Note: Descriptions are shown in the official language in which they were submitted.
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- This in~ention relates t~o battery charging, and more
particularly to the charging of: batteries connected together
in series.
Many electrical systems utllize batteries connected in
series to provide two output voltages. For example, diesel
~' powered trucks, marine equipment, and others utilize a 24 -
volt or higher supply for starting engines, etc., but require
-, onlyjl2 volts for the remaining electrical components.
;, In such systems there is presented the problem of pro-
viding proper charging of each battery, since theyrequire
different amounts of charge. For example, the battery pro- -;
viding the higher voltage output for engine starting generally
is used much less than the othe~ and therefore it requires
only a few minutes of charge to replace the 109s. The battery
providing the lower voltage output also ls used for engine
starting, but has the added demand of the remaining electrlcal
system, and therefore it requires more eharge.
~t~ T~us, ~or example, if a regulated 24 volt charge ~rom an
alternator is applied a~ the positive terminal of the higher
voltage output battery, the latter becomes ~ully charged be~ore
the lower voltage output battery. However, the voltage regu-
~i ~ lator sees only the voltage drop across the series-connected
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batteries, and there~ore allows the alternator to continue
charging until said voltage is satisfied. As a result~ the
higher voltage battery is overcharged and the lower voltage
output batte~ is undercharged, causing premature damage to
othbQtteries.
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' Efforts have been made heretofore to achieve proper
charging of each battery in dual battery systems. For example
switching systems have been provided for connecting the batt- ;
~ eries in series for starting engines, etc., and for connect-
', inging the batteries in parallel for charging. However, the ' :
additional electrical resistance contributed b~ the switch
results in the higher voltage output battery being maintained ''
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in an undercharged condition. The use of two alternators''~ ~'
', in an attempt to balance the loads, also has been found
'~, unacceptable. 'Special alternators of complex and costly, , ',
, circuitry and,physical design have been found to be econom- ~ '
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,!,j ically impracticable. ,
,, Equally unsatisfactory have been the attempts to cir- ',
i~ cumvent the battery charging problem by using high powered '
~ 12 volt starter systems, or by utilizing straight 24 voltage '~ ;
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~ systems,for charging and for all other components o the , '~ ,
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, electrical system. " , ~' ;
~;';; ~ SUMMARY OF THE INVENTION
,~ In its basic concept, this inven~ion providesa charge
, control for series-connected batteries in which the voltage
drop across the battery providing the higher voltage output
~ is utilized at a predetermined,value to switch the oharging
,, ' currant from the series-connected batteries to only the
I `~ , battery providing the lower voltage outpu~.
It is by virtue o~ the foregoing basic concept that the
principal objective of this invention is achie~ed; namely, ,,
to overcome the aforementioned difficulties and disadvantages ' '
o~ prior c~arging systems.
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Another obvect of this invention is the provision of a
dual battery charge control which is operable with conven-
tional generators and alternators as well as with conventional
voltage regulators.
Still another objective of this inven~ion is the pro-
vision of a dual battery charge control which functions
automatically to achieve proper charging of each battery
in a dualbQttery system. ~-
A further obJect of this invention is the provision of
a dual battery charge control which is of simplified con- -
i struction for economical manufacture. -~
;,~ The foregoing and other objects and advantages of this -
invention will appear from the following detailed description,
taken in connection with the accompanying drawings of pre-
ferred embodiments.
Fig. l is a schematic electrical diagram showing asso-
ciated with series-connected batteries and a conventional
alternator a dual battery charge control embodying the features
of this invention. ;
Fig. 2 is a fragmentary schematic electrical diagram
showing a modification o the charge control of Fig. 1 to
accommodate use of a conventional original equipment voltage
t~ regulator.
I; Figs. 3 and 4 are fragmentary schematic electrical dia-
i~ gr~ms show.ing a modification of a conven~ional voltage regu-
lator circuit and alternative connections thereof ~o the
battery and alternator system for association w;th the charge
control of this invention.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 1 of the drawings, two batteries
10 and 12 are shown connected together in series. The nega-
tive terminal of battery 10 is connected to common ground,
the positive terminal of said battery and the negative
terminal of the battery 12 are connected together at a -
common junction 14. An electrical conductor 16 extends from
this junction to supply an electrical system with the lower
voltage output from battey 10. The positive terminal of the
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other battery 12 is connected to an electrical conductor 18
! which supplies an engine starter or other load with the
higher voltage output provided by the serles-connected ~ ;~
batteries. Thus, for example, with each battery providing a
~;~ 12 volt output, the conductor 16 provides 12 volts to an
electrical system, while the conductor 18 provides 24 volts
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~ to an engine starter or other electric load.
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~ Figo 1 also illustrates a convantional alternator 20
: which is mechanically activated by a vehicle or other drive
engine, as by coupling thereto through a belt and pully arr-
angement, as will be understood. It will be appreciated that
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the alternator may be replaced by a conventional generator.
