Battery Safety Monitor (BSM) / Current Sense
Board (CSB) - Integrated module
Pre-charge resistor
Immersion sensor
Sheet assembly - Front view (shown inverted from
position when sheet is normally installed in
vehicle)
Insulator
Manifold hose connection
Fuse/busbar
E-connector terminal
Battery Monitoring Board (BMB)
Toe mount
Ankle mount
Front mount
Heel mount
Top mount
16 - Description
Description
General
The unique feature of the vehicle is the method of
energy storage. The electrical energy that is used to drive
the wheels via the motor and transmission is stored in the
battery.
The battery is located in the rear of the vehicle
between the passenger compartment and the trunk. The outer
body of the battery comprises of an enclosure and a front
cover. This encases all of the electrical components that are
used to store the electrical energy and regulate its
use.
NOTE: References to left hand and right hand sides
are with the battery in the upright position, as positioned
in the vehicle, viewed from the front cover side.
Components
Sheets
The battery is constructed from 11 sheets connected
in series using braided E-connectors. Electrical insulators
cover each side of the sheet. Each sheet is comprised of 9
bricks electrically connected in series. A brick is a group
of 69 cells electrically connected in parallel. A cell
refers to a single lithium-ion cell, 18 mm in diameter and
65 mm long, each rated at 2.2Ah. A battery contains 6831
individual cells. .
WARNING:
Electrical insulators cover each side of the sheet and
must not be removed without written permission from the
Service Support Team.
The sheets are secured to the enclosure and front
cover using screws, washers and sealing washers, to prevent
ingress of moisture. The sheets are secured to the
enclosure at the 'toe' area at the front lower area of the
sheet, the 'heel' area at the manifold connection area, the
'ankle' area at the lower rear of the sheet and the top of
the enclosure.The sheets are fused or unfused, identified
by 'F' or 'U' on the front label, depending on their
placement in the enclosure. The fuses are located on the
rear of the sheet, the unfused sheets are fitted with a
solid, insulated busbar. The fuses are connected between
bricks 4 and 5. The sheets are positioned as
follows:
Sheet
Type Fused (F)/Unfused (U)
1 - Battery Safety Monitor (BSM) end
U
2
F
3
U
4
F
5
U
6
F
7
U
8
F
9
U
10
F
11 - Auxiliary Power Supply (APS)
end
U
Contactors
A contactor, essentially a high voltage switch, is
fitted to either end of the enclosure. The left hand
contactor is the positive contactor and the right hand
contactor is the negative contactor. Both contactors are
identical components with a connector that connects to the
main harness.
The positive contactor connects to the Power
Electronics Module (PEM) B+ positive cable and to sheet 1
via a busbar. The negative connector connects to the
service disconnect receptacle and to sheet 11 via a
busbar.
Battery Safety Monitor (BSM)
The BSM is a single Printed Circuit Board (PCB) on
the right hand side of the battery that contains small
microprocessors that monitor and control the battery's
behavior.
Battery Monitoring Board (BMB)
A BMB is integrated into the rear of each sheet
comprising of a voltage and temperature monitoring Printed
Circuit Board (PCB). The BMB connects to the voltage and
temperature sensors via a right angled PCB connector which
connects with a connector retained in the sheet structure.
The BMB is responsible for monitoring battery voltage and
temperature using multiple voltage sense leads and
temperature sensors within each sheet.
Pre-charge Relay and Pre-charge Resistor
The pre-charge relay is a single Printed Circuit
Board (PCB) on the right hand side of the battery that
connects to the main harness using two connectors.
The pre-charge resistor is located next to sheet 1
and connects to the Battery Safety Monitor (BSM). A thermal
switch is mounted on the pre-charge resistor and will
inhibit pre-charge attempts if the resistor temperature is
too high.
Immersion Sensor
The immersion sensor is constructed from two metal
strips that lay parallel to each other and are embedded in
a plastic material. The sensor runs inside the base of the
battery enclosure and connects to the Battery Safety
Monitor (BSM).
Within the BSM is a humidity sensor which is used to
detect excessive moisture in the battery.
Auxiliary Power Supply (APS)
The APS is a DC/DC switch mode power supply located
on the left hand side of the battery which converts vehicle
battery voltage (nominally 360V) to two separate
outputs:
13.5V (DC), for the vehicle 12V system. This is
for the low voltage systems in the vehicle such as the
instrument pack and audio system;
13.5V (DC) for the PEM APS.
Specification
Feature
Specification
Capacity
147Ah at 86°F
(30°C)
Energy storage
56kWh
Maximum total current output (5 seconds,
100% charge)
863A
Maximum peak output (5 seconds)
225kW at 411V
Peak charge current continuous
109A
Peak charge current (30 seconds)
185A
Service Disconnect
A service disconnect receptacle is located on the
right hand side of the battery into which the service
disconnect plug is fitted; this is used to isolate the
electrical system during service procedures. To isolate the
vehicle, lift the latch on the service disconnect plug then
pull from the receptacle.
