CA2198013C - Method, apparatus, and communication device for charging a charge storage device which is momentarily connected to a fixed load - Google Patents
Method, apparatus, and communication device for charging a charge storage device which is momentarily connected to a fixed load Download PDFInfo
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- CA2198013C CA2198013C CA002198013A CA2198013A CA2198013C CA 2198013 C CA2198013 C CA 2198013C CA 002198013 A CA002198013 A CA 002198013A CA 2198013 A CA2198013 A CA 2198013A CA 2198013 C CA2198013 C CA 2198013C
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- Prior art keywords
- charge
- storage device
- charging
- count
- charge storage
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
- H02J7/02—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries for charging batteries from AC mains by converters
- H02J7/04—Regulation of charging current or voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
- H02J7/90—Regulation of charging or discharging current or voltage
- H02J7/92—Regulation of charging or discharging current or voltage with prioritisation of loads or sources
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
- Circuits Of Receivers In General (AREA)
Abstract
The present invention provides a method (100), an apparatus (400), and a communication device (700) for automatically maintaining a state of full charge in a charge storage device, such as a secondary battery (414), to which a fixed load (412) is momentarily connected. Since the load is fixed, a predetermined amount of charge is removed from the charge storage device each time the load is connected. A counter (404) is incremented while the load (412) is connected. From the count, the amount of charge that must be replaced can be determined. As the charge is replaced the count is decremented.
Description
21 9801 ~
WO 97/01195 , PCT/US96/05742 i, METHOD, APPARATUS, AND COMMUNICATION DEVICE FOR
CHARGING A CHARGE STORAGE DEVICE WHICH IS MOMENTARILY
CONNECTED TO A FIXED LOAD
Field of the Invention The present invention relates generally to charging systems, and more particularly to charging a charge storage device which is 10 momentarily connected to a fixed load.
Background of the Invention There is an emerging market for two-way wireless data 15 transceivers to be used with battery-operated, portable host devices such as laptop computers and "personal digital assiaLd"l~". Such wireless transceivers permit data to be exchanged among host devices in a packet format, ~onsi~li"g of a predetermined number of data bits, as well as other bits which are used in ho~c~kP.or)irlg functions such as 20 clock recovery and error detection and/or correction. When a packet is sent, the transceiver L~dn~",li~Lel- operates momentarily, followed by a time period of a much longer duration when the transceiver is either receiving or idle. The current peak drawn when the transmitter is active is much larger than the current drawn when the transceiver is 25 receiving or idle. Power for the transceiver power is supplied from the host device battery, and may pass through an interface connector defined by an industry standard such as the Personal Computer Memory Card International Association, PCMCIA. The trend to lower voltage power distribution in host devices will eventually lead to an increase 30 in the transmitter current required to maintain the same output power.
WO 97/01195 , PCT/US96/05742 i, METHOD, APPARATUS, AND COMMUNICATION DEVICE FOR
CHARGING A CHARGE STORAGE DEVICE WHICH IS MOMENTARILY
CONNECTED TO A FIXED LOAD
Field of the Invention The present invention relates generally to charging systems, and more particularly to charging a charge storage device which is 10 momentarily connected to a fixed load.
Background of the Invention There is an emerging market for two-way wireless data 15 transceivers to be used with battery-operated, portable host devices such as laptop computers and "personal digital assiaLd"l~". Such wireless transceivers permit data to be exchanged among host devices in a packet format, ~onsi~li"g of a predetermined number of data bits, as well as other bits which are used in ho~c~kP.or)irlg functions such as 20 clock recovery and error detection and/or correction. When a packet is sent, the transceiver L~dn~",li~Lel- operates momentarily, followed by a time period of a much longer duration when the transceiver is either receiving or idle. The current peak drawn when the transmitter is active is much larger than the current drawn when the transceiver is 25 receiving or idle. Power for the transceiver power is supplied from the host device battery, and may pass through an interface connector defined by an industry standard such as the Personal Computer Memory Card International Association, PCMCIA. The trend to lower voltage power distribution in host devices will eventually lead to an increase 30 in the transmitter current required to maintain the same output power.
The voltage at the transceiver may be reduced to an u"acce,oldble level when current is drawn from the host device battery due to power distribution wiring ~ 7i~ldll~e and the equivalent series resistance of the host device battery itself. The l~si~ld,,ce7 R, of an electrical 5 conductor depends on the resistivity. p. the length, 1, and the cross-sectional area, A, in the following manner:
R=PA
10 Thus, the trend toward higher printed circuit board density will increase the likelihood of higher wiring l~si~,ld,,ce. The equivalent resistance of the host device battery depends on many factors, including its chemical composition and physical parameters. Nickel cadmium (NiCd) batteries have the lowest internaMesi-,ld"c~. Nickel 15 metal hydride (NiMH) batteries are becoming more common in host devices since their energy density is 3p% to 50% higher than NiCd, and they are env;.~-"""e"la'.!y safer since they do not contain poisonous cadmium; however, they have a higher internaM7_si~,ld,lce than NiCd.
For a given battery type, small cells have a higher internaM~ ,ld"ce 20 than large cells.
It is also possible that the magnitude of the current drawn by the transmitter will exceed the limits defined for pins in the interface cor"~e, lol. Typical PCMCIA connectors pins are limited to 300 to 500 25 mA, depel~7ii"g on the connector design.
it is common for host devices to employ power management to disconnect the battery voltage from peripheral devices when the computer is turned off, or at other times in order to reduce current.
30 Peripheral interfaces, such as the PCMCIA interface, do not provide for ~ WO97/01195 2~ 9801 ~ PCI/US96/05742 a power cu""e~lion that provides a continuous connection to the battery.
A secondary battery may be safely charged in minimum time by a 5 current having a magnitude C, the ampere-hour rating of the battery.
