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AGM Batteries for House and Engines

Old 11-12-2016, 04:42 PM
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Default AGM Batteries for House and Engines

I read through some old posts, but I was hoping to get some current feedback on sealed batteries other have bought.


I need to replace 4 - 115AH batteries for the house, and 2 - 75AH for the engines.


I anchor a lot, overnight, so I am looking for a high end battery that will provide house loads over a 12 period, and accept a charge well when the genny is connected.


I need to use the standard size batteries, to fit in the noted compartment.


I have not purchased batteries in years, so any other relevant feedback is appreciated.
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Old 11-12-2016, 05:44 PM
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are those group 31's in your house? then you can go with the fireflys but they are $$

how big is your AC charger running off the gen? how big is your gen?

that will likely make a bigger charging diff then better batteries.

how much height do you have? you could measure for L16 batteries
Old 11-12-2016, 06:27 PM
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Not certain of your specific setup but purchased 3 Duracell AGM Marine Batteries from Sam's Club a few years ago, two 31's & one 27. Price point was good and I personally can't tell any difference vs OE brand of AGM's that came on boat. As a matter of fact they are currently the same age of OE batteries when they required replacement, and I've never experienced a low voltage warning since installation. My engines require group 31 AGM's for starting and I use a 27 for electronics.

I believe the Duracell's are manufactured by Deka, and yes I would buy them again.
Old 11-13-2016, 01:05 AM
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Second on the Duracell AGM, excellent batteries. I have all group 31, 2 house and 2 starting charged by a NOCO 4 bank smart charger.
Old 11-13-2016, 04:33 AM
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X3 for the Duracell from Sam's, can't beat the price ! Had mine going on five years now and still perform as day one. I plug them into a Min Kota three bank smart charger as soon as I get home after each use and they have held up thus far.
Old 11-13-2016, 04:55 AM
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Have a couple seasons on my SAMs batteries as well and very happy so far.

However, from experience with a dedicated house bank I went with 6 volt batteries from lifeline. A pair lasted 12 years and only crapped out because I left them switched to both with an inferior agm battery that was shorted and ruined them.

They are $$$ but I don't think you will find a better quality battery. Not saying to go this route merely giving my experience.

On a related note you may also want to revisit your charging system and bulk charging capabilities. Agms can take a higher bulk load than conventional flooded which may matter to you. Allows less genny running time.
Old 11-13-2016, 05:08 AM
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Originally Posted by fletcher View Post
I read through some old posts, but I was hoping to get some current feedback on sealed batteries other have bought.

I need to replace 4 - 115AH batteries for the house, and 2 - 75AH for the engines.

I anchor a lot, overnight, so I am looking for a high end battery that will provide house loads over a 12 period, and accept a charge well when the genny is connected.

I need to use the standard size batteries, to fit in the noted compartment.

If you're willing and able (decent access) to do periodic maintenance (check electrolyte level, add water if necessary), and if off-gassing isn't an issue in your installation, flooded lead-acid (FLA) batteries can be good bank for the buck.

If access sucks, if off-gassing might vent into living quarters, or if you just don't want to fool with it -- and have the bucks -- valve-regulated absorbed glass mat (AGM) batteries can work fine IF you are able to fully charge back to 100% often, mostly after every use. (Many cruisers kill their AGMs because they can't get that last 5-10% charge while away from shorepower.) AGMs are said to accept charging faster than FLAs... although that's also controlled by whether your charger has enough oomph to take advantage of that.

(Not including sealed gel cell batteries here, since your charger will likely have to deal with both start and house batteries... and battery types should be the same chemistry.)

There are excellent AGMs -- Odyssey, Northstar, Lifeline, and now maybe Firefly -- and cost reflects quality. (Our oldests Odysseys are 11 years old, but need replacing next season.) There are other AGMs that are OK, not as expensive, likely not as long-lasting, likely not as resistant to abuse. (Weight, and subsequent plate thickness, is a gauge, sometimes.)

The important factor for your start batteries isn't amp-hours capacity, but rather cold or marine cranking amps (CCAs/MCAs). Whatever your engine needs (the manual will say) or whatever your starter motor needs (the info plate will say).

For house batteries... where amp-hour capacity is important... you can sometimes fit pairs of 6V golf cart batteries into the same space configured for 12V batteries in various sizes. If six 6V golf cart batteries can fit into the space where you have four (looks like) Group 31s... wired in series/parallel to 12V... then you'd have 660 Ah instead of approx 400 Ah... and that'd maybe be better for long periods at anchor. Even 4x GCs (approx 440 Ah) would likely be better than most 4x G31s (approx 400 Ah) because the golf cart batteries are specifically intended for deep cycling.... whereas most 12V "deep cycle" batteries aren't really (that's more marketing/labeling than truth; they're usually more like "dual purpose" batteries than "deep cycle.")

