Cell Management Electronics for Lithium-Ion Battery
BEU8637-08
Independent Balancing for Two 8-Cell Batteries
Cell Voltage Monitoring and Telemetry
www.aeroflex.com/BEU
March 21, 2008
Description
The Aeroflex 8637-08 is a Lithium-Ion cell
balancing system. It controls the balancing
of one or two batteries, each consisting of
a series stack of Lithium-Ion cells to ensure
that each cell is precisely charged to its
proper level of energy and to monitor each
cell's operational voltage.
The cell balancing circuitry uses a set of
bilateral DC-DC converters which tie each
cell of a battery to a common share bus.
Cell charge is distributed among the
multiple cells so that the charge of each
cell is automatically matched to the
average charge of the other cells.
Features
●
Safety
The safety of Lithium-Ion battery
technology requires that extreme care be
taken in the provisions made for cell
charging and cell monitoring.
Precision measurements of each of the
individual cell voltages in the battery stack
and precise charge balancing to each
individual cell are critical.
The Aeroflex 8637-08 provides the
necessary precision of control and
monitoring to ensure that safety.
Discrete logic outputs are provided for
critical signaling, enabling the user to
initiate load shedding and/or to halt
charging.
Low operating losses enable continuous
operation. Continuous balancing provides
maximum protection against any one cell
becoming overcharged.
Cell Balancing to within ±5.0mV
Cell Voltage Monitoring Accuracy
±10.0mV (±20.0mV Space Mission Life)
Total Battery Voltage Monitoring
Accuracy ±0.3% of Full Scale
Supports up to 8 Lithium-Ion battery cells
in series per stack
Battery Drain Current at Balance
15mA Max for each 8 cell stack
Discrete output lines for critical signaling
with user definable thresholds:
Overvoltage Protection 4.40V typ
Cell Voltage High
4.20V typ
Cell Voltage Low
3.20V typ
●
●
●
●
●
●
MIL-STD-1553B telemetry for data
logging and monitoring
SCD8637-08 Rev A
CONTROL BOARD
OVP
HIGH
CELL
LOW
CELL
1553B
Channel A
1553B
Channel B
XFMR
XCVR
XFMR
A/D
12-BIT
12
MUX
SELECT
7
VIN
CELL BALANCE
BOARD
BALANCING
CIRCUIT
1
BALANCING
CIRCUIT
2
BALANCING
CIRCUIT
3
BALANCING
CIRCUIT
4
BALANCING
CIRCUIT
8
BATTERY
8 CELLS
+
-
+
-
+
-
+
-
CONTROLLER
BALANCING
CIRCUIT
CLOCK
DRIVER
BAL
CLK
MON
CLK
MUX
ON
OFF
RELAY
+
-
+30 VDC
POWER
SUPPLY
+12VDC
(ISOLATED)
+5VDC
-12VDC
+12VDC
PRECISION
REFERENCE
4.000V
BATTERY
HI AND LO
( 3x )
BATTERY
VOLTAGE
DIFF. AMPS
2 2 2
SHARE BUS
CONTROL BOARD
OVP
HIGH
CELL
LOW
CELL
1553B
Channel A
1553B
Channel B
XFMR
XCVR
XFMR
A/D
12-BIT
12
MUX
SELECT
7
VIN
BALANCING
CIRCUIT
13
BALANCING
CIRCUIT
14
2
BALANCING
CIRCUIT
15
BALANCING
CIRCUIT
16
BALANCING
CIRCUIT
20
BATTERY
8 CELLS
+
-
+
-
+
-
+
-
CONTROLLER
BALANCING
CIRCUIT
CLOCK
DRIVER
BAL
CLK
MON
CLK
MUX
ON
OFF
RELAY
+
-
+30 VDC
POWER
SUPPLY
+12VDC
(ISOLATED)
+5VDC
-12VDC
+12VDC
PRECISION
REFERENCE
4.000V
BATTERY
HI AND LO
( 3x )
BATTERY
VOLTAGE
DIFF. AMPS
2 2 2
SHARE BUS
Block Diagram
SCD8637-08 Rev A 3/21/08
Aeroflex Plainview
2
8637-08 Operating Details
Battery Cell Balancing
Provides 8 individual continuous balancing circuits per stack.
