DEMO MANUAL DC2064A
LTC3300-1/LTC6803-2
Bidirectional Cell Balancer
Description
Demonstration Circuit DC2064A is a bidirectional cell
balancer using two
LTC
®
3300-1
ICs to achieve active cell
balancing of up to 12 Li-Ion batteries. The board uses the
LTC6803-2
multi-cell addressable battery stack monitor to
measure cell voltages and two LTC3300-1 ICs to provide
active cell balancing. The demonstration circuit uses a two
window GUI developed for the DC2064A. One window is
a modified version of the GUI for the LTC6803-2 and also
contains a tab to control the LTC3300-1 ICs through the
DC590B USB Serial controller and the second window
reports the status of the LTC3300-1 devices. All the
functions of the LTC6803-2 GUI are supported except
that cell balancing is achieved through the LTC3300-1
ICs by transferring charge from one to six batteries per
LTC3300-1 to the stack or from the stack to one to six
batteries per LTC3300-1.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2064A
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
performance summary
Battery Voltage Range
Stack Voltage
Average Battery Balancing Charge Current (12 Cell)
Average Battery Balancing Discharge Current (12 Cell)
Average Battery Balancing Charge Current (6 Cell)
Average Battery Balancing Discharge Current (6 Cell)
Balancing Efficiency
Specifications are at T
A
= 25°C
3.2V to 4.5V (2.5V to 4.5V)*
60V Max
2.6A (Typ) (4A)*
2.4A (Typ) (3.6A)*
2.2A (Typ) (3.3A)*
2.4A (Typ) (3.6A)*
92% (Typ)
*The battery voltage range may be expanded to 2.5V-4.5V by changing resistor R
TONS
to 19.1k and resistor R
TONP
to 29.4k.
The demo board’s average balancing current is adjustable up to 4A by scaling and installing new values of RS1A and RS1B through RS12A and RS12B.
BoarD photo
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DEMO MANUAL DC2064A
Description
Power Stage Discharge Efficiency
100
100
Power Stage Charge Efficiency
95
6-CELL
EFFICIENCY (%)
EFFICIENCY (%)
90
12-CELL
95
6-CELL
12-CELL
90
85
85
80
80
75
2.6
2.8
3.0 3.2 3.4
3.6
CELL VOLTAGE (V)
3.8
4.0
75
2.6
2.8
3.0 3.2 3.4
3.6
CELL VOLTAGE (V)
3.8
4.0
Figure 1. DC2064A Size 5.5"
×
12.2"
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DEMO MANUAL DC2064A
operating principle
Operation of the LTC6803-2 is detailed in the LTC6803-2
data sheet and the operation of the DC2064A GUI is similar
to the DC1652A GUI except additional functionality was
added to control the LTC3300-1 balancing devices. Refer
to the Quick Start Guide for the DC1652B for operation
of the LTC6803-2 GUI. The DC2064A has a two window
GUI, one window based on the DC1652A GUI to control
the LTC6803-2 with a tab to control the LTC3300-1 for
battery balancing and the second window to display the
status of the LTC3300-1 based on the command and status
registers read from the LTC3300-1.
The LTC3300-1 active balancer is a power stage control
IC. The LTC3300-1 does not have a balancer algorithm
built into it. The determination of the balancing times and
directions are performed at a system level and conveyed to
the LTC3300-1 through its SPI interface. The LTC3300-1
only accepts battery charge or discharge commands.
Charge is transferred to/from a cell (battery) from/to the
stack, a series connection of adjacent cells, through a
flyback converter that is operating in boundary mode.
During discharge of a cell, the current in the primary of
a coupled inductor transformer with a turns ratio of 1:2,
ramps up to 6.25A at which point the primary switch turns
off. The charge in the primary inductor is transferred to
the secondary inductor which is connected across the
12-cell pack. This pack current then passes through the
series connected cells thus distributing the charge equally
across each cell. When charging a cell, the current, in the
secondary of the coupled inductor transformer, ramps up
to 3.125A at which point the secondary switch turns off.
The charge in the secondary inductor is transferred to the
primary inductor which is connected across the cell. The
secondary current is drawn from the series connected
cells thus removing charge equally across each cell. The
efficiency through the flyback converter is ≈92%.
Quick start proceDure
The demonstration circuit is set up per Figure 29 to evaluate
the performance of the DC2064A bidirectional cell balancer
using the LTC3300-1.
Caution: BOT6_TS and TOP6_TS turrets must not be al-
lowed to float and must be connected to their respective
top of stack-battery terminal.
Using short twisted-pair leads for any power connec-
tions, refer to Figure 29 for the proper measurement and
equipment setup. The DC2064A will support a system of
4 to 12 batteries.
