Simple Model of Ni-MH Battery Model using PSpice

Nickel-Metal Hydride 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. Ni-Mh 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=7
6.2 Discharge Time Characteristic, NS=7
Simulation Index


1. Benefit of the Model

• The model enables circuit designer to predict and optimize Ni-MH
battery runtime and circuit performance.

• The model can be easily adjusted to your own Ni-MH 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.


2. Model Feature

• This Ni-MH Battery Simplified SPICE Behavioral Model is for users who
require the model of a Ni-MH Battery as a part of their system.
• The model accounts for Battery Voltage(Vbat) vs. Battery Capacity Level (SOC)
Characteristic, so it can perform battery charge and discharge time at
various current rate conditions.
• As a simplified model, the effects of cycle number and temperature are
neglected.


3. Concept of the Model

Ni-Mh battery +
Simplified SPICE Behavioral Model
[Spec: C, NS]
Output
Characteristics
Adjustable SOC [ 0-1(100%) ]
-
• 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 Ni-mh cells are in series to
increase battery voltage level.


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
+ - N I-M H _ B A T T E R Y – e.g. NS=1 for 1 cell battery, NS=2 for 2 cells battery
TS C A LE = 1 (battery voltage is double from 1 cell)
U 1 C = 1350M
SO C = 1 SOC is the initial state of charge in percent
N S = 1 – e.g. SOC=0 for a empty battery (0%), SOC=1 for a full
charged battery (100%)

(Default values) TSCALE turns TSCALE seconds(in the real world) into a
second(in simulation)
– e.g. TSCALE=60 turns 60s or 1min (in the real world)
into a second(in simulation), TSCALE=3600 turns 3600s
or 1h into a second.

• From the Ni-Mh Battery specification, the model is characterized by setting parameters
C, NS, SOC and TSCALE.


5. Ni-Mh Battery Specification (Example)

Nominal Voltage 1.2V

Typical 1350mAh
Capacity
+ - N I-M H _ B A T T E R Y
TSC A LE = 1 Minimum 1250mAh
U 1 SO C = 1
C = 1350M Charging Current × Time 1350mA × about 1.1h
N S = 1
Discharge cut-off voltage 1.0V
Battery capacity
Battery capacity
[Typ.] is input as aa
[Typ.] is input as
model parameter
model parameter

• The battery information refer to a battery part number HF-A1U of SANYO.


Measurement Simulation
1. 8V

1. 7V

1. 6V

1. 5V

Charge: 1350mA
1. 4V

1. 3V

1. 2V

1. 1V

1. 0V
0s 10s 20s 30s 40s 50s 60s 70s 80s
V( HI )
(min.)
Ti me

• Charging Current: 1350mA × about 1.1h
TS C A LE = 60
U 1 C = 1350M
SO C = 0 SOC=0 means
SOC=0 means
N S = 1 battery start from 0%
battery start from 0%
of capacity (empty)
of capacity (empty)


− Simulation Circuit and Setting

PARAMETERS:
ra te = 1
C Ah = 1350m

H I
Charge Voltage
Charge Voltage
C 1
OUT+
V in OUT- 10n
3V
0 IB A TT
IN+
IN-

G 1
L im it ( V ( % I N + , % I N - ) / 1 m , 0 , r a t e * C A h ) 0
0 + - N I-M H _ B A T T E R Y
TSC ALE = 60
AAconstant current charger at
constant current charger at U 1 C = 1350M
rate of capacity (e.g. SO C = 0
rate of capacity (e.g. 11minute into aa
N S = 1 minute into
1×1350mA)
1×1350mA) second (in simulation)
second (in simulation)

*Analysis directives:
.TRAN 0 62 0 25m
.PROBE V(*) I(*) W(*) D(*) NOISE(*)


5.2 Discharge Time Characteristic
• Battery voltage vs. time are simulated at 0.2C, 1.0C, and 2.0C discharge rates.

1. 6V

PARAMETERS:
ra te = 1
C Ah = 1350m 1. 5V
sense
H I

1. 4V
C 1 0
IN+ OUT+ 10n + - N I-M H _ B A T T E R Y
TS C A LE = 60
IN- OUT- 0 U 1 C = 1350M 1. 3V
G 1 SO C = 1 0.2C
G VALU E N S = 1
lim it ( V ( % I N + , % I N - ) / 1 m , 0 , r a t e * C A h )
1. 2V

0 TSCALE turns 11minute into aa
TSCALE turns minute into 1C
second(in simulation), battery starts
second(in simulation), battery starts 1. 1V
from 100% of capacity (fully
from 100% of capacity (fully
charged)
charged) 2C
1. 0V

