Note: Descriptions are shown in the official language in which they were submitted.
2~2~
Ml-:T~lOD AND APPARATUS FOR C~ARGING A BATTERY IN
IIIGH AMP AND AUTOM~TIC ClkARGING MODES
FIELD OF THE INVENTION
_
This invention relates to battery chargers and more
particularly to automotive battery chargers and the like
including means for sensing the state of charge of a battery
and interruptLng the charging cycle when the battery has been
fully charged.
BACKGROUND OF THE INVENTION
Some battery chargers used in applications such as in
charging automotive batteries and the like include means fox
supplying a high charging current to the battery, for example,
40 amps to provide for rapid charging of the battery. They
may include means for reducing the charge being supplied to the
battery once the voltage of the battery has reached a
predetermined voltage. For example, in a conventional 12 volt
au~omatic battery charger, the c~arge is reduced to 0.1 amps or
less once the voltage of the battery reaches approximately 14.4
volts. The reduced charge of 0.1 amps or less is then
continuously supplied to the battery to maintain the charge on
the battery. In operation of these battery chargers, if the
battery charger continues to supply a low current charge to the
battery for extended periods of time, the water in the battery
will be converted to hydrogen and oxygen which is dissipated
6 ~ ~
from the ba~tery causing damage to the battery. In addition,
if the battery charger continues to supply a low current charqe
r to the battery for extended periods of time, the grids of the
hattery being charged will corrode at an accelerated pace,
thereby causing the battery to ail prematurely. On the other
hand, if the battery is left uncharged for a long period of
time, self discharge of the battery will cause the active
material of the battery to sulfate, thus also causing
irreversible damage to the battery.
Some battery chargers of the type including means for
sensing the state of charge of a battery and interrupting the
charging cycle when the battery has been fully charged further
include means for continuing to monitor the state of charge of
the battery and for automatically restarting the supply of
charging current to the battery when the battery's state of
charge is below full charge.
Another type of battery charger supplies only
relatively small charges to a battery, for example a charge at
the rate of 10 amps, and includes means for sensing the charge
of the battery and means for shutting off the charging current
to the battery once the voltage of the battery reaches a
predetermined voltage, for example 14.4 volts. The battery
charger will then continue to sense the charge of the battery
and if that voltage falls below a predetermined voltage, the
charger will once again supply a charging current to the
battery until the voltage of the battery is raised to 14.4
volts, and is again interrupted.
In other battery chargers, means are provided for
supplyinq a charge to the battery at a relatively high rate of
charge, such as at approximately 40 amps, or alternatively at a
2~2~6~
--3--
lower rate s~lch as at 10 to 15 amps. These battery chargers
commonly include a switch or control permitting the operator to
select the operating mode of the battery charger such that it
operates at either a high current rate or at a lower current of
approximately 10 to 15 amps.
Other bat~ery chargers have included means for
charging the battery at a high rate of charge and alternative
means for charging the battery at a lower rate, and further
including means for timing the selected rate of charqe. In
these chargers the battery is then charged at the selected rate
of charge until the timer turns off the charger.
_MMARY OF THE INVENTION
The present invention provides an improved battery
charger including means for alternatively supplying current to
a battery at a relatively high rate of charge, i.e. at a high
current, to provide for rapid charging of the battery, and at a
lower rate of charge, i.e. at a lower current, the charger
including means for sensing the relative charge of the battery
and means for switching off or severing the current to the
battery whenever the battery is being charged at the second
rate and the sensed charge of the battery exceeds a first
predetermined threshold voltage. The means for sensing also
continues to monitor or sense the charge on the battery and
causes a charging current to be supplied to the battery in the
event that the charge of the battery falls below a second
predetermined threshold voltage, i.e. slightly below a full
state of charge.
In another aspect of the invention, a timer means is
i6
provided for causing the means for chargirlg at the high rate of
charge to operate for a predeterm.ined time period, and for
thereafter causing the means fox charging at the lower rate
(automatic current on/off) to opera~e.
In another aspect of the invention, means are provided
for adjllsting the firs-t predetermined thre~shold voltage (at
which threshold the current to the battery is switched off),
the adjusting means comprising a continuously variable selector.
