[0001]The present invention relates to a battery charging profile and more particularly relates to a method and system for dynamically charging a battery to acquire higher backup and to enhance the battery life.
BACKGROUND OF THE INVENTION
[0002] In a lead acid battery which is commonly used in Inverter and UPS application, most important aspect is to acquire maximum possible backup time in minimum possible charging time. This must be done based on the specification of maximum permissible voltage and current levels. These levels are specified by a battery manufacturer. The battery charging parameters are always kept within the permissible limits to get better durability and reliability and to avoid damage to the battery. At the same time the battery must be charged at a faster rate to provide adequate backup without reducing its life. The challenge is to get a decent back up without compromising on battery's life.
[0003] In general, there are three sequential stages in any existing battery profile. The three stages or modes of the battery charging are boost mode, absorption mode, and trickle mode. In the boost mode or constant current mode, certain constant current is pumped which is maximum permitted as per the battery specifications resulting in rise of battery voltage. The current is pumped till the battery voltage increases to the permissible predefined voltage. In the absorption mode or constant voltage mode, the battery voltage is maintained to a predefined level for some predefined time and the current keep reducing itself. In the trickle voltage mode, the battery is kept at an idle voltage level. This is done to maintain the battery at charged

stage during idle operation so that the battery gravity is maintained in the trickle mode.
[0004] In prior art battery charging methods, higher current is not allowed in the boost mode as the battery voltage goes higher hence it is not advisable to pump full current as it may reduce the battery life in long run. The problem associated with such conventional boost mode charging is that the current must be maintained within limits thus reducing the backup. If the current is increased the life of battery is reduced. Similarly, in conventional absorption mode charging, higher absorption time is not allowed because if battery is already charged, it may result in over charging of battery thus compromising on battery life. If the time is kept lower, it may result in under charging of the battery thus reducing the backup time. In conventional trickle mode charging, the battery is kept at the idle voltage level from beginning, which results in lesser backup. If the voltage is kept higher all the time the life of the battery is lost. Such uncontrolled prior art battery charging methods may lead to capacity loss and also reduce the life cycle of battery.
[0005] Hence, there is a need in that art to provide a solution to address all the above mentioned problems. The present invention relates to a method and system for dynamically charging a battery by altering the target battery voltage, target battery current and absorption time as per the battery usage condition and external scenario.
SUMMARY OF THE INVENTION
[0006] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiments and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

[0007] An object of the present invention is to provide a method and system for dynamically charging a battery, which facilitates higher backup and enhances the battery life.
[0008] Another object of the present invention is to provide a dynamic battery charging method and system that is capable of changing a target battery voltage, target battery current and absorption time as per the battery usage condition and external scenario.
[0009] Yet another object of the present invention is to provide a dynamic battery charging method and system that is capable of providing a higher boost current charging from a lower battery voltage thus reducing a charging time.
[0010] Yet another object of the present invention is to provide a dynamic battery charging method and system that is capable of providing a higher absorption time in case of higher battery discharge so that the battery is sufficiently charged.
[0011] Yet another object of the present invention is to provide a battery charging method and system that is capable of providing a higher idle time voltage so that the battery is sufficiently charged in a trickle mode.
[0012] According to one aspect of the present invention, a method for dynamically charging a battery is disclosed. A regulated current is pumped to the battery until the battery voltage rises to a predetermined voltage level and then the current is decreased linearly with respect to the increasing battery voltage until the battery voltage rises to a maximum permissible voltage limit in a boost mode. The battery voltage is constantly maintained for an absorption time period based on a previous discharge level of the battery in such a way to pump adequate amount of charge into the battery in an absorption mode. The battery voltage is maintained at a higher level based on a first predetermined time slab and thereafter the battery voltage

