With regard to batteries, I will offer my experiences in recent years. With my boat not being used as often as some before I moved to Cobbs, I always seemed to be having problems using Numax leisure batteries, 110 amp hour, they frequently lost their charge, so much so that I always carried a jump starter in the boot of the car. I then decided to lash out and bought an Optima Blue Top battery which is designed for starting and delivers a 'bigger burst of power on starting. Since that time, 3 years ago, I have never had to charge it, the least it has gone down to is 12.8 volts which it was when I brought it home recently as it had been unused since the beginning of November. They are expensive but I can honestly say, this is the first time I have not had to cross my fingers on starting after a lay up.
Terry.