;~ The alternator illustrat~d i9 provided with a ground terminal
22 for connection to common ground; a power output terminal
~ - 24 ~or delivering charging current to the batteries; and a
¦ ~ield termlnal 26 ~or connection of power ~rom a voltage
regulator 28.
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The voltage regulator illus~rated is of conventional
design and includes the transistor 30 which is biased normally
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on, the transistor 32 which is biased normally o~f, the res-
istors 34, 36, 38, uncontrolled diode 40, zener diode 42,
and voltage detecting resistors 44, 46 and 48. The voltage
regulator is provided with a ground terminal 50 for connection 1;
to common gr~nd; a field supply terminal 52 for connection to ~-;
the field windings of the alternator; a power input terminal
54; and a sensing signal input terminal 56 for connection of
an external sensing signal.
Ordinarily, the sensing signal terminal56 of convention-
al, original equipment regulators is not available for
external connection. Accordingly, the charge control circuit
and voltage regulator circuit of Fig. 1 are manufactured as -
an integral unit.
The power output terminal 24 of the alternator is co~-
nected to the positive terminal of battery 12 through an
uncontrolled diode 58. This diode functions upon attainment
of a predetermined voltage at the output terminal 24 to
conduct charging current to the positive terminal of battery
. . .
12, thence ~hrough said ba~tery to the common junction 14,
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~ thence through battery 10 to common ground.
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'~ In accordance with this invention, means is provided for
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switching the output terminal 24 o~ the alternator to the
common junction 14 upon attainment o~ a predetermined voltage
drop acro~s tha battery 12 providing the higher voltage output,
whereby ~o direct charging current only through the battery
10 providing ~he lower voltage output. In the general con- ; .
cept of this invention, this i9 provided by ele~trically
actuated switch means which removably connects the output
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of the generating means to said common junction, and by
electrical switch actuator means which is connected across
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the battery providing the higher voltage output and which is
responsive to a predetermined voltage drop across said battery
to activate the switch means to connect the output of the
generating means across only thebattery providing the lower
voltage output.
In the specific embodiment illustrated in Fig. 1, the
electrically actuated switch means is provided by a silicon
controlled rectifier 60 which interconnects the power output
terminaI 24 of the alternator and t~e co~mon junction 14
between the~atteries. The silicon eontrolled rectifier is
normally off; hence, the switch means is normally open. ;~
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The electrical switch actuator means or turning on the
~j~ silicon controlled rectifier 60 includes the voltage detecting
resistors 62, 64 and 66, the zener diode 68, the transistor 70
which is biased normally off, and the resistor 72 w~ich inter- ;
connects the transistor collecDr and the gate of the silicon
controlled recti~ier 60.
The charge control of this i~vention also may include a
second electrical swltch actua~or means for turning off the
silioon controlled rsctifier 60 ~returning the switch means to
its normally open eondition). In Fig. 1 ~his turn off control
includes the transistor 74 which is biased normally off, the
,¦ resistor 76 which lnterconnects the transistor collector and
the sensing signal terminal 56 of the voltage regulator, and
¦i~ the resistors 78, 80 and 82 which, by connection across the
~, ~ batteriss 10 and 12, form therewith a bridge network.
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The operation of the charge control illustrated in Fig.
l is as follows: With the alternator 20 being driven mechani-- -
cally by the engine, the normally conducting transistor 30
of the voltage regulator provides power through terminals 52
and 26 to the alternator fields, thereby producing charging
current at the alternator output terminal 24. Since the
silicon control rectifier 60 is not conducting, charging ~
current from the output terminal cannot get through to the ; ~ -
common junction 14. Accordingly, voltage continues to rise
at the output terminal until the diode 58 conducts. There-
upon charging current is conducted through the series- .
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, connected batteries 12 and 10 to common ground. Both batteries
thus are charged.
In the normal operation of the voltage regulator, when
the voltage across the battery~10 providing the lower voltage
output reaches a predetermined value, as sensed by the voltage
regulator resistors 4~ 46 and 48, zener diode 42 fires, caus-
ing the normally off transistor 32 to conduct. The normally
on transistor 30 thus is turned off, causing the alternator
1~ ~ ~ fields to weaken and the output voltage to drop. When the
~, voltage across the battery 10 provlding the lower voltage
output drops slightly, zener diode 42 ceases conduction, ther~ , ;
by turning off the transistor 32 and turning on translstor 30,
l~ allowing the alternator output voltage to be controlled.
jl ~ ! When the voltage across the battery 12 providing the
higher voltage output reaches a predetermined value, as sensed
by resi$tors 627 64 and 66, zener diode 68 is caused to ~ire,
turning on transistor 70. Activation of this transistor
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effects activation of the silicon controlled rec-tifier 60. ~
Charging current thus is directed from the output terminal '
24 of the altern~r to the common junction 14. Since the
voltage at the output terminal 24 drops to a predetermined '
value lower than the voltage at the positive terminal of ; '
battery 12, the diode 58 ceases to conduct. Charging current '
through the battery 12 providing the higher voltage output
thus is stopped. Charging current from the output terminal
24 thereupon is directed through the activated silicon'control- ''
led rect~ier 60 to junction 14 to continue charging the
battery 10 providing the lower voltage output. This occurs l
because, thoug'h the voltage at the base of'trans~istor 70
drops to turn the latter off, thereby removing the control
signal from the gate of the silicon control rectifier 60,~the
latter is conducting direct current and there~ore continues
in its~abtivated state.
