AGM for House Batts?

Don,
12.8v while on charger .. Or just sitting there through the winter?

We've had 2 Deka AGM 8D's as house bank since 2008. Primary reason was to jack up our available Amp Hours, and to make maintenance access possible/easier. Boat is a Californian 34LRC. Primary use is cruising, not marina hopping, so we spend anywhere from overnight to a week at anchor. We don't have an onboard generator as such. An inverter is used for toaster oven, etc; refrig is a Norcold 110/12v. When not cruising, boat is plugged in at home base. Longest cruise to date was 4.5 months to Keys & back. So far all is well. If, &/or when we have to replace them, I won't hesitate to go w/AGM's again.

I almost hate to relate my experience in case I jinx something, but I purchased 6 AGMs from Xantrex in January 2003 when they closed out their UPS business. They sat in my garage for a few years, thinking 3 or so, on periodic low charge until I got around to installing them guessing 2006. They weren't quite as large as 8Ds - 152 pounds compared to 162 for the Lifelines, but all 6 of them cost me $716.10. Total, including tax. I drove up to Arlington and carried them back in my SUV.

Like many of you, my boat is mostly plugged in at my yacht club. I have them on a Link 2000, set up for AGMs, and I think the float is something like 13.95v. I've only run them down to 0 twice - once when I was calibrating the Link 2000, and a 2nd time when a nitwit at my club unplugged by power to test the outlet and forgot to plug it back (wasn't zero, but it was low). I usually leave the inverter off but had forgotten that time.

I did have one failure about 3 years ago. Smelled the rotten egg smell and, sure enough, one of them had bulged out so I removed it and dropped down the capacity in the Link 2000 accordingly.

And that's it. 10 years of service, about $100 per battery, zero maintenance, and 1 failure. And they <knock on wood> seem to be doing just fine. One thing that I assume has helped is that they are installed in what was the fish hold aft of the engine room and the temperature there hovers between water and ambient air (both cool in the PNW).

manyboats said:

Don,
12.8v while on charger .. Or just sitting there through the winter?

Click to expand...

12.8V was spring after winter storage & before hooking up to charger

That's impressive Don .... thanks.
The old shop/store Boat Electric said that I should keep the charger on always.
I suspect my AGM's are getting weak.
Upcoming usage will tell.

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?

You sound like me in that if a piece of equipment says it will do something, I tend to believe it until proven otherwise. I would trust it if I were you, but then I am simple minded.

When I replaced my battery bank this last fall I went with golf carts because it was cheap and I could get more amp hrs to fit in my existing molded in battery compartment than the alternatives. The compartment is also easily accessible for watering. There also was a minimum of work required for making the change.

I am cheap, lazy, and ignorant so I went with the solution that fit my own personality. If I was in your situation, lazy and ignorant might win out over cheap and I would just replace with similar AGMs as were installed. Not calling you lazy or ignorant, that is just what I would likely do. If the battery compartment was readily accessible for maintenance and the charger was simple to set for LA batteries, cheap might take the edge since the golf carts can be had so much cheaper.

manyboats said:

That's impressive Don .... thanks.
The old shop/store Boat Electric said that I should keep the charger on always.
I suspect my AGM's are getting weak.
Upcoming usage will tell.

Click to expand...

Eric...

RC at Compass Marine suggested I make sure they were fully charger prior to storage.
I set my ProNautic C 1250 shore charger on AGM2 setting which has a slightly higher V than the AGM1 I normally use (14.6 /13.7 Abs / Float vs 14.3 / 13.3).
RC recommended that as a way to get the charge up there as long as they weren't left on charge for extended time.
I just ran a couple of cycles until it switched to float before shutting down and disconnecting everything for the winter.

There are many good reasons for using AGM's over Flooded Lead Acid as many of you have stated, but it is a complete fallacy that AGM's can handle deep discharging better than Flooded do.
According to Trojan's own charts, their AGM's
(chart on this page Reliant AGM | Trojan Battery Company ) have a cycle life of 500 if discharged 80% and 1000 if discharged to 50%.

Their GC-2 batteries (T125, T105 etc) have a cycle life of 750 when discharged 80% and 1200 when discharged to 50%.
(chart on this page Signature Line Flooded | Trojan Battery Company ) and they have other flooded batteries that do even better that that.

Ken

The last battery change I did cost me 2 cases of beer for a crew off a fishing boat across the float in Ketchikan. It took longer to walk up to Safeway to get the beer than to change the batteries.

Tom

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.

cardude01 said:

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. &#55357;&#56834;

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?

Click to expand...

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.

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).

-Chris

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

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.

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.

FF said:

"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.

Click to expand...

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.

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.

AGM versus LA

dhays said:

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.

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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.

Gordon