Cell Management Electronics for Lithium-Ion Battery
BEU8635-12
Balancing for 12-Cell Battery
Cell Voltage Monitoring and Telemetry
www.aeroflex.com/BEU
March 3, 2008
Description
The Aeroflex 8635-12 is a Lithium-Ion cell
balancing system. It controls the balancing
of one battery 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 8635-12 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 12 Lithium-Ion battery cells in
series
Battery Drain Current at Balance
15mA maximum
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
●
●
●
●
●
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MIL-STD-1553B telemetry for data
logging and monitoring
SCD8635-12 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
12
BATTERY
12 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
VOLTAGE
DIFF. AMPS
SHARE BUS
2 2 2
BATTERY
HI AND LO
( 3x )
Block Diagram
8635-12 Operating Details
Battery Cell Balancing
Provides 12 individual continuous balancing circuits.
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 8635-12 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 12-cells.
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.
SCD8635-12 Rev A 3/3/08
Aeroflex Plainview
2
MIL-STD-1553B Telemetry & Commands
Analog or bi-level telemetry can be requested from the controller
and reported over the dual redundant 1553B interface with the
RT addresses configurable at the J1 connector.
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
Reply
Receive
Bit
Command
(Hex)
D13
0C80
Item
Telemetry Title
Status
Table I – Analog Telemetry
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Telemetry Title
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 9 Voltage
Cell 10 Voltage
Cell 11 Voltage
Cell 12 Voltage
Lowest Cell Voltage
Highest Cell Voltage
Telemetry Reply
Scale
-0.40V to 4.89V
-0.40V to 4.89V
0V to 122.88V
0V to 122.88V
0V to 122.88V
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
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
1
st
Data Word of
1553B Receive
Command (Hex)
0800
0803
0805
0806
0809
080A
0811
0812
0814
0817
0818
081B
081D
081E
0821
0822
0824
0827
0871
0872
1
Overvoltage Latch Status
1 = Set
SCD8635-12 Rev A 3/3/08
Aeroflex Plainview
3
32-Word Telemetry
To reduce data bus bandwidth usage, the 8635-12 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 8635-12 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
Cell 9 Voltage
Cell 10 Voltage
Cell 11 Voltage
Cell 12 Voltage
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Message Count
Overvoltage Latch Status
Telemetry Reply
Type
Word
Analog
Analog
Analog
Analog
Analog
-
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Analog
-
-
-
-
-
-
-
-
-
-
-
-
Analog
Bi-level
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(15:0)
D13
Item
1
2
3
4
5
6
7
8
Table IV – 8-Word Telemetry
Telemetry Title
Overvoltage Level 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
-
-
-
D(15:4)
D(15:4)
D(15:4)
D(15:0)
SCD8635-12 Rev A 3/3/08
Aeroflex Plainview
4
Additional Commands
Data Load Command
1553B receive commands consist of 2 data words to the
sub-address specified in Table V. Only the first data word is
used.
indicate that the unit is busy and cannot accept another
command.
1553B Data Wrap Around
Sub-address 30 is dedicated to data wrap around as
specified in MIL-STD-1553B.
Supported Mode Codes
The 8635-12 supports the 1553B Mode Codes in Table VI.
Table V – Commands
1
st
Data Word
of 1553B
Sub-Address
Receive
Command
(Hex)
13
14
15
-
-
0400
Table VI – 1553B Mode Codes
Mode Code Name
Transmit Status Word
Transmitter Shutdown
Override Transmitter Shutdown
Reset Remote Terminal
Mode Code Number
2
4
5
8
Item
Function Title
1
2
3
Reserved
Reserved
Reset OVP Latch
Telemetry Frame Sync Command
1553B broadcast command on sub-address 17 (any data
word) commands the 8635-12 to refresh its RT address.
Remote Terminal State Command
1553B transmit command on sub-address 21 for one data
word. The reply word will be 4000(Hex), to indicate that the
unit is ready to accept another command or 5000(Hex), to
1553B Status Flag Bits
The 8635-12 supports the following 1553B status flag bits:
1. Message Error bit
2. Broadcast Message Received bit
All other status bits are set to "0".
SCD8635-12 Rev A 3/3/08
Aeroflex Plainview
5
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