Hello ... I have the Digital Nano that is 5 years old. The pool chemistry is correct but the display started showing : Warning ! low cell volts ...... I cleaned the cell twice (remove cell, cap the one end with plug, water/acid mix for 20 minutes). When I return it to service it read 14 volts and 5 amps. After about an hour it reads 2 volts and 5 amps. The warning will only show periodically, it is not a steady warning sign. In the past it has always maintained 16 volts and 5 amps. Do I need a new cell ? Or should I try cleaning the cell again ?