In another aspect of the invention, means are provided
for adjusting the second predetermi.ned threshold voltage ~a~
which threshold the current to the battery is switched on).
The means for adjusting the second predetermined threshold
voltage comprises a continuously variable selector in one
aspect of the invention.
In another aspect of the invention, the battery :
charger includes first; second, and third discrete visual ::
indicators, means for illuminating the fi.rst indicator in -
response to the battery charger being connected to a so~lrce of
alternating current, means for illuminating the second
indicator while the current supplying means supplies charging
current to the battery at the second current rate, and means
for illuminating the third indicator in response to the
severing means severing the supply of charging current to the
battery while the second (i.e. automatic) charging xate has
been selected. The third indicator, when illuminated by the
third mentioned illuminating means, thereby provides a visual
indication that the second charging rate (i.e. automatic mode
has ~een selected, and that the current supplying means will
resume th~ supply of charging current to the battery when the
sensing means senses battery voltage below the second
~2~
predeterlnined voltage~
In ano~her aspect of the inventi.on, t:he current
supplying means compr.ises a transformer having a pr.imary
winding adapted to be electrically connected t:o a source of
alt:ernati~g cllrrent, and a secondary winding adapted to be
electrically connected to the battery, and the severing means
includes relay contacts operative to open to interrupt curxent
flow through the primary winding of the transformer to sever
the supply of charglng current to the battery when the sensing
means senses battery voltage in excess of the upper
predetermined threshold voltage.
One aspect of the invention provides a method of
charging a bat-tery comprising the steps of providing means for
supplying charging current to the battery, the current
supplying means being operable to alternatively supply current
at a first rate and at a second rate, selecting one of the .
first rate and the second rate, electronically severing the
supply at charging current to the battery when the second rate
is selected and when the battery voltage exceeds a first
predetermined threshold voltage, and electronically resumlng
the supply of current to the battery at the second rate when .
the battery voltage falls below a second predetermined
threshold voltage lower than the first predetermined threshold
voltage.
Another aspect of the invention provides a method of
charging a battery comprising khe steps of providing means for
supplying chargi.ng current to the battery, the current
supplying means being operable to selec-tively supply current at
a first rate of at least 30 amps and at a second rate,
selecting the first rate for a selected period of time and
-`` 2~2~
--6--
.. . .
~hereafter selecting the second rate, electronically severing
the supp1y of charging current to the battery when the second
rate is selected and when the battery voltage exceeds a first
predetermined threshold voltaqe, and electronically resuming
the supply of current to the battery at the second rate when
the battery voltage falls below a second predetermined
threshold voltage lower than the first predetermined threshold
voltage.
A further aspect of the invention provides a method of
. . .
charging a battery comprising the steps of providing means for
supplying at least 14 amps of charging current to the battery,
electronically severing the supply of charging cùrrent to the
battery when the bat-tery voltage exceeds a first predetermined -~
threshold voltage, and electronically resuming the supply of
current to the battery when the battery voltage falls below a
second predetermined threshold voltage lower than the first
predetermined threshold voltage.
These and other features and advantages of the
invention will become apparent to those of ordinary s~ill in
the art upon review of the following detailed description of
the preferred embodiment of the invention, which is given by
way of example, reference being made to the appended drawings.
BRIEF DESCRIPTION OF THE
VIEWS OF THE DRAWINGS
Fig. l shows a circuit schematic of a battery charger
embodying a first embodiment of the invention.
Fig. 2 shows a circuit schematic of an alternate
embodiment of the invention.
Before these embod;ments of the invention are
e~plained in detail, it is to be understood that the invention
is not limited in its application to the details of
construction, arrangement of components, and component values
set forth in the following description or illustrated in the
drawings. The invention is capable of o-ther em~odiments and of
being practiced and carried out in various ways. Also, it i5
to be understood that the phraseology and terminology employed
herein is for the purposa of description and should not be
regarded as limiting.
DE~AILED DESCRIP~ION OF THE PREFERRED
EMBODIMENT OF THE INVENTION
Shown in Fig. 1 is a circuit schematic of a battery
charger 10 embodying the invention. The charger 10 of the
illustrated e~bodiment is adapted to be used with a standard
twelve volt automotive battery 12 having a positive terminal
12A and a negative terminal 12B.
