Battery Box

New question--- I have a good bit of unused space below the floorboards between my Twins. Is there a reason that I could not build a batttery box/ boxes below this easily removed floor to free up engine room area. Basically it is the bilge I guess but there is a lot of room down there. Cables could be shortened, the FG box could be built between the stringers like my gray water tank. The bilge waterwould have to be about a foot over the bilge pump before water ever touched the battery box. Thoughts??
Steve

That's where I keep 6 golf cart batteries in my 40 Puget Trawler. A fiberglass battery box fits perfectly between the stringers. Mine are in front of my single engine, but yours should be no problem between your twins.

On my boat the cables come off and are close to the helm and batt switches, and the inverter which is mounted close by also.

Ever see what happens when sea water covers a battery? In an emergency (water over the batts) you'd lose the bank. No engine start? No bilge pump? No radio? Just something to think about.

Rodger Wrona
Rollsdoc
MT49PH

I don't run all my bilge pumps or the starter off my house batteries, but that is a good point. My house batteries are low in the bilge and my start battery is on top of the outboard stringer well up out of any bilge water. The switch to combine or separate the batteries is at the helm, again out of any reasonable water.

Although everyone's minds eye sees a different scenario, I'm hoping that I've got enough other backups going for me that I don't get more than 15 inches of water in my bilge.

Ken Buck

Regardless of the loss of power, let's not forget Ypres-You'll be dead if sea water hits the battery acid.

It'll burn the cables off the posts in minutes. Guess that's one reason we have an 8D gell in the wheelhouse that will run the electronics if the engine room floods.

Rodger Wrona
Rollsdoc
MT49PH

WOW, really? I'm not too sure I saw too many cables burned off on the boats we refloated after partially sinking during our ice storm in the PNW a few years ago. In fact, I didn't see any! Out of the 20 plus boats, many still had 12v lights that worked, or were working, as we tried to get boathouses and common covers off of them. Both at my yacht club and at work where I was working as the Fireboat Officer.

I'm curious how many people have actually seen batteries under salt water? Have you actually seen them burn off in minutes? For those of you in hurricane alley, have you seen this to be true, or is this maybe an urban myth?

Now for the record I don't doubt that eventually the salt water will conduct enough electricity to kill the batteries. And if you allow them to stay under long enough they will dilute with salt water. But "burn the posts off in minutes", I'm a skeptic.

Ken Buck

We had a boat take on water a few years ago*where the gen-set, stb'd engine went partial under and the batteries went completely under. The starters were removed and serviced, the gen-set and engine were flushed and the batteries were replaced. Don't recall of any cables being burned, but they were replaced afterwards due to salt water intrusion.

Strongly recommend placing a critical system like this well above any danger.


El Sea,
1976 44' Thompson-Suite 44
St Petersburg, Fl

WOW, really. Not an urban myth.I didn't say burn the posts off. I said cables. I saw a dive boat that sunk with at least one cable from each 8D burned off. These were new 2/O cables. Our inboard tender was swamped crossing the Gulfstream last year. When we arrived in Bimini the positive cable ends were gone from the starter and battery. The starter brush springs burned also. Ever see an outdrive bubbling in the water from a deffective battery charger? It wont last long. And total minutes can be divided by 60 if you care to convert to hours.

Sorry Ken but I've seen it happen. Guess our salinity is a little higher here on the right coast.

My error, I misquoted. "It'll burn the cables off the posts in minutes."

My misunderstanding. You said cables burn off posts in minutes and I thought you meant just a few minutes. Your example of a swamped tender crossing the Gulfstream was probably in the salt water more minutes that I was envisioning, as was the sunken dive boat. I was wrongly thinking you would have said hours or days if you meant a significant amount of time. Your last post on converting the minutes to hours makes it clear to me now, that you meant a longer period. My appologies.

If batteries are a problem down low, then the bow and stern thrusters with their huge cables are also a problem and will burn off and short out too. Sounds like a bigger problem than just keeping batteries out of the bilge. Since thrusters can't be relocated very easily, it seems like the problem is going to always be there if you have those items installed.

