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Old 13-08-2007, 01:40   #1
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The best way to get 30Amps

G'day all you more knowledgable people than me, I hope.

1st please excuse my lack of the techo words, I'm only a simple chap.

Doing a race shortly and have calculated we will use around 25-30 Amps a day on 12V. Mostly nav lights and a little stereo action. Currently 1 x 120a/h battery aboard. Charging off an outboard which puts out 5 amps odd.

The problem is that when sailing the outboard is tucked up in the cockpit so to use it we have to put it in the water. Thats OK except when racing it will slow us down and we don't want to drag that for a few hours a day.

We have a 1000 odd mile leg and estimated it may take 5 days if the weather is slow, maybe more but we seriously hope not. Fingers crossed 3 days only.

As it is a yacht race, bonus points and a cocolate fish to anyother who can sort the issue without adding weight or cost Actually if you can do that a nice bottom of rum

Any ideas on the best way to whack some Amps back in? or any other cunning plan.

At this stage thinking a cheap nasty little genny.
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Old 13-08-2007, 03:37   #2
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Let say that you get 4 hrs of good sunshine a day, you would need to produce 8 amps per hour. 2 - 100 watt solar pannels should do you with regulator. I suggest you get a second battery as well. Some would say that this is overkill by 2x.
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Old 13-08-2007, 06:42   #3
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Get LED nav lites--Doctor LED sells a nice replacement bulb for Aquasignal tricolor--which will save you 15 amp hours per day and doesn't add weight.
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Old 13-08-2007, 08:01   #4
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Saw this article 2 days ago. It should give you useful guidance. It opened my eyes. Power plucked from the air | Articles | Ocean Navigator

Pericles
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Old 13-08-2007, 11:07   #5
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I would do a couple things, being a cat owner I'm very concerned as you are about weight.

1) Get the LED nav lights and cabin lights. These will reduce your consumption to about 1/3 of what you're using now.

2) Get a single 120 watt solar panel. Weight 36lbs. It will produce around 30 amps on average for a sunny day, 15 amp for a cloudy day.

3) You're now down to bare bone elec requirements due to the LEDs (say 15 amp hours), your battery capacity should be 3 to 4 times that of your consumption, so 60 amps. Reduce your battery capacity to a 60 amp hour battery and you've just eliminated the additional weight of the solar panel. Sell the 120 hour battery, recoup some costs.

4) keep handheld GPS and VHF with spare batteries so you have communication and navigation equipment independent of the rest of the boat just to be safe and a couple bright LED flashlights as well. Bring a car charger for the batteries used for the GPS and the VHF so you can wire the charger directly up to the solar panel if need be.

5) Or the no cost option would be to take the prop off your outboard and run your outboard to charge your batteries without the additional drag of the prop. The drag from just the shaft itself should be nothing. I think the outboards produce typically around 10 amps, so 3 hours a day should do the trick.
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Old 13-08-2007, 11:32   #6
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"to anyother who can sort the issue without adding weight or cost"
Then there's only one answer: Stop using power. If your battery can provide 120AH and you are using 25-30 amp hours (not amps) per day, either you cut your consumption in half, or you could just consume the battery, run it four days without recharging it and accept that you've consumed a significant percent of its life.

How sure are you that you are burning 25-30AH per day? Is that just the radio, instruments and nav lights, or what?

I'd suggest the most effective answer (least money) is going to be buying a second battery and using it for the race. Double your stored power, and you can do it without charging. Yeah, that may add 75-100# to the boat, find someplace else to get the lead out.

Solar panels, wind chargers, those are going to be EXPENSIVE. Way more than the battery. LED nav lights...again EXPENSIVE, but if that's where your power consumption is--they might be effective enough to do the job without the second battery.

DO get that battery fully charged and equalized before the race, to make sure it is in top capacity before you start. The outboard motor won't do that.
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Old 13-08-2007, 13:35   #7
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Since you want to be making power while underway, you might take a look at towable generators - basically an underwater alternator with a small prop. Here's one example Ampair microwind, microhydro, and solar PV systems.. There are others that designed to be easily converted from wind generator to water generator. These things don't fit the bill if you are looking for cheap though - for that the led lights are probably the best bet.
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Old 13-08-2007, 20:16   #8
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"towable generators "
In a five day race, ANYTHING that might cost two hundredths of one knot for one hour each day, would be out of the question. Adding anything that makes drag to a distance racing boat is heresy. Adding weight is almost as bad.
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Old 13-08-2007, 22:52   #9
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Portable Honda 2000 Generator? You really need a battery charger on board to take good advantage of this...but it may be the cheapest solution and has lots of other good uses!
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Old 14-08-2007, 01:55   #10
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Woww, that's fantastic all. Ask and the knowledge flows, Thanks all.

LED into the nav light which seems to be the big sucker. Currently working on 10 hrs per day - 25W in 12V comes to 20Ahrs a day (thanks for that bit hellosailor). Being a tad generous with the time on as it won't be getting dark till 9pm but trying to leave some safety reserve.

To get a 25 watt equivalent in LED does anyone have any idea how that works and possible consumption? We must have '25 watts' for the rules and as we will be skirting oil fields and the like I don't want to get run down by a tired oil tanker driver, I'm way to pretty to die just yet

Apart from that we have a small amount by VHF when out of range for the handheld. A simdgen for autopilot for the odd break, it's a 2 handed race. inside lights at night. A splash of stereo which is a big sucker but then it is a bit silly sized. Otherwise we are pretty stripped down for the hard racing season. Come October I'll load the seemingly 4 tonnes of cruising gear back aboard.

