allwpilib/wpilibc/src/main/native/include/frc/simulation/BatterySim.h

/*----------------------------------------------------------------------------*/
/* Copyright (c) 2020 FIRST. All Rights Reserved.                             */
/* Open Source Software - may be modified and shared by FRC teams. The code   */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project.                                                               */
/*----------------------------------------------------------------------------*/

#pragma once

#include <numeric>

#include <units/current.h>
#include <units/impedance.h>
#include <units/voltage.h>

namespace frc::sim {

class BatterySim {
 public:
  /**
   * Calculate the loaded battery voltage. Use this with
   * {@link RoboRioSim#setVInVoltage(double)} to set the simulated battery
   * voltage, which can then be retrieved with the {@link
   * RobotController#getBatteryVoltage()} method.
   *
   * @param nominalVoltage The nominal battery voltage. Usually 12v.
   * @param resistance     The forward resistance of the battery. Most batteries
   *                       are at or below 20 milliohms.
   * @param currents       The currents drawn from the battery.
   * @return The battery's voltage under load.
   */
  static units::volt_t Calculate(
      units::volt_t nominalVoltage, units::ohm_t resistance,
      std::initializer_list<units::ampere_t> currents) {
    return nominalVoltage -
           std::accumulate(currents.begin(), currents.end(), 0_A) * resistance;
  }

  /**
   * Calculate the loaded battery voltage. Use this with
   * {@link RoboRioSim#setVInVoltage(double)} to set the simulated battery
   * voltage, which can then be retrieved with the {@link
   * RobotController#getBatteryVoltage()} method. This function assumes a
   * nominal voltage of 12v and a resistance of 20 milliohms (0.020 ohms)
   *
   * @param currents The currents drawn from the battery.
   * @return The battery's voltage under load.
   */
  static units::volt_t Calculate(
      std::initializer_list<units::ampere_t> currents) {
    return Calculate(12_V, 0.02_Ohm, currents);
  }
};

}  // namespace frc::sim