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post #1 of Old 01-11-2012 Thread Starter
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Creating an electrical system from scratch

I am planning on re-doing my electrical system on my S2 7.3. I will have limited access to shore power and no on-board power generation so I have decided to redo my power bank.

But here's where my questions start. First we, my wife and I, plan to spend up to three-four days at the time out on the water and want to get as much power available as possible so I was thinking around three batteries But I'm having problems finding what the definative "Best" type of battery would be. Any suggestions?

Next, we plan to use only led inside the cabin. The power supply will mainly power a Marine radio, a Juke Box, maybe a small fan at night, an ipod charger and an electric ice chest. Does this sound sufficient? and how do I pick the best wattage of a solar panel for charging?

Thanks in advance and any info will be apprciated. I tred finding these answers on my own but there are many differnt opions on the google.
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post #2 of Old 01-11-2012
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My wife and I spend the summer aboard our boat, with no shore power and no generator. We have two batteries, a dedicated starting battery and a house battery, both lead acid, nothing fancy. Our yanmar inboard handles charging duties when under power, and a 15 w solar panel keeps the batteries topped up...almost. About once a week we go for an hour or two power cruise, to top up the batteries. It probably is good for the engine to get a little exercise as well. A 1000 watt inverter is wired to the house battery for laptop and DVD player use. Stereo, VHF, freshwater pump, lighting,depthsounder, chartplotter and Autohelm 3000 round out the loads. It's a simple system that has served us well for several seasons. The only upgrade under consideration is a larger solar panel. 30 w would be great, 50 watts would beyond perfect.

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post #3 of Old 01-11-2012 Thread Starter
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Thanks, that really helps alot. I want it to be as good and as efficient as I can get it without overdoing it. But I thimk that we will be amp hogs here at the beginning. We really don't have the opportunity to get out and cruise but we plan to travel to other lakes here and see what we can put up with for as long as we can. I guess trying to get as close to cruising as we can and looking for what works and what doesn't.
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post #4 of Old 01-12-2012
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Quote:
Originally Posted by Lflowers230
I will have limited access to shore power and no on-board power generation...
Really? No on-board power generation at all? Not even an engine alternator? Or do you just mean that you won't have solar panels, a wind generator, or anything like that?

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Originally Posted by Lflowers230
I'm having problems finding what the definative "Best" type of battery would be.
The reason you're having problems with that is because there is no one, definitive, "best" type of battery. There are options and trade-offs and you need to figure out what trade-offs will work best for you.

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Originally Posted by Lflowers230
...and an electric ice chest.
This is going to be the killer. The other things use minimal amounts of electricity. Refrigeration uses quite a lot. You need to look at your electric ice chest and figure out how much it draws, then probably do some testing to see how much wattage it needs over the course of a day.

If you want a solar panel for charging then you need to figure out where you'll mount it so that it gets minimal shading during the course of a day (preferably NO shading!), as well as how big it can be, and of course your budget will play into this (or maybe not, if you have all the money in the world). Beyond these constraints, it is generally safe to assume that the bigger the better. But, as with batteries, there are trade-offs and you have to decide for yourself.

That's why you find so many different opinions. There is no simple, cook-book answer that will tell you exactly what you need and how to do it. You have to look at all the options that are available, decide what trade-offs you are willing to make, and then design your own system.

Good luck.
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post #5 of Old 01-12-2012 Thread Starter
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Thanks for the response.

"Really? No on-board power generation at all? Not even an engine alternator? Or do you just mean that you won't have solar panels, a wind generator, or anything like that?"

Yes. The boat only has a small o/b with no generator and I don't plan to install a wind generator. I just don't think that the WindGen would be cost effective.

I suppose we will probably weed the electric IceChest out and use ice from marina's.

As for the Solar Panel, Well, this is where I am stumped. I get it that placement and size will be a factor but I guess this narrows down my question and that is figuring out wattage for charging my Batts. Like you you said, I guess I'm gonna have to try and err to find what works.
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post #6 of Old 01-12-2012
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There are a few threads around here on sizing your solar requirements. One "rule of thumb" I recently read was you want to have one that is rated at 10% of your bank size. Now whether that is "gospel", is left for more qualified experts to chime in on. Do a search around here and on the Googs and you will probably find some good info on solar sizing. One other consideration as always is the size of your wallet as well. A good book on electrical is this one. Amazon Link. It comes highly recommended, not sure what your electrical skill set is so I thought I would add the link. Look forward to hearing about your progress as I will be doing pretty much the same thing myself to my boat.


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post #7 of Old 01-12-2012 Thread Starter
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Thanks,

First, I'm kinda R/G colorblind so that doesn't help my electrical skills much. I think I am understanding amps and I understand the part about putting my batteries in Parrallel, to add amps per batt but keeping it at 12 volt. Right?

Watts are what gets me confused in all of this. But the 10% rule sounds reasonable to me. For example I see where a battery shows the Nom Volts - 12v, and the Capacity - 75AH 20hr Rate, but how Watts comes into play for charging escapes me.

I'll keep looking and learning but I do appreciates your knowledge and keep you updated.

I also get the rationale of the thing ( can't remember what it's called) between the Solar panel and the batts to keep the batts from discharging to the Solar Panel at night.

What do you consider and good amount of amps to have available?

I just found this :Volts Watts Amps Converter Tool Calculator

Oh, Volts X Amps = Watts, hmm, so three batts, 12v at 75Ah = 2,700 Watts x 10% = 27 Watt solar panel Charger? Does that sound right?

Last edited by Lflowers230; 01-12-2012 at 02:39 PM. Reason: Math
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post #8 of Old 01-12-2012
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I was just coming back to add that the 10% rule I read was for keeping the battery banked "topped off" when you aren't on the boat. My thinking is that if you are mainly weekending and what not, that should work. I don't think the 10% rule I read was how you calculated it. It was more of if you have 100 amp hour battery then a 10 watt panel would be good to keep it topped off. As I said, I am working off of memory here and there are far more experienced folks out there in regards to this.

Main Sail is one of the most experienced folks around on this stuff. He does it for a living. Here is a link on his site where he talks about installing a 30w panel. he talks about all the hardware, electrical and mounting, you need to get it right the first time.

As for sizing your bank, you need to calculate your daily usage and go from there. Adding in a nice buffer of course. Get the book I sent the link on, it helped me a lot with the "math".

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post #9 of Old 01-12-2012
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This might be a useful resource for you:

Deep Cycle Battery FAQ
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