CAUTION: To
prevent damage to the Auxialry Power Supply (APS), the
service disconnect plug should be removed and installed
in one smooth operation.
CAUTION: To
prevent damage to the APS, wait at least 120 seconds
before reinstalling the service disconnect plug.
The installation procedure is the reverse of removal.
Refer to
FRT 16010002in the Service Manual
for procedure details.
16 - Operation
Operation
General
The battery stores electrical energy which is converted
into kinetic energy by the motor. This energy is used to
drive the vehicle.
Components
Contactor
Under normal conditions, the Battery Safety Monitor
(BSM) operates the main battery contactors in response to
commands received from the Vehicle Management System (VMS).
The VMS will instruct the BSM to energize the contactors in
anticipation of driving or charging. Typically this would
be when the key is in ON position, or when the charge cable
is connected with the key out of the ignition. The VMS will
command the BSM to open the contactors when the key is
moved to the ACC position or charging is stopped.
Battery Safety Monitor (BSM)
The BSM performs the following functions:
Communicates with the VMS via the battery CAN
bus. The VMS controls all actions of the BSM except
when action is required to ensure the immediate safety
of the vehicle and its occupants;
Controls the battery contactors. The battery
contactors switch battery power to the main output
connector;
Supplies pre-charge current to components on the
external battery bus;
Monitors the overall state of the battery. This
includes internal battery temperature, overall voltage
of the battery;
Controls the operation of the 12V Auxiliary Power
Supply (APS). The 12V APS is used to power the
vehicle's 12V system;
Supplies 12V standby power to elements of the
vehicle's electrical system that are always on.
Accepts downloads of firmware and configuration
data from the VMS. The firmware and configuration data
are stored in a non-volatile memory within the
BSM.
Inputs
The following are inputs to the BSM:
Battery source voltage - Senses input for
battery voltage measurement. Power source for the 12V
standby power supply;
Battery output voltage - Measures the output
voltage of the battery. Used to terminate pre-charge
and detect fuse status down stream of
contactors;
Isolation Voltage Monitors - These two input
measure the voltage of the positive and negative
terminal of the battery with respect to the vehicle
chassis. They are used to determine the isolation
resistance between the high voltage circuits and the
chassis;
High voltage circuitry detection - Detects
whether the Power Electronics Module (PEM) and/or the
HVAC 400V controller that powers the Air Conditioning
(A/C) compressor is connected to the battery via a
High Voltage Interlock Loop (HVIL). The contactors
will not be allowed to close and will open if the
HVIL has been opened;
12V accessory voltage monitor - Sense input for
measuring the output of the APS, sense input for
measuring the output of the 12V PEM power supply and
status input indicating that the APS temperature is
high enough to require the cooling system to
operate;
Contactor 12V power input - This is an input
from the APS intended for powering the contactors. It
is derived from the APS' main output with a 5A
current limiting circuit. This input is also used to
provide redundancy for the BSM's internal power
supply and the 12V standby power output. This
redundancy will keep the vehicle operational if the
BSM standby power supply fails. Note that if the APS
is shut down while the BSM 12V Standby power supply
has failed, it won't be possible to start the car
until external power is supplied to the BSM, or the
BSM is repaired;
Immersion sensor - Detects the presence of
moisture in the battery, due to condensation or
immersion;
Air temperature and relative humidity -
Measures the temperature and relative humidity of the
ambient air in the battery;
Controller programming interface - This is used
to configure the program memory of the embedded
microcontroller. It is used during the manufacturing
process to load the initial program into the BSM's
controller;
Battery ground fault detection - Detects low
impedance from the battery to chassis ground. The
permissible resistance is 500Kohms;
Vehicle orientation - Measures the vertical
component of gravity with respect to the vehicle
chassis which is used for determining a roll over
condition;
Battery monitor sheet alarm - Monitors a signal
from the BMBs. Presence of this signal indicates that
at least one BMB is issuing an alarm requiring the
contactors to open;
Contactor power OK - Monitors the 12V output
from the inertia switch. This is used to power the
contactor driver chips. The switch status is used to
detect between actual contactor failure and a genuine
inertia switch event.
Pre-charge/discharge resistor thermal switch
status - Monitors the pre-charge relay driver circuit
so that the BSM can be aware of the state of the
thermal switch protecting the resistor. This switch
is wired in series with the pre-charge relay coil,
preventing the resistor from overight handeating due
to continuous application of battery voltage in fault
conditions.
