Up until about 2 months ago, I had one battery that started my electric start 15 HP Johnson motor, ran my 55 lb Minn-kota trolling motor and powered my very old Eagle depth finder. Also wired to front and rear lights on my 14 ft 1972 Mirrocraft aluminum boat. Ran this way for a couple or years, but have had issues with batteries lasting very long. Switched to a new starting battery to start the motor and bought a new Marine/RV battery for the trolling motor & depth finder about a month ago. I have a 5 amp charger that I use to charge the battery after each use. Went out today and the new battery wasn't holding a charge apparently after being on the charger for a couple days. Registers 9 Volts on my voltage meter. Could there be a short or something that is draining the battery? After replacing the battery several times in the last year, there must be something other than every battery I buy being bad. I am looking for suggestions, as wiring/electrical is not my strong suit. Thanks.