Autohelm, How much power am I using?

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Bad Obsession

Bad Obsession

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May 23, 2004
3,319
I'm in the market as were . Colonial Beach
I am already planning my vacation to leave Colonial Beach next year. I am seriously considering leaving early in the morning from Colonial Beach and sailing all night, trying to reach Annapolis the next day. That is a pretty long trip. I am wondering how much power would I be using by running the Autohelm a lot and the running lights. I will keep watch and because of my job I am use to long hours and being up all night at times. I really can't depend on my wife to stand a watch, even for a few hours, because she is not interested. My boat is a 1990 Catalina 30. I run a house battery and a starting battery and that is all. I can charge off of the alternator but I wonder how often I should start the diesel to charge the batteries. Also, I wonder how long I should run the engine to charge the batteries. If anyone has any ideas on this or any suggestions I would appreciate them. I am not going add solar or anything like that. I am a coastal cruiser and I would rather make due with what I have (ie. charging off the engine).
 
N

nick maggio

Add Another house battery

I added another house battery and a battery monitor to take the guess work out.
 
Bill Roosa

Bill Roosa

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
AH usage

Your running lights (3) will draw about 2.5 amps. An autopilot will draw from 2-8 amps depending on the seas. Worst casing it This time of year it is dark for 14 hours plus a half on each side gives 15 hours of nav lights or 15 hours X 2.5 amps = 37.5 amp*hours. You didn't say how much you will be using the AP so I'll let you do the math; hours used X 5 amps = amp*hours. My Catalina 30 had two car batteries and they where good for about 25 AH each. The alternator is a car alternator and so will only trickle charge you batteries after an initial surge. I have motored all day and they did not get fully charged. The good news is they will never get overcharged ;-) 50 AH usable in the batteries and 37.5 going to the nav lights leaves 50-37.5=12.5 AH to run the AP! It is not going to happen. You will have to motor some of the way or hand steer the boat a lot. The other good news is that you can turn on just about everything when the motor is on and the batteries will still be trickel charging.
 
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Bob

1. Read a book about boat electrical systems

2. do an energy budget 3. read: http://www.sailboatowners.com/forums/pviewall.tpl?fno=21&uid=F&sku=2006290154558.71 Good luck, Bob
 
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