I just put 2oz of mineral oil (3-in-1) in each cell of my wet cell 6 volt batteries. This greatly reduces the evaporation of the water in hot climates. I'm staying in Pahrump NV right now and checked the batteries just a couple weeks ago after having been here for months. No water loss at all. Neither do I have any corrosion. I've been using the oil for over a decade and I seldom have to add water. Maybe 2X per year.
Here's how they look most
of the time. My 12 volt batteries below this tray are no maintenance batteries so they don't have removable caps and so far they're doing a great job staying corrosion free.
The oil is much less expensive and easier to deal with than the watering systems. BTW, this isn't some brand new hack, Edison recommended mineral oil.
The oil can help reduce problems if an owner has an older converter that might tend to over charge the batteries. Not completely, but somewhat. Newer converters that automatically drop to float mode are best of course, and the oil is in addition to their operation.