Maximum Cell Balancing Current Limit
Each cell is provided with a 1Amp fuse for overload interrupt
in the event of a shorted cell to protect the remaining cell
balance functionality.
Cell Balancing Accuracy
When connected to a battery, the 8637-08 provides
balancing currents into each of the battery's cells. The
directions and the magnitudes of the individual currents are
proportional to the deviations of the cell voltages from the
average cell voltage. The transfer ratio of voltage to current is
1.0 Ohm nominal and is satisfied for cell voltages of up to
4.2V.
Battery Cell Current Drawn in Off State
In the off state, the differential mode battery cell current
drawn by each cell balancing circuit is less than 50μA.
Battery Cell Voltage Monitoring
Measures cell voltages for up to two 8-cell batteries.
4V and 0V References for Calibration
Provides 4V and 0V references for cell voltage telemetry
calibration.
Battery and Cell Protection
Incorporates overvoltage protection (OVP) circuits. These
circuits monitor all of the battery cell voltages and only
register the highest of all cell voltages monitored. When a
cell voltage threshold of 4.40V is reached, the protection
circuit output changes state and latches within 50mS.
Battery Cell Overvoltage Latch Output
The status of the OVP latch is provided by telemetry as
specified in Tables II, III & IV and also as a discrete output.
Recovery from Cell Overvoltage Indication
The OVP latch is reset by a 1553B reset command or by
recycling the input power.
Highest Battery Cell Voltage Telemetry
Provides highest battery cell voltage telemetry as specified in
Tables I & IV.
Lowest Battery Cell Voltage Telemetry
Provides lowest battery cell voltage telemetry as specified in
Tables I & IV.
Test Points
Provides test points for total battery voltage, low cell
indicator and high cell indicator. Access to the total battery
voltage is provided to permit pre-charging before connection
to the battery.
SCD8637-08 Rev A 3/21/08
Aeroflex Plainview
3
MIL-STD-1553B Telemetry & Commands
(Each 8-cell battery)
Analog or bi-level telemetry can be requested from either
the primary or the redundant controller and reported over
the dual redundant 1553B interface with the RT addresses
configurable at the J1 and J4 connectors.
Analog Telemetry
Each analog telemetry item can be requested individually on
sub-addresses 18, 19 or 22.
First a 1553B receive command with one data word as
defined in Table I, which specifies the telemetry item being
requested, must be issued. After a minimum delay of 1.2ms,
the data can be retrieved by sending a 1553B transmit
command for one data word on the same sub-address on
which the request was initiated.
The 12-bit data reply is left justified in the 16-bit 1553B data
word with the four LSBs set to "0".
Bi-Level Telemetry
Bi-level telemetry can be requested on sub-addresses 18, 19
or 22.
First a 1553B receive command with one data word as
defined in Table II, which specifies the telemetry item being
requested, must be issued. After a minimum delay of 1.2ms,
the data can be retrieved by sending a 1553B transmit
command for one data word on the same sub-address on
which the request was initiated.
