Battery Location

[Jim Hawkins]

I want to have 2 - 12 volt deep cycle batteries on my boat and move them from the original place where there was only 1.
My best idea is below the starboard cockpit hatch where there is room for 2 batteries end to end, it is easily accessible, is only 5 feet to my fuse panel and will be close to the solar I mount on the aft rail.
Assuming I build an enclosure and vent the gas to the outside and secure the enclosure and batteries and balance the weight with other storage, does anyone see anything wrong with this location?
The boat is a 1984 Macgregor 25. The plywood and battery in the picture are just for reference.

 

[Benny17441]

Two concerns, (1) is that location dry with no hatch leaks? and (2)if you use a portable gas tank for an outboard would they ever be in proximity?

 

[Jim Hawkins]

Boy, you get right to the tough questions,
1. as dry as any place on my boat (the enclosure I build will be waterproof even if the hatch above isn't quite)
2. I want to make a box in the cockpit for the fuel tank but yes, a demijohn with extra gas would be down there and could be removed anytime the enclose is opened to fiddle with the batteries.

 

[Davidasailor26]

You may want to consider that Maine Sail recommends mounting batteries sideways rather than bow to stern - http://www.pbase.com/mainecruising/flooded_battery_orientation

 

[Jim Hawkins]

Thanks Davidsailor26,
That was a good article, and I take the point. It would have been nice if the author had drawn a line and arrow in each picture designating which was port etc.
Good stuff people, just what I need to know!

 

[THECUSCUS]

On a lightweight boat like the Mac, I would think that you would want the weight of the batteries as close to the centerline of the boat as possible. Also having them that far out, will put them on a steeper angle when you are heeling.

 

[Ukeluthier]

Also having them that far out, will put them on a steeper angle when you are heeling.

Ahem... do you know something about geometry that I'm not aware of?

The batteries will be tilted at the same angle as the angle of heel, regardless of whether they are on the centerline or clear out at the hull. If they are located well outboard, they will be raised or lowered farther relative to their height if located on the centerline, but the angle of their tilt will be exactly the same.

 

[Bad Obsession]

The suggestion about having them closer to the center is a valid one, but for a different reason.

My Compac 23 sits a bit stern heavy. This is due to the fact that I have two GC2 batteries in the area where there use to be only 1 battery.

On a lighter boat you need to balance out the weight. I have a 13.5 gallon water tank forward and a 22lb anchor on the bow sprit. That helps balance the weight of the batteries some, but I also have a 8hp 2cycle outboard hanging off of the stern so that doesn't help.

 

[Benny17441]

I want to make a box in the cockpit for the fuel tank but yes, a demijohn with extra gas would be down there and could be removed anytime the enclose is opened to fiddle with the batteries.

Gasoline and batteries should not be stored in the same compartment. Gasoline fumes are heavier than air and will pool in enclosed spaces and at high concentrations the mix becomes explosive. All it would take is a loose or bad connection at the battery to create a spark that would ignite the fumes. You can use a sealed container to store the gasoline and battery boxes to diminish the risk but that would be your first line of defense with no backup if something fails.

 

[Ukeluthier]

There are two different considerations at play here.

One is trim, making sure weight is balanced in the boat so that it floats on its designed lines... not bow- or stern-down, or listing to one side or the other. A boat not floating on her lines will be slower because of hydrodynamic drag.

The other consideration is moment of inertia, the distance of a heavy object from the boat's center of motion. With a typical sailboat hull shape, the center of motion is a little bit aft of midships and on the longitudinal centerline. This affects how quickly a boat moves in response to wave action, wind changes or steering input.

As a rule of thumb, heavy objects should be kept as low in the boat as possible and as close to the center of motion as is practicable.

 

[Jim Hawkins]

All good points, I really appreciate this forum and the help.
On my little boat there is nowhere where gasoline fumes can't go that's why rather than try to seal off the gas I think I should concentrate on sealing off the battery box and venting it to fresh air. I also have an outboard hanging on the opposite side as my battery placement and by distributing water and gear I have no worries about the added weight.

 

[Jim Hawkins]

As a rule of thumb, heavy objects should be kept as low in the boat as possible and as close to the center of motion as is practicable.

I think Thecuscus was probably taking into account that being out from the center there was more room for sloshing about which would have the same (I should have said similar) effect as a sharper angle.
OK, I'm looking for a center location...

 

[THECUSCUS]

Thanks Ukeluthier for explaining more correctly what I was attempting to say and meant. I pop on this forum between calls at work, and sometimes can't put my thoughts down properly because I'm rushed.