BEU8642-08 Cell Balancer (2/09)

Cell Management Electronics for Lithium-Ion Battery
BEU8642-08
Balancing for 8-Cell Battery
Cell Voltage Monitoring
Temperature Monitoring
www.aeroflex.com/BEU
February 5, 2009
Description
The Aeroflex 8642-08 is a Lithium-Ion battery
cell balancer. It provides voltage balancing
among eight series stacked cells within a
multi-cell battery to actively drive the voltage of
each cell towards the average voltage of all cells
using a patented charge-sharing technology.
Features
●
Cell Balancing of eight series stacked Lithium-Ion cells
●
Transfer Ratio: 1 ohm nominal
●
Cell Balancing to within ±10 mV
●
Temperature Monitoring
●
Cell Voltage Monitoring with high cell and low cell detection
●
Built In Test (BIT) Discrete Output
●
Suitable for a wide range of cell capacities, from less than 1 A-h to greater than 200 A-h
●
RS-232 Output for data logging
Benefits
When Lithium-Ion battery cells are charged and discharged, small differences in the internal
electrical characteristics of each cell may lead to cell voltage differences. At beginning of life, battery
manufacturers take great care to match the cell characteristics very precisely. After many charge
cycles, the characteristics diverge, causing cell voltage imbalances. Since the battery can only be
charged until the highest cell reaches the maximum allowed voltage, the remaining cells are never
fully charged. Similarily, as the battery is discharged, the battery must be disconnected when the
lowest cell reaches the minimum allowed voltage, thereby preventing the charge in the remaining
cells from being used.
By keeping the cells balanced the useful capacity and life of the battery are maximized.
The 8642-08 provides continous balancing for maximum protection against non-balance of
Lithium-Ion cells.
Safety
The 8642-08 incorporates fuses to protect the battery in the event of a balancing circuit failure, as
well as fuses to protect the 8642-08 if a battery cell fails.
The maximum balancing current supplied by the 8642-08 is 1A. All cells must be balanced to be
within 1V before connecting the 8642-08 to the battery.
High cell detection can be used to prevent overcharging. Low cell detection can be used to prevent
deep discharge.
SCD8642-08 Rev B
JTAG INPUT FOR
THRESHOLD SETTINGS
VOLTAGE REFERENCES - 2.00V AND 4.00V
THERMISTOR 1
CONDITIONING CIRCUIT
THERMISTOR 2
CONDITIONING CIRCUIT
THERMISTOR 3
CONDITIONING CIRCUIT
THERMISTOR 4
CONDITIONING CIRCUIT
RS232
OUTPUT
+28VDC
(16VDC TO 34VDC)
INPUT
EMI
FILTER
MUX
S/H
A/D
+12VDC
(FLOATING)
3TR
-12VDC
3TR
+12VDC
3TR
+5VDC
3TR
+3.3VDC
3TR
-5VDC
3TR
DC-DC
CONVERTER
MUX INPUT
SELECT
MON CLK
ON CONTROL
OFF CONTROL
EIGHT CELLS
9 WIRES
HIGH CELL
INPUTS #1 THRU #8
CONTROL
LOGIC
CELL
BALANCING
CIRCUITS
LOW CELL
BIT
(ALL OK)
LED
TEMP 1
ERROR
TEMP 2
ERROR
FLYBACK
EDGE
SHARE BUS
BAL CLK
TEMP 3
ERROR
PLL
CONDITIONING
CIRCUIT
TEMP 4
ERROR
THRESHOLD ADJ.
THRESHOLD ADJ.
TEMPERATURE SENSORS THRESHOLD
DETECTORS
REMOTE DISPLAY MODULE
(OPTIONAL)
V 1
4 . 0 0 0
Balancer Block Diagram
Organization and Application
The nominal impedance between each cell, and the
Share Bus, also known as the transfer ratio, is 1 ohm.
This ratio determines the amount of balancing current
and is based on the voltage difference between each
cell and the Share Bus. For example, a cell that is
200mV higher than the Share Bus will deliver 200mA
to the Share Bus, whereas a cell that is 100mV less than
the Share Bus will receive 100mA charging current
from the Share Bus.
The Aerof lex BEU8642-08 contains eight cell
balancing circuits. Each cell balancing circuit is
connected in parallel with one of the stacked cells of a
multi-cell Lithium-Ion battery. In operation, energy is
shared among the cells of the battery by way of the
balancing circuits.
The point in the circuit of energy exchange is called the
Share Bus, which represents the average voltage of all
the cells. Those cells having higher voltages deliver
energy to the Share Bus while those cells with lower
voltages receive energy from the Share Bus.
Aeroflex Plainview
SCD8642-08 Rev B 2/5/09
2
Technical Specifications
A. Cell Balancing
Number of Cells:
Transfer Ratio:
Cell Voltage Range:
Cell Balancing
Current:
8
1 ohm nominal (0.8 ohms to 1.39 ohms)
2.0 volts to 4.5 volts
1.0 amperes maximum
B. Cell Voltage Monitoring
Discrete Cell
Voltage Monitor
Outputs:
There are two discrete Cell Voltage Monitor Outputs: High Cell (HC) and Low Cell (LC).