The battery charger l0 includes means for sensing the
vol~age of the battery 12 when the battery 12 is electrically
connected to the charger 10. In the preferred embodiment, the
sensing means comprises a first and second voltage comparator
IClA and Icls. The comparator IClA is used to determine if the
sensed battery voltage is in excess of a first predetermined
threshold voltage, and the comparator IClB is used to determine
if the sensed battery voltage is below a second predetermined
threshold voltage. Although the comparators IClA and IClB of
the illustrated embodiment are part of a dual comparator
package, discret~ comparator packages could be used.
.
:
2 ~
The battery charger 10 further includes a voltage
divider compr.isinc3 resistors R13 and R14. The voltage across
the battery 12 ~i.e. across the positive and negative terminals
l~A and l2s, respective1y, of the battery) is applied, via a
fuse F1 (included in the charger 10), to the voltage divider
comprisinq R13 and R14. The charger 10 further includes an
electrolytic capacitor C1 in parallel connection with the
resistor R14, the parallel combination of R14 and Cl being
connected between R13 and the negative terminal 12B of the
batt:ery 12. The voltage that appears across the capacitor Cl,
using the illustrated component values, is 41~ of the battery
voltage and is applied to the non~inverting input, pin 3, of
compara~or IClA, through a resistor R7 ~that i9 included in the
charger 10). The voltage that appears across the capacitor Cl
is also applied directly to the non-inverting input, pin 5, of
the comparator IClB. The positive supply terminal, pin 8, of
the co~parators IClA and IClB i~ connected to a positive supply
voltage, which is preferably a regulated voltage. The n0gative
supply terminal, pin 4, of the comparators IClA and IClB i5
connected to ground, in the illustrated embodiment. The
output, pin 7, of the comparator IClB is connected to the
non-inverting input, pin 3, of the comparator IClA via a
s~itching diode D3 included in tha charger 10. More
particularly, the anode of the diode D3 is connected to the
non-inverting input, pin 3, of the comparator IClA, and the
cathode of the diode D3 is connected to the output, pin 7, of
the comparator IClB.
qhe battery charger 10 further includes a diode D1
having an anode connected to the output, pin 1, of the
comparator IClA. The charger 10 further includes a resistor R2
connected be~ween the cathode of the diode Dl and the
non-inverting input pin 3, of the comparator IClA.
The sensing means ~urther includes means for adjusting
the first threshold voltage, the adjus~ing means comprising a
continuously variable selector. In the illustratecl embodiment,
the means for adjusting the first threshold voltage comprises a
potentiometer P2 variable at the inverting input, pin 2, of
comparator IClA and having one end connected to a reference
voltage via a resistor R9, and another end connected to ground
via a resistor R1, the resistors R1 and RS being included in
the sensing means. Preferably, -the irst reference voltage is
a regulated voltage, and when the illustrated component values
are used, is regulated to be 6.8 volts.
The sensing means further comprises means for
adjusting the second predetermined threshold voltage. More
particularly, the means for adjusting the second predetermined
threshold voltage comprises a continuously variable selector.
~ore particula~ly, the means for adjusting the second
predetermined threshold voltaqe comprises a potentiometer P1
variable at the inverting input, pin 6, of the comparator IC1
and having one end connected to a second reference voltage via
a resistor R16, and another end connected to ground via a
resistor R15, the resistors R16 and R15 being included in the
sensing means. Preferably, the second reference ~oltage is a
regulated voltage, and, in the illustrated embodiment, the
second reference voltage is the same as the first reference
voltage.
Thus, the first and second predetermined threshold
voltages, ~hich are used to determine ~hen the charger 10
should stop and start charging, as will be outlined below, can
~2~
-10-
be adjusted in view of battery type or temperature (a battery
vol~age that represen~s a fully charged battery at one '!
~emperature does not necessarily represent a fully charged
battery at another temper~ture). In one embodiment of the
invention, the potentiometers Pl and P2 are acces.sible to the
user of the charger 10. In another embodiment, P1 and P2 are
adjustable by the manufacturer of the charger 10 (for use of
the charger 10 with a specific type of battery, for example)~
Using the illustrated component values, the first predetermined
. . .
threshold is ~djustable between 13.6 ~nd 16.2 VDC, and the
second predetermined threshold is adjustable between 13.6 and
i2.1 VDC.
