[0001] The present subject matter described herein, relates to starting of an
5 electric vehicle. More particularly, the present subject matter provides a system
that starts the electric vehicle having traction battery pack by secondary power
source having reverse charging function.
BACKGROUND
[0002] Background description includes information that may be useful in
10 understanding the present invention.
[0003] In vehicles either electric vehicles or gasoline vehicles, auxiliary
battery provides initial power or current for starting of the vehicle. If the auxiliary
battery is not charged, the vehicle will not be started by the auxiliary battery. To
start the vehicle, discharged battery is replaced with fully charged battery or
15 discharged battery is first charged before use. The auxiliary battery may get
discharged due to stray loads of the vehicle, such as head lamps in ON condition,
door remained open, key off condition for long time, direct connection of radiator
fan, and use of music system, poor SoH of battery and fan-on in ignition off
condition. During usage of electric appliances of vehicle in ignition off condition,
20 the auxiliary battery supplies power to the electric appliances that discharges the
auxiliary battery.
[0004] In the existing technologies of electric vehicle, the traction battery, i.e.,
main battery charges the auxiliary battery when auxiliary battery is at minimum
state of charge (SOC) even when the key is OFF. In this scenario, whenever the
25 auxiliary battery is at a minimum state of charge (SoC), then upper level control
unit wakes up and charges the auxiliary battery when key is OFF. The existing
technology has below mentioned technical dis-advantages and problems:
3
[0005] First, in case of high voltage traction battery, it is not safe to energize
the high voltage line outside the battery pack, i.e., in the vehicle, when the key is
OFF. This might cause electrocution injuries to operator or user of the vehicle.
[0006] Second, when key is OFF, if there is additional stray load on auxiliary
5 battery (which might be because of faulty sensor, door open, headlamps ON), the
auxiliary battery gets discharged. In order to charge up the auxiliary battery, the
energy of traction battery also gets depleted. After some time, both, traction
battery as well as auxiliary battery are in discharged condition. This might cause
unwanted energy loss and vehicle traction may not be possible without charging
10 the vehicle again.
[0007] Third, if above mentioned second scenario happens multiple times, this
may decrease the traction battery life due to increase in depth of discharge
percentage (DoD%) multiple times. It may also increase the number of cycles
which wastes the cycle life of battery. Traction battery contributes much cost in
15 electric vehicle, so traction battery should be used for traction only as much as
possible to increase the system efficiency.
[0008] Fourth, if auxiliary battery has poor health, i.e., low state of health
(SoH), then the situation may worsen and may increase the occurrence of above
mentioned scenario multiple times, which would decrease the traction battery life
20 and increase the cost of electric vehicle maintenance.
[0009] Therefore, there is a need for a system that can start the vehicle even
when the auxiliary battery is completely drained, or when the auxiliary battery has
insufficient power to activate the ECUs, required for vehicle start-up.
[0010] Therefore, there is a need for a system that can start the electric vehicle
25 having traction battery pack using secondary power source having reverse
charging function.
OBJECTS OF THE DISCLOSURE
[0011] Some of the objects of the present disclosure, which at least one
embodiment herein satisfy, are listed herein below.
4
[0012] The principal object of the present invention is to provide a system to
start an electric vehicle using secondary power source having reverse charging
function.
[0013] Another object of the present invention is to provide a system that can
5 increase life of traction battery by charging the auxiliary battery only in key on
condition.
[0014] Another object of the present invention is to provide a system that can
decrease maintenance cost of electric vehicle by increasing life and efficiency of
the traction battery by decreasing number of charging cycles.
10 [0015] These and other objects and advantages will become more apparent
when reference is made to the following description and accompanying drawings.
SUMMARY
[0016] This summary is provided to introduce concepts related to a system for
starting an electric vehicle having a traction battery by a secondary power source
15 having a reverse charging function. The concepts are further described below in
the detailed description. This summary is not intended to identify key features or
essential features of the claimed subject matter, nor is it intended to be used to
limit the scope of the claimed subject matter.
