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  #1  
Old 03-06-2010
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Onboard electrical power

I am a bit confused as to what I need here to get some electric going onboard my boat. I am looking to run a small wet/dry vac, small refrigerator, portable ac unit (or portable air cooler) basic interior and exterior lights, maybe a small stove, laptop and stereo. It seems a noisey generator is not very practical, not to mention it needs to be outside. So I am wondering if a good deep cycle battery with an inverter with do the trick? If so, I wonder how long a 105 or 120amp hr battery will keep me running before I need to recharge. If anyone here has some suggestions, please let me know, thanks.
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Old 03-07-2010
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There is a basic formula I X E = P with I = amps and E = voltage and P = watts. All the stuff that mentioned, you will have to get a bigger boat to carry all the batterys that you'll need.
Guy
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Old 03-07-2010
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First, you need to get a clue about 12 VDC electrical systems on sailboats. Running A/C off of a battery bank is really not an option. Get yourself a good book on marine 12 VDC electrical systems, like Charlie Wing's Boatowner's Illustrated Electrical Handbook, Miner Brotherton's "The 12 Volt Bible for Boats" or Nigel Calder's Boatowner's Mechanical and Electrical Manual.

Much of what you want to do can be done using 12 VDC equipment—refrigeration, wet/dry shop vac, cabin lights, navigation lights, stereo and laptop. The stove should be either a propane unit or an unpressurized alcohol unit, like an Origo.

Running any sort of AC on a boat either requires an engine driven system, which is expensive, or a generator to drive a 110 VAC A/C system—less expensive, but more of a PITA IMHO, or using shorepower to run it.

A basic 12 VDC electrical system will require:

1) Batteries—preferably at least two, one for a starting bank and one for a house bank

2) A main DC panel, preferably using circuit breakers rather than fuses

3) A main DC battery switch—I prefer the BlueSea Dual Circuit Plus series of switches, since they isolate the starting and house loads

4) A main fuse for each battery bank—like the BlueSea MegaFuse

5) A ground bus bar or post

6) Battery cables—I recommend getting them from GenuineDealz.com on the internet. They will crimp the lugs you need on the cables if you ask them to for a very reasonable fee. Use Yellow for the 12 VDC ground.

7) Wire—You can buy wire from many different sources. I like the Berkshire marine wire, as it is better than the Ancor IMHO and far less expensive. Genuinedealz also sells pretty good marine wire. Use Yellow for the 12 VDC ground.



I would also highly recommend getting the following to make the 12 VDC system more idiot-proof.

1) A battery combining relay, like the BlueSea ACR, Xantrex Echo Charge or Balmar DuoCharge. Having one of these will allow you to charge both battery banks without user intervention.

2) A good battery monitor, like a Victron BMV 600, which will let you see how much energy you are using, and what the state-of-charge of your house battery bank at any time.



If you keep the boat at a dock with shorepower, you will also want:

1) A 30-amp shorepower inlet socket

2) A main shorepower panel that has a double breaker for the incoming 110 VAC shorepower line

3) A 110 VAC-powered, three-stage, intelligent battery charger—Iota makes a good unit at a reasonable price

4) A GFCI-type 110 VAC outlet



If you keep the boat on a mooring, or plan on cruising longer term, you will probably want:

1) Some solar panels—to recharge the batteries when not connected to shorepower without running the engine

2) An MPPT charge controller for the solar panels

You should probably read the article on Solar Power on Boats I wrote on my blog.



Tools you will probably need/want:

1) A good digital multimeter—I prefer an autoranging unit

2) A good crimper for heat-shrink insulated crimp terminals, like the Ancor 702010.

3) An ultra-fine tip Sharpie marker

4) 3m White Electrical Tape

5) A good wire stripper, like the Ancor 702030.

You should also read Maine Sail's excellent article on terminating electrical wire connections.



As for equipment:

Refrigeration—the only choices are either the Engel or the Norcold portable refrigerators. These have consistently been ranked as best for 12 VDC small refrigerators. They’re actually made in the same factory IIRC. I have an Engel MT27 22-quart refrigerator on my boat. The units are dual voltage and will switch from 12 VDC to 110 VAC automatically.

