public function scheduleBatch($schedule_time, $num_batches = 2, $stagger_mins = 5) {
        $payload = array(
            'cid' => $this->cid,
            'schedule_time' => $schedule_time,
            'num_batches' => $num_batches,
            'stagger_mins' => $stagger_mins
        );
        $apiCall = 'campaigns/schedule-batch';
        $data = $this->requestMonkey($apiCall, $payload);
        $data = json_decode($data, true);
        if (isset($data['error']))
            throw new MailchimpAPIException($data);
        else
            return true;
    }