Sea Ray

Welcome to the forum.

The best option is for battery storage to permit periodic charging.

Idle batteries lose about 10% state of charge (SOC) per month, more at warmer temperatures.

Batteries permitted to remain at low SOC, under 50%, suffer permanent damage called sulfation, that decreases the capacity.

When I was winterizing my boat I would yank the six group 31 batteries and used a custom charging interconnect system I designed / built to permit safe / correct periodic charging of all batteries from a single operation.

@Bert Agostino, note that it is safer to disconnect the battery negative terminal instead of positive. The metal wrench touching the battery nut could contact nearby metal. There is more nearby metal at ground potential (voltage) than at +12V potential, so removal of all battery negative wires first, followed by +12V wires is safer. Care must be followed regardless when working on the unfused battery wires.

You should pull them out and bring store them in a cool dry place with a battery maintainer attached. Wouldn't use Trickle chargers,. They are used to charge a battery that has been drained and should be pulled off once the battery is charged. A maintainer can be kept on the battery the entire time you're storing it.

Thank you all for taking the time to reply. I've learned some new words/terms/acronyms: SOC and Sulfation. I made note of disconnecting the negative terminal.

I've tried both taking them out or leaving them in. There's no difference except I don't have to lift them. Most important thing is to top off the fluid and charge them. I don't even disconnect them. Batteries usually last me five seasons.

Ahoy there, 3 years ago I replaced my 3 batteries with larger heavier batteries and realized 3 80 lb batteries were no fun taking out of the engine compartment so I stated to leave a shore power cord attached and coiled up on the swim platform so I could actually charge them once a month in the winter (also did not disconnect the batteries). Just make sure anything that may drain them is turned off and don't forget the in cabin fume detectors.

Assuming you are hauling the boat, does it have a drain plug? Are you wrapping the boat? If the answer to both questions is no then you will want to leave the batteries in and hooked up so your boat doesn't sink on land.

This is my first season with a powerboat, having had a sailboat for the past eight years. I decided to bite the bullet and pay for heated indoor storage. No more draining every pipe and dealing with shrink wrapping or a custom cover. My 400 Sundancer has 5 batteries, and having wrestled with replacing 2 of them in July, I decided to leave them in the boat!

The answer to this question depends on what type of batteries you have.

If they are lead acid batteries, then they should be disconnected at haul out placed on a battery maintainer. If you can have power to your boat via and extension cord, this is easy. If not, then you should remove them from the boat and keep them on a maintainer at home. A third option would be to access the boat once a month with a battery charger, but this is less then ideal and takes time.

If you let your lead acid batteries discharge for long periods of time over the winter without maintaining their charge, this greatly reduces their life and will lead to frequent replacement.

If your batteries are AGM (absorbed glass matt) batteries, which are the preferred type for the marine market, then disconnect them at haul out and leave them in the boat.

AGM batteries will not discharge over time like lead acid batteries so they will be happy just resting out a long winter. Thusly, AGM batteries will outlive lead acid type by a factor of three to four or longer.