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Old 02-03-2013, 23:24   #1
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How many watts? And how many 12v batteries

I just purchased my first boat. A Columbia contender 24...no too shabby for a 19 year old kid. As of right now the only thing electric in it is the VHF and the lights. I'm going to switch everything to LEDs add a stereo, maybe a plotter a couple of small fans and enough juice to charge laptop, cellphone, and camera. How many 12vs would I need and also how many watts in solar panels would I need for something like that. Any other tips trick or help is always appreciated.
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Old 02-03-2013, 23:38   #2
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Re: How many watts? And how many 12v batteries

As a ballpark figure (by saving you the math behind it)...on a daily basis, you will need about 150 Amp. To translate that into Watt Power, multiply it by your battery's output voltage 12 V...this is equal to 1800 Watt (1.8 KW). This would require 5 solar panels (@ 360 W output - 80% daily solar exposure). Because of available space on your boat, you may not be able to install 5 solar panels, then you'd want to add a wind power generator to compensate for your requirements. Have fun! Mauritz
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Old 02-03-2013, 23:45   #3
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Re: How many watts? And how many 12v batteries

The devil is in the details.
It's difficult to answer without details of your location, type of laptop, hours of usage etc but for a ball park figure I would be looking at 100-150w of solar and about 200Ahrs of battery capacity.
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Old 03-03-2013, 00:11   #4
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Re: How many watts? And how many 12v batteries

Congrats on your boat purchase. Since most of us are cruisers we tend to up the ante for solar production and storage. With your loads combined with you dumping the hot, inefficient incandescents for LEDs, a single 140 watt panel and (2) 6 volt golf cart batteries in series will handle your needs with ease.

Large screen laptop @ 8 hours of use 70 w-hr
LED cabin lights, nav lights, anchor lights normal usage per day 40 w-hr
Chart plotter 6 watts at 24 hours 144 w-hr
(2) fans 20 watts each X 8 hours 320 w-hr
Stereo, that is up to you. Volume level pleasing to a 50 year old, 10 watts 8 hours 80 w-hr. For a 19 year old and a lot of bass, takes too much power.
Charging cell phones and camera 10 w-hr

Total 664 w-hr. 140 watt panel at 5.25 hours of sun exposure = 735 w-hr
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Old 03-03-2013, 00:16   #5
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Re: How many watts? And how many 12v batteries

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..this is equal to 1800 Watt (1.8 KW). This would require 5 solar panels (@ 360 W output - 80% daily solar exposure). Mauritz

Think that is a bit much, its a 24ft boat without a fridge. Allow a bit of leeway for living in a NE US state so some cloudy days and I think Noelex is close to the mark.

Worth doing a search on mounting solar panels we have discussed it at length on here over the years.

Pete
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Old 03-03-2013, 01:11   #6
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Re: How many watts? And how many 12v batteries

I have 350 watts of panels and 5 house batteries.
Tend to use more in port than at sea due to more computer time. Plus at Sea My wind generator helps. Runs Refer/Freezer and a few gps and Vhf no problem. Only have SSB on for an hour or so each morning. have gone more than 35 days at a time without running engine.
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Old 03-03-2013, 05:05   #7
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Thumbs up Re: How many watts? And how many 12v batteries

Hell yeah man, good for you!

Everyone here's talking strictly math when it comes down to electrical demand. Let's talk specifics and budget first. First, where is the boat? Back yard, mooring, or dock? Right away that'll change what I would recommend. Secondly, where is the boat going? Are you setting her up for a mooring and weekend sailing, micro liveaboard in a city that's otherwise unaffordable (that's what I'm doing), trailer sailor, island hopping with buddies, afternoon sail and fish, etc?

If its a matter of afternoons and hangouts you can make do with a pair of deep cycles from walmart. For about 80$ each and charge them at home. If you're looking for more full term, go with the math, figure how many amps you use daily, triple that to get your battery bank size, and figure the total solar to handle slightly more than your total useage per day to make up for clouds and when you want to blast your stereo (which by the way really will use more electricity the louder you play it).

At the moment you can get solar panels on amazon for about 1$ a watt including shipping. If you're technically inclined you can make a small wind turbine/water generator from an appropriately sized treadmill motor encased in pvc and either pvc blades or a used prop, if you go that rout do more research online, there are guys online that'll send you everything you need besides the enclosure and dummy load for a charging circuit for around 20$.

If you do any new wiring try to use marine grade, the individual strands on marine wired are tinned and resist corrosion, not a place to skimp unless you enjoy tracing wires every day to find the bad connections.

