Custom excerpt length WooCommerce product

In the end I used substr to deal with the excerpt length inside the slider function. Set is at 140 chars from the beginning. This works quite well:

function featured_products_slider()
{

    $args = array(
        'post_type' => 'product',
        'meta_key'   => '_featured',
        'meta_value'    =>  'yes',
        'post_status' => 'publish'
    );

    $featured   = get_posts($args);

    foreach ($featured as $post) {
        $thumb_id = get_post_thumbnail_id($post, 'featured');
        $imageUrl = wp_get_attachment_url($thumb_id);
        $permaLink=     get_permalink($post);
        $authorID   =   $post->post_author;
        $post_excerpt     =   get_the_excerpt( $post );
        $productIntro = substr($post_excerpt, 1, 140);
        $title  =   $post->post_title;
        $date = get_the_date('M j, Y', $post->ID);
        ?>
            <li>
                <div class="featured-post-slide">
                    <div class="post-background" style="background-image:url('<?=$imageUrl;?>');"></div>
                    <div class="shadow"></div>
                    <div class="post-content">
                        <h1 class="slide-title">
                            <a href="https://wordpress.stackexchange.com/questions/256529/<?=$permaLink?>"><?=$title?></a></h1>
                        <p>
                            <?= $productIntro ?>
                        </p>
                        <a href="https://wordpress.stackexchange.com/questions/256529/<?=$permaLink?>" title="<?=$title?>" class="button stroke more-link">Shop now</a>
                    </div>
                </div>
            </li>
            <?php
    }
}