However, o\~l,eaLi"g can occur as near full charge is reached if this current is delivered continuously. A secondary battery may be charged for several hours at a current of .1 C, or continuously at .05C or less.
All charge storage devices, including batteries, e~.e, ience charge 10 leakage at a low rate when idle. The charge lost in this manner must be replaced to maintain full capacity.
Prior-art methods for ~o"L~u'';ng the flow of charge include co"""el- ially available battery management and remaining energy 15 indicator ICs, and charge ~ o"l~ . Such ICs are not suitable for the application described since they do not auto"~dli~ally initiate the charging process following diacol",e~L of the load, or may not monitor ~ ondiLiuns to prevent overcharging.
Accordingly, there is a need for a charge storage device and a method for controlling the flow of charge such that stored charge is lldll~rt:n~:d to a load at a predetermined rate when the load is ,,,ulllellldlily connected, and replaced by a charging source at a lower rate i"""edidL~ly following disconnect of the load so that the I~:clldly;ll9 process is likely to be completed while the charging voltage is available.
Brief Description of the Drawings ~ 30 W09710119s 21 9801 3 PCTIIJS96/05742 FIG. 1 is a flow diagram of one embodiment of steps for a method of co"l-~" ,9 the flow of cha!ge in accordd"ce with the present invention.
FIG. Z is a graphical depiction of one embodiment of the flow of charge in accordance with the present invention.
FIG. 3 is a flow diagram of a second embodiment of steps for a method of controlling the flow of charge in a~co,-ld,)ce with the present invention.
FIG. 4 is a block diagram of one embodiment of an apparatus for charging a battery in accordance with the present invention.
1 5 FIG. 5 is a flow diagram of a third embodiment of steps for a method of controlling the flow of charge in accordance with the present invention.
FIG. 6 is a block diagram of a second ~",bo~ii"~el~L of an apparatus for charging a battery in acr orddllce with the present invention.
FIG. 7 is a diagram of one embodiment of a communication device c~"",.,ri~i"g an apparatus for charging a battery in accordance with the present invention.
Detailed Description of Preferred Embodiments The present invention provides a method and apparatus for autor,lalic.,l!y IlldillLdill;~l9 a state of full charge in a charge storage device, such as a secondary battery, to which a fixed load is momentarily connected. Since the load is fixed, a predetermined ~ WO 97/01195 2 1 9 8 0 1 3 PCT/US96/05742 amount of charge is removed from the charge storage device each time the load is conne~LeLI, thus, the amount of charge that must be replaced can be determined from the duration of time that the load is connected.
The charge ~qDIscHARGEl drawn from the charge storage device when the load is connected for a time ~tDISCHARGE is given by ~qDISCHARGE LOAD ~tDlSCHARGE' [equation l ]
where iLoAD is the current supplied to the load. ~tDI5cHARGE may be measured by i"~ ",~"li"g a counter at a first predetermined rate, f1;
1 0 thus, ~tDlSCHARGE=f ~~DlscHARGE-couNT~ [equation 2]
The charge, ~qcHARGE delivered to the charge storage device during a time when the load is di~col)lle~led, ~tCHARGE~
~qCHARGE jCHARGE ~tCHARGE~ [equation 3]
where iCHARGE is the current supplied to the ioad. ~tCHARGE may be measured by in~rt:",e"li"g a counter at a second predetermined rate, f2;
thus, tCHARGE f ~ ~CHARGE_COUNT. [equation 4]
and Z O jLOAD . f ~ ~ DISCHARGE-COUNT = jCHARGE ~ f ~ ~ CHARGE-C~UN~ ~ [ equ ation 5 ]
The ratio of the charging current to the load current may be determined by, t:dl I dl IY;I 19 equation 5 --~ ~, DISCHARGE COUNT
CHARGE =, . - - - [CqUat;On 6]
ILOAD --~ ~ CHARGE_COUNT
25 The charge removed during discharge by the load has been completely replaced when ~DISCHARGE_COUNT--~,CHARGE_COUNT = 0; [equation ;']
2 1 ~8~ 1 3 6 thus, CHARG~ = f2 = [equation 8]
jLOAD f I
Typically, jCHARGE ~ jLOAD; thus, fz < f1, and the rate at which the counter counts is less when the charge storage device is receiving 5 charge than when it is delivering charge.
The present invention may include means for replacing the charge at a slower rate when a temperature threshold is ~oYrPer~ In this case the counter will count at a rate f3 < fz.
FIG. 1, numeral 100, is a flow diagram of one embodiment of steps for a method of controlling the flow of charge in acco,dd"ce with the present invention. The load is connected to the charge storage device for a discharging time (102). A counter is i,,~l~,,,e,,led based on 15 the .li~chd,y;"g time (104). The charge storage device receives charge for a time based on the count (106). The count is decremented during the charge time (108). The charging is t~rr~ ldled when the count is zero (1 1 0).
FIG. 2, numeral 200, is a graphical depiction of one embodiment of the flow of charge in accordance with the present invention. Charge is Lrdll~r~ d from the charge storage device when the load is connected, resulting in momentary discharge (202, 206, and 210).
During discharge (202), the counter output increments at a corrr-~,uondi"g rate, f1 (216). During charge replacement (204), the counter output decrements at a corresponding rate, f2 (218). In a similar manner, discharge (206) is followed by charge replacement (208); however, the charge replacement process is interrupted by discharge (210). Charge replacement (212) corresponds to the total of the remaining unreplaced charge from discharge (206) and the discharge (Z10). When the charge replacement process is completed, 21 98~1 3 ~ WO 97/01195 , , PC'rlUS96/05742 trickle charge (214) is activated to replace charge which may be lost due to leakage.
FIG. 3, numeral 300, is a flow diagram of a second emL)o.li",t:"L of 5 steps for a method of controlling the flow of charge in accordd"ce with the present invention. When a load is connected to the charge storage device (302), the counter is i"~,~",t:"led at a pl~d~le"";,led counting rate (304). The counter continues to count while charge is being removed.