The battery charger 10 further includes means for
regulating voltage so that the first and second predetermined
threshold voltages do not change. The illustrated voltage
regulating means includes voltage regulator IC2, which provides
~8 volts (DC) in the illustrated embodiment, connected to the
battery, and a zener diode D4 that is fed by the voltage
regulator IC2, through a resistor R17 that is also included in
the regulating means. In the illustrated embodiment, the diode
D4 is a 6.8 volt zener diode. The 8 volts set by the voltage
regulator IC2 supplies the comparators XClA and IClB at pin 8,
while the 6.8 volts set by the zener diode D4 is used as the
first and second reference voltage with the potentiometers Pl
and P2. The first and second predetermined threshold voltages
are thus kept stable over a range of variations of loads on the
charger 10 and temperatures.
The voltage regulating means further includes a
silicon rectifying blocking diode D2 supplying current to the
voltage regulator IC2 from the positive terminal 12A of the
ba~tery 12 via the fuse Fl. The diode D2 prevents the charger
10 from a~tempting to char~e the battery 12 if the battery is
connec~ed back~ards and the battery voltage polarity is
reversed. The voltage regulating means further includes a
capacltor C2 connected between one end of the resistor R17 and
ground, and a capacitor C3 connected between the other end of
-the resistor R17 and ground, the capacitor C3 being provided to
filter out potential electrical noises.
The battery charger 10 includes means for supplying
charging current to the battery, the current supplying means
being operab.le to alternatively 5upply current at a first and
second rate, the first rate providing for high rate charying of
the battery, i.e., at least 30, and preferably 40, charging
amps - charging amps being defined as amps supplied to the
battery while the battery is being charged as opposed to being
boosted, and the second rate being at least 14, and preferably
15, charging amps.
In the illustrated embodiment, the current supplying
means comprises a transformer X1,~ such as transformer having a
primary winding XlA having a first end XlAA, a second end XlAC,
and a tap XlA8 between the first end XlAA and the second end
XlAC, and adapted to be electrically connected to household
alternating current (e.g. 120 VAC), and a secondary winding XlB
adapted to be electrically connected to the hattery 12. In the
illustrated embodiment, the ratio of the number of turns
between the tap XlAB and the second end XlAC to the number of
turns of the portion of the secondary winding XlB that can ~:
supply cu~rent to the battery 12 at any one time ~i.e. between
the centertap of the secondary winding XlB and the anode of one
of the diodes D6 or D7) is 7.88:1, and the ratio of the number
.
,
-12-
of turns of the entire primary winding XlA to t:he portion of
the secondary wi.nding XlB that can supply current to the
battery 12 at any one time (i.e. between the centertap of the
secondary winding XlB and the anode of one of the diodes D6 or
D7) is 9.41:1. The charger 10 includes diodes D6 and D7 having
anodes respectively connected to opposite ends of the secondary
winding XlB. The diodes D6 and D7 have cathodes that are
adapted to be connected to the positive terminal 12A of the
battery 12 to supply positive current to the positive terminal
12A. The secondary winding XlB includes a centertap collnected
to the negative terminal 12B of the battery to supply negative
current to the negative terminal 12B. The charger 10
optionally, but preferably, further includes an ammeter A
connected to the secondary winding XlB for series connection
with the battery 12.
More particularly, in the .illustrated embodiment, when
the first charging rate i.s selected, only the portion of the
primary winding X1A between the tap XlAB and the end XlAC of
the primary wincling XlA is energiæed with 120 volts of
alternating current. When the second charging rate is
selected, the entire primary winding XlA, between the ends XlAA
and XlAC, is selectively energiæed with 120 volts of
alternating currentO
The charger 10 further includes means for severing
(i.e., æero current, no trickle current) the supply of charging
current from the transformer Xl to the battery 12 when the
second charging rate is selected and when the sensing means
senses battery voltage and for resuming the supply of current
to the battery at the second charging rate when the severing
means senses battery voltage below the second predetermined
,
2~2~5~
-13-
threshold volta~e.