The workout, if done correctly (please correct me if I'm wrong) we get to mid 20's maybe 30 Amp hours daily if pushed and stereo is very heavily limited. I'm not sure how you work this battery capacity/reserve thing so are erring a little on the cautious side just in case. Don't want to get race officials pinging me for 'stealth sailing' at night.

I worked it out like this -
Thingy X is 25 watts.
Devide 25 by 12V to get 2.08 Amps. .
Thingy X on for 10 hours a day so 10 x 2.08 is 20.8 Ahrs used.
Correct or cock-up?

I am assuming I'll never get to use all 120Ahrs in a 120 Ahr battery from what I've read here. Any idea what one could get out of a 120Ahr for short duration but big drain situations wityhout completely killing it? meaning, if it all goes horribly bad how many Amp hours could I reasonably expect to get assuming it was full and we couldn't charge anymore. It is only a few months old and gets some low level in and out flow each week currently.

Who said 'Equalise' the battery, what does that mean? Sounds like a good thing even if I don't know what it means.

All other lights have gone to LED already which saved massive. Those new lights use next to nothing, nice.

GPS's are heldheld and VHF handheld as well as wired in one. The handhelds will be on when required and off otherwise. They want us to make lots of calls so we don't disappear, how caring.

Didn't realise solar panels whack out that sort of numbers, nice. Will investigate that one.

Prop off the outboard, that's damn cunning. Will trial that one to suss speed lose. Might be surprisingly small.

As Hellosailor (done some racing I see) said drag is a nasty and a big no no. Saying that I do like the towing concept otherwise and are going to suss that for the not speed critical times. Sounds nice and simple.

The Honda 2000 was/is the current plan. Damn nice units with 55Amp output if we are talking that Aussie made one. Just though I'd avail myself of the learned forumites to see if they knew better ideas. Guess what? you do.

Now don't go away all. I'm going to digest this lot and will return will questions, probably silly but that's just me. This Elictrickery stuff is all a bit gobbledgook to me. Not so much this evening as it was this morning though.

Thanks again, you're all wonderful and I'm feeling the Cruisers Forum love What did we do before forums like this?
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Old 14-08-2007, 02:32   #11
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Quote:
Originally Posted by GMac

I worked it out like this -
Thingy X is 25 watts.
Devide 25 by 12V to get 2.08 Amps. .
Thingy X on for 10 hours a day so 10 x 2.08 is 20.8 Ahrs used.
Correct or cock-up?
Methinks you got it! You're right to be a little conservative. Dpending on age of boat/wiring there could be a fair amount of resistance in the systems = higher amps...

Wind, towed and outboard-in-the-water all add drag. Solar doesn't (appreciably).

Less power consumption is better.

I vote for 110w or so of solar power, one battery and LEDs to cut usage.

I was gonna suggest forgoing the tunes but man, 5 days on a boat without tunes?
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Old 14-08-2007, 02:46   #12
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Originally Posted by GMac
LED into the nav light which seems to be the big sucker. Currently working on 10 hrs per day - 25W in 12V comes to 20Ahrs a day (thanks for that bit hellosailor). Being a tad generous with the time on as it won't be getting dark till 9pm but trying to leave some safety reserve.

To get a 25 watt equivalent in LED does anyone have any idea how that works and possible consumption? We must have '25 watts' for the rules and as we will be skirting oil fields and the like I don't want to get run down by a tired oil tanker driver, I'm way to pretty to die just yet
I agree that reducing consumption is the best way to go. Upping the battery bank will work too, but only for fairly short-duration sailing. If you have to recharge while at sea, you're better off trimming the consumption.

A nav-light doesn't have to burn a particular number of watts, it just has to put out a specified amount of light, at the correct colors. Do some searching here for discussions about various LED options. Anyway, my old incandescant tricolor lamp drew 2.1A, and my LED replacement draws 0.25A. If the tricolor is on for 10 hours a day, the LED unit saves me 18.5AH per day. This will have a big effect on your power budget.
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Old 14-08-2007, 04:21   #13
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Tunes... Oh yeah, 5 days of his yacking and/or snoring. I'd lose it for sure I though of one of these fandagled MP3 players but I like being able to hear my environment, it's saved me greif more than once, so that's out.

The rules state a 25W globe so I'm guessing a lesser but better LED would be rule legal. Better just check that, they can be damn pickky.

If I can slash 18Ahrs a day out I'm quids in. So conservitly using 12 Ahrs a day for 5 days is 60 Ahrs or 1/2 the battery.

We could easily get 13hrs of good sun a day, say 10 so it gets up off the horizon a bit. A 60W solar panel puts out 5Ahrs full speed, say 2 allowing for yucky stuff. 10hrs x 2Ahrs = 20 less estimated 12Ahrs means extra stereo. A real sunny day masses more stereo. I like the plan.

It can't be that simple.

Flaws, corrections, comments , cunning plans please
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Old 14-08-2007, 06:18   #14
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The Dr LED tricolor bulb is only US$60, but doesn't seem to have COLREGS approval. I've got one installed, but haven't had the time to go out in the dinghy and see how it looks a mile or two away.

Lopolights puts out both a 1nm and 2nm approved tricolor which draw about o.4 amps, but they are $350 and $500. The 25 watt bulb rule must have been put in by the boats with inboard engines, but 25 watts in a aquasignal tricolor will give you a lot more than 2nm range.

Better borrow a solar panel and hope for sunny skies. We used to wiretie one to the back lifeline with an adjusting string to the backstay for long distance races.
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Old 14-08-2007, 07:06   #15
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Another word of advice--whatever your solution, try it out before you start the race!
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