function save_installation_charges( $cart_item_data, $product_id ) {

        if( isset( $_REQUEST['wcic_installation_charges'] ) && !empty($_REQUEST['wcic_installation_charges']) ) {

            /* This is where the installation charges is stored with cart item as variation */
            $cart_item_data[ 'wcic_installation_charges' ] = $_REQUEST['wcic_installation_charges'];

            /* below statement make sure every add to cart action as unique line item */
            $cart_item_data['unique_key'] = md5( microtime().rand() );
        }

    return $cart_item_data;
}
add_action( 'woocommerce_add_cart_item_data', 'save_installation_charges', 10, 2 );