When no load is connected (302), and the counter output is zero m(306), charging is disabled (314) and trickle charging is enabled (318) in order to replace charge lost due to leakage.
When no load is connected (302), and the counter count is non-zero (306), and the charging voltage is available (308), then the charging source is enabled (312), and the counter is decremented at a predetermined dec,~",e"li"g rate (316).
When no load is connected (302), and the counter count is non-zero (306) and the charging voltage is not available (308), then the counter count is held (310) until the charging voltage is available.
FIG. 4, numeral 400 is a block diagram of one embodiment of an apparatus for charging a secondary battery in accordance with the present invention. A charger (402) contains a counter (404), a clock (406), a charge controller (436), a charging current source (418), and a trickle charge source (420).
The counter (404) receives through a counter input (440) that is a clock signal generated by the clock (406). The clock signal is generated at either a first predetermined rate f1, or a second W097/01195 2 1 980 1 3 PCT/US9610~742 p,~dele,r"i"ed rate fz, as directed by the charge controller (436) through clock control input (434). The connection of a load (412) to a secondary battery (414) through a switch (416) is sensed through a load sensor input (422). A charge controller (436) drives this counter 5 and operates on various factors in order to set the counter clock speed (440) the counter state (432), and the direction of the count (438).
Such factors include the presence or absence of a load (412) by sensing (422) the state of the switch (416), The presence or absence of a charging voltage source (408) as indicated by the switch (410), and the 10 counter output (430).
The clock (406) contains two clock frequencies f1 and fz.
Frequency f1 is the clock frequency at which the counter advances during the presence of a load. Frequency f2 is the clock frequency at 15 which the counter dew~r"e~ as energy is being restored back into the charge storage device which in this case is a secondary battery (414).
These two clocks are selected by the charge controller via a selection input (434) and are fed into the counter at the clock input (440). The fl /f2 ratio is set based on the knowledge of the load current which is 20 constant in an on-off digital d,Up' cdlioll, the time available for charging the battery and the vendor's recommended battery charging characteristics.
The charging current source (418) is driven by the charge 25 controller a source input (426) and it is enabled when the counter output is non-zero (430), the charging voltage source is available (428), and the load is disconnected (416). The current source (420) represents the trickle charge current. This source is activated by the charge controller through a trickle charge control (424) after the 30 charging is terminated.
2 1 980~ 3 ~ WO97/01195 PCT/US96/05742 FIG. 5, numeral 500, is a flow diagram of a third embodiment of steps for a method of conL~" ,9 the flow of charge in aCC01 iance with the present invention. The embodiment in figure 5 is similar to that in figure 3 except for a battery-temperature sensing scheme which sets a 5 variable charging rate. The variable charging rate is employed to improve the battery charging efficiency as it deteriorates with the rising t~",~,e,dL.Ire while being charged.
The counter (50Z) is operably coupied to receive a load presence 10 or absence signal. For L~ d"s"liLLe,- applications, the load presence signal ~502) may be the l,d,l~",iLLed data.
First, the initial state will be analyzed where the battery is full as indicated by the zero counter output (506) and no ioad is present 15 (50Z). In this case, charging remains disabled (514) and trickle charging is enabled ~518). The trickle charge is employed in order to maintain the battery fully charged by compensating for the on going self discharge and capacity deterioration with age.
Second, a load is connected to the battery. As a result a counter starts to in~l~r"e"l at a predetermined counting rate in order to maintain a discharge unit record of the drained energy. When the load is terminated (502), the counter output which is now non-zero, remains in this state (510) until a charging source voltage (508) is sensed. If the temperature of the battery (520) is below a given threshold indicating normal temperature, charging commences at a first pred~:L~ il ,ed charging rate (512), and the counter begins to decrement at a first predetermined de~,~",e"li"g rate (516). If the battery ter,l~.erdLure is exceeds a set threshold indicating high battery temperature, charging cur"r"t:"ces at a second predetermined charging rate (522), and the counter de~ ",~"L~ at a second predetermined 2 ~ 980 1 3 de~r~")~"lillg rate (524). This continues until all lost energy has been restored and the counter output is zero again.
The temperature-depel-d~"L charging rate is used to improve the 5 charging efficiency as the battery temperature rises. Typical batteries such as NiCds begin to heat up during charging when they reach about 70% of their full capacity. Maintaining the same charging rate will cause the battery to overheat and its charging efficiency to diminish.
To overcome this problem, the charge is put into the battery at a 10 slower rate. A variable charging rate is therefore particularly useful in this case. The sensing of the battery temperature can be acco"l~ l,ed by a heat sensor element located within the battery pack.
Typically, a charging rate reduction of an order of magnitude is adequate.
FIG. 6, numeral 600, is a block diagram of a second embodiment of an apparatus for charging a battery in accordance with the present invention. Figure 6 is similar to figure 4 except for the temperature dependent charging rate discussed earlier in figure S.
A charger (602) contains a counter (604), a clock (606), a charge controller (636), a charging current source (618), a trickle charge source (620). The counter (604) can increment, decrement, or stay in hold while tracking the charged and discharged energy. The charge 25 controller (636) which drive this counter operates on various factors in order to set the counter clock speed (640), the counter state (632), and the direction of the count (638). Such factors include the presence or absence of a load (612) as indicated by sensing (422) the state of the switch (616). The presence or absence of a charging voltage source 30 (608) as indicated by the switch at (610), and the counter output (630).