is maintained at an ideal voltage level based on a second predetermined time slab in a trickle mode. The target battery voltage, target battery current and absorption time is changed as per the battery usage condition and external scenario.
[0013] In the boost mode, higher boost current charging is provided from the lower battery voltage to reduce the charging time. The boost current charging is reduced as the battery voltage starts increasing so that the battery stays within the maximum permissible voltage limit. In the absorption mode, the higher absorption time is provided in case of higher battery discharge in such a way that the battery is sufficiently charged. The absorption time period is varied based on the previous discharge level. In the trickle mode, higher idle time voltage is provided for the first predetermined time slab in such a way to increase the backup. The battery is settled at the nominal idle battery voltage for all the idle time after the first predetermined time slab.
[0014] According to another aspect of the present invention, a battery charging system is disclosed which includes an input sense mains transformer and an input signal processor coupled to a microcontroller, a pulse width modulation (PWM) driver and a charging transformer. The system pumps a regulated current to the battery until the battery voltage rises to a predetermined voltage level and decreases the current linearly with respect to the increasing battery voltage until the battery voltage rises to a maximum permissible voltage limit in a boost mode. The system constantly maintains the battery voltage for an absorption time period based on a previous discharge level of the battery in such a way to pump adequate amount of charge into the battery in an absorption mode. The system also maintains the battery voltage at a higher level based on a first predetermined time slab and thereafter maintaining the battery voltage at an ideal voltage level based on a second predetermined time slab in a trickle mode.

[0015] The input sense mains transformer converts an input AC mains to low
voltage via a step down sense transformer. The input signal processor process the
input signals and the battery voltage signal and measures the charging current through
shunt in terms of a shunt voltage. The microcontroller senses all the input signals,
5 measures them and processes the data and drives the PWM signals as per target
current and duty cycle. The PWM driver drives a MOSFET as per signal given from
the microcontroller. The charging transformer high voltage winding side is connected
to a main input and a low voltage winding side is connected to the MOSFET bridge
which is driven through the microcontroller to get the desired charging current. The
10 battery is composed of a lead-acid battery. The battery charging method and system is
capable of changing the target battery voltage, target battery current and the absorption time as per the battery usage condition and external scenario in the boost mode, the absorption mode and the trickle mode.
15 BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The disclosed embodiments may be better understood by referring to the
figures, in which like reference numerals refer to identical or functionally-similar
elements throughout the separate views, further illustrate the present invention and,
20 together with the detailed description of the invention, serve to explain the principles
of the present invention.
[0017] FIG. 1 illustrates a block diagram of a dynamic battery charging system,
in accordance with an exemplary embodiment of the present invention;
25
[0018] FIG. 2 illustrates a circuit diagram of a pulse width
modulation (PWM) driver section of the battery charging system, in accordance with
an exemplary embodiment of the present invention;
6

[0019] FIG. 3 illustrates a flowchart of operations illustrating a method for dynamically charging the battery, in accordance with an exemplary embodiment of the present invention;
5 [0020] FIG. 4 illustrates a detailed flowchart of operations illustrating a method
for dynamically charging the battery, in accordance with an exemplary embodiment of the present invention; and
[0021] FIGS. 5A-5C illustrates a graphical representation of a battery charging
10 cycle, in accordance with an exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The particular values and configurations discussed in these non-limiting
15 examples can be varied and are cited merely to illustrate at least one embodiment and
are not intended to limit the scope thereof.
[0023] In the following, numerous specific details are set forth to provide a
thorough description of various embodiments. Certain embodiments may be practiced
20 without these specific details or with some variations in detail. In some instances,
certain features are described in less detail so as not to obscure other aspects. The level of detail associated with each of the elements or features should not be construed to qualify the novelty or importance of one feature over the others.
25 [0024] The claimed subject matter has been provided here with reference to one
or more features or embodiments. Those skilled in the art will recognize and appreciate that, despite of the detailed nature of the exemplary embodiments provided here; changes and modifications may be applied to said embodiments without limiting or departing from the generally intended scope. These and various other adaptations
7