My experience is that I've had batteries sitting in the lowest part of the bilge in three different boats for over 20 years and haven't had any problem. Apparently others have had problems. I'll just keep hoping I don't sink in a place so far away from everything and everyone else that I get stranded. As always your experience may vary and each boater has to decide which risks he is willing to take.

Ken

I have to agree the risk is worth it. Place the house batteries down low in a good high sided battery box.
In doing so I would also ensure I had my emergency equipment mainly HF and VHF radios powered by a separate 12 volt power source (battery) installed in a safe place above the main deck.
I don't know about the US but this (the radio battery)is a survey requirement in Australia.

Benn

All good thinkin'.... I keep a group 24 battery charged in a cabinet on the sundeck. I guess this could be considered a back-up for the BP/electronics. Would not take long to wire up to a component. Any ideas what the USCG would be looking for on these battery boxes? I am still inclined to construct with FG, the floor serving as the lid...........
Steve

Any ideas what the USCG would be looking for on these battery boxes? I am still inclined to construct with FG, the floor serving as the lid...........

For an un inspected vessel there are no particular rules .

For USCG there are battery boxes that have approval, look at Jamestown Marine. site.

Big not expensive and with bolt downs built in.

FF

If you're not putting in a store bought box you want to at least be sure to have the batteries secured. Even though they weigh a lot they can slide in a heavy sea, so some type of tie down is prudent. If you are planning to build a plywood/fiberglass covered box make sure you secure it to the stringers. Screws/lag bolts will work. The strength needed to keep the box from starting to slide is much less than what's needed to stop 6 already sliding T105's when you come down a steep wave and make that stop at the bottom.

Surveyors will also require a cover on top of the batteries so that something can't drop accidentally on top and short out the terminals. I would think that if your sole is a non conductive material, that might work ok. My engine room sole is covered with diamond plate metal on top and plywood underneath. (not a knee friendly surface by the way) Someone could turn the floorboard over and put the metal surface down, so, I also have the fiberglass top to my battery box in place. It's a pain to take off two covers but might someday be important.

Ken Buck

Blue Seas makes boxes.

Charles,
Good to hear from you! Sounds like good advice on the battery sizes and construction. I have a hankering to try my hand at some FG construction- so I'm sure that if not this project - then at least the gray water tank. Are your house batteries above floor level?
Also, did you see my post on the galley sole? Any thoughts there? It*has dropped about *1/2".
Steve

Nother' question........... Any idea of the stringer construction on this Chung Hwa? FG encapsulated beams? If I were to install SS lag bolts into a predrilled hole in the stringer for a battery box installation or support beam mounting - wonder should I put a sealant. Maybe resin? Any chance this is a solid FG beam? Thoughts anyone?

-- Edited by Forkliftt at 20:07, 2008-01-20

When you're working with epoxy, put a vinyl dropcloth down on your table.* The epoxy won't stick to it.

DS

Interesting observation about the vinyl dropcloth. I was reading an old PMM from '02 this weekend about vacuum infusion process and as I recall a vinyl bag was wrapped and taped around the component and the resin was "drawn" in. I wondered how the bag was not glued to the resin. Apparently the two don't bond.By the way- I went into Kemah Hardware this morning (Texas) and saw that they have all sorts of fiberglass supplies. Could be a good source for supplies.
Steve

Forklift - I had the opportunity last fall to visit a boat builder here on Vancouver Island who uses the Vacuum Infusion Process to a very large scale when building their 50 to 60 foot trawlers. It is really something to see as the vacuum is pulled down and the workers get all the wrinkles out of the top sheet and then they open the valve to suck in the resin. Better yet, they mix the resin by the garbage can full !! In only moments the entire object is saturated with resin. If the workers are good at their job the finished piece needs very little sanding to end up with a smooth surface. These people are using this process to make very large sections that are very strong yet comparatively light in weight.

Too bad it takes so much equipment to do large surfaces as it would be a great way to build a boat at home.

John