Your wallet will have to govern your own shopping, but were it me -- access isn't great, I prefer less off-gassing, and I like to simplfy maintenance when possible anyway -- I'd probably look first at Odyssey AGMs for your start batteries (high CCAs/MCAs), and pairs of Lifeline 6V GCs for your house batteries. I might consider the Firefly Carbon Foam Group 31 batteries for the house batteries instead, i.e., if I had to stay with 12V batteries or G31s specifically, because they are said to be more resistant to deep cycling abuse... but they're also big buck$$$$. Or Lifeline (I think) makes some "taller G31s" (sort of a misnomer) with more capacity that might be worth a look of space is such a serious determinant.

Or if you go with FLAs, I dunno about start batteries, but Trojan T105 GCs (or their taller versions, if you have space) would be the house bank recommendation.

-Chris

Last edited by ranger42c; 11-13-2016 at 05:19 AM.
Old 11-13-2016, 07:44 AM
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Good feedback on all accounts, thank you.


I am still at the "dangerous stage" in regards to battery knowledge, but learning.


The house batteries I have now are Group 31, and under a bed, and a pita to access so I need to stay with AGM, mainly for off gassing concerns.
I will google the Duracells, and other brands, thanks for the tips.


I am also intrigued by these carbon Fire Fly batteries. I know they are more $, but I am willing to pay it, if they will hold up as long as they advertise. Panbo seems to like them, and there are some good you tube vids.


I currently have 12V, 105AH (pic from manual I posted notes 115 but that is incorrect) Lifeline AGM's for the house loads. Here is the kicker: the boat, and the batteries are only 2 years old. The gen is 7.5KW. I believe the house battery charger is a Cristec, 60A. At anchor, the house batteries drop down to 12.1V after 10-12 hours, and that is with all items off, except an anchor light. The overnight voltage decline, at anchor, has gotten worse with time. The galley frig is an Isotherm, and its current draw is not excessive, and its not cycling too often.


[QUOTE Many cruisers kill their AGMs because they can't get that last 5-10% charge while away from shorepower.) [/QUOTE]


Copy that. I know they don't like to get low, and I immediately connect to shore power at the dock, and run the gen in the am and pm and night on anchor, but that may be my problem. Just surprised I am only getting 2 years out of these Lifelines, and concerned I may drop new ones in, and have the same issues if the charging system/process is flawed. Any ideas regarding some basic tests that can be done to assess this situation?

Last edited by fletcher; 11-13-2016 at 07:54 AM. Reason: edit
Old 11-13-2016, 08:30 AM
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Have you called Lifeline? Those batteries are still under warranty. Have you tested the batteries? If you have all 4 batteries connected in one bank, one bad battery will draw down the others.

Check your charger also, make sure it is set for AGM batteries. Check the charging voltage at the battery terminal with a multimeter. I had a Xantrex charger ruin some batteries because the charging voltage was too high.
Old 11-13-2016, 09:09 AM
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Originally Posted by fletcher View Post
The house batteries I have now are Group 31, and under a bed, and a pita to access so I need to stay with AGM, mainly for off gassing concerns.

I am also intrigued by these carbon Fire Fly batteries. I know they are more $, but I am willing to pay it, if they will hold up as long as they advertise. Panbo seems to like them, and there are some good you tube vids.

I currently have 12V, 105AH (pic from manual I posted notes 115 but that is incorrect) Lifeline AGM's for the house loads. Here is the kicker: the boat, and the batteries are only 2 years old. The gen is 7.5KW. I believe the house battery charger is a Cristec, 60A. At anchor, the house batteries drop down to 12.1V after 10-12 hours, and that is with all items off, except an anchor light. The overnight voltage decline, at anchor, has gotten worse with time. The galley frig is an Isotherm, and its current draw is not excessive, and its not cycling too often.

[QUOTE Many cruisers kill their AGMs because they can't get that last 5-10% charge while away from shorepower.)

Copy that. I know they don't like to get low, and I immediately connect to shore power at the dock, and run the gen in the am and pm and night on anchor, but that may be my problem. Just surprised I am only getting 2 years out of these Lifelines, and concerned I may drop new ones in, and have the same issues if the charging system/process is flawed. Any ideas regarding some basic tests that can be done to assess this situation?

Got it, ref under the bed and off-gassing. Same choice I'd have made in that situation.

Don't know that I'd invest in Firefly until I solved the issue about why your Lifeline AGMs are seeming to lose life... Yes, call Lifeline.

You can take them someplace to do a load test, but that'd be a lot of work... Maybe just check individual voltages after charging/resting first, before deciding what's next. (Lifeline may want that info, too.) Charge for 24 hours. Rest for 24 hours. Then test voltages on each individual battery to see what you've got. Could be all similar, or could be one battery drawing down the rest... hard to say, until you check that.

