hi; i have a bottom line depth finder/side finder unit; i was fishing on a local lake and decided to leave the area that i was fishing; i cranked up my boat and turned the depth finder off because i was not using it very much at the time; after i reached my new destination i turned the unit on to scan a open water spot and the unit said system failure:; check battery; i checked all connections to the battery and they were good;tried it again and again and again and it read the same thing; can anyone help me out with this; thanks