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Old 14-09-2008, 16:14   #1
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Batteries ? ? ?

I am going to replace the batteries in the boat. Now, I have two 6v T- 105 golf cart batteries in each engine compartment. These are a combo starting & house bank. I am going to get two group 27 starting batteries, then have a seperate house bank. I will be recharging them with solar panels, wind gen, engine alt, and gen set.

The question is what kind to get? ? ?

Flooded golf cart batteries or AGM?

Thanks
Dan
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Old 14-09-2008, 17:44   #2
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Are your batteries readily accessible for service? If so, you can't beat conventional flooded cell batteries over the lifetime of the bank, with respect to total charge/discharge cycles over the lifetime, capacity (more available amp-hours per cycle), and cost per lifetime total of amp-hours. If the batteries are harder to get to, consider the AGMs or equivalent sealed batteries. I use Surrette 6 volt 4D batteries in series, two identical banks (one for house bank, one for engine start and high draw applications when the engine is running: windlass, seawater washdown pump, watermaker, etc.). It keeps me from spiking the electronics when I start the engine.
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Old 14-09-2008, 19:18   #3
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Flooded batteries can be made very close to maintenence-free by adding an automatic irrigator (made for RVs).
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Old 15-09-2008, 13:57   #4
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AGM problem

AGMs have been found to have 'memory' problems-you have to fully charge them every time you charge them or lose capacity. So, conventional batteries with these: Water Miser Safety Vent Battery Cap
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Old 15-09-2008, 14:08   #5
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I had a similar decision to make earier this year. So, like you, I set out to read all there was. When my research ended, I ended up at Walmart. Group 27, 12V , deep cycle, 115 amp hour ,wet cell batteries were $60 bucks apiece.

No matter how I sliced or diced it, this was the biggest bang for the battery buck and the RV guys have been using them with great results for years.

As an aside, with the old starting batteries installed my starboard engine took 20 seconds of cranking to start, while the port engine took 2 seconds. After installing the new batteries, they both start instantaneously.
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Old 15-09-2008, 14:16   #6
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Its best to keep all the batteries on the boat the same, either wet, gell or agm, so that they all charge at the same rates to the same voltages. That will keep your charge management simple. A common solution is from Xantrax for charging from multiple sources and running an inverter. I just installed a watering system for my oversized L-16's and am still kicking myself for not getting it when I first heard about it. All my boat work clothes have holes from dripping battery acid on them. That's how they became BWCs to begin with!
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Old 15-09-2008, 14:35   #7
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Battery memory myth

No lead-acid battery (AGM included) exhibits a so-called "memory effect". It has been shown that even in the case of Ni-Cad batteries if a proper acceptance voltage is used for recharging no problems with capacity recovery will be experienced (barring other effects of aging, or damaging phenomenon).
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Old 16-09-2008, 13:31   #8
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I found this to be a good read on the topic:

True, AGM's do require rethinking your charging system, but I personally think the advantages of being able to take a quicker at a higher rate charge, being totally sealed, and not needing to overcharge as much to top off to be major advantages on a sailboat.

Comparing Marine Battery Technologies
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Old 16-09-2008, 14:10   #9
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I had excellent resulats with gel batteries that came on two of my boats. I never got around to equalizing and used them pretty hard. Having said that, I would never pay the tarrif for them new. Way too expensive. 6 volt Golf Cart batteries in series are cheap and excellent if you have the room.
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Old 16-09-2008, 14:20   #10
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I have just switched from flooded 8D batteries to DC AGMs for the house bank

Early days to see if it was a wise decision but I have followed all the advice about intelligent charging and large enough capacity to maximize their expected lifespan for a cruiser’s mode of use.

One issue I did notice is that after many years of the House Battery compartment being subject to acid vapors and spills during servicing, the plywood floors and surrounding supporting timbers were weakened because of saturation with caustic fluids…so I ended up replacing them and scrubbing down and repainting the whole area.

IMHO ….The clean, no maintenance installation under my dinning salon favors the AGMs
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Old 16-09-2008, 14:51   #11
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clean is nice. One thing I noticed on a boat I had with 6 Golf cart batteries was that it pretty much never needed water. Is it possible that with a 125 amp high output alternator/regulator, you never really boil them that much when they are one bank?
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Old 16-09-2008, 15:45   #12
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Thanks for all the information. I've been debating on what battery (brand) to use as replacement for the 6 batteries on two house banks. Prices range enormously but seems olike any decent deep cycle wet acid will give 5 years service on a smart charger with equalizing. I can get an Interstate 750 CCA (25A for 160 min) for $75 each so cannot justify West Marine's $114 special, and others at $140+. Before I do the swap out, am I missing something?
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Old 16-09-2008, 17:28   #13
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It's all about plate thickness, thicker last longer. Plates are lead. Lead weighs more. One indicator would be battery weight. I wouldnt assume they are all the same any more than I would assume expensive are better.....
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Old 16-09-2008, 17:46   #14
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And after reading through the windsun.com FAQ pages I can see how naive my questions and comments are. There is deep cycle and there is marine deep cycle which by and large isn't the same. Naturally, I'd prefer solid plates rather than coarse sponge, but... cost is a factor too. So maybe marine with adequate amp-hour capacity. And after the read, I sure won't use a deep cycle for engine starting. More to ponder, but feel like I'm homing in on an answer - a compromise as usual between cost and performannce. Thanks for the comments...
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Old 16-09-2008, 19:59   #15
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I went to wal mart today and beought two car batteries for the starting bank, one each engine. Now I am looking for some 6V golfcart batteries. Anyone have a good source? I would like to get some T-105's. that is what I have as my dual house/starting banks now. One side is only reading 12.8 V on a full charge, you think it is bad or still good? In the battery pages of ebay there is an add for a method of refurbing old batteries, think it's worth the $10. I could use the 4 T-105's now as a house bank and save a bundle.

Dan
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