If you receive the error message "Unable to create label: 8340 (Package 1 - Special service BATTERY is invalid.)" when booking a FedEx shipment, this means that FedEx does not support batteries for the selected service and format combination.
The best thing to do is to get in contact with your FedEx account manager for advice. Unfortunately FedEx is unable to provide us with an exhaustive list of service and format combinations for which battery shipments are supported.
Should you need any further support or have any other questions, please just get in touch!