置的充电电池管理方法

Citations (5)

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GB2253312A (en) * 1991-02-25 1992-09-02 Nokia Mobile Phones Ltd Battery powered apparatus incorporating charging controller
EP0593770A1 (fr) * 1992-03-16 1994-04-27 4C Technologies Inc. Chargeur rapide et procede de charge rapide pour accumulateur au nickel-cadmium
US5329219A (en) * 1993-04-28 1994-07-12 Motorola, Inc. Method and apparatus for charging a battery
DE19520619A1 (de) * 1994-06-03 1996-01-11 Hitachi Koki Kk Batterieladegerät mit Überwachung der Batteriespannung und/oder der Temperatur in relevanten Abtastintervallen
US5550453A (en) * 1994-01-24 1996-08-27 Motorola, Inc. Battery charging method and apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2253312A (en) * 1991-02-25 1992-09-02 Nokia Mobile Phones Ltd Battery powered apparatus incorporating charging controller
EP0593770A1 (fr) * 1992-03-16 1994-04-27 4C Technologies Inc. Chargeur rapide et procede de charge rapide pour accumulateur au nickel-cadmium
US5329219A (en) * 1993-04-28 1994-07-12 Motorola, Inc. Method and apparatus for charging a battery
US5550453A (en) * 1994-01-24 1996-08-27 Motorola, Inc. Battery charging method and apparatus
DE19520619A1 (de) * 1994-06-03 1996-01-11 Hitachi Koki Kk Batterieladegerät mit Überwachung der Batteriespannung und/oder der Temperatur in relevanten Abtastintervallen

Non-Patent Citations (2)

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Title
FREEMAN D: "BATTERY MANAGEMENT TACKLES ALTERNATIVE BATTERY TECHNOLOGIES IN ADVANCED PORTABLE SYSTEMS", WESCON '94. WESTERN ELECTRONIC SHOW AND CONVENTION, ANAHEIM, SEPT. 27 - 29, 1994, 27 September 1994 (1994-09-27), INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, pages 303 - 308, XP000532590 *
GROSS S: "CHARGE CONTROL OF NICKEL CADMIUM BATTERIES", CONVERSION TECHNOLOGIES (CONTINUED), ELECTROCHEMICAL CONVERSION, BOSTON, AUG. 4 - 9, 1991, vol. 3, 4 August 1991 (1991-08-04), INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, pages 341 - 346, XP000299739 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1345304A4 (fr) * 2000-11-24 2006-02-01 Tokyo R & D Kk Systeme de charge de bloc-batterie
CN102024997A (zh) * 2009-09-10 2011-04-20 富港电子（东莞）有限公司 电子装置的充电电池管理方法

Also Published As

Publication number Publication date
AU8433998A (en) 1999-02-16
JP2001511639A (ja) 2001-08-14
EP0998780A1 (fr) 2000-05-10

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