Outputs
The following are outputs from the BSM:
Contactor drive - Output to energize the main
contactor coils;
12V standby power - 12V power for distribution
to parts of the vehicle that require 12V power to be
supplied continuously. A 12VDC standby power supply
is distributed to the BMBs and to the VMS using a
low-power Direct Current (DC) to DC converter;
12V CAN Bus power - 12V to the secondary side
of the optically isolated CAN interface of each
Battery Monitoring Board (BMB) taken from the 12V
standby power output;
High voltage bus pre-charge relay driver - A
driver circuit for the relay which activates the
battery bus pre-charge function;
High voltage bus discharge -Switches the
pre-charge resistor across the battery output when
the contactors are open;
Battery bus pre-charge - A current-limited
output which bypasses the negative contactor. It is
used to limit inrush current as capacitive loads are
connected to the propulsion or auxiliary high voltage
buses. The pre-charge circuit must supply enough
current to meet this requirement with the input
capacitance presented by the PEM and the A/C
compressor. The VMS will ensure that resistive loads
are off during this time;
APS main output enable - Logic output which
enables the 13.5V DC/DC converters used to power the
vehicles 12V electrical systems;
APS PEM output enable - Logic output which
enables the 12V DC&/DC converters used to power
the PEM's 12V electrical systems activated and
deactivated in response to commands from the
VMS;
CSB power - Provides power to the isolated
current sensor.
Current Sensor Board (CSB)
The CSB is a processor integrated into the BSM. It
performs the following functions:
Monitors the net current flowing into and out
of the battery, and keeps a short-term history of
that energy by integrating the current over
time;
Provides a reading of instantaneous
current;
Communicates with the VMS via the CAN bus. The
VMS controls all actions of the BMBs.
Inputs
Battery current - Senses input for battery
current measurement;
Battery voltage - Senses input for battery
voltage measurement;
12VDC standby power supply - Power source for
CSB circuitry, from the BSM. The CSB incorporates
circuitry to transfer power across the isolation
barrier which separates its battery-referenced
circuitry from the rest of the system.
Battery Monitoring Board (BMB)
The BMB performs the following functions:
Communicates with the VMS via the CAN
bus.
Monitors the voltage across each of the
individual parallel groups of bricks using 11
separate voltage sense leads.The VMS requests the
voltage readings at regular intervals.
Monitors the sheet temperature at a number of
physical locations within the sheet using 4 remote
temperature sensors. The sensors are in thermal
contact with selected cells within the sheet. The VMS
requests the temperature readings at regular
intervals.
Discharges individual bricks when commanded by
the VMS and in coordination with the other BMBs in
order to balance the state-of-charge of each of the
bricks within the battery.
Accepts downloads of firmware and configuration
data from the VMS. The firmware and configuration
data are stored in a non-volatile memory within the
BMB.
Monitors each brick for voltage above or below
a fixed threshold. If any brick voltage falls outside
this threshold, a signal is transmitted to the BSM
which controls the main contactors. This function is
implemented independently of the firmware executed by
the BMB's microcontroller. It is intended to protect
each brick against overcharging or voltage reversal.
Voltage reversal will occur if the internal resistor
in each cell in a brick enters it's high resistance
state.
The voltage of each brick is monitored
individually. Common sensing leads are used to sample the
voltage from bricks that are directly connected together
via the current collection plates in the sheet.
Independent sense leads connect the bricks on either side
of the fuse integrated into each sheet.
The sheet alarm is a mechanism for rapidly
communicating conditions detected by the BMB that require
an immediate response by the BSM, by immediately opening
the main contactors, in order to prevent damage or
failure within the battery. The following conditions will
cause a sheet alarm signal to be generated:
Cell reversal - Any brick voltage below a
threshold which indicates that a voltage of reversed
polarity of up to the entire battery voltage may be
applied to the brick imminently.
Overvoltage - Any brick above a defined safety
threshold indicating that overcharging may be
occurring due to the failure of the battery charging
control mechanisms that would normally prevent
over-charging.
Conditions or events detected by the BMB
microcontroller firmware. These might include brick
voltage too low or too high for cell life, but not
necessarily extreme enough to present a hazard or
temperatures within the sheet outside defined
operating limits.
The following describes the BMB's response to
possible fault conditions:
Sheet fuse failure - If the sheet fuse fails,
the BMB will no longer receive voltage rendering it
inoperable.
Complete discharge - The BMB monitors the sheet
input voltage. If voltage drops below 18V, the power
supply will enter a low-current standby mode in order
to maximize the time that will elapse before the
cells reach a dangerously low state of charge. There
is a 10 second time constant associated with the
input voltage detection circuit so the BMBs don't cut
out during short voltage dips caused by short
intervals of extremely high current demand from the
battery.
