When your equipment is worn out or not working at its full capacity, replace it with the American FarmWorks 4V Battery for ESP2M-FS, ESP2M-Z, SS-440 and SS-740 Chargers. Designed for select products, this 4V replacement battery will get your charger back in perfect working order. Please note that most chargers can hold a charge long after they have been unplugged or disconnected from the battery, and an unplugged charger can still shock you. The consumer assumes all risk when repairing or utilizing a charger that has been 'repaired' or modified. In addition, all warranties are null and void and state of federal inspections and approvals (such as UL, CE) are terminated once the charger has been opened.