[0017] In an embodiment, the present subject matter relates to a system for
20 starting an electric vehicle with a traction battery by secondary power source
having a reverse charging function. The system is implemented in the traction
battery pack. The master battery management system (BMS) coupled with a
plurality of slave battery management system (BMS), each of slave BMS from the
plurality of slave BMS manages a battery module of a battery string of the traction
25 battery pack of the electric vehicle. The master BMS comprising a BMS
controller, an optical isolator that coupled with a secondary power source to
supply the low voltage (LV) from the secondary power source to a low power
DC-DC converter when a normally closed (NC) relay (R1) is closed. The low
power direct current (DC) - direct current (DC) converter is coupled with high
5
voltage (HV+, HV-) line of the battery string, an electronic control unit, and the
optical isolator to convert the high voltage (HV) to low voltage (LV) and activate
the ECU by supplying the low voltage (LV) to perform a plurality of safety
checks on the electric vehicle. The BMS controller starts the electric vehicle based
5 on inputs received from the electronic control module turning ON the P relay and
N relay to transmit high voltage (HV) from the battery string to power electronic
module (PEM) and high power DC-DC converter.
[0018] In an aspect, one end of the normally closed (NC) relay (R1) is
coupled with the BMS controller and the plurality of slave BMS and other end is
10 coupled with the secondary power source or ground (LV_GND), a semiconductor
diode (D3) is provided in between the normally closed (NC) relay (R1) and the
BMS controller, a semiconductor diode (D1) and a semiconductor diode (D2) are
provided in between the normally closed (NC) relay (R1) and the plurality of
slave BMS.
15 [0019] In an aspect, the semiconductor diode (D1), the semiconductor diode
(D2), and the semiconductor diode (D3) restrict the back flow of current from the
normally closed (NC) relay (R1).
[0020] In an aspect, the optical isolator comprises a light emitting diode
(LED) that is coupled with the resistor to receive the low voltage (LV) from the
20 secondary power source and a photo transistor coupled with the low power DCDC converter to turn ON the low power DC-DC converter when light is emitted
by the light emitting diode (LED).
[0021] In an aspect, the low power DC-DC converter is turned ON when
traction battery voltage is within predefined range and no under voltage (UV),
25 over voltage (OV), under temperature (UT), over temperature (OT) alarm signals
are present.
[0022] In an aspect, the ECU is coupled with an auxiliary battery, and a
combination of semiconductor diode (D4) with a parallel low voltage relay
6
provided in between the ECU and the auxiliary battery where the low voltage
relay is controlled by the ECU.
[0023] In an aspect, the secondary power source has reverse charging
function, where the secondary power source connects with the master BMS by
5 means of universal serial bus (USB) port or wireless adapter.
[0024] In an aspect, the secondary power source can be selected from but not
limited to mobile phone, smart watch, power bank, personal computer etc.
[0025] In another embodiment of the present subject matter, a method for
starting an electric vehicle using secondary power source having reverse charging
10 function is described. The method comprising supplying, by the secondary power
source, low voltage (LV) power to an optical isolator; turning ON, by the optical
isolator, low power DC-DC converter; and converting, by the low power DC-DC
converter, high voltage (HV) power to low voltage (LV) power.
[0026] In an aspect, the method includes activating, by the low power DC-DC
15 converter, the electronic control unit by supplying the low voltage (LV) to
perform a plurality of safety checks on the electric vehicle; and starting, by the
BMS controller, the electric vehicle based on inputs received from the electronic
control unit by transmitting high voltage (HV) from the battery string to power
electronic module (PEM) and high power DC-DC converter.
20 [0027] In an aspect, the method includes turning OFF, by the BMS controller,
the low power DC-DC converter by opening normally closed (NC) relay (R1).
[0028] Various objects, features, aspects, and advantages of the inventive
subject matter will become more apparent from the following detailed description
of preferred embodiments, along with the accompanying drawing figures in which
25 like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The illustrated embodiments of the subject matter will be best
understood by reference to the drawings, wherein like parts are designated by like
numerals throughout. The following description is intended only by way of
7
example, and simply illustrates certain selected embodiments of devices, systems,
and methods that are consistent with the subject matter as claimed herein,
wherein:
[0030] Fig. 1 illustrates architecture of electric vehicle with traction battery
5 pack and auxiliary battery, in accordance with an embodiment of the present
subject matter; and
[0031] Fig. 2 illustrates a method for starting an electric vehicle using system
of fig. 1, in accordance with an embodiment of the present subject matter.
