Second Battery Location for a 150 Sport

Electrical and electronic topics for small boats
LCnSac
Posts: 38
Joined: Tue Mar 29, 2016 7:42 pm

Second Battery Location for a 150 Sport

Postby LCnSac » Tue Feb 14, 2017 2:10 am

Without thinking this through, I mounted a Terrova trolling motor (40-lbs) on the starboard bow [of a 15-Foot Boston Whaler boat] and a second deep-cycle battery (55-lbs) in the boat's side console next to the starting battery. Now the boat lists to starboard five to ten degrees when I'm alone in the boat. With a passenger on the thwart seat the boat trim is fine.

My proposed solution is to add a second 6-gallon fuel tank (more than 35-lbs) under the thwart seat on the port side, and relocate the deep-cycle battery to the port side somewhere.

--Where is the best place to mount the second battery on the port side of a Boston Whaler 150 SPORT?

--What is the proper mounting? I am assuming two footman loops screwed to the deck with proper preparation.

I'm sure I'll have to upgrade the trolling motor wiring as the battery will be quite a ways away now.

Another possible option is to eliminate the second fuel tank and carry it when needed, and mount the battery under the thwart.

--What is the safe distance from a battery box to a fuel tank?

Thank you.

Jefecinco
Posts: 1592
Joined: Fri Oct 09, 2015 6:35 pm
Location: Gulf Shores, AL

Re: Second Battery Location for a 150 Sport

Postby Jefecinco » Tue Feb 14, 2017 9:15 am

I would consider the total power requirement for your 150 Sport with the objective of using a single high capacity AGM battery for engine starting and the trolling motor. Do you really need a 55 pound deep cycle battery to operate the trolling motor? Perhaps a single group 31 AGM would get the job done if your trolling motor is well sized to your Sport?

If you are concerned about being unable to start your engine after trolling you can take a micro battery along for jump starting. Your engine may also be capable of starting by hand with a recoil or pull rope. Mounting your trolling motor aft would also simplify the wiring requirements. This would add weight aft but overall it could be worthwhile.

If your starting battery is located aft as in the Sport 15s you could add your second battery there.
Butch

jimh
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Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
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Re: Second Battery Location for a 150 Sport

Postby jimh » Tue Feb 14, 2017 1:32 pm

On all small boats the distribution of weight like a 55-lbs battery affects the boat's trim, often quite substantially, depending on the hull form. There is no way to overcome the effects on the static trim, other than to redistribute the weight. It may be possible to correct for trim when underway with trim tabs, but I don't see that as a workable solution on a 15-foot boat.

For advice on the minimum distance that should be maintained between a fuel tank and a lead-acid storage battery, I recommend consulting with the American Boat and Yacht Council (ABYC) recommendations. I don't know exactly where you can find them on-line for free; try some searching. There usually are excerpts from the ABYC recommendations posted, but not the complete set of recommendations.

Modern on-deck fuel tanks are no longer vented to the atmosphere except under conditions of extreme pressurization that might cause damage. On that basis an on-deck fuel tank should not be emitting gasoline in a vapor form.

Lead-acid batteries can emit hydrogen gas if the battery design is a conventional flooded cell and vented construction. Typically this occurs during charging when the battery state of charge is already at full-charge and further charging current begins to boil off the electrolyte. To prevent outgassing, do not overcharge the battery. If you are concerned about hydrogen gas emission from the batteries, change to a sealed battery, which for marine use will typically be an absorbed glass mat (AGM) lead-acid battery.

In general, there should not be any electrical sparking occurring at a battery; if there were some sparking it would be abnormal and probably due to poor connection at the battery terminals. You would likely notice this problem before very long.

In general, in order for there to be a risk of gasoline vapor exploding or for hydrogen vapor to explode there must be a particular density in the air. As long as the on-deck battery and the on-deck fuel tank are exposed to open air and thus well vented, I don't think there is a high risk of explosion--I assume that was the focus of your inquiry about the distance between them.

It is common on small open boats for the battery and fuel tank to be located near each other.