Overcharging - The BMB can withstand a sheet
voltage of at least 50 V without any degradation of
performance.
Shorting of voltage and temperature sense
wiring - The input impedance of all inputs (except
those used to power the BMB) is such that continuous
unintended connection to any part of the sheet will
not damage the BMB. The inputs from which operating
power is obtained are protected by 0.375 A fuses
which will limit fault current to values below the
safety limits of the sense wiring.
Firmware failure - The BMB has a hardware
watchdog circuit built in. This can be used to reset
the controller. There is also an external reset,
activated by specific conditions on the BMB input
signal. This feature in implemented entirely in the
hardware.
Hardware failure - Most hardware failures will
be detected by non-functioning of the BMB
(communication with the VMS will be lost). However,
some hardware failure modes are not detectable
without redundant hardware features, and others are
possibly damaging to the battery, or can affect user
safety.
Safety - Isolation between high voltages and
the user is maintained by the use of isolation
components designed for the purpose with
specifications in excess of that required for basic
insulation the high voltage system. The low voltage
user-accessible circuits connected to the BMB are all
grounded to the vehicle chassis, which, in turn, is
connected to a safety ground when the vehicle is
connected to a charging station. If there is a
breakdown of the high voltage isolation in the BMB,
the resulting fault current will pass directly to the
chassis and be detected by the isolation fault
detection mechanism in the BSM.
Undetectable hardware failures - This type of
failure mode consists of changes in BMB calibration
such that the voltage or temperature reported by the
BMB is sufficiently in error to cause hazardous
conditions within the battery. The most likely cause
of these failures is Electrostatic Discharge (ESD) or
high transient voltages at the BMB inputs.
Pre-charge Relay and Pre-charge Resistor
When the contactors close, the inrush currents and
peak voltage are extremely high, this may cause damage or
even possible welding of the contactors contacts. The
pre-charge resistor allows the capacitance on the high
voltage bus to charge slowly before the contactors close.
The voltage across the contacts is reduced and there is
little or no inrush current.
When the key is turned to the ON position, the
vehicle initiates the process to pre-charge pre-charge
and close the battery contactors in preparation for
driving. The pre-charge relay is used to ensure that
pre-charge process is completed before the contactors
close.
Immersion Sensor
The two metal strips of the sensor are embedded in
the plastic material close to each other but they do not
touch forming an open circuit. If the enclosure develops
a leak or if coolant is present, the liquid will bridge
the two contacts completing the circuit. The BSM detects
this signal and will not close contactors if the circuit
is closed.
NOTE: If a new immersion sensor is installed,
ensure that there is NO continuity between the two
connector pins.
Auxiliary Power Supply (APS)
The BSM enables the APS on command from the VMS.
The APS powers most of the 12 V devices in the vehicle,
the main battery contactors, and the control circuits
within the PEM. Typically, the APS will be enabled when
the ignition switch is in the ACC or IGN positions. The
VMS will also command the BSM to enable the APS whenever
the hazard flashers or interior lights are activated,
door latching or unlatching is required, or the driver
desires leaving the parking lights on while away from the
vehicle.
Battery Fault Detection
High Voltage Interlock Loop (HVIL)
PEM
Battery
Heating, Ventilation, Air Conditioning (HVAC)
400V controller
Battery Safety Monitor (BSM)
The HVIL is a monitoring system embedded in the BSM
used to monitor the battery high voltage circuit. The
system is designed to shut down the high voltage electrical
systems if the HVIL is broken in the event the HVIL is
broken, or not allow the high voltage battery contactors to
close if the loop is opened. If the HVIL is broken, high
voltage is immediately removed from the high voltage
components and the system is discharged.
The HVIL can be also be broken if the following
conditions occur:
The battery to Power Electronics Module (PEM) or
PEM to HVAC cable is disconnected or broken;
The PEM lid switch opens (which is located inside
the PEM);
Battery Ground Fault Detection
Low impedance between the battery and the conductive
parts of the vehicle structure may occur at:
Any cell in the series string within the
battery;
The internal battery wiring;
The 400V bus wiring;
Any device connected to the 400V bus inside or
outside the battery.
The battery has a high valued resistive center tap to
the vehicle chassis. All devices connected to the battery
bus are designed to have reinforced grade insulation
between the battery bus connected circuits and the
remaining parts of the device. If the current flowing
through the resistive center tap to chassis exceeds a
specified threshold, an unacceptably low resistance exists
between the high voltage circuit and the chassis. Measuring
the current to ground from the taps alternately (with
filtering to eliminate false triggering due to noise) will
reveal the presence of unacceptably low impedance to
chassis. The fault condition is used to take some
corrective action, such as preventing charging or
drive.
