Simple Model of Lead-Acid Battery Model using LTspice

Lead-Acid 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. Lead-Acid 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=3
6.2 Discharge Time Characteristic, NS=3
Library Files and Symbol Files Location
Simulation Index


1. Benefit of the Model

• The model enables circuit designer to predict and optimize Lead-
Acid battery runtime and circuit performance.

• The model can be easily adjusted to your own Lead-Acid 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 Lead-Acid Battery Simplified SPICE Behavioral Model is for users who
require the model of a Lead-Acid 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

Lead-Acid battery
+
Simplified SPICE Behavioral Model Output
[Spec: C, NS] 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 Lead-acid 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 = 1, 50, or 100 [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(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 Lead-Acid Battery specification, the model is characterized by setting
parameters C, NS, SOC and TSCALE.


5. Lead-Acid Battery Specification (Example)

Nominal Voltage 2.0 [Vdc] /Cell

Capacity 50Ah

Rated Charge 0.1C10A

Voltage Set 2.23 [Vdc] /Cell

Charging Time 24 [hours] @ 0.1C10A
Battery capacity
[Typ.] is input as a
model parameter

• The battery information refer to a battery part number MSE Series of GS YUASA.


Measurement Simulation

Voltage: 2.23V

Current: 5A (0.1C10A)

(hour)

• Charging Time: 24 [hours] @ 0.1C10A

SOC=0 means
battery start from 0%
of capacity (empty)


 Simulation Circuit and Setting

Charge Voltage

A constant current charger at
rate of capacity (e.g. 150A)

1 hour into a second
(in simulation)
.TRAN 0 24 0 25m
.LIB lead-acid_battery.sub



0.1C10A

0.23C10A

0.65C10A
1.0C10A

(hour)

SOC=1 means
battery start from
100% of capacity



A constant current discharger at
rate of capacity (e.g. 150A)

TSCALE turns 1 hour into a second(in
simulation), battery starts from 100%
of capacity (fully charged)
.TRAN 0 10 0 25m
.STEP PARAM rate LIST 0.1, 0.23, 0.65, 1
.OPTIONS ABSTOL=1.0E-9


@25C

0.1C10A
1.0C10A
0.25C10A
0.6C10A

[0-100%]

Simulation
1.2
Mesurement

(% of Rated Capacity)
1.0
Simulation
0.8
0.6
0.4
0.2
• Nominal Voltage: 2.0V 0.0
• Capacity: 50Ah 0 1 2 3
Discharge Rate (Multiples of C)



A constant current
discharger at rate of
capacity (e.g. 150A)
(in simulation)

.TRAN 0 10 0 100m


6. Extend the number of Cell (Example)

Lead-Acid needs
3 cells to reach
this voltage level
Basic Specification

Voltage - Rated 6.0 [Vdc] /Cell

Capacity 100Ah

The number of cells Rated Charge 0.1C10A
in series is input as
a model parameter Voltage Set 2.23V*3 [Vdc] /Cell

Charging Time 24 [hours] @ 0.1C10A

Voltage  Rated 6
NS  
Lead - Acid Nominal Voltage 2.0

• The battery information refer to a battery part number MSE-100-6
of GS YUASA.



The battery needs 24 hours to be fully charged

Charge Voltage: 6.69V

Charge Current: 10A (0.1C10A)

(hour)

• Charging Current: 10A (0.1C10A)



Charge Voltage

(in simulation)
.TRAN 0 24 0 25m



0.1C10A

0.25C10A
0.6C10A

1.0C10A

(hour)

• Voltage - Rated: 6.0V
• Discharging Current: 10A(0.1C), 23A(0.23C), 65A(0.65C), 100A(1.0C)


Parametric sweep “rate”
for multiple rate
discharge simulation

(in simulation)

.TRAN 0 10 0 25m

Library Files and Symbol Files Location
…¥Simulation

Copy/
Paste C:¥Program Files¥LTC¥LTspiceIV¥lib¥sub
into

Copy/
Paste
into 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


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=3....................... Charge_Time(NS)
5. Discharge Time Characteristic, NS=3................... Discharge_Time(NS)


Simple Model of Lead-Acid Battery Model using LTspice

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