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gitanopw 10-11-2012 04:40 AM

Elec-tricky-ty Dilema - Battery Wiring
Greetings all…
I have been hard at work attempting to refit a 34 Prout Event, which adopted me about a year ago… She was sailed from Florida, down the western side of South America, ending up in Palau (about 5 years)… After being on a mooring here for 3.5 years, she decided to adopt me and I took it upon myself to try to restore her to her former beauty…

Palau is a paradise island nation in the middle of the ocean… Some 850 miles southwest of Guam, 550 miles east of the Philippines… Beautiful place… Been out here for 17 years… The only problem with paradise is that there are no real hardware stores, horribly expensive wannabe internet services, no formally trained (or even remotely able) diesel mechanics, electricians, etc., etc., etc… Everything must be brought in. We just live out here (we have two small businesses and I am a retired Marine), day by day and try and stay out of trouble….

So, having said that… I think that I should not try to bore you too much but must add that before this project started, I had no knowledge of diesel engines, or elec-trick-ity… Zip, none… So, I have had to remind myself about the good old college days, when cramming was a way of life… I have read a ton of books (now have quite a library on all things sailboat)… Spent countless hours, on the slowest form of internet known to man, finding info I needed (and not covered by the books) in forums, youtube, etc., etc….

So… The diesel is running (purrrrrssss)… Have completely rebedded all hardware, windows, and everything else that is stationary or moves on deck… Have completely gutted the interior and am in the process of re doing that… Have two aft bulkheads out and awaiting re-wire… Which brings me (finally) to my having to ask for help from all you experienced and helpful sailors…

I have figured out and have a pretty good handle on the wiring, capacities, fusing, and installation of same, along with all the components which make up the DC and AC systems… I have started to put together my electrical systems diagram, and will post it as soon as I finish drawing it out in the computer. My batts will be here next week (six weeks in transit) and I still have to bring in the wire and all the attaching gear for the entire job…

My question, albeit stupid, is how do i figure out how big a gauge wire I need to connect the batteries within two separate banks of 6 volt 230AH EGC2's (the East Penn batts from Sam's Club).. One bank (house) will have 6 batts, the cranking bank 2… I have found about 5 or 6 recommended ways of hooking them up in series and parallel to come out with a 12 volt system… But, I still don't have a warm and fuzzy feeling as to what size wire I need to tie them all up… Nothing seems to point to that specifically… Help? (promise to make any follow up posts shorter???) :)

Thanks a bunch…


denverd0n 10-11-2012 08:51 AM

Re: Elec-tricky-ty Dilema - Battery Wiring
Well, the short answer is, as big as you can manage. When wiring batteries in series and/or parallel you want as little voltage loss as possible.

The long answer depends on how far apart the batteries are and exactly what your wiring diagram for them looks like.

asdf38 10-11-2012 12:53 PM

Re: Elec-tricky-ty Dilema - Battery Wiring
The proper way to approach it is to figure out what you need from the banks in terms of current and work backwards from there.

You should set your system up so you can start from either bank, this will almost certainly be your largest load and this will inform your wiring decision. Whatever gauge wire is needed for that starting load should be carried all the way back to both banks (through battery switches) AND should be used for the wiring between batteries within the bank for both safety and simplicity.

Normally your 3 pairs of 6-volt batteries in parallel in the house bank will see only 1/3 total bank current each, however unless you have fuses enforcing this it can't be guaranteed. That's why I'd use the same wire throughout the whole bank, for both safety and simplicity.

As for fusing, I think you want one fuse for each bank as close to the bank as possible assuming the batteries within the bank are close to one another - if you have any crazy, long runs within the bank you'd want to consider fusing those in addition. I'm not positive of the code here but I think that's right. Again the fuse is sized to protect the wire and both wire and fuse should be sized larger than your largest draw (again, probably the starter).

EDIT: Also consider getting an automatic charge relay so you don't have to do any manual switching between banks. There's lots written about that here.

Stu Jackson 10-11-2012 02:11 PM

Re: Elec-tricky-ty Dilema - Battery Wiring
1. Here's the 6V wiring stuff: Golf Cart batts re-positioning & wiring diagrams

2. Here's battery wiring ideas:

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings -

3. Here's a lot of other electrical material, which includes the above:

Electrical Systems 101

4. Battery and other wire sizing: do a Google search, there are a lot of sources out there, or do a search on this board with "wire sizing" by "Maine Sail" - he's referenced a handy sizing website many times. I've used this, too: The West Advisor: Marine Wire

Good luck.

chef2sail 10-11-2012 02:16 PM

Re: Elec-tricky-ty Dilema - Battery Wiring
Follow Mainesails directions to a "T" and get a Victron battery monitor. Your combiner should allow starting from both batteries when starting battery doesnt have enough juice. Also should keep large 6-6 volt bank as seprate house with over 660 ah to use.

Do you have solar to charge?


gitanopw 10-11-2012 07:45 PM

Re: Elec-tricky-ty Dilema - Battery Wiring
Thank you gentlemen... It is truly great you guys share your knowledge and experience so readily... I thank you... Funny thing is, I feel like I've known a couple of you guys for quite some time... I have been reading and learning from this forum for almost a year now (too stupid to post anything), and I have to admit, I would go broke if I got a bil for all the great info I have learned and been able to apply on Manta... Can't thank you guys enough... Maybe if you Sailed out here to Palau...? Oh, last thing... Even though Maine Sail didn't come to my rescue, I do have to thank him for taking a chance on me and sending me some of that great butyl tape... I used it all up and I think I need three more rolls... Thanks to you all... I will post some pics of my progress... Maybe you will allow me to pick your vast knowledge reservoirs a bit more...? Dave

Stu Jackson 10-11-2012 09:09 PM

Re: Elec-tricky-ty Dilema - Battery Wiring
Glad to help, anytime. Maine Sail did help, since I link to some of his material in my links.

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