Each output circuit is an NPN transistor, rated at 100 mA and 40 VDC, suitable for
driving an LED. The transistor turns on when the measured cell voltage of any cell is
outside the set limits. For example, if the HC limit is set at 4.200 volts, the transistor
turns on if any measured cell voltage is greater than 4.200 volts. If the LC limit is set at
3.200 volts, the transistor turns on if any measured cell voltage is lower than 3.200
volts.
Hysteresis:
Each detection circuit has a hysteresis of 30 mV. For example, the HC limit turns on
when any cell voltage exceeds 4.200 volts. It remains on until the voltage drops below
4.170 volts.
Voltage
Measurement
Accuracy:
Cell voltage monitoring accuracy is + 10 mV, over the range of 2.000 volts to 4.500
volts.
C. Temperature Monitoring
Number of sensors:
Sensor Type:
4 (Typically located in battery)
NTC Thermistor Type: Keystone RL0503-55.36K-122-MS 100KΩ
Thresholds:
Each sensor has an Upper Threshold (UT) and a Lower Threshold (LT). For example, the
UT may be set at 70°C and the LT may be set at 0°C.
Processing:
Threshold voltages for Sensors 1 and 2 are set by the Control Logic. Thresholds for
Sensors 3 and 4 are set by separate analog circuits. The Sensor 1, 2 circuits and the
Sensor 3, 4 circuits are independent, so that a failure in either section does not affect
the performance of the other section.
Setting of Analog
Thresholds:
The analog thresholds (Sensors 3 and 4) are set by potentiometers, with resolution of
1°C.
Temperature
Accuracy:
Discrete
Temperature
Monitor Outputs:
Measurement accuracy of the 8642-08 unit (independent of the accuracy of the
thermistors) is less than + 3°C, over the range of -10°C to +80°C.
There are four Temperature Sensor Monitor outputs (one for each sensor). Each output
circuit is an NPN transistor, rated at 100 mA and 40 VDC, suitable for driving an LED.
The transistor turns on when the measured temperature is outside the set limits. For
example, if the limits are set at 0°C and 70°C, the transistor is off when the temperature
is between 0°C and 70°C, and turns on when the temperature is less than 0°C or
greater than 70°C, within the specified accuracy limits.
Aeroflex Plainview
SCD8642-08 Rev B 2/5/09
3
D. Built In Test (BIT) Discrete Output
BIT Functions:
BIT Output:
The Control Logic autonomously performs a series of internal tests to verify that
the circuits are operating correctly. These tests include measuring:
2V reference
4V reference
Power Supply Monitor
PLL frequency
PLL closed loop
Open/shorted temperature sensors (all 4)
The "All OK" LED is lit and the discrete output is high when no errors are
detected by BIT.
E. Power Supply
Input Voltage:
Brownout
Protection:
F.
The balancing unit meets all functional requirements for input voltages from
16.0 VDC to 34.0 VDC.
No damage (to either the 8642-08 card or the battery) can occur for any input
voltage between 0 VDC and 34.0 VDC.
On/Off Control Circuit
Latching Relay:
A latching relay is included on the card. When this relay is latched (turned on),
the DC-DC converter output voltages are on, and the balancing card operates.
When the latching relay is reset (turned off), the balancing card is inactive. The
latching relay is magnetically latched, and maintains its state without power.
On Command:
The On command must be a pulse with amplitude of 16.0 volts to 34.0 volts
and pulse width of 10.0 milliseconds or greater.
Off Command:
The Off command must be a pulse with amplitude of 16.0 volts to 34.0 volts
and pulse width of 10.0 milliseconds or greater.
G. Settings in Nonvolatile Memory
Nonvolatile
Memory:
The Control Logic contains a nonvolatile memory which holds settings for
certain functions.
These settings can be customized at the factory.
These settings include the following:
1) Hi Cell limit (1.25mV/bit)
2) Lo Cell limit (1.25 mV/bit)
3) Hi Temp 1 limit (2’s complement degrees C)
4) Lo Temp 1 limit (2’s complement degrees C)
5) Hi Temp 2 limit (2’s complement degrees C)
6) Lo Temp 2 limit (2’s complement degrees C)
7) Hi/Lo Cell hysteresis (1.25mV/bit)
8) In Balance limit (1.25mV/bit)
9) Out of Balance limit (1.25mV/bit)
10) Balancing duty cycle [1/(n+1)]
Aeroflex Plainview
SCD8642-08 Rev B 2/5/09
4
H. On Board LED Indicators.
LED
Indicators:
There are 8 LEDs on the top side of the 8642-08 for quick status of the
following parameters:
1) BAL ACTIVE: This LED is on when the balancer clock is functioning
properly.
2) ALL OK: This LED is on when there are no errors detected by the BIT
circuit, which monitors the following parameters:
a. 2V internal reference
b. 4V internal reference
c. Power Supply Monitor
d. PLL frequency
e. PLL closed loop
f. Open or shorted temperature sensors (all 4)
3) TEMP ERR 4: This LED is on when the temperature sampled by sensor 4
is not within the range set by sensor 4’s upper and lower thresholds.