[0032] The figures depict embodiments of the present subject matter for the
10 purposes of illustration only. A person skilled in the art will easily recognize from
the following description that alternative embodiments of the structures and
methods illustrated herein may be employed without departing from the principles
of the disclosure described herein
DETAILED DESCRIPTION
15 [0033] The detailed description of various exemplary embodiments of the
disclosure is described herein with reference to the accompanying drawings. It
should be noted that the embodiments are described herein in such details as to
clearly communicate the disclosure. However, the amount of details provided
herein is not intended to limit the anticipated variations of embodiments; on the
20 contrary, the intention is to cover all modifications, equivalents, and alternatives
falling within the scope of the present disclosure as defined by the appended
claims.
[0034] It is also to be understood that various arrangements may be devised
that, although not explicitly described or shown herein, embody the principles of
25 the present disclosure. Moreover, all statements herein reciting principles, aspects,
and embodiments of the present disclosure, as well as specific examples, are
intended to encompass equivalents thereof.
[0035] The terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting of example embodiments. As
8
used herein, the singular forms “a",” “an” and “the” are intended to include the
plural forms as well, unless the context clearly indicates otherwise. It will be
further understood that the terms “comprises,” “comprising,” “includes” and/or
“including,” when used herein, specify the presence of stated features, integers,
5 steps, operations, elements and/or components, but do not preclude the presence
or addition of one or more other features, integers, steps, operations, elements,
components and/or groups thereof.
[0036] It should also be noted that in some alternative implementations, the
functions/acts noted may occur out of the order noted in the figures. For example,
10 two figures shown in succession may, in fact, be executed concurrently or may
sometimes be executed in the reverse order, depending upon the functionality/acts
involved.
[0037] In addition, the descriptions of "first", "second", “third”, and the like in
the present invention are used for the purpose of description only, and are not to
15 be construed as indicating or implying their relative importance or implicitly
indicating the number of technical features indicated. Thus, features defining
"first" and "second" may include at least one of the features, either explicitly or
implicitly.
[0038] Unless otherwise defined, all terms (including technical and scientific
20 terms) used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which example embodiments belong. It will be further
understood that terms, e.g., those defined in commonly used dictionaries, should
be interpreted as having a meaning that is consistent with their meaning in the
context of the relevant art and will not be interpreted in an idealized or overly
25 formal sense unless expressly so defined herein.
[0039] Non-limiting Definitions
[0040] In the disclosure hereinafter, one or more terms are used to describe
various aspects of the present disclosure. For a better understanding of the present
9
disclosure, a few definitions are provided herein for better understating of the
present disclosure.
[0041] Battery Management System (BMS): A battery management system
(BMS) is any electronic system that manages a rechargeable battery (cell or
5 battery pack), such as by protecting the battery from operating outside its safe
operating area, monitoring its state, calculating secondary data, reporting that
data, controlling its environment, authenticating it, and / or balancing it.
[0042] High Voltage (HV): High voltage is defined as voltage in range 30 to
1000 VAC or 60 to 1500 VDC.
10 [0043] Low Voltage (LV): Low voltage is defined as voltage in range 0 to 30
VAC or 0 to 60 VDC.
[0044] Power Electronic Module (PEM): Power electronic module provides
the physical containment for several power components, usually includes inverter
and motors.
15 [0045] State of Charge (SoC): The SoC of a battery is defined as the ratio of
its current capacity to the nominal capacity. The nominal capacity is given by the
manufacturer and represents the maximum amount of charge that can be stored in
the battery.
[0046] Depth of Discharge (DoD): A battery’s depth of discharge (DoD)
20 indicates the percentage of the battery that has been discharged relative to the
overall capacity of the battery.
[0047] State of Health (SoH): The SoH of a battery is a figure of merit of the
condition of a battery (or a cell, or a battery pack), compared to its ideal
conditions.
25 [0048] DC-DC converter: A DC-DC converter is an electronic circuit or
electromechanical device that converts a source of direct current (DC) from one
voltage level to another.
