So Far, handling a wet cell battery IN A SUITABLE CONTAINER without dropping it, or bashing it into things, has not been an issue. I would not try to handle a bare battery that size and weight because it has no handles, and is messy to touch. A VENTED sealed container could also work, if a reliable system is able to do the correct charging scheme.

 

There's pros & cons to every solution. Pick the one that works best. If getting it out of a hull is a pita, then don't remove it. I not sure if any bear will be on the boat to knock over small solar panel. A small 50watt panel is all that is needed to maintain most "car" sized batts. 20watt daily is substantial joules for batt maintaining.

 

I'm saying expect the unexpected - bird poop on a solar panel, the wind wearing out cables, or on land animals knocking things over, water getting in. Or the charge controller died or it needed a reboot (thanks Morningstar).

Nothing is worse than finding dead, sulphated batteries on site after the charging scheme failed.

For the boat (or a car), if the battery is still connected during vehicle storage, the parasite drains are important to know and take into consideration.
A "50W" guideline is OK if the days aren't too short or cloudy, treeline is low etc. Thinking the full solar output power is always there is another myth. Here we can have a month of cloud during winter.

 

I'm saying expect the unexpected - bird poop on a solar panel, the wind wearing out cables, or on land animals knocking things over, water getting in. Or the charge controller died or it needed a reboot (thanks Morningstar).

Nothing is worse than finding dead, sulphated batteries on site after the charging scheme failed.

For the boat (or a car), if the battery is still connected during vehicle storage, the parasite drains are important to know and take into consideration.
A "50W" guideline is OK if the days aren't too short or cloudy, treeline is low etc. Thinking the full solar output power is always there is another myth. Here we can have a month of cloud during winter.

This sulfation I hear about. Tell me more is that why I need a charger overwinter.

 

Lead acid batteries are best stored kept at 100% charge. A mains-powered maintainer or a float charger, or a solar charger system is what I would recommend you use.

If you leave them sitting there, they are slowly (self) discharging and moreso with any boat parasite drains such as the nav, radio, a light left on etc. If your battery is losing say 10% charge per month, left for 3 months, it's down to 70% charge and stubborn sulfate crystals are forming in it. It just means the battery will have a shorter life maybe 2-3 years.

Lead sulfate crystals always accumulate in the plate's pores during discharge. They are small and most are dissolved/reversed during charging - but not if the battery is left discharged for a long time. Then bigger crystals form and these are impossible to get rid of.
For 150 years, people have tried to come up with methods to reverse sulfation- but nothing really works on the bigger sized crystals. Voodoo or snake oil is on par with the many methods out there. Scanning electron microscopes are used by researchers nowadays to see this, there are many research papers on the topic.
The crystals are a mineral- an insulator covering the plates making them electrically smaller. This is why the batteries age, capacity goes down with age, it's sulfate buildup. (corrosion is another big fail mechanism).

I would look at how much cash you have invested in the batteries, I think they spend a lot of their life sitting there, in storage so some solution pays off better than doing nothing.

 

The crystals are a mineral- an insulator covering the plates making them electrically smaller

Minn Kota and others have desulfating cycles to help keep the plates clean, I just not sure any will run a cycle in some auto schedule.

I recommend the OP reach out to Minn Kota (aka Johnson Controls) to discuss further.

 

I looked and Minn Kota chargers do not seem to have any desulfation modes.

The modern NOCO and CTEK chargers, if they "see" a high impedance (badly sulfated) battery they will pulse charge for a while until the terminal voltage comes up to say 12V. Many smart chargers will not inititate charging if they only see 1-2V though. Of course a battery is damaged or worse if it's flat dead for any length of time.

 

I looked and Minn Kota chargers do not seem to have any desulfation modes.

Mine does, but it's a manual button press to run that cycle.
Or did you mean none of MK's have auto cycle?

A fresh batt should last many years free from plate issues. Maybe AGM is a better choice?