Al~hough one skilled in the art will readily realize
that alternative embodiments are possible, the sensing means
and the severing means of the illustrated embodiment are used
exclusively when the second chargin~ rate has been selected.
In the illustrated embodiment, the severing means
includes a relay K1 having contacts 23 and 22 operative to open
to sever current flo~ through the primary winding of the
transformer to sever the supply of charging current -to the
battery when the sensing means senses battery voltage in excess
of the first predetermined threshold voltage. In the
illustrated embodiment, the relay!K1 is rated for 10 amps
through and 120 volts AC across the contacts 20 and 22. The
relay Kl further includes a coil 24. Application of 12 vol~s
across the coi.l ~4 results in the clo~ing of the contacts 20
and 22. ~he contacts 20 and 22 open when the coil 24 is not
energized (i.e. when no voltage is applied across the coil
24). The coil 24 has a first end 26 connected to the cathode
of diode D2, and a second end 28. The contact 20 is connected
to the end XlAA of the primary winding XlA.
The severing means further includes a correct
transistor Ql having an emitter connected to the voltage
regulating means. More particularly, the emitter of -the
transistor Ql is connected to the ~8 volts output of the
regulating means. The transistor Ql also has a base connected
to the output, pin 1, of the comparator IClA, via resistor R4.
The severing means further includes a resistor R5 connected
between the emltter and the base of the transistor Q1, as well
as a resistor ~3 connected between the emitter of the
transistor Ql and the output pin 1, of the comparator IClA.
The sev~ing means further includes a npn transistor
Q2 having an emitter connected to ground, a collector, and a
base. The severing means ~urther includes a resistor R11
connected between the base and the emitter of the transistor
Q2j and a resistor ~10 connected between the c:ollector of
transistor Ql and the base of transistor Q2. The severing
means further includes a resistor R12 connected between the
collector of the transistor Q2 and the end 28 of the coil 24.
The severing means further includes a diode DS having a anocle
connected to the end 28 of the coil 24, and a cathode connected
to the end 26 of the coil 24.
In operation, when the voltage of the battery 12 is
less than or equal to the threshold voltage set by the
potentiometer P1, then the output, pin 7, of IClB is pulled
down to zero volts. This pulls the non-inverting input, pin 3,
of the comparator IClA low through the switching diode D3, and
causes the voltage at the output, pin 1, of the comparator IClA
to be pulled down to zero volts. This turns on the pnp
transistor Q1 which turns on the npn transistor Q2, thereby
resulting in the coil 24 of the relay Kl being energized. When
the battery becomes charged, the output, pin 7 of the
comparator IClB will go to +8 VDC, causing the switching diode
D3 to be back-biased. This causes the voltage at the
non-inverting input, pin 3, of the comparator IClA to be
governed by the voltage across the electrolytic capacitor Cl
through the input resistor R7. When the voltage of the battery
12 reaches the threshold voltage set by the potentiometer P2,
the output, pin 1 of the comparator IClA will become +8 VDC.
This turns off the transistors Ql and Q2r de-energizing the
relay Xl and thus disconnecting the 120 VAC source from the
~2~ 6
primary XlA of ~he transEormer X1 of the charger. The sensing
means, regulatinq ~eans, and severing means are powered by the
battery 12 when the charger lO is off (i.e. 120 VAC is not
applied to the primary of the charying transf~rmer), and are
powered by the charger when the charger is on.
The battery charger 10 urther includes means for
alternatively selecting the first charging rate and the second
charging rate.
The battery charger 10 includes lines 50 and 52
adapted to be connected -to a hot and a neutral line,
respectively, of the source of household 12~ volt alternating
current. In the preferred embodiment, the lines 50 and 52
terminate in a 3-pronged connector for connection to the hot
and neutral lines. The 3-pronged connector preferably has a
ground pin connected in a conventional fashion to a cabinet
(not shown) housing the battery charger 10. The line 50 is
connected to an end XlAC of the transformer primary winding XlA.