10
[0049] Optical Isolator: It is an electronic component that transfers electrical
signals between two isolated circuits by using light.
[0050] Diode: A diode is a two-terminal electronic component which is PN
junction that only conducts current in one direction.
5 [0051] These and other advantages of the present subject matter would be
described in greater detail with reference to the following figures. It should be
noted that the description merely illustrates the principles of the present subject
matter. It will thus be appreciated that those skilled in the art will be able to devise
various arrangements that, although not explicitly described herein, embody the
10 principles of the present subject matter and are included within its scope.
[0052] Main objective of the present invention is to provide a system to start
an electric vehicle using traction battery when auxiliary battery is complete
discharged and unable to start the electric vehicle. Further, the present system
charges the discharged auxiliary battery only in key on condition or vehicle start
15 condition.
[0053] The present invention can be implemented in any electric vehicle
having traction battery and auxiliary battery. Further, the present invention
overcomes all the technical problems as mentioned in the background section by
restricting charging of the auxiliary battery in key off condition and solving
20 technical problem of starting the vehicle when the auxiliary battery is completely
discharged or is below 7V, and disable to start the vehicle as explained below.
[0054] Exemplary Implementations
[0055] To this, as shown in fig. 1, traction battery pack 300 comprises a
battery string 301, a plurality of slave battery management system (BMS) 100,
25 and a master battery management system (BMS) 200. Further, the battery string
301 is coupled with the power electronic module (PEM) 310 by high voltage
(HV) line through P relay 301a and N relay 301b. When the P relay 301a and the
N relay 301b are closed, the high voltage (HV) is supplied to the PEM 310 from
the battery string 301 and converted into low voltage (LV) for operating coupled
11
auxiliary loads 306, such as fan, headlamp, tuner, etc., and an auxiliary battery
308.
[0056] When the auxiliary battery 308 is charged and voltage level is more
than a predefined threshold voltage (Vth), the auxiliary battery 308 supplies the
5 low voltage to an electronic control unit (ECU) 304 to check all the safety
measures, such as airbag deployment, safety conditions of the traction battery
pack and any discharge or leakage of current from the battery. Upon checking all
safety measures, the ECU 304 turns ON the P relay 301a and the N relay 301b to
power up the high voltage line to supply high voltage (HV) to the high power DC10 DC converter 309.
[0057] When the auxiliary battery 308 is fully discharged or not able to start
the vehicle, the present subject matter provides a system to start the electric
vehicle using a secondary power source, such as mobile phone, power bank, handheld computing device having a reverse charging function.
15 [0058] The master BMS 200 of the traction battery pack 300 comprises a
BMS controller 201, an optical isolator 203 that is coupled with a secondary
power source 302 through universal serial bus (USB) port or wireless adapter
provided in the electric vehicle cabin, and a low power direct current (DC) - direct
current (DC) converter 204. The low power DC-DC converter 204 is coupled with
20 high voltage (HV+, HV-) line of the battery string 301 to convert the high voltage
(HV) to low voltage (LV) for starting the electric vehicle.
[0059] The optical isolator 203 comprising a light emitting diode (LED) 203a
and a photo transistor 203b. One end of the light emitting diode (LED) 203a is
connected with the secondary power source 302 by a resistor 202 and other end of
25 the LED 203a is connected with a normally closed (NC) relay (R1). Other end of
the NC relay (R1) is grounded. When the NC relay (R1) is closed the LED 203a
will be conducting. When the NC relay (R1) is opened, one end of the NC relay
(R1) is not connected to ground.
12
[0060] The NC relay (R1) comprises a coil and a switch. The NC relay (R1) is
coupled with the plurality of slave BMS 100 to receive inputs or alarm signal
regarding, under voltage (UV), over voltage (OV), under temperature (UT), and
over temperature (OT). Further, a semiconductor diode (D1) is provided in
5 between the NC relay (R1) and the plurality of slave BMS 100 transmitting the
UV/OV alarm signal voltage. Similarly, a semiconductor diode (D2) is provided
in between the NC relay (R1) and the plurality of slave BMS 100 transmitting the
UT/OT alarm signal voltage. Further, a semiconductor diode (D3) is provided in
between the NC relay (R1) and the BMS controller 201. The semiconductor
10 diodes D1, D2, and D3 are positioned in such a way that they restrict flow of
current from the NC relay (R1) to the plurality of slave BMS 100 and the BMS
controller 201, respectively.