~ WO97/0119S 2 1 980 1 3 PCT/US96/05742 .1 The clock (606) incorporates three clock frequencies f1, f2, and f3. Frequency f1 is the clock frequency at which the counter advances during the presence of a load. Frequency f2 is the clock frequency at which the counter de~ ",e"Ls as energy is being restored back into the 5 battery (614) at normal temperature. Frequency f3 r~p~Se"l~ the clock frequency at which the counter de~ "t:"l~ while the near-full battery is being charged at above normal temperature. The three clocks are selected by the charge controller via a selection signal (634) and are fed into the counter at a clock input (640) with f1 >f2>f3. The 10 f1 /f2 ratio is set based on the knowledge of the load current which is constant in an on-off digital d,uplicdLion~ the time available for charging the battery, and the vendor's ~ecor"",~"ded battery charging ~ hdl d~lel i~lic~. The f2/f3 ratio is also battery dependent with f2 being typically an order of magnitude higher.
The charging current source (618) is driven by a charge controller signal (626) and it is enabled when the counter output is non-zero (630), the charging voltage source is available (628), and the load is disconnected (616). The current source (620) represents the trickle 20 charge current. This source is activated by a charge controller signal (624) after the charging process is terminated. A battery heat sensing element (638) drives a second charge controller signal (640).
FIG. 7, numerai 700, is a diagram of one embodiment of a 25 communication device comprising an apparatus for charging a battery in accordance with the present invention. A charger (702) contains the blocks described in the charger (402) in figure 4. A charge storage device (714) or battery undergoes charge and discharge cycles. A load (712) is presented to the battery during momentary lldllSIIIi~siOIls~ A
30 switch (716) indicates the presence or absence of a load. A signal (722) senses the presence or absence of the load and is input to the charger (702). A wireless transceiver device (750) is depicts a typical ~ ' ~
WO 97101195 PCT/US961057~2 liun where a battery and a charger can be located. A portable computer (748) is used to provide wireless links to other users via the wireless transceiver device (750). A cable (740) provides the data and power links between the wireless transceiver (750) and the computer 5 (748). This interface is accomplished through a PCMCIA adapter (738).
The computer main power source (708) or primary battery is the voltage charging source used to charge the battery as described earlier.
A switch (710) indicates the availability or absence of the charging voltage source. In typical portable computers, this switch opens up 10 when the computer is turned off.
R=PA
10 Thus, the trend toward higher printed circuit board density will increase the likelihood of higher wiring l~si~,ld,,ce. The equivalent resistance of the host device battery depends on many factors, including its chemical composition and physical parameters. Nickel cadmium (NiCd) batteries have the lowest internaMesi-,ld"c~. Nickel 15 metal hydride (NiMH) batteries are becoming more common in host devices since their energy density is 3p% to 50% higher than NiCd, and they are env;.~-"""e"la'.!y safer since they do not contain poisonous cadmium; however, they have a higher internaM7_si~,ld,lce than NiCd.
For a given battery type, small cells have a higher internaM~ ,ld"ce 20 than large cells.
It is also possible that the magnitude of the current drawn by the transmitter will exceed the limits defined for pins in the interface cor"~e, lol. Typical PCMCIA connectors pins are limited to 300 to 500 25 mA, depel~7ii"g on the connector design.
it is common for host devices to employ power management to disconnect the battery voltage from peripheral devices when the computer is turned off, or at other times in order to reduce current.
30 Peripheral interfaces, such as the PCMCIA interface, do not provide for ~ WO97/01195 2~ 9801 ~ PCI/US96/05742 a power cu""e~lion that provides a continuous connection to the battery.
A secondary battery may be safely charged in minimum time by a 5 current having a magnitude C, the ampere-hour rating of the battery.
However, o\~l,eaLi"g can occur as near full charge is reached if this current is delivered continuously. A secondary battery may be charged for several hours at a current of .1 C, or continuously at .05C or less.
All charge storage devices, including batteries, e~.e, ience charge 10 leakage at a low rate when idle. The charge lost in this manner must be replaced to maintain full capacity.
Prior-art methods for ~o"L~u'';ng the flow of charge include co"""el- ially available battery management and remaining energy 15 indicator ICs, and charge ~ o"l~ . Such ICs are not suitable for the application described since they do not auto"~dli~ally initiate the charging process following diacol",e~L of the load, or may not monitor ~ ondiLiuns to prevent overcharging.
Accordingly, there is a need for a charge storage device and a method for controlling the flow of charge such that stored charge is lldll~rt:n~:d to a load at a predetermined rate when the load is ,,,ulllellldlily connected, and replaced by a charging source at a lower rate i"""edidL~ly following disconnect of the load so that the I~:clldly;ll9 process is likely to be completed while the charging voltage is available.
Brief Description of the Drawings ~ 30 W09710119s 21 9801 3 PCTIIJS96/05742 FIG. 1 is a flow diagram of one embodiment of steps for a method of co"l-~" ,9 the flow of cha!ge in accordd"ce with the present invention.
FIG. Z is a graphical depiction of one embodiment of the flow of charge in accordance with the present invention.
FIG. 3 is a flow diagram of a second embodiment of steps for a method of controlling the flow of charge in a~co,-ld,)ce with the present invention.
FIG. 4 is a block diagram of one embodiment of an apparatus for charging a battery in accordance with the present invention.
1 5 FIG. 5 is a flow diagram of a third embodiment of steps for a method of controlling the flow of charge in accordance with the present invention.
FIG. 6 is a block diagram of a second ~",bo~ii"~el~L of an apparatus for charging a battery in acr orddllce with the present invention.
FIG. 7 is a diagram of one embodiment of a communication device c~"",.,ri~i"g an apparatus for charging a battery in accordance with the present invention.
Detailed Description of Preferred Embodiments The present invention provides a method and apparatus for autor,lalic.,l!y IlldillLdill;~l9 a state of full charge in a charge storage device, such as a secondary battery, to which a fixed load is momentarily connected. Since the load is fixed, a predetermined ~ WO 97/01195 2 1 9 8 0 1 3 PCT/US96/05742 amount of charge is removed from the charge storage device each time the load is conne~LeLI, thus, the amount of charge that must be replaced can be determined from the duration of time that the load is connected.
