Help with catamaran wiring and layout

Yikes. reading through some of the exchanges here just reminds me how little I know. Fortunately I am just getting started with the wiring for my cat project, and may be able to avert a few headaches with your help.

First I just have a few basic questions and will make a few comments just to see if I am on a good course. My boat is a 36' sailing cat that will primarily be used for day/ weekend trips.

Power sources are twin tohatsu 9.8’s with alternators, and one 100 watt solar panel w controller.(Renogy).

Minimum power requirements will be engine starting, led strip lights in each hull and and on deck, one bilge pump in each hull, one wash down pump on deck, two digital depth sounders, nav/anchor, spotlight, compass and spreader lights, vhf, and stereo sound system, charging ports for phones, etc.

OK, my thinking is that I should have three independent 12 volt systems, because of the layout and distance between hulls, and so I could spilt the loads up , and avoid isolator switches. Is this better than an integrated system?

.Seems the power hogs will be wash down pump, stereo and vhf. (correct?) The third battery could live in the steering console, (amidships aft) and be powered by 100w solar only , for the nav lights, and vhf (occasional use)? Battery is a standard deep cycle “car” sized- don’t know the amps, but at least it would be portable. I do have a set of jumper cables aboard.

Question: will 100 watt solar panel support a stereo (sometimes i like it loud) with occasional (rare) vhf transmissions?

Any brand recommendations for stereo system? I have been looking at those bose systems and will want to store the music in an i pod or something.

The starting batts in each hull (one per motor) are a bit larger, though not golf cart size.

Any comments appreciated.

another Question; I read somewhere that too much battery capacity can damage an alternator. So, would i have that risk if i added another battery to my starting bank?
*
*Thanks!

 

Sounds good to have separate systems per hull, you could easy run a cable set to connect if you like.
As an example, my wife & I lived aboard for a couple of years comfy on a 33' cat, had a single Yamaha 9.9 4/ with limited charging, 2 x 40W solar panels & a single bank of 3 x 78 AH small truck batteries. Back up starting was via hand start, only used twice due to low charge- late night party. Had stereo, small tv, lighting & pumps for fresh water, solar regulator was good, batteries were healthy after 7 years. No refridgeration as great shops close by & if cruising would pay the butcher to bag/cryovac/pull down & then would bury in shave ice from fish co-ops, could go 7-10 days with a nice leg roast for the kettle barby on the last day...
Jeff.

 

Hey Jeff, your power requirements sound about like mine

My thinking is that if I had a situation where one of the motors would not start I could just unhook the battery from the console, take it down below and hook up the jumper cables. The battery is easy to get to and not too heavy. It is a 500 amp "marine" battery. It would be charged with the 100 watt solar panel. I don't have it hooked up yet.
For starters, I just have to figure out how much usage the solar panel will support. Does this mean that if I have a 500 watt stereo, I will be using about 42amps/hour? (500/12=~41.6) And so the battery ,if fully charged would go flat in about 12 hours? (500amps/41.6=~12 hrs?) If this is all about right, then that at least gives me an idea. I wanted to have VHF, and Nav lights hooked up also though. Maybe I could split off the steaming lights, and spreader lights to go to one of the tohatsu batteries, to lessen the load on the solar batt.

then there are the tohatsu alternators, which put out about 6 amps peak- a little less than the solar panel, and I will rarely be running them all day, so I am guessing their batteries should be loaded up much lighter. Any comments appreciated.

 

Close, Charly.

You can only effectively get half the rated amps out of a battery.

So... 500 watt load (stereo on 10 volume setting) would be 6 hours.

Do not discharge standard lead/acid batteries below 50%. It dramatically shortens the life.

 

OK, so the stereo power requirement would be defrayed by about 8 amps per hour by the solar input (100 watt/12=~8 amps) . If we just plug in,say six hours of good sun=~ 48 more amps/day to burn- roughly another hour of Crosby Stills and Nash, or total seven hours of loud stereo. Roughly speaking. I could live with less than that, so I am thinking (hope) i would still have room for a few VHF transmissions, etc. Correct me if I am wrong here; VHF at 25 watts means continuous transmission for one hour consumes only 25 watts (significantly less than the full blast stereo)??

 

You have the basic idea right on defraying the battery drain, but again, in real life, it doesn't work exactly as you'd expect.

Solar panels are greatly affected by shadows from rigging, clouds, solar angle and length of day (solar insolation) and of course, sunset.

Then, there are also losses when the solar charge controller is operating and even the fact that the energy you put into a battery doesn't all come back out.

So... solar is quite tricky. Ask the manufacturer to give you real output for your geographic location.