Yes, check your charger is set to the right profile. Whatever Lifeline wants for bulk/absorption and float. That said... your banks are mis-matched a bit. Is it two separate starting batteries, one for each engine in separate banks? So house, start 1, and start 2 are individual banks? If so, you've got a charger trying to deal with a 400Ah bank and two 75Ah banks... and it may be getting mixed signals. Even if the two start batts are in one single bank, you've still got a 400Ah bank and a 150Ah bank, maybe not similar enough for even a "smart" charger to get it right. Outcome, anyway, might be that you've been charging some too high and some too low.

Next, think about maybe some hidden loads. Our CO detectors, for example, are always on when the DC main is on. The shower sump runs from time to time when the ACs have been running. The freshwater pump runs from time to time. Anchor light, of course, but maybe some other electronics stuff still on, too? Anchor or depth alarms? (Our AIS transmitter is mostly always on unless I remember to leap through a hoop or two to shut it off.) And then maybe the fridge cycles more than you realize, at least in hot weather.

FWIW, our house batteries are often down to about 12.2V (about 50% SOC) after about 10-12 hours, too. We've got about 600Ah total for the house (split into two banks, each running about half the house load). We've usually just run the genset and charger 2x/day... and do our cooking and water heating at the same time. IOW, maybe your situation is about normal.

Our oldest bank is going down the tubes, though, so recently we've had to start charging 3x/day and voltage is still WAY down in the morning.

-Chris

Last edited by ranger42c; 11-13-2016 at 09:52 AM.
Old 11-13-2016, 09:21 AM
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Throwing in my $.02 for the Duracell batteries at sams. I've seen them for $149-$179 in the 31 group.
Old 11-13-2016, 11:14 AM
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Here is a good 2 part read about batteries.http://www.marxrv.com/12volt/12volt.htm hope it helps.
Old 11-13-2016, 12:51 PM
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Originally Posted by sidelock View Post
Here is a good 2 part read about batteries.http://www.marxrv.com/12volt/12volt.htm hope it helps.
That's a "good read" if you know nothing about batteries or series-parallel wiring, and you don't mind getting contradictory information.
Old 11-13-2016, 01:12 PM
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60a charger with a 7.5k gen is tiny.

with a 440ah agm bank you should be over 100a charging. that will save battery life and less gen run time. (less fuel) if you don't want an inverter / charger consider adding a 2nd 60a battery charger. or think about adding an inverter / charger.

you should also get a battery monitor like the victron 700/702. you say your battery voltage drops over night but you probably have no idea on the AH usage. which is important to know why they are dropping. if they are droping to 12.1v with minimal load then they are bad.
Old 11-13-2016, 02:29 PM
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Thanks for the continuing advice, and the battery article. I have moved out of the danger zone, and I am now on the bunny slopes.

The boat is French, and some aspects have been a bit screwy, compared to the Sea Ray we
Previously had.

I agree, that 60 amp charger appears to be on the small side. The data sheet indictes it is a three stage bulk charger and is designed to charge both deep cycle and starter batteries, but I am a bit suspicious of that.

The boat is still under warranty (5 year warranty) so I am hesitant to replace battery chargers or make other major changes at this point.

I am leaning towards doing some basic tests as noted, verify the charger has appropriate setpoints and then replace the batteries with new AGM's but I won't spend the money on the fireflies At this point. I will keep close tabs of the battery voltage and will just have to run the generator more to keep above the low voltages while anchored.

Still mulling this over, so I will probably be back with more questions soon.
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Old 11-13-2016, 02:41 PM
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Originally Posted by fletcher View Post
I will keep close tabs of the battery voltage and will just have to run the generator more to keep above the low voltages while anchored.

.
or you figure out why you are drawing so much over night and fix the draw issues. and run the gen less. which you need an amp gauge / battery monitor for.
Old 11-13-2016, 04:16 PM
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Agree.


I can only see V and A.


I am drawing 1-2 Amps at night, and it can spike up to 7 or 8 Amps when the reefer kicks on periodically.


Either way, it is a small current draw for the batt's to drop to 12.0V overnight.


Originally Posted by smac999 View Post
or you figure out why you are drawing so much over night and fix the draw issues. and run the gen less. which you need an amp gauge / battery monitor for.
Old 11-13-2016, 04:33 PM
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I don't overnight much on the batteries, but I have 8 Optima Blue Top group 34 batteries--a pair for each engine and four for the house bank. They seem to work fine and are widely available. I got mine from O'Reilly's Auto Parts, but others have gotten good prices at amazon.com with free shipping. Mine are not the easiest to access, so the AGMs work well.
Old 11-14-2016, 04:11 AM
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Originally Posted by fletcher View Post
I agree, that 60 amp charger appears to be on the small side. The data sheet indictes it is a three stage bulk charger and is designed to charge both deep cycle and starter batteries, but I am a bit suspicious of that.