4) TEMP ERR 3: This LED is on when the temperature sampled by sensor 3
is not within the range set by sensor 3’s upper and lower thresholds.
5) TEMPE ERR 2: This LED is on when the temperature sampled by sensor 2
is not within the range set by sensor 2’s upper and lower thresholds.
6) TEMP ERR 1: This LED is on when the temperature sampled by sensor 1
is not within the range set by sensor 1’s upper and lower thresholds.
7) LOW CELL: This LED is on when the voltage on any of the 8 cells falls
below 3.20 volts.
8) HIGH CELL: This LED is on when the voltage on any of the 8 cells
exceeds 4.20 volts
I.
Serial Output
RS232 Serial Digital
Output:
Continuously outputs the following values:
2V reference voltage
4V reference 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
Thermistor 1 temperature
Thermistor 2 temperature
Thermistor 3 temperature
Thermistor 4 temperature
Power supply monitor voltage
These values are outputted in a comma separated value ASCII format at
115.2K BAUD, 1 stop bit and no parity.
NOTE: When the optional remote LCD display is connected to the 8642-08,
the measurement update rate is slowed to approximately every 30 seconds per
cycle (about 2 seconds per data unit). This is because the data is now being
sent to both the remote display and the RS232 port.
Aeroflex Plainview
SCD8642-08 Rev B 2/5/09
5
J.
Remote LCD Display (Optional)
Continuously outputs the following values:
Built-in test status
2V reference voltage
4V reference 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
Thermistor 1 temperature
Thermistor 2 temperature
Thermistor 3 temperature
Thermistor 4 temperature
Power supply monitor voltage
K. Preconditioning
Function:
L.
A voltage applied between this pin and CELL_RTN, to pre-charge the input
capacitors to match each balancer cell’s voltage with its mating battery cell’s
voltage, which prevents large in-rush currents when the battery is connected to
the balancer.
Mechanical Requirements
Mechanical Size:
The dimensions of the Balancing Card shall be in accordance with the board
outline. The edge measurements are as follows:
Upper Side: 9.00”
Right Side: 5.38”
Left Side: 4.00”
Bottom Side (Connector Side): 7.25”
Connector Types:
Positronic Asia PTE. LTD. – GFSH928M3H
– GFSH928F1H
On Board
Mating Connector
Aeroflex Plainview
SCD8642-08 Rev B 2/5/09
6
Pinouts vs Description
Back View
Pin
#
Description
Pin
#
Pin
#
Description
Pin
#
Description
1
+28VDC
13
OFF LO
25
OUTPUT RTN
37
TS4 RTN
2
NC
14
NC
26
NC
38
CELL RTN
3
+28V RTN
15
PRECONDITIONING
27
RS232 OUT
39
CELL 8+
4
+28VDC
16
NC
28
NC
40
CELL 7+
5
NC
17
TEMP 1 OUT
29
NC 1/
41
CELL 6+
6
+28V RTN
18
TEMP 2 OUT
30
TS1
42
CELL 5+
7
NC
19
TEMP 3 OUT
31
TS1 RTN
43
CELL 4+
8
NC
20
TEMP 4 OUT
32
TS2
44
CELL 3+
9
NC
21
HI CELL OUT
33
TS2 RTN
45
CELL 2+
10
ON HI
22
LO CELL OUT
34
TS3
46
CELL 1+
11
ON LO
23
BIT OUT
35
TS3 RTN
12
OFF HI
24
NC
36
TS4
Description
1/ Factory Test Point
Aeroflex Plainview
SCD8642-08 Rev B 2/5/09
7
9.00
5.38
GFSH928M3H
1.38
0.35
2.40
2.69
7.25
Board Outline
Aeroflex Plainview
SCD8642-08 Rev B 2/5/09
8
Standard Configuration
Power Requirement
83 mA Typ at +28VDC
Operating Temperature
0°C to +70°C
Storage Temperature
-40°C to +85°C
Dimensions
See Board Outline
Weight
14.1oz (400 gm)
Ordering Information
MODEL NUMBER
BEU8642-08
EXPORT CONTROL:
EXPORT WARNING:
This product is controlled for export under the International Traffic in
Arms Regulations (ITAR). A license from the U.S. Department of
State is required prior to the export of this product from the United
States.
Aeroflex’s military and space products are controlled for export under
the International Traffic in Arms Regulations (ITAR) and may not be
sold or proposed or offered for sale to certain countries. (See ITAR
126.1 for complete information.)
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www.aeroflex.com
[email protected]
Aeroflex Microelectronic Solutions reserves the right to
change at any time without notice the specifications, design,
function, or form of its products described herein. All
parameters must be validated for each customer's application
by engineering. No liability is assumed as a result of use of
this product. No patent licenses are implied.
Our passion for performance is defined by three
attributes represented by these three icons:
solution-minded, performance-driven and customer-focused
SCD8642-08 Rev B 2/5/09
9
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