Lithium Ion Battery
Simplified SPICE Behavioral Model
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
1
Contents
1. Benefit of the Model
2. Model Feature
3. Concept of the Model
4. Parameter Settings
5. Li-Ion Battery Specification (Example)
5.1 Charge Time Characteristic
5.2 Discharge Time Characteristic
5.3 Vbat vs. SOC Characteristic
6. Extend the number of Cell (Example)
6.1 Charge Time Characteristic, NS=4
6.2 Discharge Time Characteristic, NS=4
Library Files and Symbol Files Location
Simulation Index
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
2
1. Benefit of the Model
• The model enables circuit designer to predict and optimize battery
runtime and circuit performance.
• The model can be easily adjusted to your own battery specifications
by editing a few parameters that are provided in the datasheet.
• The model is optimized to reduce the convergence error and the
simulation time.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
3
2. Model Feature
•
This Li-Ion Battery Simplified SPICE Behavioral Model is for users who
require the model of a Li-Ion Battery as a part of their system.
•
Battery Voltage(Vbat) vs. Battery Capacity Level (SOC) Characteristic, that can
perform battery charge and discharge time at various current rate conditions,
are accounted by the model.
•
As a simplified model, the effects of cycle number and temperature are
neglected.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
4
3. Concept of the Model
+
Li-Ion battery
Simplified SPICE Behavioral Model
[Spec: C, NS]
Adjustable SOC [ 0-1(100%) ]
Output
Characteristics
-
• The model is characterized by parameters: C, which represent the battery
capacity and SOC, which represent the battery initial capacity level.
• Open-circuit voltage (VOC) vs. SOC is included in the model as an analog
behavioral model (ABM).
• NS (Number of Cells in series) is used when the Li-ion cells are in series to
increase battery voltage level.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
5
4. Parameter Settings
Model Parameters:
C is the amp-hour battery capacity [Ah]
– e.g. C = 0.3, 1.4, or 2.8 [Ah]
NS is the number of cells in series
– e.g. NS=1 for 1 cell battery, NS=2 for 2 cells
battery (battery voltage is double from 1 cell)
SOC is the initial state of charge in percent
– e.g. SOC=0 for a empty battery (0%), SOC=1 for
a full charged battery (100%)
(Default values)
•
TSCALE turns TSCALE seconds into a second
– e.g. TSCALE=60 turns 60s or 1min into a second,
TSCALE=3600 turns 3600s or 1h into a second,
From the Li-Ion Battery specification, the model is characterized by setting parameters
C, NS, SOC and TSCALE.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
6
5. Li-Ion Battery Specification (Example)
Nominal Voltage
3.7V
Nominal
Capacity
Battery capacity
is input as a
model parameter
Typical
1400mAh (0.2C discharge)
Charging Voltage
4.20V±0.05V
Charging Std. Current
700mA
Charge
1400mA
Discharge
2800mA
Max Current
Discharge cut-off voltage
•
2.75V
The battery information refer to a battery part number LIR18500 of EEMB BATTERY.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
7
5.1 Charge Time Characteristic
Measurement
Simulation
Capacity=100%
Voltage=4.20V
Current=700mA
(minute)
SOC=0 means
battery start from 0%
of capacity (empty)
• Charging Voltage: 4.20V±0.05V
• Charging Current: 700mA (0.5 Charge)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
8
5.1 Charge Time Characteristic
 Simulation Circuit and Setting
Over-Voltage Protector:
(Charging Voltage*1) - VF of D1
Input Voltage
1 minute in seconds
.TRAN 0 200s 0 0.5s
.LIB li-ion_battery.sub
.LIB dmod.sub
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
9
5.2 Discharge Time Characteristic
•
Battery voltage vs. time are simulated at 0.2C, 0.5C, and 1C discharge rates.
0.2C
0.5C
TSCALE turns 1 minute in seconds,
battery starts from 100% of capacity (fully charged)
1C
.TRAN 0 300s 0 0.5s
.STEP PARAM rate LIST 0.2, 0.5, 1
.LIB li-ion_battery.sub
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
(minute)
10
5.3 Vbat vs. SOC Characteristic
Measurement
Simulation
0.2C
0.5C
1C
Simulation
Discharge Capacity
(%vs. 0.2C)
1.2
• Nominal Voltage: 3.7V
• Capacity: 1400mAh (0.2C discharge)
• Discharge cut-off voltage: 2.75V
1.0
0.8
0.6
0.4
Mesurement
0.2
Simulation
0.0
0
0.2
0.4
0.6
0.8
1
Battery Discharge Current (vs. C Rate)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
11
5.3 Vbat vs. SOC Characteristic
 Simulation Circuit and Setting
1 minute in seconds
.TRAN 0 300s 0 0.5s
.STEP PARAM rate LIST 0.2, 0.5, 1
.LIB li-ion_battery.sub
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
12
6. Extend the number of Cell (Example)
Li-ion needs 4
cells to reach this
voltage level
Basic Specification
The number of cells
in series is input as
a model parameter
•
Output Voltage
DC 12.8~16.4V
Capacity of Approximately
4400mAh
Input Voltage
DC 20.5V
Charging Time
About 5 hours
The battery information refer to a battery part number PBT-BAT-0001 of BAYSUN
Co., Ltd.
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
13
6.1 Charge Time Characteristic, NS=4
The battery needs 5 hours to be fully charged
Capacity=100%
Voltage=16.8V
Current=880mA
(hour)
• Input Voltage: 20.5V
• Charging Voltage: 16.8V
• Charging Current: 880mA (0.2 Charge)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
14
6.1 Charge Time Characteristic, NS=4
 Simulation Circuit and Setting
Over-Voltage Protector:
(Charging Voltage*4) - VF of D1
Input Voltage
1 Hour in seconds
.TRAN 0 10s 0 0.05s
.LIB li-ion_battery.sub
.LIB dmod.sub
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
15
6.2 Discharge Time Characteristic, NS=4
16.4V
Output
voltage
range
0.5C
12.8V
1C
(hour)
• Charging Voltage: 16.8V
• Charging Current: 880mA (0.2 Charge)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
16
6.2 Discharge Time Characteristic, NS=4
 Simulation Circuit and Setting
Parametric sweep “rate”
1 Hour in seconds
.TRAN 0 2s 0 0.05s
.STEP PARAM rate LIST 0.5, 1
.LIB li-ion_battery.sub
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
17
Library Files and Symbol Files Location
…\Simulation
Copy/
Paste
into
Copy/
Paste
into
C:\Program Files\LTC\LTspiceIV\lib\sub
C:\Program Files\LTC\LTspiceIV\lib\sym
1. Copy the library files (.lib) from the folder …\Simulation\.sub\, then paste into the folder C:\Program
Files\LTC\LTspiceIV\lib\sub
2. Copy the symbol files(.asy) from the folder …\Simulation\.asy\, then paste into the folder C:\Program
Files\LTC\LTspiceIV\lib\sym
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
18
Simulation Index
Simulations
Folder name
1. Charge Time Characteristic.................................
Charge_Time
2. Discharge Time Characteristic.............................
Discharge_Time
3. Vbat vs. SOC Characteristic..................................
Discharge_SOC
4. Charge Time Characteristic, NS=4.......................
Charge_Time(NS)
5. Discharge Time Characteristic, NS=4................... Discharge_Time(NS)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2011
19