The charge ~qDIscHARGEl drawn from the charge storage device when the load is connected for a time ~tDISCHARGE is given by ~qDISCHARGE LOAD ~tDlSCHARGE' [equation l ]
where iLoAD is the current supplied to the load. ~tDI5cHARGE may be measured by i"~ ",~"li"g a counter at a first predetermined rate, f1;
1 0 thus, ~tDlSCHARGE=f ~~DlscHARGE-couNT~ [equation 2]
The charge, ~qcHARGE delivered to the charge storage device during a time when the load is di~col)lle~led, ~tCHARGE~
~qCHARGE jCHARGE ~tCHARGE~ [equation 3]
where iCHARGE is the current supplied to the ioad. ~tCHARGE may be measured by in~rt:",e"li"g a counter at a second predetermined rate, f2;
thus, tCHARGE f ~ ~CHARGE_COUNT. [equation 4]
and Z O jLOAD . f ~ ~ DISCHARGE-COUNT = jCHARGE ~ f ~ ~ CHARGE-C~UN~ ~ [ equ ation 5 ]
The ratio of the charging current to the load current may be determined by, t:dl I dl IY;I 19 equation 5 --~ ~, DISCHARGE COUNT
CHARGE =, . - - - [CqUat;On 6]
ILOAD --~ ~ CHARGE_COUNT
25 The charge removed during discharge by the load has been completely replaced when ~DISCHARGE_COUNT--~,CHARGE_COUNT = 0; [equation ;']
2 1 ~8~ 1 3 6 thus, CHARG~ = f2 = [equation 8]
jLOAD f I
Typically, jCHARGE ~ jLOAD; thus, fz < f1, and the rate at which the counter counts is less when the charge storage device is receiving 5 charge than when it is delivering charge.
The present invention may include means for replacing the charge at a slower rate when a temperature threshold is ~oYrPer~ In this case the counter will count at a rate f3 < fz.
FIG. 1, numeral 100, is a flow diagram of one embodiment of steps for a method of controlling the flow of charge in acco,dd"ce with the present invention. The load is connected to the charge storage device for a discharging time (102). A counter is i,,~l~,,,e,,led based on 15 the .li~chd,y;"g time (104). The charge storage device receives charge for a time based on the count (106). The count is decremented during the charge time (108). The charging is t~rr~ ldled when the count is zero (1 1 0).
FIG. 2, numeral 200, is a graphical depiction of one embodiment of the flow of charge in accordance with the present invention. Charge is Lrdll~r~ d from the charge storage device when the load is connected, resulting in momentary discharge (202, 206, and 210).
During discharge (202), the counter output increments at a corrr-~,uondi"g rate, f1 (216). During charge replacement (204), the counter output decrements at a corresponding rate, f2 (218). In a similar manner, discharge (206) is followed by charge replacement (208); however, the charge replacement process is interrupted by discharge (210). Charge replacement (212) corresponds to the total of the remaining unreplaced charge from discharge (206) and the discharge (Z10). When the charge replacement process is completed, 21 98~1 3 ~ WO 97/01195 , , PC'rlUS96/05742 trickle charge (214) is activated to replace charge which may be lost due to leakage.
FIG. 3, numeral 300, is a flow diagram of a second emL)o.li",t:"L of 5 steps for a method of controlling the flow of charge in accordd"ce with the present invention. When a load is connected to the charge storage device (302), the counter is i"~,~",t:"led at a pl~d~le"";,led counting rate (304). The counter continues to count while charge is being removed.
When no load is connected (302), and the counter output is zero m(306), charging is disabled (314) and trickle charging is enabled (318) in order to replace charge lost due to leakage.
When no load is connected (302), and the counter count is non-zero (306), and the charging voltage is available (308), then the charging source is enabled (312), and the counter is decremented at a predetermined dec,~",e"li"g rate (316).
When no load is connected (302), and the counter count is non-zero (306) and the charging voltage is not available (308), then the counter count is held (310) until the charging voltage is available.
FIG. 4, numeral 400 is a block diagram of one embodiment of an apparatus for charging a secondary battery in accordance with the present invention. A charger (402) contains a counter (404), a clock (406), a charge controller (436), a charging current source (418), and a trickle charge source (420).
The counter (404) receives through a counter input (440) that is a clock signal generated by the clock (406). The clock signal is generated at either a first predetermined rate f1, or a second W097/01195 2 1 980 1 3 PCT/US9610~742 p,~dele,r"i"ed rate fz, as directed by the charge controller (436) through clock control input (434). The connection of a load (412) to a secondary battery (414) through a switch (416) is sensed through a load sensor input (422). A charge controller (436) drives this counter 5 and operates on various factors in order to set the counter clock speed (440) the counter state (432), and the direction of the count (438).
Such factors include the presence or absence of a load (412) by sensing (422) the state of the switch (416), The presence or absence of a charging voltage source (408) as indicated by the switch (410), and the 10 counter output (430).
The clock (406) contains two clock frequencies f1 and fz.
Frequency f1 is the clock frequency at which the counter advances during the presence of a load. Frequency f2 is the clock frequency at 15 which the counter dew~r"e~ as energy is being restored back into the charge storage device which in this case is a secondary battery (414).
These two clocks are selected by the charge controller via a selection input (434) and are fed into the counter at the clock input (440). The fl /f2 ratio is set based on the knowledge of the load current which is 20 constant in an on-off digital d,Up' cdlioll, the time available for charging the battery and the vendor's recommended battery charging characteristics.
The charging current source (418) is driven by the charge 25 controller a source input (426) and it is enabled when the counter output is non-zero (430), the charging voltage source is available (428), and the load is disconnected (416). The current source (420) represents the trickle charge current. This source is activated by the charge controller through a trickle charge control (424) after the 30 charging is terminated.
