isUsingBattery(platform = process.platform) {
    switch (platform) {
      case 'darwin':
        return isUsingBatteryDarwin();

      case 'freebsd':
      case 'openbsd':
        return isUsingBatteryBsd();

      case 'linux':
        return isUsingBatteryLinux();

      case 'win32':
        return isUsingBatteryWindows();
    }

    logger.warn(`Battery status is unsupported on the '${platform}' platform.`);

    return null;
  }
Indicates whether the host is running on battery power.  This can cause
performance degredation.

@private
@method isUsingBattery
@for HardwareInfo
@param {String=process.platform} platform The current hardware platform.
                                          USED FOR TESTING ONLY.
@return {null|Boolean} `true` iff the host is running on battery power or
                        `false` if not.  `null` if the battery status
                        cannot be determined.