Boaters ask me all the time
Q:what's up with my boat batteries? they only last a year or two. The same battery in my car lasts 5 to 10 years
A: batteries can loose up to one percent of their charge per day while your boat is not used .in your car you recharge the battery every time you start the motor starting the motor in most cases uses 2-4%of the capacity of the battery and the alternator puts it rite back in keeping the battery 95% charged all the time
so lets say you let the boat set 4 months at this point the battery is just about dead even before you go to start the boat . this cycling up and down kills the batteries
If you would like to take better care of your batteries and give them a chance to last as long as they do in a car they need to maintained kept charged especially in the winter . A discharged battery will freeze just like a water pipe or engine block when water is left in them . Most will prefer to take the batteries out during the winter and charge them with a trickle type charger over night a couple times a month . during the summer the new solar panels are nice and the price has come down considerably the last couple of year If you have not used the boat in the last three weeks or so a small charger the night before you plan on going boating. And remember to keep the battery and especially the cable connections clean and tight . If you been having problems with the longevity of the batteries in you boat this usually makes all the difference in the world