Electrical System write up

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kuriti
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Electrical System write up

Post by kuriti » Sun Apr 08, 2012 2:38 pm

I have seen very little on the forums about electrical systems and it has caused me many hours of grief figuring out, so I thought I would share. I bought this 50 AmpHour AGM battery on Amazon, the cheapest place I could find it. These have really good ability to hold a charge and won’t leak:

http://www.amazon.com/Universal-Power-4 ... 529&sr=8-1

The thing that has given me the most consternation is how to secure the battery upright in an acceptable manner. I kept having nightmares of getting into a squall and being glued to the helm, listening to the 30lb block wreaking havoc down below. I tried to build a small shelf out of wood, but didn’t like the outcome or the amount of space it took up. So, I decided to use two part foam. I didn’t need a lot, so I bought it from this model rocket vendor:

http://www.siriusrocketry.biz/ishop/ind ... cts_id=771

Most foam sold is for flotation and is 2lbs in density, which is not very dense. This foam is 6lbs density and just right for my needs. For foam, lower density means less air and harder foam. You can actually make high density foam less dense by adding a drop or two of water, but you can’t make less dense foam more dense. Anywho, I fiber glassed the inside of the boat box with some cloth to firm it up, then taped up a cardboard box inside to the dimensions I wanted the foam to fill to. Then came the foam. Here is a good website on how to use it. Follow his directions and it is pretty straightforward.

http://bertram31.com/proj/tips/foam.htm

It was fun and I actually ended up thinning it with 2 drops of water on the second pour. Temperature is important for the foam to expand and it was cold, so I used a lamp as a heater. I think it would have expanded more, even without the water, had it been warmer. It is easy to add layers and it bonds well, so I recommend several small pours which allow you to make up for areas where it expands too much in the middle. I think it would be a good idea to wrap the battery in wax paper and suspend it where you want it, then pour, so the foam would fill around a bit and give you a ledge to keep the battery in place, but I didn’t. Once to the level I wanted, I trimmed the foam with a bread knife and box cutter/chisel. It really turned out nice and bonds very well to the hull.
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Final step in securing the battery was to screw in some padeyes where I will use a piece of webbing to snug the battery to the side of the box. I could only upload 3 pics, so you will have to use your imagination on that.

Next is the circuitry. First, I am not an electrician and I don’t recommend you do any wiring if you are not competent, I am just sharing what I did. If you don’t know anything about electronics (like me), the Don Casey book is good, but really too complicated for what we need. I struggled for resources, but figured it out with a buddy’s advice. I will walk through the circuits from the battery hot lead back to the battery ground.

I installed fresh switches and circuit breakers into the original Clark panel which I wanted to preserve. I chose circuit breakers instead of fuses; they sell them at WestMarine that fit into the panel. The hot wire from the battery goes to the first circuit breaker. I crimped the 8ga battery lead and a 10ga wire using a spade connector that fit the circuit breaker. The 10ga wire is a jumper and feeds the next breaker even if the first one opens. The second circuit breaker has the jumper from the first and its own jumper wire continuing the jump to the third circuit breaker. Each circuit breaker is then fed to its own switch. The switch in turn leads to a discrete circuit on the block terminal. The current only flows through a circuit if the amperage is within the circuit breakers capacity (it’s closed) and the switch is closed.
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The hot wires from the switches come into the terminal block. If you didn’t have many devices, you could run the hot wires form the switches directly to the devices. However, I wanted to have space to expand and I don’t think it would be as tidy (safe) putting a bunch of spade splitters on the switch. The wires coming in from the right (pic below) are from the switches. The two wires leaving the top terminal from the left side feed the bow and stern lights. Both of mine are LED, so don’t draw much current, but I still used insulted 10ga wire, just to overbuild. The second circuit has a small speaker amplifier, a usb charger I homemade from an old car charger and the interior dome light (also LED). Instead of having three wires on one terminal, I used jumpers to connect three terminals to the same hot wire from the switch. These three terminals are now all the same circuit. The last circuit is for a cigarette lighter for temporary devices and I intend to add a depth finder and bilge pump later. Don’t be confused by its wires leading up when the others are going down. This is only because it would mount in the panel above it, where all the other wires are headed to other parts of the boat and are routed down.
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From the hot terminal, the wires go out to the device you want to power and come back as negative wires. The negative wires are all attached to the negative bus on the left. A bus is different from a block. A bus is just a slab of metal, so everything attached shares the same amount of charge, unlike the terminal block where each circuit is isolated (unless you have a jumper joining them). So the negative bus is finally attached to an 8ga wire back to the battery.