2 1 980~ 3 ~ WO97/01195 PCT/US96/05742 FIG. 5, numeral 500, is a flow diagram of a third embodiment of steps for a method of conL~" ,9 the flow of charge in aCC01 iance with the present invention. The embodiment in figure 5 is similar to that in figure 3 except for a battery-temperature sensing scheme which sets a 5 variable charging rate. The variable charging rate is employed to improve the battery charging efficiency as it deteriorates with the rising t~",~,e,dL.Ire while being charged.
The counter (50Z) is operably coupied to receive a load presence 10 or absence signal. For L~ d"s"liLLe,- applications, the load presence signal ~502) may be the l,d,l~",iLLed data.
First, the initial state will be analyzed where the battery is full as indicated by the zero counter output (506) and no ioad is present 15 (50Z). In this case, charging remains disabled (514) and trickle charging is enabled ~518). The trickle charge is employed in order to maintain the battery fully charged by compensating for the on going self discharge and capacity deterioration with age.
Second, a load is connected to the battery. As a result a counter starts to in~l~r"e"l at a predetermined counting rate in order to maintain a discharge unit record of the drained energy. When the load is terminated (502), the counter output which is now non-zero, remains in this state (510) until a charging source voltage (508) is sensed. If the temperature of the battery (520) is below a given threshold indicating normal temperature, charging commences at a first pred~:L~ il ,ed charging rate (512), and the counter begins to decrement at a first predetermined de~,~",e"li"g rate (516). If the battery ter,l~.erdLure is exceeds a set threshold indicating high battery temperature, charging cur"r"t:"ces at a second predetermined charging rate (522), and the counter de~ ",~"L~ at a second predetermined 2 ~ 980 1 3 de~r~")~"lillg rate (524). This continues until all lost energy has been restored and the counter output is zero again.
The temperature-depel-d~"L charging rate is used to improve the 5 charging efficiency as the battery temperature rises. Typical batteries such as NiCds begin to heat up during charging when they reach about 70% of their full capacity. Maintaining the same charging rate will cause the battery to overheat and its charging efficiency to diminish.
To overcome this problem, the charge is put into the battery at a 10 slower rate. A variable charging rate is therefore particularly useful in this case. The sensing of the battery temperature can be acco"l~ l,ed by a heat sensor element located within the battery pack.
Typically, a charging rate reduction of an order of magnitude is adequate.
FIG. 6, numeral 600, is a block diagram of a second embodiment of an apparatus for charging a battery in accordance with the present invention. Figure 6 is similar to figure 4 except for the temperature dependent charging rate discussed earlier in figure S.
A charger (602) contains a counter (604), a clock (606), a charge controller (636), a charging current source (618), a trickle charge source (620). The counter (604) can increment, decrement, or stay in hold while tracking the charged and discharged energy. The charge 25 controller (636) which drive this counter operates on various factors in order to set the counter clock speed (640), the counter state (632), and the direction of the count (638). Such factors include the presence or absence of a load (612) as indicated by sensing (422) the state of the switch (616). The presence or absence of a charging voltage source 30 (608) as indicated by the switch at (610), and the counter output (630).
~ WO97/0119S 2 1 980 1 3 PCT/US96/05742 .1 The clock (606) incorporates three clock frequencies f1, f2, and f3. Frequency f1 is the clock frequency at which the counter advances during the presence of a load. Frequency f2 is the clock frequency at which the counter de~ ",e"Ls as energy is being restored back into the 5 battery (614) at normal temperature. Frequency f3 r~p~Se"l~ the clock frequency at which the counter de~ "t:"l~ while the near-full battery is being charged at above normal temperature. The three clocks are selected by the charge controller via a selection signal (634) and are fed into the counter at a clock input (640) with f1 >f2>f3. The 10 f1 /f2 ratio is set based on the knowledge of the load current which is constant in an on-off digital d,uplicdLion~ the time available for charging the battery, and the vendor's ~ecor"",~"ded battery charging ~ hdl d~lel i~lic~. The f2/f3 ratio is also battery dependent with f2 being typically an order of magnitude higher.
The charging current source (618) is driven by a charge controller signal (626) and it is enabled when the counter output is non-zero (630), the charging voltage source is available (628), and the load is disconnected (616). The current source (620) represents the trickle 20 charge current. This source is activated by a charge controller signal (624) after the charging process is terminated. A battery heat sensing element (638) drives a second charge controller signal (640).
FIG. 7, numerai 700, is a diagram of one embodiment of a 25 communication device comprising an apparatus for charging a battery in accordance with the present invention. A charger (702) contains the blocks described in the charger (402) in figure 4. A charge storage device (714) or battery undergoes charge and discharge cycles. A load (712) is presented to the battery during momentary lldllSIIIi~siOIls~ A
30 switch (716) indicates the presence or absence of a load. A signal (722) senses the presence or absence of the load and is input to the charger (702). A wireless transceiver device (750) is depicts a typical ~ ' ~
WO 97101195 PCT/US961057~2 liun where a battery and a charger can be located. A portable computer (748) is used to provide wireless links to other users via the wireless transceiver device (750). A cable (740) provides the data and power links between the wireless transceiver (750) and the computer 5 (748). This interface is accomplished through a PCMCIA adapter (738).
The computer main power source (708) or primary battery is the voltage charging source used to charge the battery as described earlier.
A switch (710) indicates the availability or absence of the charging voltage source. In typical portable computers, this switch opens up 10 when the computer is turned off.
Claims (12)
1. A method for charging a charge storage device which is momentarily connected to a fixed load, the method comprising:
incrementing, using a counter, a count based on a discharge time, the discharge time occurring at a first predetermined rate when the charge storage device is connected to the fixed load;
initiating a charging at a second predetermined rate that is less than the first predetermined rate of the charge storage device for a charge time when the fixed load is disconnected, and the length of the charge time is based on count;
decrementing the count during the charge time; and terminating the charging of the charge storage device when the count is zero.
incrementing, using a counter, a count based on a discharge time, the discharge time occurring at a first predetermined rate when the charge storage device is connected to the fixed load;
initiating a charging at a second predetermined rate that is less than the first predetermined rate of the charge storage device for a charge time when the fixed load is disconnected, and the length of the charge time is based on count;
decrementing the count during the charge time; and terminating the charging of the charge storage device when the count is zero.