Lights—I’d go LED with the lighting. It will be more reliable and lower draw than going with either CF, Incandescent or Halogen lighting.

Interior Lights—I’d recommend getting SensiBulb LED-based interior cabin lights. They are the best in terms of color, area of coverage and durability.

Navigation Lights—I'd highly recommend getting USCG-certified LED-based navigation lights, like the AquaSignal Series 32 navigation lights. These will be lower-maintenance, lower energy use, and higher reliability than traditional incandescent navigation lights.

Stereo—Get a good car stereo, unless you need one that is water-resistant. If you have to mount it near the companionway, get a marine unit instead. Read Camaraderie’s excellent article on stereos and speakers.

Stove—The simplest would be to get an unpressurized Origo alcohol stove. It requires no complex installation... just bolt the mounting bracket for it in place and mount the stove. It is available in both gimballed and non-gimbaled mounts.

Shopvac—You can either get a small 110 VAC wet/dry shopvac, or get a 12 VDC powered unit. The 110 VAC units are a bit nicer and more reliable IMHO, but you'll need to have either a shorepower connection or an inverter and a larger battery bank.

Air conditioning—Yeah, not gonna happen. And it really isn’t necessary in most areas. Get some good 12 VDC fans and a couple of windscoops. For fans, I like the Hella Turbos and the Caframo Boras. The Hellas are better for bulkhead mounted fans, since they pivot at the center of the fan fixture. The Caframo Boras are nicer fans IMHO, with three speeds, instead of the two and an electronic switch, rather than mechanical.



A Bit About Batteries

Properly sizing the batteries is something that takes a bit of work. An 120 amp-hour battery really isn’t all that useful, especially if you have high loads on it. The higher the load, relative to the battery size, the lower the effective battery capacity will be. This is why the 20-hour rating is always higher than the 5-hour rating for the same battery. For instance. The 20-hour rating on your example battery is 120 amp-hours or a 6-amp load for 20 hours. If you were to put a 20-amp load on the same battery, it would not give you six hours of use. It would probably give you something more like four-hours of use, or 80-amp-hours total. This is due to the Peukert factor or rating.

Now, lead-acid batteries generally do much better if they are not deeply discharged. Discharging them beyond the 50% level will generally shorten their effective lifespan. So, an 120 amp-hour battery really should only be used for 60-amp-hours or so at the 20-hour rate of discharge. This is one reason I recommend getting a good battery monitor. If you know that you’re constantly running the batteries down below the 50% level, you will realize that you really have to increase your house battery bank size to get the maximum life out of them.


Charging batteries—or why you need an intelligent battery charger.

As for how long you can go between recharging the batteries. That all depends on the size of the battery bank and the loads on it. I would point out that lead-acid batteries don’t charge at a constant rate.

Bulk Phase—Up to about 80–85% charge level, they charge fairly quickly. This is the bulk charging phase, and on wet-cell batteries is about 20–25% of the battery bank’s capacity in amperage. So, for a 200 amp-hour bank, it would charge at 40-50 amps until it reaches this point.

Absorption Phase—Then the amount of current the batteries will accept will drop drastically. This is called the absorption phase. The voltage of the charger will also drop as well. It may well take longer to get from 85% to 99% than it did to get from 50% to 85% because of this.

Float Phase—This is the third charging stage or phase, and the batteries are essentially nearly fully charged at this point. The battery charger drops the voltage down to about 13.5 VDC and the amperage is minimal. The battery charger’s main purpose at this point is to keep the batteries topped off. Most rechargeable batteries self-discharge and without the float phase, would slowly discharge over time.