The means for selecting the first charging rate and
the second charging rate comprises a switch SW manually movable
(by the user of the battery charger) between a position 62
thigh or fask charge mode~ and a position 64 (automatic mode)
to connect the lead 52 to the tap XlAB or to the contact 22,
respectively. When the switch SW is moved to the position 62,
120 volts of alternating current is provided to the transformer
primary between the tap XlAB and the end XlAC. When the switch
SW is ~oved to the position 64, 120 volts of alternating
current is provided to the transformer primary between the ends
XlAA and XlAC, when khe con-tacts 20 and 22 are closed.
Thus, means are provided for alternatively selecting
the first charging rate and thP second charging rate.
20~5~
-16~
Ir~ ~he preferred embodiment, the switch SW is further
manually movable to an "off" position 60 to disconnect the lead
52 from the transformer primary XlA.
The batte~y charger lO further includes first, second,
and third discrete visual indlcators, means for illuminating
the irst indicator in response to the battery charger ~eing
connected to the source of alternating current, means for
illuminating the second indicator while the supplying means
supplies charging current to the battery at the second current
rate, and means for illuminating the third indicator in
response to the severing means severing the supply of charging
cur~ent to the battery while the second (i.e. automatic)
charging rate has been selected. The third indicator, when
illuminated by the third mentioned illuminating means, thereby
provides a visual indication that the second charging rate
(i.e. automatic mode~ has been selected, and that the current
supplying means will resume the supply of charging current to
the battery when the sensing means senses battery voltage below
the second predetermined ~oltage. More particularly, in the
illustrated embodiment, the first visual indicator is a red
neon light, NEl, connected in the battery charger 10 between
the leads 50 and 52, the second visual indicator is an amber
neon light NE2, connected across the primary winding XlA of the
transformer Xl, between the ends XlAA and XlAC, and the third
visual indicator is a green neon light NE3 having one end
connected to the contact 20 and another end connected to the
contact 22. Thus, by way of electrical connections in the
battery charger 10, means are provided for llluminating the
fixst indicator in response to the battery charger being
connected to the source of alternating current, for
-17-
illumillating ~he second indicator while the supplying means
sopplies charging current to the ba-ttery at the second current
rate, and for illuminating the third indicator in response to
the severing means severing the supply of charcling current to
the battery while the second li.e. automatic~ charging xate has
been selected. The third indicator, when illuminated by the
third mentioned illuminating means, thereby provides the visual
indication that the second charging rate (i.e. autornatic mode)
has been selected, and that the current supplying means will
resume the supply of charginq current to the battery when the
sensing means senses battery voltage below the second
predetermined voltage. The red, amber, and green neon
indicators are preferably arranged vertically or horizontally
in traffic light order.
The battery charger lO of the preferred embodiment of
the invention includes a fan 70 connected between the tap XlAB
of the transformer primary and the lead 50, and operative to
cool the battery charger lO ~hen the means for selectively and
alternatively connecting the first and second charging means to
the battery l2 connects the first charging means to the battery
12.
Shown in Fig. 2 i9 an alternative embodiment of the
invention, a portion of which is identical to the embodiment
shown in Fig. l, like reference numerals indicating like
componen~s~ which portion will not again be described in detail.
In the alternative embodiment of the in~ention sho~n
in Fig. 2, the means for alternatively selecting the first
charging rate and the second charqing rate comprises timer
means, including a timer motor, for selectinq the first rate
for a selected period of time and for selecting the second rate
2 ~
-18-
after the selectecl period of time expires. More particularly,
in the illllstrated embodiment, the timer means comprises a
timer Tl operati.ve to connect the lead 52 to the tap XlAB (fast
charge mode) for a per~od of time selected by the user of the
battery charger 10, and to thereafter connect the lead S2 to
the contact 22 (automatic mode). The timer T1 can also be
operated by the user of the battery charger 10 to connect the
second charging means to the battery without the first current
supplying means first being connected to the battery 12. An
appropriate timer Tl is an electromechanical timer such as
Model CX 43706 by Ma].lory Timers, Valparaiso, Indiana; or Model
MS 65 by Corpono and Pons (divisiorl of Eaton Controls
Products), 76530 Grand-Couronne, France.
Various of the features of the invention are set forth
in the following clai~s.
