Is a battery an ignition source?

[LinedTheBlind]

Hi,

I've got a small duck boat with electric start outboad motor. I've been considering mounting the starter battery in a storage space next to the portable gas tank, but I'm not sure if that would be safe. The storage compartment has one side open facing the cockpit. (The boat has high sides and an open cockpit about 4x8 feet). The gas tank has a vent on its' cap. The boat is trailered and always travels on the highway for 30+ minutes before starting. I'm assuming this sufficiently vents the vapors from the boat when it's lanched but, what about after 3 hrs of hunting. Would it still be safe to start the engine with the battery that close to the gas tank.

I couldn't find any info on the coast guard page or on here. Thanks.

[bruceb]

Any battery can be an ignition source- if a terminal is a little loose or damaged by water, a spark can (and will ) happen when you try to draw power. Not often, but I would not chance it. I assume your boat is partly decked? Gas vapors sink, and if you are in still air, can easily build up to an explosive mix. A sailboat exploded in my area a few years ago from a similar mistake. They had opened a hatch before starting the outboard, but I think that only gave the bilge enough oxygen to catch. I think I would try to separate the battery from the fuel tank and/or use a proper bilge blower.

[marshmat]

The Canadian small-craft standards ( http://www.tc.gc.ca/publications/EN/...HR/TP1332E.pdf ) consider a fuel tank space like you describe to be an open space, ie. no ventilation system required, if it has at least one square foot open to the atmosphere for every ten cubic feet of volume (0.34 m^2 per m^3) and no long unvented spaces in which a flame could propagate, per TP1332E 2004 6.3.3. Note that if there are spaces lower down in the boat that are not open, and where fuel vapours could collect, they need a ventilation system.

That same standard, sec. 6.5.1, requires that any space containing a battery must provide a means for hydrogen to escape.

So, if gasoline vapour (which sinks) can get out to the atmosphere, and hydrogen (which rises) can similarly escape, it is my understanding that there would be no prohibition on having the battery and the gas tank in the same compartment.

If either of these vapours would be trapped in the compartment, you could be risking an explosion and would need to fit a proper spark-proof blower, underway ventilation system, etc.

[bruceb]

I think my concern is that at least some "duckboats" have partly enclosed decks, and some hunters even use a camo tarp over themselves and the cockpit . I guess it all depends on how hard you have to work to trick the ducks. Bruce

[alan white]

I'd recommend a battery switch (marine enclosed type) for any boat that is covered by a tarp. It could be located to one side just under the aft deck. Flip the battery off and no sparks should occur (should the bilge pump suddenly go on and a bad battery connection exists). Rare to have this happen, but my guess is the 10cubic foot per one square foot rule mentioned would be broken using a tarp. The switch is also a good idea when the boat sits on a trailer between uses, a way to ensure no energy is lost to minor shorts or the pump running.

[LinedTheBlind]

Thanks for the response guys. I think I'll work on an exterior vent for the tank.