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post #11 of 37 Old 08-01-2015
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Re: Battery choices for offshore use

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Originally Posted by Irunbird View Post
Nope- no refrigeration, no a/c, none of that. This is a really simple boat- all nav lights are led's, plotter is Raymarine e7D, all instruments are new Raymarine but I do have a power hungry-ish autopilot (my biggest current draw), and I've settled on around 350-400 ah's with a 100w solar panel for cruising/racing as long as a week away from the dock (I know that huge sentence is a run-on and my Mom/Grandmother would not be proud..).

The main reason I like the idea of sealed batteries is for the obvious; they're sealed and I won't have to go through the major headache of redesigning my battery boxes to accommodate a sealed box, that and I *think* (correct me if I'm wrong) they can be drained down 80% from full without killing them occasionally.

If your longest run is one week away from the dock any of the Premium AGM batteries (Lifeline, Odyssey, Northstar, Firefly) should suffice. I would not however take any of them but Firefly to 80% DOD on a regular basis.

The Odyssey can occasionally be cycled to 80% DOD but will have less than half the factory rated cycles of a Firefly when doing so. If you are designing for 80% DOD then your battery options are slim, unless you want to replace them on a regular basis..

6V GC2's are still the best value.. For an AGM I would go Firefly because the cost per Ah and cycle is far less than any of the other AGM batteries.

For example a G31 Firefly vs. an Odyssey based on reasonable usable Ah's looks like this...

Odyssey 100Ah = 50Ah usable for $340.00 = $6.80 per usable Ah

Firefly 110Ah = 88Ah usable for $425.00 = $4.83 per usable Ah

We then have designed cycle life of 1000 cycles to 80% DOD for the Firefly and 400 cycles to 80% for the Odyssey. To equal the 1000 cycle design life with an Odyssey requires discharging the Odyssey to only 65% SOC...

Still the GC2 6V flooded batteries are a significantly less expensive battery...

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post #12 of 37 Old 08-01-2015
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Re: Battery choices for offshore use

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Originally Posted by killarney_sailor View Post
I think the Oasis batteries are quite good. Their technology allows you to draw them down further than a conventional battery without damaging them. The problem is that they have become victims of their own success. They are producing them on a very small line that was set up to make prototypes. Their current (sorry) demand is now very high and they are very hard to get at this point.
Yes they are a bit hard to get but not impossible. When you build a good product demand increases and it sometimes takes time to get production in-line with demand. I think of them a bit like Rolls Battery, a small factory with hand made batteries and a premium product....

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No immediate plans to ramp up production which might reduce the price as well.
Don't know where you heard this but it is not what Kurtis has lead me to believe. It is just not going to happen overnight but it is being worked on. Expanding a battery factory is a large undertaking...

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post #13 of 37 Old 08-01-2015
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Re: Battery choices for offshore use

Aren't Gel batteries a good option for a sealed battery that can take a deep discharge occasionally, without leaving a mark? Need to have a charging system that is compatible, but that's not hard to engineer.


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Re: Battery choices for offshore use

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Aren't Gel batteries a good option for a sealed battery that can take a deep discharge occasionally, without leaving a mark? Need to have a charging system that is compatible, but that's not hard to engineer.
Yes absolutely but they are more persnickety with charge voltages and temp compensation. They also don't have as high an acceptance rate for as long as AGM's do..

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Re: Battery choices for offshore use

With a 100W solar panel as the primary charging source, that's about 35AH per day in the best case. So charge acceptance rates probably would not be significant here, and if there's a Genasun charge controller on that panel, it can probably be set or programmed (or replaced without extreme expense) to work properly with AGMs or gels.

Even Deka says outright that their gels can be cycled deeper and more often than their AGMs and that probably makes gel the best setup for this boat.

Both gel and AGM are better suited to long idle periods than lead acid, without trickle charging, although all are better off with it. And the solar primary charger makes that easy enough.

A local battery distributor may be able to suggest specific sizes he has available, and prices for gel as well. If you don't need them "right now" but can wait for a delivery to get to him...won't matter if he has them in stock or not. Costco stores often have almost random inventory on batteries, many will just unhelpfully tell you "Come in, sure, we have it all" and that often is not the case. Especially for gels!
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post #16 of 37 Old 08-01-2015
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Re: Battery choices for offshore use

AGMs are the worst choice for any bank that will be neglected. Reading Maine Sail's posts on this are very clear.

AGM Battery Issues (from Maine Sail)
AGM Batteries - Making The Choice - SailboatOwners.com

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
Darn AGM Batteries - SailboatOwners.com

Still, after 50 years or so, wet cell batteries remain the best bang for your buck. And golf carts for true deep cycles.

Stu Jackson, Catalina 34, 1986, M25 engine, Rocna 10 (22#), Maple Bay, BC, Canada
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post #17 of 37 Old 08-01-2015 Thread Starter
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Re: Battery choices for offshore use

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AGMs are the worst choice for any bank that will be neglected. Reading Maine Sail's posts on this are very clear.
Trust me, that ain't gonna happen again! I may be a slow learner, but I'm not that slow! Now that we've settled into somewhat of a routine here, I've got time to properly take care of all the stuff on the boat- batteries (believe it or not) are one small challenge here in Tampa.. I'm still trying to figure out how people sail here with all of this lightning bouncing around every afternoon!
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post #18 of 37 Old 08-02-2015
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Re: Battery choices for offshore use

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Trust me, that ain't gonna happen again! I may be a slow learner, but I'm not that slow!
Not neglected means fully charged at least once a week.

Brian
Living aboard in Victoria Harbour
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Re: Battery choices for offshore use

I think Gel would be the way to go, given the OP's defined needs (spill proof, off the grid charging and able to take a deep discharge hit occasionally). Proper charge controllers are necessary, of course, but that goes for any type.

The only downside is availability. There aren't too many that make them anymore, however, I don't believe they are going away. Powered wheelchairs use them.


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post #20 of 37 Old 08-02-2015 Thread Starter
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Re: Battery choices for offshore use

Part of my problem is/was having used a cheap car charger (which I know now is a no-no), and I'll probably get one that will be dedicated to the boat and not live on the shelf in the garage. I also think I might need a battery monitor rather than just going by voltage. Can anyone suggest reasonable brands or makes (ideally something that does not need to be hard wired in to the boat)?

Last edited by Irunbird; 08-02-2015 at 05:16 PM.
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