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Old 09-15-2012
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One battery or two?

Hi all,

I just bought a 22' swing keel boat (DS22). I am an experienced dinghy sailor and also had some experience crewing on a tall ship, but not much in between! The boat I bought has two very flat batteries, one is beyond salvaging, the other is reading just over 12V after a day of charging. They are both 1000A. The boat has an electric start for the outboard, although I am more than happy to just pull the starter chord. There is a bilge pump, some lights, a radio, water pump for a sink. That's about it. So do you think I really need two batteries? I will be day sailing and maybe spend the odd night on board. I am also thinking of installing a solar panel for trickle charging, so the number of batteries will influence the decision on what panel to get.

Thanks
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Old 09-15-2012
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Re: One battery or two?

A solar panel is a good idea to keep the battery(s) charged between trips. This link shows how to size and properly install a small panel.
Installing A Small Marine Solar System Photo Gallery by Compass Marine at pbase.com

Your batteries may have 1000 cranking amps but they are probably about 100 AH or less each.

With you use and no need to have a battery for engine starting one good battery should be fine.
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Old 09-16-2012
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Re: One battery or two?

Thanks for the advice Brian and for the very helpful article about solar panels.

Richard
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Old 09-16-2012
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Re: One battery or two?

All you need is one battery and as others have said a solar panel is a good idea.

Walmart deep cycle batteries come with a good warrenty.

Get a 10 watt or bigger panel, think about where it is going to be mounted and remember if it gets shaded even a little output will drop to near zero. . Marine quality if you are sailing in salt water. Flexible ones do not seem to last as well as rigid.
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Old 09-16-2012
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Re: One battery or two?

I would get 2 6 volt golf cart batteries and put them in series to ake 1 -12volt one. The foot print for those two will equal the size of a group 31 which is what others are recommending and give you 200 amp hours instead of 110 ah. Remember usable ah is 1/2 of the rated ah.

Even though this may seem a lot more than you need, one mistake people make is to not have enough, they add a few equipment items and viola they find they are short. You may in the future add a VHF, portable 12 volt cooler, stero, more lights , depth finder etc.

The cost isnt that great and you can get these on sale at SAMs./ BJ for cheap.

Thy can be charged by the olar panel easily also.

Dave
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Old 09-16-2012
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Re: One battery or two?

I just installed a Solartech 40 watt panel on the pushpit with a Morningstar SunGuard 4.5A controller and an inline fuse, with slightly greater electrical needs than your set up. The system works great and keeps my 2 12 volt batteries charged enough to run an autopilot, lights and pressurized water, and start the engine on extended cruises. It fully charges the batteries for weekend sailing.

https://picasaweb.google.com/lh/phot...d_Pypui1WA098E
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Re: One battery or two?

Its always good to have redundancy on a boat. I personally believe one should have at least 2 batteries & a battery switch. I once bought a powerboat w/ no switch & 1 battery, never saw that on a boat before. I'd recommend a Ganz solar panel. They are a little pricey but are very high quality & designed for boats. You can even step on them w/ out breaking them. I would also recommend some portable emergency LED running lights, just in case & to change out all the lights on the boat to LEDs.
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Old 09-16-2012
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Re: One battery or two?

If this were me....I am going to swag that not much amperage is needed to start a 10HP out board, so reality says, if you do not want to hand pull start it, I would get a "U1"? size starting battery. Should have plenty of umph to get an outboard going. Its a larger lawn mower starting battery.

I would then have a 2nd house batter or just this one, that is in the size 24, 27 or 31 range. I had a 24, now a 31, either works for me, and I doubt I use much more ahr than you on my 28' boat. If I cruised more, vs daysail/race useage, then two getting me intot the 200-300 ahr range would be better.

Not sure frankly there is a right or wrong for how you are using the boat. be it one or two batteries frankly.

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Old 09-16-2012
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Re: One battery or two?

I think it's gonna be hard to say until you start using it in "real life" situations...

You say you have two "pretty flat/dead" batterys... will one cover it or do you need two...?

I'm in the same situation with two "not great" batteries.. Old car batts I threw in the boat (not new)... they kinda sorta make it thru the weekend with similar usage to yours....

So will one good/new deep cycle handle my needs..? Maybe....

But I think for next year I'll have two new deep cycles, cause I'm limping thru on these but would probably use more if it were available....
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Old 09-17-2012
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Re: One battery or two?

Before I installed my solar panel, I rotated in a freshly-charged battery from home every so often out of a set of 3 newer batteries. As I typically motored very little, my batteries were slowly being depleted, especially as I became more reliant on the autopilot. I used a charger at home to charge the removed battery. Lugging batteries on and off the boat and switching them out became old very fast.

If you want a new deep cycle marine battery, join Costco and pick one up there for $90. While you are at it, you can also buy a hot dog and a soda for $1.50.
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