Simple Model of Ni-MH Battery Model using LTspice

Nickel-Metal Hydride BatterySimplified 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

Library Files and Symbol Files Location

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.


• 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.

2. Model Feature


3. Concept of the Model


Ni-Mh batterySimplified SPICE Behavioral Model

[Spec: C, NS]

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.

Output Characteristics

4. Parameter Settings

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


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%)

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.

Model Parameters:

(Default values)

5. Ni-Mh Battery Specification (Example)

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


Nominal Voltage 1.2V

Capacity

Typical 1350mAh

Minimum 1250mAh

Charging Current Time 1350mA about 1.1h

Discharge cut-off voltage 1.0VBattery capacity

[Typ.] is input as a model parameter

Battery capacity [Typ.] is input as a model parameter

5.1 Charge Time Characteristic


• Charging Current: 1350mA about 1.1h

(min.)

Measurement Simulation

Charge: 1350mA

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

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

5.1 Charge Time Characteristic Simulation Circuit and Setting

.TRAN 0 62 0 0.025

.LIB ni-mh_battery.sub


Charge VoltageCharge Voltage

A constant current charger at rate of capacity (e.g.

11350mA)

A constant current charger at rate of capacity (e.g.

11350mA) 1 minute into a

second (in simulation)1 minute into a

second (in simulation)

5.2 Discharge Time Characteristic

.TRAN 0 360 0 100m

.STEP PARAM rate LIST 0.2, 1, 2



0.2C

1C

2C

(min.)

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

TSCALE turns 1 minute into a second(in simulation), battery starts

from 100% of capacity (fully charged)

TSCALE turns 1 minute into a second(in simulation), battery starts

from 100% of capacity (fully charged)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 1 2 3 4 5

Act

ual C

apac

ity(%

of R

ated

Cap

acity

)

Discharge Rate (Multiples of C)

Mesurement

Simulation

5.3 Vbat vs. SOC Characteristic


• Nominal Voltage: 1.2V• Capacity: 1350mAh• Discharge cut-off voltage: 1.0V

2700mA

Measurement Simulation

Simulation

1350mA270mA

(Ah)

5.3 Vbat vs. SOC Characteristic Simulation Circuit and Setting


.TRAN 0 360 0 100m

.STEP PARAM rate LIST 0.2, 1, 2


A constant current discharger at rate of

capacity (e.g. 11350mA)

A constant current discharger at rate of

capacity (e.g. 11350mA)

1 minute into a second (in simulation)

1 minute into a second (in simulation)

6. Extend the number of Cell (Example)

• The battery information refer to a battery part number HHR-150AAB01F7

of Panasonic.


Voltage - Rated 8.4V

Capacity 1500mAh

Structure 1 Row x 7 Cells Side to Side

Number of Cells 7

Basic Specification

2.1

4.8

VoltageNominal MH-NiRatedVoltage

NS

The number of cells in series is input as a model parameter

The number of cells in series is input as a model parameter

Ni-MH needs 7 cells to reach

this voltage level

Ni-MH needs 7 cells to reach

this voltage level

6.1 Charge Time Characteristic, NS=7

• Charging Current: 300mA (0.2 Charge)


Voltage

(hour)

The battery needs 5 hours to be fully charged

6.1 Charge Time Characteristic, NS=7 Simulation Circuit and Setting

.TRAN 0 5.2 0 2.5m



1 hour into a second (in simulation)


Charge VoltageCharge Voltage

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

6.2 Discharge Time Characteristic, NS=7


(hour)

0.2C

1C

0.5C

6.2 Discharge Time Characteristic, NS=7 Simulation Circuit and Setting

.TRAN 0 6 0 2.5m

.STEP PARAM rate LIST 0.2, 0.5, 1

.OPTIONS RELTOL=0.01



Parametric sweep “rate” for multiple rate discharge simulation

Parametric sweep “rate” for multiple rate discharge simulation



Library Files and Symbol Files Location


…\Simulation

C:\Program Files\LTC\LTspiceIV\lib\sub

C:\Program Files\LTC\LTspiceIV\lib\sym

Copy/Paste into

Copy/Paste into

Copy/Paste into

Copy/Paste into

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.................................

2. Discharge Time Characteristic.............................

3. Vbat vs. SOC Characteristic..................................

4. Charge Time Characteristic, NS=7.......................

5. Discharge Time Characteristic, NS=7...................

Charge_Time

Discharge_Time

Discharge_SOC

Charge_Time(NS)

Discharge_Time(NS)

Simple Model of Ni-MH Battery Model using LTspice

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