and combinations of the embodiments provided here are within the scope of the disclosed subject matter as defined by the claims and their full set of equivalents. Like numbers refer to like elements throughout.
5 [0025] The present invention relates to a method and system for dynamically
charging a battery, which facilitates higher battery backup and enhances the battery life. The system is capable of changing the target battery voltage, target battery current and absorption time as per the battery usage condition and external scenario. This present invention, is capable of providing a higher boost current charging from a
10 lower battery voltage thus reducing the charging time and hence increasing the
backup. The method and system provides a higher absorption time in case of higher battery discharge so that the battery is sufficiently charged to increase the backup time. The method and system also provides a higher idle time voltage so that the battery is sufficiently charged in a trickle mode.
15
[0026] Referring to FIG. 1 a block diagram of a battery charging system (10) is illustrated, in accordance with an exemplary embodiment of the present invention. Note that in FIGS. 1-5, identical or similar parts or components are generally indicated by identical reference numerals. The battery charging system (10) generally
20 includes an input sense mains transformer (11), an input signal processor (12), a
microcontroller (14), a pulse width modulation (PWM) driver (16) and a charging transformer (18). In a preferred embodiment the battery charging system (10) is used to charge a lead acid battery which is commonly used in Inverter and UPS application. The lead acid batteries are charged in three stages, which are boost mode (33) or
25 constant current mode, absorption mode or constant voltage mode (35), and trickle
mode (37). Generally, the boost mode applies the bulk of the charge and takes up roughly half of the required charge time, the absorption mode continues at a lower charge current and provides saturation, and the trickle mode compensates for the loss caused by self-discharge.
8

[0027] In a preferred embodiment, the battery charging system (10) is capable
of changing the target battery voltage, target battery current and the absorption time as
per the battery usage condition and external scenario in the boost mode (33),
5 absorption mode (35), and trickle mode (37). The input sense mains transformer (11)
converts an input AC mains to low voltage with the help of a step down sense
transformer. This input sense mains transformer (11) monitors and signal another
circuit, for instance the microcontroller (14) about the presence or absence of the ac
mains voltage. This voltage is then fed to the input signal processor (12) for
10 processing. The input signal processor (12) processes all input signals like AC mains
sense, battery voltage and battery current so that they can be fed to the microcontroller (14) for measurement.
[0028] The battery voltage signal is processed to keep it within sensing range of the microcontroller (14). The charging current is measured through shunt in terms of shunt voltage. The microcontroller (14) senses all the input signals, measures them and processes the data. The microcontroller (14) also drives signals from the PWM driver (16) as per target current and duty cycle. The microcontroller (14) is used to monitor the fault condition and protects the battery charging system (10). The PWM driver (16) drives the MOSFET (17) as per signal given from the microcontroller (14). The PWM driver (16) applies the digital transistor–transistor logic (TTL) signal coming from the microcontroller (14) to power section through the MOSFET gate. Drain of the MOSFET (17) are further connected to the charging transformer (18). The PWM driver (16) is the charge controller that charge the batteries and block reverse current and prevent battery overcharge.
[0029] Referring to FIG. 2 a circuit diagram of the pulse width
modulation (PWM) driver section (16) of the battery charging system (10) is
illustrated, in accordance with an exemplary embodiment of the present invention.
30 The detailed component level schematic of the PWM driver (16) is given in FIG.2 for
9