Recommended Cell Connection Sequence
The recommended cell connection sequence is to connect
the V
–
connection first followed by connecting cells 1
through cell 12. Disconnection of the cells should follow
this sequence in the reverse order with the V
–
connection
being removed last. Connecting the V
–
connection first and
removing last is recommended because the V
–
connection
is the ground reference for the circuitry within the demo
board. After connecting the V
–
, all other cell connection
sequence is less critical as long as the cell circuit
capacitances are matched as they are in the demo board.
Following the recommended cell connection removes the
possibility of excessive voltage on any of the lower cells
due to an imbalance in cell circuit capacitance.
Follow the procedure outlined in the DC1835A Quick
Start Guide for general use of the modified LTC6803-2
GUI window. The 4-bit board ID code that is set by the
A0 through A3 jumpers on the DC2064A must match the
board Address box in the LTC6803-2 GUI window shown
in Figure 2 for each board in the system.
Figure 2. Board Address Box
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DEMO MANUAL DC2064A
Quick start proceDure
The Voltage Comparator box must be turned off and the
VREF must remain on during balancing. Set window by
using the Up/Down arrows to the right of the box. See
Figure 3.
Click the START CELL VOLT button followed by the READ
CELL VOLT to verify that the batteries are connected and
that the LTC6803-2 can read the battery voltages.
Figure 3. Voltage Comparator Box
The DC2064A GUI periodically checks for OV and UV
measured on the cells when balancing. To avoid the
program from suspending balancing from an OV or UV
measurement during normal operation, the OV and UV
values must be entered in the VOV and VUV text boxes
on the LTC6803-2 tab shown in Figure 4.
Figure 6. Start Cell Voltage Read Box
To access the LTC3300-1 screen, click on the LTC3300-1
tab in the upper left of the LTC6803-2 GUI window.
Figure 7. LTC3300-1 Screen Select Box
Within this window you can manually select which cells
are to be discharged by clicking the cell’s DISCHARGE
button and which cells are to be charged by clicking the
cell’s CHARGE button.
Figure 4. VOV and VUV text boxes
Once this is done, Click the WRITE CONFIG button and
verify that the configuration was set correctly by clicking
the READ CONFIG.
Figure 8. Balance Mode Select Boxes
Figure 5. Write Configuration Box
To write this configuration, the WRITE button followed by
the SEND button must be clicked. To enable the balancers,
the EXECUTE button followed by the SEND button must be
clicked. To pause the cell balancers, the SUSPEND button
is clicked followed by clicking the SEND button. This will
turn off all balancers until the EXECUTE button is clicked
followed by clicking the SEND button. This will resume
the previous settings of the cell charge/discharge settings.
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DEMO MANUAL DC2064A
Quick start proceDure
To do this, select the DISCHARGE or CHARGE button for
the desired cell, then enter the time in seconds into the
cells “BALANCE TIME” text box. Press the enter key on
the key board or select another button in the GUI to load
the time. When all the desired balance actions and times
have been entered, select the “Balance Cells” START but-
ton to start the balancing sequence.
Figure 9. Write/Execute Command Box
To change any of the settings “on the fly”, a new charge/
discharge setting is entered using the respective CHARGE
and DISCHARGE buttons followed by clicking the WRITE
button followed by the SEND button and then the EXECUTE
button followed by the SEND button. To disable any cell
from operating, the cell’s NONE button must be clicked
in the balance mode box followed by clicking the WRITE
button followed by the SEND button and then the EXECUTE
button followed by the SEND button.
The LTC3300-1 GUI allows the user to program the balancer
to charge or discharge each cell for a specific amount of
time. The LTC3300-1 is a power stage control IC. The
determination of the balancing times and directions are
done at the System level and conveyed to the LTC3300-1
through its SPI communications port. In order to perform
a timed balance, the TIMED BALANCE check shown in
Figure 10 must be selected to have access to the timed
balance controls as shown in Figure 27.
Figure 11. Balance Cells Start Box
The START button will display PAUSE. The balancing
algorithm will first turn off all cells, then set all cells to
be balanced. The cells will run until the first cell(s) have
elapsed their balance time. At this time all cell balancing is
suspended, the completed cell’s balancing action is set to
“None”, the remaining times to balance are recalculated,
then the remaining cells continue to balance until the next
cell(s) have completed. This sequence continues until all
of the balance times have elapsed.
Selecting the PAUSE button while the balancer is running,
will shut off the active cell and pause the timer. The START
button now displays CONTINUE. Selecting the CONTINUE
button again will start the active cell balancing and continue
the timer. After the last cell has completed balancing, all
the cells are turned off. The START button will again display
START. Selecting the RESET button will reset all the cell
actions and times to the previous entered settings.
The LTC3300 STATUS window displays the status of all
LTC3300-1 ICs in the system. This GUI is updated every
time the LTC3300-1 status or command registers are read.
When the balancer timer is running, the command register
is read after each execute command is sent.
Figure 10. TIMED BALANCE Check Box
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