Battery Cycling

Battery cycling CC-CV-CC.

Note: This method is experimental and may be subject to change.

This method implements CC-CV-CC Cycling with Delta-I-V and Passed Charge.

Each cycle consist of:

1. Charge at a CC (Constant Current) using Chronopotentiometry. When the target voltage is reached (the upper cut-off voltage limit), switch to CV (Constant Voltage) using Chronoamperometry and maintain the applied voltage for a defined period time or until the minimum current is reached (the lower cut-off current limit).
2. Discharge at a Constant Current (using Chronopotentiometry) until the lower target voltage is reached (the lower cut-off voltage limit).
3. Plot a point at defined time intervals.
4. Send I-V versus time data
5. Send the capacity per charge / discharge step, also known as passed charge (Qpass). The capacity values are absolute and are converted to mAh.

Alternatively for point 3, use "deltas" to reduce data transfer and optimize points.

The time interval will be used for controlling, but some points may be skipped:

• Delta V: when voltage is being measured, plot a point only when a certain variation is reached.
• Delta I: when current is being measured, plot a point only when a certain variation is reached.
• Delta t: plot a point at this defined interval anyway, even if the variation is not met.

The underlying methodscript is described in this application note: https://www.palmsens.com/knowledgebase-article/advanced-battery-cycling-with-methodscript/

Supported devices:

• Nexus
• EmStat4 series (EmStat4S, EmStat4X, MultiEmStat4)

Methods:

• render –

  Render the template with model parameters.

• to_methodscript –

  Convert to MethodSCRIPT class.

Attributes:

• id (Literal['bc']) –

  Unique method identifier.

• potential_max (int) –

  Maximum potential to charge to (units: mV).

• current_min (int) –

  Minimum current to stop the CV charge step (units: μA).

• potential_min (int) –

  Minimum potential to discharge to (units: mV).

• current_charge (int) –

  Constant current to charge with (units: μA).

• current_discharge (int) –

  Constant current to discharge with (units: μA).

• cycles (int) –

  Number of charge and discharge cycles.

• interval (int) –

  Interval time of each measurement point (units: s).

• max_time (int) –

  Maximum duration of each step (if the cut-off is not met) (units: s).

• delta_v (int) –

  Minimum potential variation required for plotting data in CC steps (units: μV).

• delta_i (int) –

  Minimum current variation reuqired for plotting data in the CV step (units: nA).

• delta_t (int) –

  Maximum time without plotting data (units: ms).

• cell_on_ocp (bool) –

  Turns cell on with the measured OCP (Nexus only).

• mains_frequency (Literal[50, 60]) –

  Set the DC mains filter in Hz.

id: Literal['bc'] = 'bc'

potential_max: int = 4300

current_min: int = 5

potential_min: int = 2500

current_charge: int = 100

current_discharge: int = -100

cycles: int = Field(default=100, gt=0)

interval: int = Field(default=100, ge=0)

max_time: int = Field(default=3, ge=0)

delta_v: int = Field(default=100, gt=0)

delta_i: int = Field(default=500, gt=0)

delta_t: int = Field(default=100, ge=0)

cell_on_ocp: bool = False

mains_frequency: Literal[50, 60] = 50

render() -> str

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def render(self) -> str:
    """Render the template with model parameters.

    Returns
    -------
    script : str
        Complete MethodScript code for this method.
    """
    template = env.get_template(self._template)
    return template.render(
        model=self,
        timestamp=datetime.today().replace(microsecond=0),
        version=__version__,
    )

to_methodscript() -> MethodScript

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def to_methodscript(self) -> MethodScript:
    """Convert to MethodSCRIPT class.

    Returns
    -------
    method: MethodScript
        MethodScript class.
    """
    script = self.render()
    return MethodScript(script=script)