I am leaning towards doing some basic tests as noted, verify the charger has appropriate setpoints and then replace the batteries with new AGM's but I won't spend the money on the fireflies At this point. I will keep close tabs of the battery voltage and will just have to run the generator more to keep above the low voltages while anchored.

Still mulling this over, so I will probably be back with more questions soon.

Sounds like reasonable approach.

I'd guess the charger probably is appropriate for deep cycle and starting batteries, but... a serious mismatch in bank size can still be an issue.

(We had a mismatch on ours, too. Two 300Ah dual-purpose (start + house) banks and one 68Ah genset start bank. Solved it by removing the genset battery (the genset alternator charges that anyway), and separating the two large banks onto their own separate chargers. One bank's new 70-amp charger is also an inverter now, too, so that was a related upgrade I was able to insert into the system at the same time.)

And then the 60-amp part still means you're only charging that house bank at the rate of about .14C max (60/420), which doesn't really take much advantage of the faster AGM's acceptance rate. Which means you'd need to be running your genset quite a bit longer during each charging period for the absorption rate to have to most affect. It could be that you've just not been charging the batteries enough while you're out, so that overall capacity has maybe been affected over time... even if you return to fully-charged once you've returned to the dock/shorepower. (IOW, "fully charged" -- approx 12.8V -- doesn't necessarily mean you still have 100% capacity anymore.) Maybe the Lifeline guys can comment on all that.

(We were undersized, too, with a single 40-amp charger on two 300Ah banks... or .06C (20/300) for each bank. Now we're at least at .13C for one bank (40/300) and .23C (70/300) for the other.)

Ref the chart you posted: look specifically at Lifeline's data, instead. Might or might not match, since some makers' data varies about what voltage indicates what state of charge (SOC).

If you do buy new Lifelines, 4x 6v GC batteries would very likely fit in the same space as the 12V Lifeline G31s you have now, assuming there's headroom for the slightly taller GCs. The GC batteries are said to be true deep cycle batteries, so 440Ah (approx) would likely be better for your house situation. If you also have some extra height available above that in your box, Lifeline has some taller 6V versions that will give you even more capacity.

-Chris

Last edited by ranger42c; 11-14-2016 at 06:22 AM.
Old 11-14-2016, 05:50 AM
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Great info, thank you Chris. Good to hear you have your electrons in balance on your boat.

Never had to deal with battery issues before. Stuff just worked, but it has been interesting to learn more about the subject.

The gen has its own charger, but providing a separate one for the house and engines as you note makes sense. Need to think about that more.

The 6v size batteries are also interesting. The article posted likes those as well.

Originally Posted by ranger42c View Post
Sounds like reasonable approach.

I'd guess the charger probably is appropriate for deep cycle and starting batteries, but... a serious mismatch in bank size can still be an issue.

(We had a mismatch on ours, too. Two 300Ah dual-purpose (start + house) banks and one 68Ah genset start bank. Solved it by removing the genset battery (the genset alternator charges that anyway), and separating the two large banks onto their own separate chargers. One bank's new 70-amp charger is also an inverter now, too, so that was a related upgrade I was able to insert into the system at the same time.)

And then the 60-amp part still means you're only charging that house bank at the rate of about .14C max (60/420), which doesn't really take much advantage of the faster AGM's acceptance rate. Which means you'd need to be running your genset quite a bit longer during each charging period for the absorption rate to have to most affect. It could be that you've just not been charging the batteries enough while you're out, so that overall capacity has maybe been affected over time... even if you return to fully-charged once you've returned to the dock/shorepower. (IOW, "fully charged" -- approx 12.8V -- doesn't necessarily mean you still have 100% capacity anymore.) Maybe the Lifeline guys can comment on all that.

(We were undersized, too, with a single 40-amp charger on two 300Ah banks... or .06C (20/300) for each bank. Now we're at least at .13C for one bank (40/300) and .23C (70/300) for the other.)

Ref the chart you posted: look specifically at Lifeline's data, instead. Might or might not match, since some makers' data varies about what voltage indicates what state of charge (SOC).

If you do buy new Lifelines, 4x 6v GC batteries would very like fit in the same space as the 12V Lifeline G31s you have now, assuming there's headroom for the slightly taller GCs. The GC batteries are said to be true deep cycle batteries, so 440Ah (approx) would likely be better for your house situation. If you also have some extra height available above that in your box, Lifeline has some taller 6V versions that will give you even more capacity.

-Chris

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