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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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  #1  
Old 09-28-2011
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Figuring my electrical requirements. 2 Q's?

I am getting my tiny sailboat ready for a two week cruise I plan to take in the next few months down in the Keys. I am revamping my electrical system and I want it to be adequate for my needs, although they are minimal in my opinion.

I am figuring up my daily amp hours and I am stumped on how to determine how much I should allow for charging my electronics like my handheld vhf, cell phone, video camera, and my mobile tablet. I will be using them moderately, possibly one full discharge per item per day except for the vhf.
Any guesses? Any ideas on how to figure that out?

I believe I will be charging them through cigarette lighter sockets since I have a 12v system only.

Right now I am at about 12 amp hours per day in my total usage of things like: gps, auto pilot, anchor light, nav lights, and led interior lights. (I plan on using a manual bilge pump)

My other question is:
I hope to be able to charge my batteries up with a solar panel or possibly two. I would rather stay away from having to use shore power unless I had too. Right now I have a new solar panel that is rated at 2 amp hours a day which isn't much.

If my power consumption was about 14 amp hours a day, them I should have about 16 amp hours a day capacity in my solar panel system them correct?

Thank you all for your opinions!
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  #2  
Old 09-28-2011
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My solar panel is a:

Sunsei solar charger 400, 400mA, 15V (6W)

Maybe my assumptions on the solar panel output could be off?
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Old 09-28-2011
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Hi

That is a pretty small solar panel - really built to maintain batteries when they are not in use rather than charging them after use. Your assumptions are correct as in a sunny climate you usually figure 5 hours at full panel output. There is loss because you have to put more AH into your batteries than you use - about 110%.

Your estimate of 12 AH per day sounds low - how are you estimating this?

Do all the items you wish to charge have 12 volt chargers? If so they will have a sticker on them that lists amps and voltage.

How large is your battery bank? Normally it should be sized so you can go for 2 or 3 days without charging - you can't rely on solar every day. And in the third day you want to be able to recharge the battery (batteries) fully if possible after several usage.
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Old 09-28-2011
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I came to my 12 amp hour usage by calculating the amps used by each item and multiplying that by how many hours I expect to use each item on a 24 hour basis.

As I said earlier my requirements are minimal on my 17' boat consisting of an autopilot, gps, nav and anchor lights, interior led light and then charging various electronics. I think that's pretty basic really and a lot less than most boats. I am a bit of a miniamlist, I do a lot of backpacking so I more or less camp on the boat.
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Old 09-28-2011
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My battery bank as of now is one regular deep cycle wet boat battery (same size as a car battery). I plan on upgrading it if need be.

I will check on my chargers this afternoon and report back.
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Your assumptions look reasonably correct to me. My first boat was similar and I used about 14AHrs day.
There are a couple of ways to measure or guess the consumption of the VHF cell phone etc.
1. Measure it with a multimeter (clamp on is easiest) it will vary through the charge cycle, but you can estimate an average.
2. Look at the devises battery capacity convert this to the equivalent in AHrs at 12v then add a fudge factor for the charges inefficiency (I would multiply it by 2)

They vary a lot but a starting figure might be (to recharge from a flat battery assuming 12v chargers))
VHF 3 Ahrs
Cellphone 1.5 Ahrs
Video camera 2 Ahrs
Tablet 5 Ahrs
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Old 09-28-2011
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Good topic! This is very close to our setup...
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