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Old 07-09-2014, 17:04   #1
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Batteries

I am hauling the "Keefer" out at the end of the month for a bottom cleaning, blister repair, through hull fittings glass over, paint, and head removal.

I will be converting the boat over to LED navigation and cabin lighting while this is going on. I will be running a fish finder and VHF radio except while anchored.

I bought the boat with (4) batteries installed. I am wondering if I could downsize to (2) batteries giving the reduced load. I am also adding a solar panel for charging.

I am leaving my shore power 30 amp load center and and circuits alone. That system seems to be very solid.

I am not doing any extended cruises. The longest it will be out is 2-3 days at a time.
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Old 07-09-2014, 17:53   #2
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Re: Batteries

Of course you can. You could even reduce to 1 battery (assuming you are talking 12V batteries). Your load has nothing really to do with how many batteries you install, that is all about how often you will need to charge them.

BUT, other than some weight there really isn't any disadvantage of having more batteries why do it?
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Old 07-09-2014, 18:30   #3
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Re: Batteries

Would help to know what size batteries. Are the really big or little tiny batteries? Maybe give the model and amphour capacity.

You don't mention what kind of engine. Inboard so you need a battery to start it or outboard with a pull start? If you need a battery to crank the engine it is really good to keep at least one battery separated for that.
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Old 08-09-2014, 03:11   #4
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Re: Batteries

Sorry for the lack of details yesterday guys. I was pretty tired after I got home. My Islander 26' originally had a inboard engine and it was removed some time before the past owner bought it. There is a 8 HP Tohatsu hanging off the stern now. The electrical system looks to be in it's original state although messy.

I spent a good part of yesterday morning going over the existing wiring (bird nest) and chasing down dead ends. Nothing out of the ordinary, just your typical old circuits that were used for "something or other".

The shore power panel and circuits are in great condition overall. The 12 volt system will be redone. The boat is set up with a 4 battery configuration....(2) port and (2 )starboard. A 120 volt battery charger. It also has 2 older (small) solar panels that I will remove and replace with something more modern. Each battery box hold (2) batteries and the dimensions of the boxes are 11" X 13".

Most of the "birds nest" appears to be the old charging system wiring, and sloppy runs added over the years. My goal is to come up with a simple layout for the new system. I will be nosing around looking for ideas over the next couple months.
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Old 08-09-2014, 03:50   #5
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Re: Batteries

Hey Old Snipe,

I have just been through a very similar process to that which you are contemplating. We had a nominal 400AH battery bank, but it quickly became evident the useable capacity was a lot less than that.
I just separated all of the batteries, checked their capacity using a simple voltage/load/timer combo. Identified the single 200AH AGM was totally kaput, so off to the scrap metal guys with that one. The remaining pair of 100AH Calcium batteries are both running at about 20AH useable each. Not great, but good enough for weekending for now. (Note, finding $20 battery charger on a boat is probably NOT a good sign.)

After three abortive attempts at rewiring, gave up, gutted the whole lot and started again. SO glad I did. Once I pulled it all out, and threw out all the speaker wires in the lighting circuits, pieces of wire with multiple screw cap junctions, bits of copper oxide with plastic coating masquerading as wire, then put all the good stuff in another pile, graded by size, I had less than one tenth of the number of useless cables and had identified numerous points of serious potential failure. Now I know what EVERY wire in the boat does, instead of HOPING I knew. I know every wire is logically and functionally protected by the right sort of switch/fuse/circuit breaker.

It may seem like a lot at the start, but I think it is worth gutting it, on a simple boat like ours, it is just not that a daunting job and the peace of mind is priceless. I think each of my attempts at improving the wiring actually made me more aware of what I had not really dealt with.

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Old 08-09-2014, 04:26   #6
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Re: Batteries

Two battery boxes 11X13" with two batteries each. This would be fairly small batteries and I don't know of a true, deep cycle battery in that size.

Assuming that is the inside dimension of the box then I'm guessing the batteries are size Group 27. A combo starting/deep cycle type battery of this size will be rated about 100 amp hours. From fully charged you could use at best half of this to avoid damaging the battery. If you don't have enought solar or shore power to keep the battery fully charged then maybe 25-30% of the rated capacity.

You don't say but I further assume the outboard is not electric start so you only have to supply battery for the house needs.

Only way to determine how much battery you need is to do an energy budget. Add up everything on the boat that uses electricity and how many hours per day you will use it. Add up the total amp hours and multiply by 2 or 3 to get the battery capacity you need.
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Old 08-09-2014, 04:46   #7
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Re: Batteries

I just ripped all the wiring out of my boat as well. I can recommend expresssch as a great simple wiring schematic tool.

For what you are doing you are going to have shore power to charge the batteries and solar when away from dock. You need to figure out your daily needs by creating an energy budget, Then decide whether you get enough solar to meet those needs, or run a daily deficit. If you run a deficit you need to size the battery bank so that you don't go <50% capacity within 3 days.

I'd recommend trying to meet daily needs as regular 50% discharges will greatly reduce battery life.

You may find interesting stuff in a couple of the threads I have started.

This thread is just a view of what I pulled out.

Circuit, Wire, Fuse Size

This thread is what I am planning to put back in.

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Old 09-09-2014, 14:20   #8
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Re: Batteries

Do you have 2 sets of six volt batteries or 4 twelve volt batteries?
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Old 10-09-2014, 03:08   #9
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Re: Batteries

Zil............... (4) 12 volt. (2) in each box
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