Table II – Bi-level Telemetry
1st Data
Word of
1553B
Receive
Command
(Hex)
0C80
Item
Telemetry Title
Status
Reply
Bit
Table I – Analog Telemetry
(Each 8-cell battery)
1
Item
Telemetry Title
Telemetry Reply
Scale
-0.40V to 4.89V
-0.40V to 4.89V
0V to 61.44V
0V to 61.44V
0V to 61.44V
0V to 5.12V
1 Data Word of
1553B Receive
Command (Hex)
0800
0803
0805
0806
0809
080A
0811
0812
0814
0817
0818
081B
081D
081E
0828
082B
082D
082E
0830
0833
0835
0836
0871
0872
st
Overvoltage Latch Status
1 = Set
D13
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
4V Reference
0V Reference
Total Battery Voltage 1
Total Battery Voltage 2
Total Battery Voltage 3
Share Bus Voltage
Cell 1 Voltage
Cell 2 Voltage
Cell 3 Voltage
Cell 4 Voltage
Cell 5 Voltage
Cell 6 Voltage
Cell 7 Voltage
Cell 8 Voltage
Cell 13 Voltage
Cell 14 Voltage
Cell 15 Voltage
Cell 16 Voltage
Cell 17 Voltage
Cell 18 Voltage
Cell 19 Voltage
Cell 20 Voltage
Lowest Cell Voltage
Highest Cell Voltage
1/ For Battery A.
⎫
⎬
⎭
⎫
⎬
⎭
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
1/
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
2/
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
0V to 5.12V
2/ For Battery B.
SCD8637-08 Rev A 3/21/08
Aeroflex Plainview
4
32-Word Telemetry
To reduce data bus bandwidth usage, the 8637-08 supports
a 32-word telemetry request on sub-address 20 as defined
in Table III.
First a 1553B receive command with one data word of
AAAA(Hex) must be issued. After a minimum delay of
1.2ms, the data can be retrieved by sending a 1553B
transmit command for 32 data words on sub-address 20.
Reply word 31 is a modulo-16 message count. This counter
increments by one for each valid telemetry request.
The 12-bit analog data reply is left justified in the 16-bit
1553B data word with the four LSBs set to "0"..
8-Word Telemetry
To reduce data bus bandwidth usage, the 8637-08 supports
an 8-word telemetry request on sub-address 24 as defined
in Table IV.
First a 1553B receive command with one data word of
5555(Hex) must be issued. After a minimum delay of 1.2ms,
the data can be retrieved by sending a 1553B transmit
command for 8 data words on sub-address 24.
Reply word 8 is a modulo-16 message count. This counter
increments by one for each valid telemetry request.
The 12-bit analog data reply is left justified in the 16-bit
1553B data word with the four LSBs set to "0".
Table III – 32-Word Telemetry
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Telemetry Title
4V Reference
Total Battery Voltage 1
Total Battery Voltage 2
Total Battery Voltage 3
Share Bus Voltage
Reserved
Cell 1 Voltage
Cell 2 Voltage
Cell 3 Voltage
Cell 4 Voltage
Cell 5 Voltage
Cell 6 Voltage
Cell 7 Voltage
Cell 8 Voltage
Reserved
Reserved
Reserved
Reserved
Cell 13 Voltage
Cell 14 Voltage
Cell 15 Voltage
Cell 16 Voltage
Cell 17 Voltage
Cell 18 Voltage
Cell 19 Voltage
Cell 20 Voltage
Reserved
Reserved
Reserved
Reserved
Message Count
Overvoltage Latch Status
1/ For Battery A.
Telemetry Reply
Type
Word
Analog
Analog
Analog
Analog
Analog
-
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Reply Bits
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:4)
D(15:0)
D13
Item
1
2
3
4
5
6
7
8
Table IV – 8-Word Telemetry
Telemetry Title
Overvoltage Latch Status
Reserved
Reserved
Reserved
0V Reference
Lowest Cell Voltage
Highest Cell Voltage
Message Count
Telemetry
Type
Bi-level
-
-
-
Analog
Analog
Analog
Analog
Reply
Word
1
2
3
4
5
6
7
8
Reply Bits
D13
D15
D15
D15
D(15:4)
D(15:4)
D(15:4)
D(15:0)
⎫
⎬
⎭
⎫
⎬
⎭
Analog
Analog
Analog
Analog
Analog
Analog
1/
Analog
Analog
-
-
-
-
Analog
Analog
Analog
Analog
Analog
Analog
2/
Analog
Analog
-
-
-
-
Analog
Bi-level
2/ For Battery B.
SCD8637-08 Rev A 3/21/08
Aeroflex Plainview
5
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