[0061] In case there is any alarm signal generated by the plurality of slave
BMS 100, the signal passes through the semiconductor diode D1 or D2 or Dn or
15 all to open the NC relay (R1) and break the connection between the secondary
power source 302 and the optical isolator 203.
[0062] The photo transistor 203b of the optical isolator 203 is coupled with
the low power DC-DC converter 204 to turn ON the low power DC-DC converter
204 when light is emitted by the LED 203a. Upon receiving low voltage (LV)
20 from the secondary power source 302 and the NC relay (R1) is closed, the optical
isolator 203 conducts and the LED 203a emits light towards the photo transistor
203b. Upon receiving the lights, the phototransistor 203b conducts and turns ON
the low power DC-DC converter 204.
[0063] The low power DC-DC converter 204 converts the high voltage (HV)
25 from the battery string 301 to the low voltage (LV) and supplies the same to the
ECU 304.
[0064] To prohibit flow of the low voltage (LV) from the low power DC-DC
converter 204 to the auxiliary battery 308 and the auxiliary loads 306 while
supplying to the ECU 304, a semiconductor diode ‘D4’ is provided in between the
30 auxiliary battery 308 and the auxiliary loads 306. Further, a low voltage relay 305
13
is provided in parallel with the semiconductor diode ‘D4’ to allow flow of low
voltage from the auxiliary battery 308 to the ECU 304 during turn OFF condition
of the low power DC-DC converter 204. The low voltage relay 305 is controlled
by the ECU 304 and is a normally open relay. When the high power DC-DC
5 converter 309 supplies the low voltage to the auxiliary battery 308, the auxiliary
load 306, and the ECU 304, the ECU 304 closes the normally open low voltage
relay 305.
[0065] Upon receiving the low voltage (LV) form the low power DC-DC
converter 204, the ECU 304 performs all safety checks before turning ON the P
10 relay 301a and the N relay 301b. When all safety checks are performed and all
safety checks are satisfying the predefined conditions, the ECU 304 turns ON the
P relay 301a and the N relay 301b. The high power DC-DC converter 309
receives the high voltage (HV) from the battery string 301 and supplies the low
voltage (LV) to the auxiliary battery 308 and the ECU 304 through the low
15 voltage relay 305.
[0066] After the high power DC-DC converter 309 is turned ON, the BMS
controller 201 sends a control voltage through the semiconductor diode ‘D3’ to
open the NC relay (R1). When the NC relay (R1) is open, the established
connection between the secondary power source 302 and the optical isolator 203
20 breaks and the LED 203a does not emit light. The optical isolator 203 turns OFF
the low power DC-DC converter 204.
[0067] The present process to start the electric vehicle from the secondary
power source 302 having reverse charging function takes a few seconds, for
example, 2-5 seconds to start the vehicle. Once the vehicle is started, the reverse
25 charging function can be turned OFF in the secondary power source 302.
[0068] In another embodiment, a circuit breaker 307 that can be automatic or
manual is provided in between the auxiliary battery 308 and the ECU 304. The
circuit breaker 307 is provided to ensure that the low voltage from the low power
DC-DC converter 204 does not reach the auxiliary battery 308.
14
[0069] In another embodiment, a semiconductor diode ‘D5’ is provided in
between the USB port or wireless adapter from power source 303 that charges the
secondary power source 302 and controlled by the ECU 304. The semiconductor
diode ‘D5’ ensures that no voltage reaches the power source 303 from the USB
5 port or wireless adapter.
[0070] Fig. 2 illustrates a method 400 for starting an electric vehicle using
secondary power source 302, in accordance with an embodiment of the present
disclosure. The order in which the method 400 is described is not intended to be
construed as a limitation, and any number of the described method blocks may be
10 combined in any order to implement the method 400, or an alternative method.
[0071] At block 402, the method includes supplying, by the secondary power
source 302, low voltage (LV) to an optical isolator 203.