0. 9V
*Analysis directives: 0s 60s
V( HI )
120s 180s 240s 300s 360s
(min.)
.TRAN 0 360 0 100m Ti me

.STEP PARAM rate LIST 0.2,1,2

Measurement Simulation
1.6
0.2C (270mA)
1.5 1.0C (1350mA)
2.0C (2700mA)
1.4

1.3

1.2

1.1 270mA
1350mA

C
V
g
a
o
e
1.0 2700mA

]
[
t
l
0.9
0 250 500 750 1000 1250 1500
Discharge Capacity [mAh]

Simulation
1.2
1.0
TS C A LE = 60
U 1 C = 1350M 0.8
SO C = 1 0.6
N S = 1 0.4
Mesurement
0.2
C
A

• Nominal Voltage: 1.2V
p
a
u
y
c

Simulation
t
i
l
%
C
R

0.0
p
d
e
a
o
y
c
)
(
t
f
i

• Capacity: 1350mAh 0 1 2 3 4 5
• Discharge cut-off voltage: 1.0V Discharge Rate (Multiples of C)



PARAMETERS:
ra te = 0 .2
C Ah = 1350m
sense
H I

C 1 0
IN+ OUT+ AAconstant current
constant current 10n + - N I-M H _ B A T T E R Y
discharger at rate of TSC ALE = 60
IN- OUT- discharger at rate of 0 U 1 C = 1350M
G 1
capacity (e.g. 1×1350mA)
capacity (e.g. 1×1350mA) SO C = 1
G VALU E N S = 1
lim it ( V ( % I N + , % I N - ) / 1 m , 0 , r a t e * C A h ) 11minute into aa
minute into

0

.TRAN 0 296.4 0 100m


6. Extend the number of Cell (Example)

Ni-MH needs 77
Ni-MH needs
cells to reach
cells to reach
this voltage level
this voltage level
Basic Specification
TS C A LE = 3600 Voltage - Rated 8.4V
U 1 SO C = 1
C = 1500M
Capacity 1500mAh
N S = 7
The number of
The number of Structure 1 Row x 7 Cells Side to Side
cells in series is
cells in series is
input as aamodel
input as model Number of Cells 7
parameter
parameter

Voltage − Rated 8.4
NS = =
Ni - MH Nominal Voltage 1.2
• The battery information refer to a battery part number HHR-150AAB01F7
of Panasonic.


The battery needs 5 hours to be fully charged
12. 6V

11. 9V

11. 2V

10. 5V

Voltage
9. 8V

9. 1V

8. 4V

7. 7V

7. 0V
0s 1s 2s 3s 4s 5s 6s 7s 8s 9s 10s
V( HI ) (hour)
Ti me

• Charging Current: 300mA (0.2 Charge)



PARAMETERS:
ra te = 0 .2
C Ah = 1500m

H I
Charge Voltage
Charge Voltage
C 1
OUT+
V in OUT- 10n
12V
0 IB A TT
IN+
IN-

G 1
L im it ( V ( % I N + , % I N - ) / 1 m , 0 , r a t e * C A h ) 0
0 + - N I-M H _ B A T T E R Y
TSC ALE = 3600
U 1 C = 1500M
SO C = 0
N S = 7
11hour into aasecond
hour into second
(in simulation)
(in simulation)
.TRAN 0 5.2 0 2.5m


11. 2V

10. 5V

9. 8V

9. 1V

0.2C
8. 4V
0.5C

7. 7V 1C

7. 0V

6. 3V
0s 1. 0s 2. 0s 3. 0s 4. 0s 5. 0s 6. 0s
V( HI ) (hour)
Ti me

• Voltage - Rated: 8.4V
• Discharging Current: 300mA(0.2C), 750mA(0.5C), 1500mA(1.0C)


Parametric sweep
Parametric sweep
“rate” for multiple rate
“rate” for multiple rate
discharge simulation
discharge simulation
PARAMETERS:
ra te = 1
C Ah = 1500m
sense
H I

C 1 0
IN+ OUT+ 10n + - N I-M H _ B A T T E R Y
TSC A LE = 3600
IN- OUT- 0 U 1 C = 1500M
G 1 SO C = 1
G VALU E N S = 7
lim it ( V ( % I N + , % I N - ) / 1 m , 0 , r a t e * C A h ) 11hour into aasecond
hour into second
(in simulation)
(in simulation)

0

.TRAN 0 6 0 2.5m
.STEP PARAM rate LIST 0.2,0.5,1

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=7....................... Charge_Time(NS)
5. Discharge Time Characteristic, NS=7................... Discharge_Time(NS)


Simple Model of Ni-MH Battery Model using PSpice

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