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Old 13-11-2010, 10:48   #1
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Design Advice on Solar / Regulator / Battery Bank Setup

hi i am in the process of designing my electrical system and would appreciate any advice on the following plans so far.the design is for a 40ft power cat which i will be living on and cruising the islands of the andaman sea in thailand mainly.
it will be powered by 2 honda 50 hp outboards,charging capacity of 17a each (34 total).
i am putting in 8 x 80w 12v solar panels (actual rating 17v x 4.6a).so if the regulator feeds the batteries at approx 13v x (4.6a x 8 panels) the total watts max fed in should be around 478.all these panels will be wired parrallel.
i will use a 60 amp solar regulator between the panels and the battery bank.(this may be overkill,any comment here please? )
the battery bank will be 5 x 120a 12v lead acid n type truck batteries with handles.these also will be wired in parrallel.(6 x 100a is an option,any comment here please ?)
i am trying to keep it as simple as possible and as much of the system 12 volt as possible.basically i will be running the whole boat and starting the 2 motors of the 1 big battery bank.
drawing amps in 12v will be a 12v fridge,autopilot,depth sounder,gps,12v laptop,bilge pumps,nav lights,interior and cockpit lighting most of which will be led,5 small fans.
drawing amps through a 240v invertor ( not sure on size, any comment here please) will be 1 lcd screen (used wisely),i regular laptop,2 moblie phone charges,1 toaster.
there will be a windlass with a circuit braker before the bank as well.at least one engine will be started every time the windlass is operated.

the reason i have chosen these panels and batteries quoted is because that is what is available here at the best price.

any ideas and comments on this would be greatly appreciated.

thks
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Old 13-11-2010, 11:08   #2
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forgot to add there will be a battery monitoring system display unit showing amps in,voltage and amps coming out somwhere in line
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Old 13-11-2010, 11:12   #3
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640w of solar should allow for reasonable and even a couple of unreasonable power demands.
The Toaster worries me . Electric toasters use more than an unreasonable amount of energy. You need a propane means of toasting.
Also I do not think 1 battery bank is wise. You need an independent start battery.(unless you can hand start the outboards)
The laptop and mobile phone would be more efficiently powered with a 12v DC to DC converter
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Old 13-11-2010, 12:18   #4
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Quote:
Originally Posted by noelex 77 View Post
640w of solar should allow for reasonable and even a couple of unreasonable power demands.
The Toaster worries me . Electric toasters use more than an unreasonable amount of energy. You need a propane means of toasting.
Also I do not think 1 battery bank is wise. You need an independent start battery.(unless you can hand start the outboards)
The laptop and mobile phone would be more efficiently powered with a 12v DC to DC converter
.
thanks for the advice i will look into the propane toasting and the dc to dc converter.
i just did a 2 week trip on a friends 35 ft mono with a 27hp yanmar.he has 350watts of solar,5x100amp batteries and he starts motor,runs the whole show off one bank,no prob.i need to check how many amps the outboards chew on startup, i am sure it will be less than the yanmar.i could totally isolate 1 smaller starter battery and put a small say 5 or 10watt trickle charge solar panel on it.
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Old 13-11-2010, 13:22   #5
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Inverters are energy hogs. They have a hight current drain even when not powering anything and take a lot of energy for even small demand. Don't have any equipment that needs AC power that will be on for long periods of time like the fans. Get DC fans which are available through truck/motor home stores if you don't want to buy from a boat chandlery.

Assuming that you have good sun and the panels won't be shaded by anything on the boat, your generation capacity should be more than adequate. Be aware that any overcast, no matter how thin, or shading of panel in the middle of the day greatly decreases panel output.

Have a separate starting battery so you aren't stuck if something goes wrong with the house bank.
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Old 13-11-2010, 14:45   #6
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Doocruiser:

With 640 watts of solar panels you would benefit from a MPPT controller. These cost roughly $100 more than a non MPPT controller but will increase charging by about 100 watts. Be sure and wire the panels with large wire. You will probably need #6 for the final run to the controller to keep the voltage drop reasonable.

"Truck batteries" are almost certainly not true deep cycle batteries. The cheapest deep cycle batteries are 6V golf cart batteries (available everywhere) wired in series/parallel.

Use a separate Group 24 or 27 starting battery and wire it with a 1,2,all switch with the deep cycle batteries connected to 1 and the starting battery connected to 2. The common terminal is connected to the starter and house loads. Start on 2 and then switch to all with the engines running and then switch to 1 when you kill the engines.

Except for the toaster, all of the other AC loads can be powered with a cheap 150W cigarette lighter inverter.

Your daily on the hook amphour usage will be somewhere in the 100-150 range. Your 640 watts of panels will produce about 250 amphours of 12 V power on a sunny tropical day, so you should be easily in balance, particularly with the large battery bank to balance out the cloudy with the sunny days.

David
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Old 13-11-2010, 15:35   #7
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So far so good but you've got to know the loads and times before you can make sure you're on the right side of the battery situation. You need to know how much current each item draws and how many hours/day they run. Once you know those numbers you need to divide the loads into cruising/passagemaking and on the hook/mooring. The highest consumptiion should be your guide.

I've always preferred 6V deep cycle "golf cart" batteries because if one fails, I can generally get another as easily as a 12V, and if not, I've got a spare 6V in case. They're also lighter in weight than a comparable 12V battery.

The current wisdom seems to indicate one huge battery bank, the reasoning being, as far as I can determine, that the battery depletion will be less on a big bank than two banks. For a long time I sailed with 2 house battery banks, alternating days of operation. If you know your wiring, and one battery goes down you can either disconnect it from the bank or throw the switch and isolate it.

Some folks lump the engine start battery into the house but I'm not sure I want the unfortunate experience of having every battery on board unable to start the engine so I keep my engine start battery isolated from the house bank.

Your 2 17A alternators will probably put out a realistic 25A for about 300AH charge capability. 640AH batteries at 75% capacity would be about 480AH (figuring a 180AH load, which isn't unrealistic on a long passage), but you've got a 30% charge penalty. That indicates that you'll need 620AH to charge them back to full (which generally never happens unless you've got one monster charging system). I tend to think you've got the charging portion of the cruise done.

You've got two engines and if you go with2 battery banks, chances are you're going to need some kind of combiner/controller to allow both alternators to work together yet be separated in case one fails. That generally means a dual bank charger.

No doubt the biggest load is going to be the windlass, but on a cat, chances are you'll be anchoring in water a bit shallower than us monohulls. I'd want to make sure the voltage drop from battery to windlass is less than 3% and wires properly sized and fused.

I'd ditch the toaster unless it's a deal killer.

I don't know about cell phone coverage but the power draw is small, ditto the LCD screen and associated hardware if you're aware of the loads. One of the biggest loads I have is my battery operated power tools and a good, strong 120VAC drill.
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