[0072] At block 404, the method includes turning ON, by the optical isolator
203, low power DC-DC converter 204 when the optical isolator 203 conducts. A
15 photo transistor 203b of the optical isolator 203 is coupled with the low power
DC-DC converter 204 to turn ON the low power DC-DC converter 204 when
light is emitted by the light emitting diode (LED) 203a.
[0073] At block 406, the method includes converting, by the low power DCDC converter 204, high voltage (HV) power to low voltage (LV) power. The low
20 power DC-DC converter 204 is coupled with high voltage (HV+, HV-) line of the
battery string 301 in order to convert the high voltage (HV) to low voltage (LV)
for starting the electric vehicle.
[0074] At block 408, the method includes activating, by the low power DCDC converter 204, the electronic control unit 304 by supplying the low voltage
25 (LV) to perform a plurality of safety checks, such as airbag deployment, safety
conditions of the traction battery pack or any discharge or leakage of current from
the battery on the electric vehicle.
15
[0075] At block 410, the method includes starting, by the BMS controller 201,
the electric vehicle based on inputs received from the electronic control unit 304
by transmitting high voltage (HV) from the battery string to power electronic
module (PEM) 310 via high power DC-DC converter.
5 [0076] At block 412, the method includes turning OFF, by the BMS controller
201, the low power DC-DC converter 204 by opening normally closed (NC)
Relay (R1).
[0077] With the present subject matter, an electric vehicle can be started by
using a secondary power source, for example, mobile phone, power bank,
10 handheld computing device, etc., having reverse charging function.
[0078] It will be understood by those within the art that, in general, terms used
herein, and especially in the appended claims (e.g., bodies of the appended
claims) are generally intended as “open” terms (e.g., the term “including” should
be interpreted as “including but not limited to,” the term “having” should be
15 interpreted as “having at least,” the term “includes” should be interpreted as
“includes but is not limited to,” etc.). It will be further understood by those within
the art that if a specific number of an introduced claim recitation is intended, such
an intent will be explicitly recited in the claim, and in the absence of such
recitation no such intent is present. For example, as an aid to understanding, the
20 following appended claims may contain usage of the introductory phrases “at least
one” and “one or more” to introduce claim recitations. However, the use of such
phrases should not be construed to imply that the introduction of a claim recitation
by the indefinite articles “a” or “an” limits any particular claim containing such
introduced claim recitation to inventions containing only one such recitation, even
25 when the same claim includes the introductory phrases “one or more” or “at least
one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should
typically be interpreted to mean “at least one” or “one or more”); the same holds
true for the use of definite articles used to introduce claim recitations. In addition,
even if a specific number of an introduced claim recitation is explicitly recited,
16
those skilled in the art will recognize that such recitation should typically be
interpreted to mean at least the recited number (e.g., the bare recitation of “two
recitations,” without other modifiers, typically means at least two recitations, or
two or more recitations). Furthermore, in those instances where a convention
5 analogous to “at least one of A, B, and C, etc.” is used, in general such a
construction is intended in the sense one having skill in the art would understand
the convention (e.g., “a system having at least one of A, B, and C” would include
but not be limited to systems that have A alone, B alone, C alone, A and B
together, A and C together, B and C together, and/or A, B, and C together, etc.).
10 In those instances where a convention analogous to “at least one of A, B, or C,
etc.” is used, in general such a construction is intended in the sense one having
skill in the art would understand the convention (e.g., “a system having at least
one of A, B, or C” would include but not be limited to systems that have A alone,
B alone, C alone, A and B together, A and C together, B and C together, and/or A,
15 B, and C together, etc.). It will be further understood by those within the art that
virtually any disjunctive word and/or phrase presenting two or more alternative
terms, whether in the description, claims, or drawings, should be understood to
contemplate the possibilities of including one of the terms, either of the terms, or
both terms. For example, the phrase “A or B” will be understood to include the
20 possibilities of “A” or “B” or “A and B.”
[0079] While the foregoing describes various embodiments of the invention,
other and further embodiments of the invention may be devised without departing
from the basic scope thereof. The scope of the invention is determined by the
claims that follow. The invention is not limited to the described embodiments,
25 versions or examples, which are included to enable a person having ordinary skill
in the art to make and use the invention when combined with information and
knowledge available to the person having ordinary skill in the art.