Correct regarding your VHF.

Also, your 500 watt stereo should consume significantly less power than 500 watts... because you're not trying to blow your speakers at max volume the whole time you use it.

You may have to just go with some Neil Young.

Thread drift: Where did you get your rig? Need one as well and am not located too far from where you are.

 

Yeah, there are going to be some significant shadows. I plan to mount mine forward on the awning frame. It will double as a spray shield . I know that sounds crazy, but I am going to try it there anyways. Later when i can afford it, I may convert to the flexible panels and mount them atop the awning, but even there there will be shadows from the boom etc.

Mast is from US spars in Gainsville. Sails sail covers and rigging are from Sails by Morgan from Cocoa. Scott Morgan coordinated the mast stepping. Wires etc came from Sailing Services in Miami, also through Scott. Ill be posting more about it all on the build thread as soon as i have the time to get some pics.

 

We should have different words for the power rating of audio stuff, microwave ovens, VHF radio etc. because calling it all "watts" is too confusing.

The 500 watt stereo will not burn a 6 amp fuse (6 times 12 is 72 watts!) The stereo watts are peak music power, that means the amplifier can produce a 500 watts pulse for just a tiny fraction of a second. That's good because otherwise your speakers would go up in smoke. So the number 500 says something about the amount of noise, not the power consumption.

The VHF can deliver 25 watts of RF energy to the antenna when you press the talk button. It can do that for a few minutes until a thermal safety circuit cuts the power. During transmission the set draws approx. 5 amps because the efficiency is only 50%.

A 1000 watts microwave really draws 1000 watts but doesn't put more than 650 watts in the chicken you want to thaw. So there the number 1000 refers to the current consumption.

And finally the 100 watts of the solar panel: here the number 100 is the peak voltage times the peak current on a clear day with the panel looking straight to the sun. The electrical energy reaching your battery is approx. 80%, if the sun is at 45 degrees only 40% remains.

 

Thanks guys, I have learned a lot from this exchange already.

Next thing I guess to do is prioritize and figure the loads of the other most important items, i.e. nav/anchor lights and engine starting.

After more thinking about it, I guess there is nothing to lose (other than the expense) by mounting a parallel switch near the console for emergency starting if the one engine battery per side won't cut it. These batteries are about 30 feet apart.

It would be nice to have separate panels with plenty of breakers and batt condition meters in each hull, but I may have to go with less. Anyone have any supplier/brand recommendations?

 

solar strip lights

I just ordered a 16 foot strip to try out on the deck. It was only 14 bucks from amazon, so I don't expect much. I will let y'all know how they work out. Anybody else using these?

 

For sound equipment the power rating that is important is RMS. That is the equivalent to DC power.

 

Thanks Ike!

Guys, I just want to stop and encourage anyone serious about learning boat building stuff to check out Ike's site if you haven't already. I finally got around to clicking through his basic electricity section. I wish I had done so much sooner. He, and folks like him have made the world a better place. Thanks Ike!

http://newboatbuilders.com/pages/design.html

 

I got the solar panel mounted and the controller hooked up... so far so good.
It services the independent battery that is stored at the helmstation console.

I fished all the wires from the mast- anchor, tricolor, spreader lights, steaming light, and still have room to hook up the stereo and vhf.

I bought one of these blue sea deck panels with breakers and switches (image)

The thing is,The panel comes stock with 15 amp breakers. the smallest breaker they make is three amps. So I bought one of these fuse panels to go along with it, and now I am confused about how to hook it all up.It would be so much simpler to just wire up the breaker panel and be done with it.

Questions: What size fuses should protect the masthead lights? Is a three amp breaker too much?

The fuse panel only has one positive connection on the battery side for the whole panel, and a screw on the load side of each breaker to connect to each individual appliance. The breaker panel has the same thing- so I can't just wire straight across (or can I?)- IOW have a fuse in line and a breaker in line also, then the positive wire to the load? I could just wire in an in-line fuse, but that would seem to defeat the purpose of having a fuse block, excpet I need the negative bus anyways.

Any comments appreciated.

 

Charly, the breakers protect the wires, not the lights.

Your breakers are there to pop if a current greater than 15 amps appears in the wire, which would indicate a short or some other major problem. The breakers kerp your wire from becoming like a toaster heating element and catching your boat on fire.

This is all the breaker is for. You don't need the fuses.

Wire the positive side to a breaker, then off to the positive side of the load.

Next, wire the negative side of the load to the negative bus inside the breaker panel.

Done.

 

I'll wire your boat if you do my tiller arms!