A final note about the stereo system. I think music is required on a boat; listening to Buffet or reggae while sailing is not optional to me. So, I bought a very small amp made for motorcycles/snowmobiles. I think it is something like 25watts per channel. Then I got two 3” polyplaner speakers and will attach them to the bridge over my hatchway where I am running my cleats for singlehanded set up. Instead of using a head unit, which would suck more power, I have repurposed an old 12v phone charger. I cut the wires that led to the cigarette plug and soldered spade connectors that attach to my terminal block. Then, I cut off the end that led to the phone and soldered it to an old USB cable. There are online guides to this process. Finally, I bought a Bluetooth receiver from Monoprice for $20 that is powered via the USB cable. I then can send tunes to the Bluetooth receiver from my phone in the cockpit, which in turns sends the signal via a standard 3.5m male to male headphone cable to the amp. The amp is powered via its own dedicated lead on the same circuit.

Hope this helps someone!

Kuriti

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Diarmuid
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Re: Electrical System write up

Post by Diarmuid » Mon Apr 09, 2012 3:44 pm

Nice! You are really making this boat over. (Thks, BTW, for your standing rigging info -- I have a new forestay coming from Rigging Only.) We carry a very large battery (Group 27 -- 115AH), because we use a trolling motor for aux power. It lives in a molded box, level with the bulkhead (Mk1) and alongside the keel box. Strapped to the stbd quarterberth. I suppose it could leak if inverted, tho that might be the least of our worries.;)

Definitely fuse any wire carrying real current, or that might carry real current if shorted. Not much room for a dedicated breaker panel on the SJ21, but you can fuse each wire near the battery. I like the automotive-type in-line fuse holders. It will be interesting to see if your battery effects the boat's trim, being outboard. As designed, these boats had, like, two wires on em. Now we have six circuits going to the batt (running lts, bilge pump, 12V in cabin, 12V in cockpit for GPS, tillerpilot, and the 50A trolling motor run.)

Almost got the boat ready, yay. All we need to to tidy up the standing rig, swap out a few control lines, fix a few broken stitches on our sails, and replace the bloody bilge bloody pump that died after 3 bloody months. Shoreline claims to have sent a new one, but it isn't here yet. Oh well. Don't need it til the boat goes on the mooring.

kuriti
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Re: Electrical System write up

Post by kuriti » Mon Apr 09, 2012 6:08 pm

Thanks for the compliment. i have gotten to the age where "good enough" isn't, especially with kids on board. I guess we are even now on idea sharing since I stole your idea for bulkheads and installed them this weekend.

I am not really worried about the battery weight as it is only 30 pounds. I will put the water and other heavy portables in the other box. I just wanted it out of the way and it is smaller in volume than yours or a typical car battery. I was thinking about an inline fuse for the battery hot lead and thought maybe it was overkill, but now I will do it. I couldn't post a final pic, but i hope it goes without saying that i glued the boards inside the battery compartment where the switches reside.

I am really ready to get on the water too. i have done a ton of work this winter and have a few more posts to share before I am through. I am working on a custom gas can that will fit in the lazarette and some comments on the drill/hollow/fill method for through deck fittings. I have a single-handed pamlico sound trip planned in two weeks and a cape lookout with the family in four.

cheers!

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Diarmuid
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Re: Electrical System write up

Post by Diarmuid » Tue Apr 10, 2012 3:14 pm

Definitely fuse any wire big enuf to start a fire if shorted. Things arc & short so easily on a boat. I'd say any wire bigger than ~18g. should have a fuse. They are cheap, & if placed in line don't require much space. (Another reason I like the automotive fuses is the ease of pulling them out to isolate a circuit. Plus no glass tube to break.) Wires should be fused as close to the battery as possible.

A fat wire attached to a battery can get white hot in seconds if shorted. We run our house & shop off very large batteries (24V), & on the few occasions we crossed wires, it was astounding how much damage it did. Far worse than shorting 110VAC. Less deadly to humans, but there's way more current in low-voltage DC.