2. The method of claim 1 wherein charging the charge storage device uses a primary battery.
3. The method of claim 1 wherein the charge storage device is a secondary battery.
4. The method of claim 1 wherein charging occurs when the fixed load is disconnected, the count is nonzero, and a charging voltage is available.
5. The method of claim 1 wherein the charge time is longer than the discharge time.
6. The method of claim 1 wherein a trickle charging occurs when the count equals zero.
7. The method of claim 1 further comprising a step of measuring the temperature of the charge storage device.
8. The method of claim 7 wherein charging the charge storage device is at a slower rate when the temperature of the charge storage device exceeds a predetermined threshold.
9. An apparatus for charging a charge storage device which is momentarily connected to a fixed load, the apparatus comprises:
a charging voltage source for providing a voltage signal;
a charge controller, powered by the voltage signal, for monitoring when the fixed load is connected to the charge storage device, and determining a direction and rate of a count;
a clock, operably coupled to the charge controller, for receiving the rate of the count and providing a clock signal;
a counter, operably coupled to the clock and the charge controller, for counting the cycles of the clock signal in the direction determined by the charge controller, wherein the counter increments a count based on a discharge time, the discharge time occurring at a first predetermined rate when the charge storage device is connected to the fixed load; and a charging current source, operably coupled to the charge controller and charging voltage source, for charging the charge storage device when the direction of count is decreasing, wherein the charging current source initiates a charge at a second predetermined rate that is less than the first predetermined rate of the charge storage device for a charge time when the fixed load is disconnected, and the length of the charge time is based on the count.
a charging voltage source for providing a voltage signal;
a charge controller, powered by the voltage signal, for monitoring when the fixed load is connected to the charge storage device, and determining a direction and rate of a count;
a clock, operably coupled to the charge controller, for receiving the rate of the count and providing a clock signal;
a counter, operably coupled to the clock and the charge controller, for counting the cycles of the clock signal in the direction determined by the charge controller, wherein the counter increments a count based on a discharge time, the discharge time occurring at a first predetermined rate when the charge storage device is connected to the fixed load; and a charging current source, operably coupled to the charge controller and charging voltage source, for charging the charge storage device when the direction of count is decreasing, wherein the charging current source initiates a charge at a second predetermined rate that is less than the first predetermined rate of the charge storage device for a charge time when the fixed load is disconnected, and the length of the charge time is based on the count.
10. The apparatus according to claim 9, further comprising:
a trickle charge source, operably coupled to the charging voltage source and the charge controller, for replacing leakage current in the charge storage device when the count is stationary.
a trickle charge source, operably coupled to the charging voltage source and the charge controller, for replacing leakage current in the charge storage device when the count is stationary.
11. The apparatus according to claim 9, further comprising:
a temperature sensor, operably coupled to the charge storage device, for measuring the temperature of the charge storage device and inputting the temperature into the charge controller to be used in the determination of the rate of the count.
a temperature sensor, operably coupled to the charge storage device, for measuring the temperature of the charge storage device and inputting the temperature into the charge controller to be used in the determination of the rate of the count.
12. A communication device comprising an apparatus for charging a charge storage device which is momentarily connected to a fixed load, the apparatus comprises:
a charging voltage source for providing a voltage signal;
a charge controller, powered by the voltage signal, for monitoring when the fixed load is connected to the charge storage device, and determining a direction and rate of a count;
a clock, operably coupled to the charge controller, for receiving the rate of the count and providing a clock signal;
a counter, operably coupled to the clock and the charge controller, for counting the cycles of the clock signal in the direction determined by the charge controller, wherein the counter increments a count based on a discharge time, the discharge time occurring at a first predetermined rate when the charge storage device is connected to the fixed load; and a charging current source, operably coupled to the charge controller and charging voltage source, for charging the charge storage device when the direction of count is decreasing, wherein the charging current source initiates a charge at a second predetermined rate that is less than the first predetermined rate of the charge storage device for a charge time when the fixed load is disconnected, and the length of the charge time is based on the count.
