LiFePO4 Battery Simplified SPICE Behavioral Model (PSpice Version)

1. LiFePO4 Battery
Simplified SPICE Behavioral Model
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020 1

2. Contents
1. Benefit of the Model
2. Model Feature
3. Concept of the Model
4. Parameter Settings
5. LiFePO4 Battery Model Characteristic
6. LiFePO4 Battery Specification (Example)
6.1 Charge Time Characteristic
6.2 Discharge Time Characteristic
6.3 Vbat vs. Capacity Characteristic
Simulation Index
2All Rights Reserved Copyright (C) Bee Technologies Corporation 2020

3. 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
3All Rights Reserved Copyright (C) Bee Technologies Corporation 2020

4. • This LiFePO4 Battery Simplified SPICE Behavioral Model is for users who
require the model of a LiFePO4 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.
2. Model Feature
4
Equivalent circuit of LiFePO4 Battery model
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020
0
0
IN+
IN-
OUT+
OUT-
E1
Voc(Vsoc)0
Vsoc
MINUS
PLUS
Rseries
batt
IN-
OUT+
OUT-
IN+
G1
Ibatt
Ccapacity

5. 3. Concept of the Model
5
LiFePO4 battery
Simplified SPICE Behavioral Model
[Spec: C, NS]
Adjustable SOC1 [ 0-1(100%) ]
+
-
• The model is characterized by parameters: C, which represent the battery
capacity and SOC1, 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 LiFePO4 cells are in series to
increase battery voltage level.
Output
Characteristics
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020

6. -+
U1
LIFEPO4_BATTERY
C = 100
SOC1 = 1
NS = 1
TSCALE = 1
4. Parameter Settings
C is the amp-hour battery capacity [Ah]
– e.g. C = 50, 100, or 200 [Ah]
SOC1 is the initial state of charge in percent
– e.g. SOC1=0 for an empty battery (0%), SOC1=1
for a full charged battery (100%)
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)
TSCALE turns TSCALE seconds (in the real world)
into a second (in simulation)
– e.g. TSCALE=60 turns 60s or 1min into a second,
TSCALE=3600 turns 3600s or 1h into a second,
• From the LiFePO4 Battery specification, the model is characterized by setting
parameters C, SOC1, NS and TSCALE.
6
Model Parameters:
(Default values)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020

7. Time
0s 4Ks 8Ks 12Ks 16Ks 20Ks
1 V(BAT) 2 I(IBATT)
2.0V
2.4V
2.8V
3.2V
3.6V
4.0V
1
0A
10A
15A
20A
25A
2
>>
V(X_U1.SOC)*100v
-20 0 20 40 60 80 100 120
V(BAT)
2.0V
2.8V
3.2V
3.6V
4.0V
SEL>>
0
20
40
60
80
100
120
0 0.2 0.4 0.6 0.8 1
Capacity(%)
Discharge (C)
5. LiFePO4 Battery Model Characteristic
7All Rights Reserved Copyright (C) Bee Technologies Corporation 2020
Cell Voltage (NS=1) 3.2V
Over-charge Voltage 3.8V
Discharge Cut-off Voltage 2V
Internal Resistance 1.51m
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
0 0.2 0.4 0.6 0.8 1
Voltage(V)
Capacity x100 (%)
0.125C 0.2C
0.33C 0.5C
1C
Charging Characteristics (0.2C at 25C)
Discharge Voltage Profiles

8. -+
U1
LIFEPO4_BATTERY
C = 100
SOC1 = 1
NS = 4
TSCALE = 1
6. LiFePO4 Battery Specification (Example)
• The battery information refer to a battery part number PSL-BTP-121000 of
Power-Sonic.
8
Nominal Voltage 12.8V
Rated Capacity Typical 100Ah (Constant Current of 0.33C)
Max Current
Charge 80A
Discharge 100A
Discharge Cut-off Voltage 10V
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020
LiFePO4 needs 4 cells to
reach this voltage level

9. PARAMETERS:
rate = 0.2
CAh = 100
N = 4
0
V1
{5V*N}
IBATT
-+
U1
LIFEPO4_BATTERY
C = 100
SOC1 = 0
NS = {N}
TSCALE = 1
BAT
0
C1
10nF
IN-
OUT+
OUT-
IN+
G1
Limit(V(%IN+, %IN-)/0.1m, 0, rate*CAh ) 0
Voch
{(3.8V*N)-9.026m}
DMOD
D1
0
Time
0s 4Ks 8Ks 12Ks 16Ks 20Ks 24Ks
1 V(BAT) 2 I(IBATT)
10V
12V
14V
16V
1
0A
8A
16A
24A
2
>>
V(X_U1.SOC)*100v
-20 0 20 40 60 80 100 120
V(BAT)
10V
12V
14V
16V
SEL>>
6.1 Charge Time Characteristic
9
Current=20A Voltage=15.2V
Measurement Simulation
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020
Over-charge Voltage
(3.8V x NS) – VD1

10. 0
BAT
0
0IN-
OUT+
OUT-
IN+
G1
limit(V(%IN+, %IN-)/0.1m, 0, rate*CAh )
PARAMETERS:
rate = 0.125
CAh = 100
C1
10nF
-+
U1
LIFEPO4_BATTERY
C = 100
SOC1 = 1
NS = 4
TSCALE = 1
IBATT
Time
0s 5Ks 10Ks 15Ks 20Ks 25Ks 30Ks
V(BAT)
10.0V
10.8V
11.2V
11.6V
12.0V
12.4V
12.8V
13.2V
13.6V
14.0V
SEL>>
V(X_U1.SOC_DCH)*100v
0
20
40
60
80
100
6.2 Discharge Time Characteristic
10
0.33C
0.125C
0.2C
Battery voltage vs. Time are simulated at 0.125C, 0.2C, 0.33, 0.5C and 1C discharge rates
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020
0.5C1C

11. 0
20
40
60
80
100
120
0 0.2 0.4 0.6 0.8 1
Capacity(%)
Discharge (C)
10.0
10.4
10.8
11.2
11.6
12.0
12.4
12.8
13.2
13.6
14.0
0 0.2 0.4 0.6 0.8 1
Voltage(V)
Capacity x100 (%)
0.125C 0.2C
0.33C 0.5C
1C
6.3 Vbat vs. Capacity Characteristic
11All Rights Reserved Copyright (C) Bee Technologies Corporation 2020
Battery voltage vs. Capacity(%) are simulated at 0.125C, 0.2C, 0.33, 0.5C and 1C discharge rates
Measurement Simulation
0
BAT
0
0IN-
OUT+
OUT-
IN+
G1
limit(V(%IN+, %IN-)/0.1m, 0, rate*CAh )
PARAMETERS:
rate = 0.125
CAh = 100
C1
10nF
-+
U1
LIFEPO4_BATTERY
C = 100
SOC1 = 1
NS = 4
TSCALE = 60
IBATT

12. Simulation Index
12
Simulations Folder name
LiFePO4 Battery Model Characteristic.........
LiFePO4 Battery Specification (Example)
Charge Time Characteristic……...................
Discharge Time Characteristic......................
Vbat vs. Capacity Characteristic.....................
Charge_Time (x1_T1)
Discharge_Time (x1_T1)
Charge_Time (x4_T1)
Discharge_Time (x4_T1)
Discharge_SOC (x4_T60)
All Rights Reserved Copyright (C) Bee Technologies Corporation 2020