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Old 03-17-2016, 08:21 PM   #41
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My PO installed two 8D AGMs at $800 each for a total of $1600. The equivalent wet cell GC's would cost about $400 total. Pretty big cost penalty to not have to deal with adding water periodically. Sure is nice though! My cruising pattern has me reaching full charge when i dock overnight in a marina every few days. One of the biggest changes that i've made to my pattern with this boat is to discharge both batteries in parallel down to 60% SOC rather than running a single batt down to 20-30% SOC each cycle. Hopefully they will last a long, long time.

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Old 03-18-2016, 07:32 AM   #42
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Originally Posted by cardude01 View Post
I have relatively new (1 year) Lifeline AGMs in my boat's house bank. 4 group 31s. My boat was set up for AGM batteries when it was built in 2008, and being a relatively unenlightened big boat owner with few skills, I elected to leave the charging setup alone and go back with AGMs.

The boat has a Charles charger, Balmar alternator and regulator set to AGM settings. Next time I might go with golf cart batteries since by that time I might know enough to change things over. At my current slow/steep learning curve that's still doubtful. ��

Question: my charger (Charles 5000 60amp) stays on all the time when at the dock, and I assume the charger is stepping down to a float charge level, but I have never put a volt meter on the batteries to check that. It is set to the AGM battery setting. The charger is the one that came with the boat when it was built in 2008. Am I being too trusting of this 8 year old charger?
Not "too trusting", but if you want to know how it's supposed to work, read the documentation that came with it. If you don't have it, download it off the Internet.

I agree with your assumption that the charger is varying the charge rate based on the charge of the batteries.

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Old 03-18-2016, 08:00 AM   #43
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1) FWIW, we have AGMs; oldest multi-function bank (3x G31s: start one engine, half the house, electronics suite) will be starting 11th season today. Always on the charger when we're in port. Charge 2x/day when at anchor. Seldom discharged below 50%. Sat through winter while the boat was on blocks fine with no charging; started fully charged, down a couple 10ths when they launched yesterday. IOW, so far, it's holding voltage although slightly lower than when new. Selected more because of other features, especially ease of maintenance (hard to reach).

2) Seems a common thought on Cruisers Forum that AGMs left uncharged don't do well. That "cruising" regime doesn't match our own lifestyle, since we're seldom anchored out that long at any one time (seldom more than a week or so) and since I'm not afraid to start the genset... In any case, we've had no issues.

3) 6V AGM golf cart batteries exist... so it's doesn't have to be an either/or. I'll probably switch that oldest G31 bank to 6Vs when the time comes. Critical in our application to check engine starting requirements (minimum required CCAs/MCAs).

South River, Chesapeake Bay
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Old 03-18-2016, 08:35 AM   #44
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Very timely post by Ben Ellison on exactly this topic:

Gizmo's house battery replacement: consulting with Cole, Collins, Calder, Schwab & you

Edit: For those of you with TLDR syndrome, here's a set of tips from the PS series:

Don't Kill That New AGM Battery
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Old 03-18-2016, 09:10 AM   #45
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Your/Panbo's link to this one:

AGM Battery Care - Inside Practical Sailor Blog Article

describes precisely how I've been managing my AGM banks. Maybe that has something to do with them working so well for me.
Richard Cook
Dream Catcher (Nordic Tug 37)
New Moon (Bounty 257, Volvo KAD44P)
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Old 03-18-2016, 09:16 AM   #46
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So, AGM vs LA seems to come down to cost (gouge factor), convenience, application, on board charging effectiveness, operation and maintenance. Sounds like boating to me.
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Old 03-18-2016, 09:57 AM   #47
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Originally Posted by FF View Post
"So what the hell is standard crusing practice? and how is the "standard cruiser" using and charging batteries"

"Std cruising" for folks that prefer to anchor out and not run from power pole to power pole is to almost NEVER have the house bank back to 100% full. 85% SOC down to 50% seems the norm , with an over sized batt bank to allow for the sloe capacity loss from undercharging LA batts.

The time it takes , many hours for the last 5-15% is way beyond what most folks will operate a noisemaker for.

And a 8 hour main engine run might not be long enough for 100% either.

The only folks that have a chance of a proper recharge have well installed solar

or a wind generator for the anchorage to listen to 24/7

Rain Dog post 14 seems to have it right.

No full 100% recharge , tiny service life.
Yes. Solar Panels are perfect for that last top up.

LAst summer, one of the reasons I tried to always have a 6 to 8 hour cruise on the days we travelled was to make sure the batteries ended up fully charged.
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Old 03-22-2016, 08:20 AM   #48
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Rolls vs FullRiver

I fitted new house bank batteries on our Selene soon after purchase. Because of accessibility I fitted 2x8D FullRiver AGMs (200lbs each) for one bank, and 2x8D Rolls lead/acid batteries for the other bank. I had originally intended to fit Rolls in both positions but gave up because of difficult access.
With hindsight I wish I had fitted the FullRiver AGMs in both banks. I sold the boat in 2014, and the new owners finally replaced the batteries this year!! Those batteries were 9 years old!! The Rolls are reputed to be long-lived (8 years?) but the AGMs did just as well. In addition, the AGMs charged much faster, were not position sensitive, and required NO maintenance. My advice is to pay the bit extra and go for the AGMs. When I bought them they were actually priced similar to the Rolls. My only hesitation at the time was the Chinese manufacturer, but they performed very well and far longer than most batteries can claim.
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Old 03-22-2016, 10:50 AM   #49
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AGM versus LA

Originally Posted by dhays View Post
Many sailboats came with terrible alternators as well (like my 80amp Hitachi) that has a really hard time fully charging a battery even when I motor to my next destination.
Dave hit on one of the problems for AGM batteries. In addition, your alternator on your engine should put out high voltages for AGM. Most will want to see 14.6 volts for bulk charging. Most engines are set up for 13.8 or so. A smart charge controller like the one made by Balmar can help get you high voltages.


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