a charging voltage source for providing a voltage signal;
a charge controller, powered by the voltage signal, for monitoring when the fixed load is connected to the charge storage device, and determining a direction and rate of a count;
a clock, operably coupled to the charge controller, for receiving the rate of the count and providing a clock signal;
a counter, operably coupled to the clock and the charge controller, for counting the cycles of the clock signal in the direction determined by the charge controller, wherein the counter increments a count based on a discharge time, the discharge time occurring at a first predetermined rate when the charge storage device is connected to the fixed load; and a charging current source, operably coupled to the charge controller and charging voltage source, for charging the charge storage device when the direction of count is decreasing, wherein the charging current source initiates a charge at a second predetermined rate that is less than the first predetermined rate of the charge storage device for a charge time when the fixed load is disconnected, and the length of the charge time is based on the count.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/492,552 | 1995-06-20 | ||
| US08/492,552 US5617008A (en) | 1995-06-20 | 1995-06-20 | Method, apparatus, and communication device for charging a charge storage device which is momentarily connected to a fixed load |
| PCT/US1996/005742 WO1997001195A1 (en) | 1995-06-20 | 1996-04-26 | Method, apparatus, and communication device for charging a charge storage device which is momentarily connected to a fixed load |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2198013A1 CA2198013A1 (en) | 1997-01-09 |
| CA2198013C true CA2198013C (en) | 2000-06-06 |
Family
ID=23956715
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002198013A Expired - Fee Related CA2198013C (en) | 1995-06-20 | 1996-04-26 | Method, apparatus, and communication device for charging a charge storage device which is momentarily connected to a fixed load |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5617008A (en) |
| EP (1) | EP0777916A4 (en) |
| CN (1) | CN1157058A (en) |
| AU (1) | AU689721B2 (en) |
| CA (1) | CA2198013C (en) |
| WO (1) | WO1997001195A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6138178A (en) * | 1997-01-29 | 2000-10-24 | Fuji Photo Film Co., Ltd. | Controlled device storing multiple drivers that judges and downloads a particular driver corresponding to a controller's operating system having an identical or greater version number |
| US6194874B1 (en) | 1999-03-17 | 2001-02-27 | Telefonaktiebolaget Lm Ericsson (Publ) | System and method for maintenance charging of battery cells |
| KR100639731B1 (en) * | 1999-09-03 | 2006-10-31 | 엘지전자 주식회사 | Battery packs and how battery packs work |
| KR20010049026A (en) * | 1999-11-30 | 2001-06-15 | 서평원 | Apparatus and method for battery refresh in cordless telephone |
| US6252378B1 (en) | 2000-01-10 | 2001-06-26 | Snap-On Technologies, Inc. | Usage counter for portable jump-starting battery unit |
| GB2368495B (en) | 2000-10-23 | 2004-06-30 | Ericsson Telefon Ab L M | Monitoring circuit |
| US6859012B2 (en) * | 2003-02-21 | 2005-02-22 | Thomson Licensing, S.A. | Battery charging apparatus |
| US20050037241A1 (en) * | 2003-08-15 | 2005-02-17 | Intersil Americas Inc. | Power source selector and controller for multiple battery power supply |
| US20060226812A1 (en) * | 2005-03-30 | 2006-10-12 | Joseph Patino | Method and system for charging batteries with improved cycle life |
| US7804278B2 (en) * | 2007-02-16 | 2010-09-28 | O2Micro International Ltd. | Topology and method for dynamic charging current allocation |
| US20080301483A1 (en) * | 2007-05-28 | 2008-12-04 | Sandisk Il Ltd. | Surge-Protected Peripheral Devices |
| CN106785129B (en) * | 2016-11-11 | 2019-03-29 | 常州普莱德新能源电池科技有限公司 | Real-time statistical method, system and the electric vehicle of power battery charge and discharge number |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT331357B (en) * | 1974-01-11 | 1976-08-25 | Jungfer Akkumulatoren | ELECTRICAL DISPLAY DEVICE FOR THE CHARGE STATE OF A SECONDARY BATTERY |
| AT346429B (en) * | 1976-11-16 | 1978-11-10 | Jungfer Akkumulatoren | ELECTRICAL DISPLAY DEVICE FOR THE CHARGE STATE OF A SECONDARY BATTERY |
| DE2902334A1 (en) * | 1979-01-22 | 1980-07-31 | Siemens Ag | Digital integrated nickel cadmium accumulator charge monitor - employs bidirectional counting of clock pulses actuated by current flowing to or from accumulator |
| DE3031887C2 (en) * | 1980-06-28 | 1984-09-20 | Lucas Industries Ltd., Birmingham, West Midlands | Procedure for charging a traction battery |
| DE3049047A1 (en) * | 1980-12-24 | 1982-07-01 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Automatic charging system for accumulator battery - has pulse counter for charging pulses and electronic control for actuating recharging or maintenance charging |
| US4455523A (en) * | 1982-06-07 | 1984-06-19 | Norand Corporation | Portable battery powered system |
| US4679000A (en) * | 1985-06-20 | 1987-07-07 | Robert Clark | Bidirectional current time integration device |
| FR2586482B1 (en) * | 1985-08-23 | 1988-02-19 | Abiven Jacques | DEVICE FOR MONITORING A BATTERY |
| GB8625035D0 (en) * | 1986-10-18 | 1986-11-19 | Husky Computers Ltd | Battery charge state monitor |
| EP0288013A1 (en) * | 1987-04-21 | 1988-10-26 | Siemens Aktiengesellschaft | Apparatus for charging a battery |
| EP0307117B1 (en) * | 1987-08-27 | 1995-04-19 | Nec Corporation | Battery status indicating arrangement |
| US5136620A (en) * | 1990-12-31 | 1992-08-04 | Eaves Stephen S | Battery charge cycle counter |
| US5117173A (en) * | 1991-02-22 | 1992-05-26 | Motorola, Inc. | Integrated battery cycle counter |
| DE4112987C2 (en) * | 1991-04-20 | 1995-02-23 | Bosch Gmbh Robert | Device for determining the state of charge of a rechargeable battery |
| US5440221A (en) * | 1992-07-08 | 1995-08-08 | Benchmarg Microelectronics, Inc. | Method and apparatus for monitoring batttery capacity with charge control |
-
1995
- 1995-06-20 US US08/492,552 patent/US5617008A/en not_active Expired - Fee Related
-
1996
- 1996-04-26 WO PCT/US1996/005742 patent/WO1997001195A1/en not_active Ceased
- 1996-04-26 AU AU55736/96A patent/AU689721B2/en not_active Ceased
- 1996-04-26 CA CA002198013A patent/CA2198013C/en not_active Expired - Fee Related
- 1996-04-26 EP EP96913133A patent/EP0777916A4/en not_active Withdrawn
- 1996-04-26 CN CN96190657A patent/CN1157058A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| US5617008A (en) | 1997-04-01 |
| AU689721B2 (en) | 1998-04-02 |
| WO1997001195A1 (en) | 1997-01-09 |
| CN1157058A (en) | 1997-08-13 |
| CA2198013A1 (en) | 1997-01-09 |
| EP0777916A4 (en) | 1998-09-02 |
| EP0777916A1 (en) | 1997-06-11 |
| AU5573696A (en) | 1997-01-22 |
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