Quote:
Originally Posted by sailguy40 View Post
I am a bit confused as to what I need here to get some electric going onboard my boat. I am looking to run a small wet/dry vac, small refrigerator, portable ac unit (or portable air cooler) basic interior and exterior lights, maybe a small stove, laptop and stereo. It seems a noisey generator is not very practical, not to mention it needs to be outside. So I am wondering if a good deep cycle battery with an inverter with do the trick? If so, I wonder how long a 105 or 120amp hr battery will keep me running before I need to recharge. If anyone here has some suggestions, please let me know, thanks.
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Last edited by sailingdog; 03-07-2010 at 01:16 AM.
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Old 03-07-2010
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yeah what he said.
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  #5  
Old 03-07-2010
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ok i have a formosa 41 i live on. i have 3 rather large solar panels and i am planning to get a wind genny. i have a honda 2kw genny...lol.....i also have 2 battery banks--one is a d8--i call 3 man and a boy batt as it takes that many to lift it--is for starting the engine, a perkins 4-108. i use the house battery bank--4 of the trojan 6v golf cart batts --they are good and last many years when properly maintained----i have to recharge every day if i use the laptop every night---if i use in daylight and the batteries charge more than i use, i am golden. i use propane stove--as the electric ones use waaay too much electricity and are not efficient enough for onboard use...i rarely use a vacuum cleaner--i clean by hand the surfaces we know of on land as floors..lol--i have teak and holly soles....i use led lighting in the dark and many of those ar ebattery operated as i donot like to waste electricity --my exterior lights are solar powered ....walkway lighting--inexpensive and efficient...i have engine operated refrigeration i rarely use...no need to use fridge for keeping foods cold..lol....many keep well without fridge....there is a book--12 v bible---donot remember the name other than 12 v bible--get it----is white with red and black lettering...in many chandleries--could be nigel calder--donot remember--is excellent---all in all, you will need to use a generator to charge stuff--the sun isnt always strong enough to keep batts charged--my capacity is more than yours by more than 2 times--i have 2X235 amps with 235 amps each bank. the electric stove will not be supported by those batteries--you will need to adjust your usage and needs as you find the capacity not tolerable lol....sorry--but true.....if you are at a dock you will be fine--if on a mooring or at anchor, you will need to find a different method of doing things or add to what you have....
i am not being a smart ass but i found these facts to be true--without all the math ....
a small one burner electric hot plate will take 150 amps per hour ..thru the invertor....so in less than one hour you willnot be able to use the battery anymore----keep it simple--use propane--is more efficient and when used correctly with safety features is excellent...l e d lighting with internal batteries, the walkway lights with solar on each...i have my boats on moorings and i cruise in others boats regularly---have had boats since 1990 for residences---on docks and on anchor and on moorings--if i can help you with anything except math, let me know--the mathematical answer is waaay awesome--but folks like me cannot unnerstan it..lol...i just know what i can get away with and what works...goooodluck...

Last edited by zeehag; 03-07-2010 at 04:27 PM. Reason: boatkat isunt gud speeler--broakd speelchix
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Old 03-08-2010
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Sailguy40,
Not much to add to SailingDog's good info just one suggest one more thing. Before you do anything else do an electricity use audit. In other words write down all the devices you have that use electricity along with the estimated hours of use per day for each device (for example you have an anchor light that runs for 6 hours and it draws 1.5 amps/hour = 9 amps) Use sailguy26 you guys aren't related are you?) formula for converting watts to amps if needed. Add all this up and it will give youi at least a first cut at what size battery bank you need. Then you can start planning how to set it up.
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Old 03-08-2010
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As you do that energy audit, remember that each item really adds up money-wise, as it means more charging and storing of electricity. Figure out your minimum and expand from there in future years.

Regards,
Brad
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Old 08-24-2010
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As previously mentioned the battery capacity is critical. I personally use 4 6v golf cart style batteries (in series and then paralleled) with a total capacity of 450 Ah).

Aside from capacity, in my opinion the two biggest bangs for the buck are a simple portable genset like the Honda EU2000i and a high output alternator.

I tie the genset directly to my shore power which leads into my 3 stage battery charger. When running the generator I have my AC outlets, and switch between water heater and battery charger.

I personally use little light, fridge a few hours a day, regular use of water pump, shower pump and what not and my laptop. I will use about 30-90 Ah a day while at anchor which is some 1-4 hours running the genset. When sailing I run more equipment, but usually not the laptop so things even out.

Remember to try and never run your batteries below 50%, in my case that is no more than 225 Ah before a recharge. Keep the batteries maintained with fluids as well so they have long life. The last bit of charge is the slowest as well which is usually better handled by plugging into shore power rather than run the genset or motor.

One last thought as well, it is always a good idea to keep a separate bank of batteries for starting and running the engine to ensure you do not run down the house and cannot start the engine.

Cheers
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