When our circuits multiplied to rat's nest proportions, we added a Blue Sea bus.

http://bluesea.com/category/82/35/productline/186

Image

These are inexpensive, marinized, and have a cover to prevent your spi pole from accidentally bridging the terminals. There's much debate over whether your bilge pump should be fused, or wired hard to the battery. We fused ours, but with a pretty hefty fuse & wiring to suit. They make fuses that illuminate (LED) when blown, so you would know your pump was inoperable.

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2208cruiser
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Re: Electrical System write up

Post by 2208cruiser » Wed Apr 18, 2012 5:12 am

Great writeup! Thanks for all of the details.

I re-did my electrical a number of years back similarly - it is worth it to use terminal blocks, and I soldered the wires to the spade connectors (which might be overkill). So far, no problems after several years. The load on my electrical system includes: VHF, Depth Sounder, Autopilot, Cabin lights (two 8w fluorescents), Running lights (red/green, white), Masthead light, bilge pump, cigarette lighter (for portable accessories).

I used to have a group 24 car battery, but it proved insufficient during the nine day 2008 Desolation sound cruise. To be fair, I tried using one of those coolers with the cold plate that runs off 12v - I am sure that pretty much flattened my poor battery. No worries, my 8hp Honda has a generator, so we could recharge our digital camera batteries. Next year, for a Barkley Sound cruise of about the same duration, I bought a group 24 deep cycle battery, rated at 80 amp-hours, and weighs about 50 lbs! Turns out it is really an overkill for my loads, even 10 day trips.

The AGM battery is probably a good idea too. My deep cycle is a flooded cell battery with caps, and during an exciting 2 hour beat to windward on San Francisco bay, through the chop and 15-20 knots of wind, I discovered that my battery had tilted in the battery box and lost about 20% of its electrolyte! Not good! So I have a new to-do: secure the battery box. It did come with a nylon strap, which I did not use. Lesson learned! For weekending and fleet racing, I usually use a much smaller/lighter spare 12v car battery.

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Diarmuid
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Re: Electrical System write up

Post by Diarmuid » Wed Apr 18, 2012 4:35 pm

Another trick if you just want enuf juice for a handheld GPS and running lights in the evening: Bring a jump-starter pack.

Image

First year on our boat, that's all we used for our electrical needs. Pigtailed a 12V male plug to the boat's wire harness & plugged it right into the jump pack. They are light, don't spill, & have low self-discharge rates.

corbinstein
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Re: Electrical System write up

Post by corbinstein » Thu May 24, 2012 2:31 pm

The area where you've placed the battery on mine is not cut open...
Is it possible to cut this area open like yours is?
Mine is an older '75 model SJ21 and looks similar, just doesn't have the cutouts with the wood tops...

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cklamp
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Re: Electrical System write up

Post by cklamp » Thu May 24, 2012 5:09 pm

corbinstein, mine is the same, not cut open, but it's on my list of things to do. I could use it for some extra storage.

I don't see any reason why you shouldn't be able to cut it open.

Later
C
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kuriti
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Re: Electrical System write up

Post by kuriti » Mon May 28, 2012 3:36 pm

Sure, break out the sawsall :twisted: . Mine has an inset designed into the fiberglass to accommodate the wood, which you wouldn't have. You would need to figure something out, but you could also cut the hole bigger than mine, which would be nice.

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Diarmuid
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Re: Electrical System write up

Post by Diarmuid » Tue May 29, 2012 4:05 am

One caveat about opening the molded liner areas. They may have been sealed for a reason! Does anyone know if a SJ21 has positive flotation with the cabin swamped? Just giving the volume of the liner a crude hairy eyeball, I'd bet it's pretty darn close to enuf air to keep the gunwhales at sea level ... at least for a while. Maybe long enuf to make other arrangements.;)

My point is, we might want to think twice about cutting holes willy-nilly into these compartments, esp. since most of them communicate with one another to some degree. We've opened two of them on our Mk1: the starboard 'sink' bulge has a flip-down front door with a so-so twist latch. Not a positive seal. The starboard quarterberth has a plastic Bowmar access hatch, latching w/ a fairly positive seal. (It was cut in to add a stringer where the trailer bunks were denting the hull.)

Having all those openings, all with easy passage between them, started making me nervous. So I fitted pieces of plywood to close off the passages & carefully squirt-foamed them into place. Might not stop a proper gusher, but it should slow things down.

We like the newly-opened stowage, but maybe we should consider the value of sealed air chambers, too. :D

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