We claim:

1. A master battery management system (BMS) (200) coupled with a plurality
of slave battery management system (BMS) (100), each of slave BMS (100)
from the plurality of slave BMS (100) manages a battery module of a
5 battery string (301) of a traction battery pack (300) of an electric vehicle,
the master BMS (200) comprising:
a BMS controller (201);
characterized in that
an optical isolator (203) coupled with a secondary power source
10 (302) to supply the low voltage (LV) from the secondary power
source (302) to a low power Direct Current (DC)- Direct Current
(DC) converter (204) when normally closed (NC) relay (R1) is
closed;
the low power DC-DC converter (204) coupled with high voltage
15 (HV+, HV-) line of the battery string (301), an electronic control
unit (304), and the optical isolator (203) to:
convert the high voltage (HV) to low voltage (LV); and
activate the ECU (304) by supplying the low voltage (LV) to
perform a plurality of safety checks on the electric vehicle;
20 and
the BMS controller (201) starts the electric vehicle based on
inputs received from the electronic control module (304) by
transmitting high voltage (HV) from the battery string (301)
to a high power DC-DC converter (309).
25 2. The master BMS (200) as claimed in claim 1, wherein one end of the
normally closed (NC) relay (R1) is coupled with the BMS controller (201)
and the plurality of slave BMS (100) and other end is coupled with the
second power source (302) or ground (LV_GND), a semiconductor diode
(D3) is provided in between the normally closed (NC) relay (R1) and the
30 BMS controller (201), a semiconductor diode (D1) and a semiconductor
18
diode (D2) is provided in between the normally closed (NC) relay (R1) and
the plurality of slave BMS (100).
3. The master BMS (200) as claimed in claim 2, wherein the semiconductor
diode (D1), the semiconductor diode (D2), and the semiconductor diode
5 (D3) restrict flow of current from the normally closed (NC) relay (R1).
4. The master BMS (200) as claimed in claim 1, wherein the optical isolator
(203) comprises a light emitting diode (LED) (203a) that is coupled with the
resistor (202) to receive the low voltage (LV) from the secondary power
source (302) and a photo transistor (203b) coupled with the low power DC10 DC converter (204) to turn ON the low power DC-DC converter (204) when
light is emitted by the light emitting diode (LED) (203a).
5. The master BMS (200) as claimed in claim 4, wherein the low power DCDC converter (204) is turned ON when traction battery voltage is within
predefined range and no under voltage (UV), over voltage (OV), under
15 temperature (UT), over temperature (OT) alarm signals are present.
6. The master BMS (200) as claimed in claim 1, wherein the ECU (304) is
coupled with an auxiliary battery (308) and a combination of semiconductor
diode (D4) with a parallel low voltage relay (305) is provided in between
the ECU (304) and the auxiliary battery (308).
20 7. The master BMS (200) as claimed in claim 1, wherein the secondary power
source (302) has reverse charging function, where the secondary power
source (302) connects with the master BMS (200) by means of universal
serial bus (USB) port or wireless adapter.
8. A method (400) for starting an electric vehicle using secondary power
25 source (302) having reverse charging function, the method (400)
comprising:
supplying (402), by the secondary power source (302), low voltage
(LV) power to an optical isolator (203);
turning ON (404), by the optical isolator (203), low power DC-DC
30 converter (204); and
19
converting (406), by the low power DC-DC converter (204), high
voltage (HV) power to low voltage (LV) power.
9. The method (400) as claimed in claim 8, wherein the method (400)
comprises:
5 activating (408), by the low power DC-DC converter (204), the
electronic control unit (304) by supplying the low voltage (LV) to
perform a plurality of safety checks on the electric vehicle; and
starting (410), by the BMS controller (201), the electric vehicle
based on inputs received from the electronic control unit (304) by
10 transmitting high voltage (HV) from the battery string (301) to power
electronic module (PEM) (310) and high power DC-DC converter (309).
10. The method (400) as claimed in claim 11, wherein the method (400) further
comprises:
turning OFF (412), by the BMS controller (201), the low power
15 DC-DC converter (204) by opening normally closed (NC) relay (R1).