# Battery (System-Level)

Generic system level battery

• Library:
• Simscape / Driveline / Sources

## Description

The Battery (System-Level) block represents a generic self-discharging battery. You can use the block to model hybrid and battery electric drives at a medium-level fidelity for drive cycle analysis. The block is a simplified version of the Battery (Simscape Electrical) block and uses the same parameters, where applicable. This will aid your transition to a higher fidelity model, if necessary. The Battery (System-Level) does not support battery fade, aging, dynamics, or temperature dependent properties. You can access these features using the Battery (Simscape Electrical) block.

You can choose to simulate a battery with finite or infinite charge. The block can also help you to determine how decreased voltage affects performance and control requirements. To learn more about observing battery performance, see Plot Basic Characteristics for Battery Blocks (Simscape Electrical).

### Battery Model

When you set Battery charge capacity to `Infinite`, the block treats the battery like a resistor and a constant voltage source in series. When you set Battery charge capacity to `Finite`, the block treats the battery like a resistor and a charge-dependent voltage source in series. In this case, the voltage is a function of charge and has the following relationship:

`$V={V}_{0}\left(\frac{\text{SOC}}{1-\beta \left(1-\text{SOC}\right)}\right)$`

where:

• `SOC` (state-of-charge) is the ratio of current charge to rated battery capacity.

• V0 is the voltage when the battery is fully charged at no load, as defined by the Nominal voltage, Vnom parameter.

• β is a constant that is calculated so that the battery voltage is V1 when the charge is AH1. Specify the voltage V1 and ampere-hour rating AH1 using block parameters. AH1 is the charge when the no-load (open-circuit) voltage is V1, and V1 is less than the nominal voltage.

The equation defines an approximate relationship between voltage and remaining charge. This approximation replicates the increasing rate of voltage drop at low charge values and ensures that the battery voltage becomes zero when the charge level is zero. The advantage of this model is that it requires few parameters, which are typically available on manufacturer datasheets.

### Variables

To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables and Initial Conditions for Blocks with Finite Moist Air Volume.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see Modify Nominal Values for a Block Variable.

### Assumptions and Limitations

The block assumes that self-discharge resistance does not depend on the number of discharge cycles.

## Ports

### Conserving

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Electrical conserving port associated with the positive battery terminal.

Electrical conserving port associated with the negative battery terminal.

Thermal conserving port associated with heat transfer.

#### Dependencies

To expose this port, set Thermal port to `Model`.

## Parameters

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### Main

No-load voltage across the battery when it is fully charged.

Internal connection resistance of the battery.

Option to simulate finite or infinite battery charge capacity.

Maximum battery charge. Ampere-hours refer to the number of hours that the battery can discharge 1 Amp. You can specify an initial charge target as a variable.

#### Dependencies

To enable this parameter, set Battery charge capacity to `Finite`.

Fundamental battery output voltage when the charge level is equal to the Charge AH1 when no-load voltage is V1.

#### Dependencies

To enable this parameter, set Battery charge capacity to `Finite`.

Battery charge level corresponding to the no-load output voltage you specify for the Voltage V1 when charge is AH1 parameter.

#### Dependencies

To enable this parameter, set Battery charge capacity to `Finite`.

Option to simulate self-discharge resistance. The block simulates this effect as a resistor across the terminals of the battery.

#### Dependencies

To enable this parameter, set Battery charge capacity to `Finite`.

Resistance across the battery terminals that represents self-discharge.

#### Dependencies

To enable this parameter, set Battery charge capacity to `Finite` and Self-discharge to `Enabled`.

### Thermal Port

Option to expose the thermal port and include thermal effects in your model.

Thermal energy required to change the component temperature by a single degree. The greater the thermal mass, the more resistant the component is to temperature change.

## Version History

Introduced in R2022a