When the voltage at the output terminal 24 of the alter- r
nator drops to a predetermined value relatl~e to the common
junction 143 current sto*s flowing.
When the voltage across the battery 12 is providing the
higher voltageoutput drops (the voltage across the battery 10
providing the lower voltage output remains at regulated vol-
tage), the base of transistor 74 goes negative to a predeter- ' ' '
m'ined value wlth respect to the common junction 14, as d~ter- ''
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mlned by the bridge network, transistor 74 is activated. This
in turn, effects firing o~ zener diode 42, ther~y acti~ating
transistor 32 and deactivating transistor 30. The alterna- '
~ ~ tor output thus is stopped, ~hereupon ~he silicon controlled ' '
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rectifier 60 is deactivated.
When the voltage across the battery ~ providing the
lower voltage output starts to drop, the base of transistor
74 become more positive with respect to the common junction
14, whereupon transistor 74 is turned off. The voltage
regulator thereupon assumes control and the voltage at the
I . alternator output terminal 24 rises until diode 58 conducts,
whereby once again to.re-establish the series charge through
the batteries 10 and 12.
It will be understood that the turn-off control for the
silicon controlled rectifier may be omitted for some appli- .. :
cations as, for example, when the battery providing the -:;.
higher voItage output is used only for starting and engine ; .
j - and charging is not.needed until after a subsequent start.
¦ : In such applications the silicon controlled rectifier.is
~ : tuxned off simply by stopping the engine. .
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.: ~ig. 2 illustrates a modification of the turn-off control .:.
for the silicon controlled rectiier, to accommodate the use
of an original equipment voltage regulator 2Br, rather than
incorporating a voltage regulator in the charge:control, as ;:
in Fig.. l. For this purpose a transistor 84 is interposed ~.
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between the collector of transistor 74 and the power input
terminal 54 o~:the voltage regulator. Thus, when the voltage
across the battery 12 providing the higher voltage output . . ~ .
drops, the base o~ txansistor 74 goes negativewith respect
to the common junction 14, activating the transistor 7~. This
effects deactivation of transistor 84 which is biased normal- , :
ly on. Deactivation o transistor 84 removes power input to.
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the regulator and effects deactivation of transistor 30,
thereby stopping power to the alternator fields and deacti-
vating the alternator and silicon controlled rectifier.
Fig. 3 illustrates a modification of the voltage regu-
lator arrangement shown in Fig. 1. Thus, the conductor 86
interconnecting the resistors 36 and 44 in Fig. 1 is re-moved,
and the voltage regulator power source is provided by the
conductor 88 connected to the output terminal 24 of the :~
alternator. This arrangement is desirable for situations
wherein more efficient charging at the higher potential is
required, as for example when the battery 12 providing the
higher volta6e ~tput su~ies other loads in addition to
engine starting. Regulator senslng across batter~ 10, through
~ransistor 74, is utilized as in Fig. 1.
Fig. 4 illustrates a further modiication of Fig. 1 to
accommodate the use of original equipment alternators 20~
which are designed for the nominal voltage~of the sum of the ,-
two serles-connected batteries. In this arrangement, as in
Fig. 3, the oonductor 86 interconnecting the resistors 36
and 44 in the voltage regulator o~ Fig. l is omitted. How-
ever, power source for the voltage regulator is supplied
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; through conductor 90 connected direc~ly to the higher voltage
~ ~ ~erminal of ~attery 12.
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From the foregoing it will be appreciated that the present
invention provides a charge control of simplified and there-
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~ ~- fore economical construction whlch unctions effectively to
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provide precise charging o~ each of a pair o batteries con-
nected together in séries, and is versatile in its applicabili~
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~ ty to a wide variety of conventional charging systems.~
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It will be apparent to those skilled in the art that
various changes may be made in the type, number, and arrange-
ment of components described hereinbefore~ For example, the
control may be provided for use with positive ground systems,
by substituting NPN type transistors for the PNP types illus- -
trated, and reversing the polarities of the diodes. The
original equipment voltage regulator 28' o Fig. 2 may be ~ ;~
integrated with the associated control circuitry, if desired.
The control may be associated with any desired combination
of battery voltages other than tihe lZ volt batteries 10 and
12 described. For example, with battery 10 being 12 volts,
battery 1~ may be 6 volts to provide a total of 18 volts; ~-
20 volts to provide a total o~ ~ volts; 24 volts to provide
a total of 36 volts; and many other combinations. These and ,
other changes may be madé without dieparting from the spirit
of this invention. -
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