My assumptions on your budget here are the opposite what everybody else is assuming, If you've got a ton of money saved for refitting your boat I apologize for assuming otherwise.

Either way, if you're planning to do any amount of work on the boat on your own grab a copy of This Old Boat, by Don Casey, either at the library or bought from a book store. I just checked my copy for price but I lost the dust cover long ago.

Good luck Dillon,
If you're in the New England area PM me and we can race sometime this summer
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Old 03-03-2013, 05:25   #8
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Re: How many watts? And how many 12v batteries

Congratulations on your first boat. I started with a 24 foot Bristol and still have many fond memories cruising with her.

I do fine most days on my 30 foot sailboat with 150 watts of 12 volt solar. Of course your mileage may vary.
On a typical day at anchor I have:
1) An Engel Refridgerator/Freezer operating in freezer mode
2) A small Sony boom box for playing the radio and Cd's along with a VHF radio monitoring traffic.
3) A Carfamo fan or two
4) LED cabin, cockpit, anchor and running lights for after sun down.
5) Occasional charges of cell phones and other devices
6) Underway I have a chart plotter, AIS, depth and speed instruments running too
150 watts works for my needs. I also have on board a Honda 2000 generator that is primary used to charge a 48 volt electric propulsion battery bank but, can be used to charge the 12 volt house bank too. You did not say if you have an engine with an alternator that could also help charge things if needed. If not you might consider having a small backup generator perhaps a Honda 1000. Though I think 150 watts of solar would do you fine.
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Old 03-03-2013, 06:28   #9
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Re: How many watts? And how many 12v batteries

We have 320w of solar and this usually covers our needs, the fridge using almost half of its output, so yeah i agree 150w would probably be enough.
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Old 03-03-2013, 06:48   #10
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Re: How many watts? And how many 12v batteries

Congrats on your first boat!!

Keep it fun and simple. Toss in the number of batteries you can easily fit/afford. Same with the solar panel(s).

Yes, you can figure out exactly the loads, batt capacity and solar sizing, but with your first boat I would keep it basic. That doesn't mean you will be limited in the fun you get from the boat. Besides, if you fall in love with sailing you will be buying another boat in 2-3 years anyway.

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Old 03-03-2013, 07:07   #11
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Re: How many watts? And how many 12v batteries

The amount of wattage you'll need, is about 50% more of what your calculated consumption is. Added electronics "toys" will absorb some of the extra wattage; not to mention, some wattage loss due to heat. That's why, aim for the 150 W consumption target. Mauritz
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Old 03-03-2013, 10:12   #12
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Re: How many watts? And how many 12v batteries

The laptop can be the energy hog. Even more then refrig. When I purchased my last laptop, the most important criteria was watts used. So I purchased a $200 netbook that will run 8 hours on about 100 watts of charge. Most laptops with fast processors and big screens will use 60-80 watts an hour.

As others have said, depending on how much you use the stereo and computer, you might get by with one 130 watt panel and 200 amps of batteries. Or you might need twice that. The big thing is if your at anchor then you'll want to charge the toys during mid day.

To put that in perspective, I have a small fridge, small netbook, led and CCF lighting and not a lot else and I use about 750-800 watts a day, every day. I have four group 27 batteries and 230 watts of solar panels (2). That carries my day to day loads. A larger laptopor a boom box would mean I would need a third solar panel.
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Old 03-03-2013, 10:33   #13
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Re: How many watts? And how many 12v batteries

SailorChic...lots of batteries and power consumption...ummm...considering opening a bookie joint? Mauritz
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Old 03-03-2013, 10:41   #14
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Re: How many watts? And how many 12v batteries

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Originally Posted by Teknav View Post
As a ballpark figure (by saving you the math behind it)...on a daily basis, you will need about 150 Amp. To translate that into Watt Power, multiply it by your battery's output voltage 12 V...this is equal to 1800 Watt (1.8 KW). This would require 5 solar panels (@ 360 W output - 80% daily solar exposure). Because of available space on your boat, you may not be able to install 5 solar panels, then you'd want to add a wind power generator to compensate for your requirements. Have fun! Mauritz
"you will need about 150 Amp..."
Uh.... I dont think so... my boat used less than that in the tropics with refrigeration, laptop, ham etc... I think DeckOfficer has it pretty close..... 50-65 amps perday... if you are using all those things.... which you probably arent.
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Old 03-03-2013, 10:46   #15
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Re: How many watts? And how many 12v batteries

dillon - did you buy the boat in titusville florida?
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