It may be time for a new cell. You don't indicate where you are.
If in the USA, contact Quality Light Metric, 7095 Hollywood Blvd, Hollywood 90028, tel (323) 467-2265.
If you are in the UK, try the manufacturer Megatron Ltd in London. Telephone +44 (U) 20 8365 9797. E-mail firstname.lastname@example.org