better understanding. +VBatt and -VBatt are the terminals where battery is connected.
The battery is charged through the PWM driver (16). Although not separately
illustrated, a variety of additional circuitry and features may be included in the battery
charging section of the PWM driver (16) according to the disclosed embodiments. The
5 PWM driver (16) includes output transistors that may be bipolar transistors and/or
external to an integrated circuit device containing other charger elements.
[0030] As noted, the disclosed battery charger circuitry may be part of the PWM driver (16) that integrates most or all of the key portable power components and
10 functionality. The PWM driver (16) provide control signals to the charging
transformer (18) thereby supporting a plurality of charging modes (33, 35 and 37). The charging transformer (18) is the power stage transformer to which mains input is connected on high voltage winding of the transformer (18). At low voltage winding side the MOSFET Bridge is connected. MOSFET (17) are being driven through the
15 microcontroller (14) to get the desired charging current.
[0031] FIG. 3 illustrates a flowchart of operations illustrating a method (20) for dynamically charging the battery, in accordance with an exemplary embodiment of the present invention. The battery is charged through the PWM driver (10) of the battery
20 charging system (10) that provides control signals to the charging transformer (18)
thereby supporting a plurality of charging modes (33, 35 and 37). Initially, regulated current is pumped to the battery until the battery voltage rises to a predetermined voltage level, as indicated at block (22). The current is decreased linearly with respect to the increasing battery voltage until the battery voltage rises to a maximum
25 permissible voltage limit in the boost mode (33), as shown at block (24).
[0032] In a preferred embodiment, the maximum permissible voltage and
current limits are specified by a battery manufacturer, based on design consideration.
The higher boost current charging from the lower battery voltage is provided to reduce
30 the charging time. The boost current charging is reduced as the battery voltage starts
10

increasing so that the battery stays within the maximum permissible voltage limit. For
example, in the boost mode (33) maximum full current of 20A is allowed that gets
reduced down to 4A dynamically and in inversely proportional to rise of battery
voltage.
5
[0033] Thereafter, as indicated at block (26), the battery voltage is constantly
maintained for an absorption time period based on a previous discharge level of the
battery in such a way to pump adequate amount of charge into the battery in the
absorption mode (35). The higher absorption time is provided in case of higher battery
10 discharge in such a way that the battery is sufficiently charged. The absorption time
period is varied based on the previous discharge level. For example, in the absorption
mode (35) the absorption time is dynamically set to as low as 30 minutes and as high
as 4 hours depending upon amount of discharge battery underwent in last discharge
cycle.
15
[0034] The battery voltage is maintained at a higher level based on a first
predetermined time slab and thereafter the battery voltage is maintained at an ideal
voltage level based on a second predetermined time slab in a trickle mode (37), as
illustrated at block (28). The higher idle time voltage is provided for the first
20 predetermined time slab in such a way to increase the backup. The battery is settled at
the nominal idle battery voltage for all the idle time after the first predetermined time
slab. For example, in the trickle mode (37), 6 hours of high idle voltage is allowed
which is then reduced to normal idle voltage thus maintaining the battery in good
charge stage without compromising on battery life.
25
[0035] Note that the embodiments discussed herein generally relate to the lead
acid battery. It can be appreciated, however, that such embodiments can be
implemented in the context of a variety of battery types used for mobile
communication devices and laptops. The disclosed embodiments is also used to
30 charge batteries other than SMF Pb-Acid chemistries, like Li-Ion and Li-Ion Polymer
11

batteries. The solution can be implemented in all applications where battery charging is required.
[0036] FIG. 4 illustrates a detailed flowchart of operations illustrating a method 5 (30) for dynamically charging the battery, in accordance with an exemplary embodiment of the present invention. Initially, as shown at block (32), the battery current and voltage limits are set as follows: IBatt Max = 18A (as per set configuration), VBatt Max= 14.5 V (as per set configuration), VBoost = 13.2 V (as per set configuration). A determination is made whether VBatt < VBoost, as depicted at block (34). If VBatt < 10 VBoost then IBatt Target = IBatt Max and VBatt Target = VBatt, as depicted at block (36). If not, another determination is made whether VBatt< VBatt Max as indicated at block (38). If VBatt< VBattMax then IBatt_Target= IBatt_Max - k (VBatt- VBoost) and VBattTarget = VBatt, as depicted at block (40).
15 [0037] If not, a determination is made whether VLastDisch