Week 5 Battery characteristics using drive cycle

WEEK -4

Configuration of Generic Battery Model 

Generic battery model / Block in SIMULINK is generally used to represent system of Rechargeable batteries. 

The parameters of the Battery model can be modified according to a particular type of battery with its charging and discharge characteristics.

Ports:

Conserving Ports:

• (+)  -  Specialized Electrical Conserving Port representing the Positive Battery Terminal
• (-)  -  Specialized Electrical Conserving Port representing the Negative Battery Terminal

Output Port:

• m - Multiple Vector signal output port giving out SoC%, Current and Voltage Signals. A bus selector block can be used to get each output seperately.

REFERENCE BATTERY : LIR18650 (NMC Type) by EEMB Co. Ltd

BASIC SPECIFICATIONS:

CONFIGURATION:

The parameters of the default Battery Model is modified with respect to Values from Datasheet of LIR18650 (NMC type) battery.

The characteristics of the battery model can be plotted with the parameter values without any simulation using PLOT button. 

 CHARACTERISTICS:

• The first Subplot gives the Discharge characteristics of the battery when it is discharged at NOMINAL CURRENT (1.3A) value.
• The Second Subplot gives the comparison of Discharge characteristics of the battery when it is discharged at Current flow rates of 0.25C, 0.5C, 1C, 2C and 4C.
• It is clear from the Nominal Discharge curve of the battery that at 0.5C discharge rate, the battery is able to discharge for about 2 hours before reaching the cut-off voltage value. The following table gives comparison of discharge time with respect to dicharge current rates.

• Hence with increased levels of Current discharge rates, the range of the battery is also reduced drastically.

WEEK - 5 

GENERIC MODEL DISCHARGE & CHARGE WITH UDDS Cycle

SIMULINK MODEL:

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Model Deep View:

A basic battery model of a Lithium Ion battery is configured as shown above. The model consists of

• Battery
• Signal Builder Block
• Controlled Current Source

Signal Builder Block is used to generate signals (Current Signals) depicting the load on the battery. Hence inorder to replicate a real time scenario, UDDS drive cycle data is used as a reference for signal. For simulation, a current signal corresponding to the change in speed in UDDS drive cycle is made and the same is imported to the signal bulider block.

Actual UDDS Drive cycle :

Current Signal Corresponding to UDDS Drive Cycle:

This Current signal is further used to study the Discharge-characteristcs of the configured model.

Battery block is set to Lithium ion battery type with the following parameters:

1) Parameters:

Temperature and aging effects are not considered, keeping the configuration simple.

2) Discharge Characteristics:

• Battery Parameters and Discharge characteristics are modified with reference to the LIR18650 (NMC Type) Battery DataSheet. 

Controlled current source block generates equivalent controlled current signals with respect to the input signal coming from the signal builder block.

SIMULATION RESULTS:

The battery is initially at 100% SoC and is simulated with reference to the reference current signal.

• SoC Plot:

Battery SoC falls from 100% to 91.2% after simulation for a period of 1371s. 

• The highest power demand (peak) in UDDS Drive cycle is at around 200 seconds contributing to the highest discharge of the battery pack where the SoC of the battery pack drops from 98.2% to 96.3% in just 84 seconds.
• The drop in power demand after the peak demand makes the battery to get charged from 96.3% to 96.8% in 45 seconds time.

Hence the simulation of Generic Battery Model with UDDS drive cycle is done and the Discharge & Charge characteristics have been understood.