Are The AGM Worth 2X The price Of PB?

[admiralslater]

Our Outremer had 4 type 31 life line agms when we purchased . last year we had enormous difficulty with their capacity. The boat sat on mooring unused for about 2 years .
It has 500 watts of solar and mppt controllers . the boat had no battery charger installed .We installed a BC but never really spent time at a dock.By the end of the trip the batteries were dead by 10 pm each day .
If they where operating correctly we had enough capacity . I don't blame the batteries they where abused
My research /reading ,such as it is leads me to believe that almost any type of battery can do the job IF the charging requirements are met .
We have purchased but not installed yet 5 Carbon plate Firefly batteries from Hybrid Power(CF vendor). Mostly because of the recovery capability,which we need because as with most cruisers we may not get them fully charged every day.

[reed1v]

Would never suggest buying a big 2 volt battery new. Buy used. Commercial salvage stores, industrial yards, and so forth have them for a fraction of the price. Even tractor and heavy equipment resale yards have them. Farm implement stores, (no not the garden nursery types) use to have them. A good 2 volt will sell at the price of the lead inside. figure 30-80 bucks each. Easy to recondition. Marine salvage yards use to have them and probably still do.

Your looking at the plaid pants and manicured fingers catering stores. Go to real marine stores.

[Schooner Chandlery]

Originally Posted by reed1v

We used 2volt cells purchased from naval salvage(submarines) that lasted over 18 years. Simple to maintain, huge capacities, and servicable in any port around the world. Of course each weighted 60 pounds. We had two banks so close to half ton of batteries. Like old farm batteries, the plates were huge. Just add distilled water, keep clean, and keep the contacts covered with a plastic spray. More wattage than most homes consume. The advantage of single 2 volt cells is that if one goes bad, easy to replace(assuming your a weight lifter).

Did i mention they are cheap to buy and can be infinity abused without impairing their ability to recover full charge.

So outta curiosity how big are these? You need 6 per 12V...the OP would want/need 12 per his 24V system.

[a64pilot]

I am in a similar situation. I have a Lifeline AGM bank with Solar and a Diesel genset.
I plan on getting to 100% charge twice a week, I expect it will take 8 hours or so of generator running to get there, and when the batteries can accept it, I have 185 amps of charger to throw at them.
I'm looking , hoping for 5 years out of them, by that time I expect LifePo to be mature enough so that it's not a DIY job and or too expensive. My charge source are already LifePo capable, I think My outback 80 is ,but not sure.

From what I can gather, 10 years in a boat that doesn't live in a Marina isn't realistic for a an AGM bank, or any bank really, not counting Submarine batteries.
Where in the world can you get those things?

I went AGM due to sizing restrictions, those or maybe Gels are all that would fit in my box, I think Golf Cart batteries would have been much better, cost 1/3 as much so even if they only last half as long, your still ahead.

[AussieCat]

Now that's like asking a group of fisherman what's the best burley? Always sure to start an argument. Just from my own experience if you have solar & wind (you didn't state output of these) your batteries should never run down. I'd go AGM every time. Had 2 banks of 2 x 150ah (200ah wouldn't fit) in the Tasman we just sold. The set that came with the boat I finally replaced two years ago were stamped nearly 12 years old. Like any thing only buy good quality brands and their well worth the money. We always leave the fridge / freezer on 24 / 7 and sometimes are absent for 2 - 4 weeks at a time. Never had any issues with the AGMs. Even when we were on the hook for days at a time we never had to run engines to top up batteries. Other is safety factor of course, I'd prefer not to have more acid cell batteries on board than I have to. Quiet often house batteries are mounted in the living areas under seats etc. If you haven't already done so change over to LED lighting. Well worth the $ss and have no impact on the batteries. Have just put dep on 43' FP Belize and will upgrade the house to AGMs as well.

[Sternwake]

I went with a Northstar group27 AGM mostly to experiment with AGM's rather than just reading about them.

What I have noticed, it its extreme ability to crank my engine quickly. A single group27 spins it faster than 2 27 flooded marine batteries could when fully charged.

It laughs at extreme charging currents. I regularly feed a 90AH battery 62 to 90 amps when depleted to 50%.

It holds higher voltage than a group31 USbattery could for the same AH removed from it, under the same load.

I have cycled it hard and heavy. It does not enjoy low and slow solar only recharges, even if the sun is out long enough for amps to taper to 0.4 at 14.46v. After 4 to 5 solar only recharges, voltage held under load sags noticeably and then falls off a cliff on cycle 6 or 7.

One high amp recharge from 50% depletion seems to return performance, as long as I hold 14.46 as long as it takes for amps to taper to 0.4 or less.

It will eventually taper to 0.0x amps at 14.46. At this point I can bump voltage to 15.3 and within a few seconds amps have again tapered to somewhere under 0.05 to maintain this voltage.

I have over 200 deep cycles to 50% and sometimes deeper on this 25 month old battery. The last time I took 50AH+ from it just a few days ago, in 6 or 7 hours, it maintained 12.1 volts while still under a 3.5 amp load.

Perhaps Voltage quickly would drop off after this ~50 SOC % grey area, but so far it appears as if this battery still has more than its rated capacity, and I attribute that to being able to high amp recharge it and hold absorption voltage long enough to reach an authentic 100% charged.

If I could not do this, the battery would likely be in the process of failing right now.

I hope to make this battery last until Lifepo4 falls to within my initial financial grasp, but if I have to get a dedicated house/Aux battery again, it will be a Flooded t-1275 at 150AH from Trojan. For less than 2/3 the price of this 335$ Northstar-27 and have 60 more AH capacity.

So this AGM might be both my first and last. I like it, but I don't need it, and it is petulant when it does not get high amp recharged, or has to deal PSOC cycling for 4 or more cycles in a row.

Also after PSOC cycling for 4+cycles, it then takes tremendous amounts of time for amps to taper from 5 at 14.46v to 0.4 amps. Something like 8 hours at absorption voltage just to reset it to its maximum remaining capacity/performance. If I fail to give it enough time at absorption, then its performance is less than impressive, and cumulatively less so.

[hellosailor]

I would suggest that if someone does not understand the differences in AGM batteries (and none of them have "tubular" plates, some of them are "spiral wound" plates, others are flat) and one does not have a specific need for one of the differences of AGM batteries, then one should simply buy wet lead acid batteries for 30%-50% less price.


And I say that as an AGM fan (not a zealot but a fan) because, among other reasons, an AGM battery will never leak acid and burn a hole in my clothes, carpet, or anything else.

[reed1v]

Originally Posted by hellosailor

I would suggest that if someone does not understand the differences in AGM batteries (and none of them have "tubular" plates, some of them are "spiral wound" plates, others are flat) and one does not have a specific need for one of the differences of AGM batteries, then one should simply buy wet lead acid batteries for 30%-50% less price.


And I say that as an AGM fan (not a zealot but a fan) because, among other reasons, an AGM battery will never leak acid and burn a hole in my clothes, carpet, or anything else.

Lead acid batteries are mostly foolproof, and if kept in sturdy, waterproof boxes will not be a problem burning anything. We vented them just like the fuel tanks. Secondly, almost anywhere around the world there are thousands of shops that will rebuild your batteries for very little money. So for about $200 bucks you can get a big used system, rebuild it for about $50 bucks, and have virtually brand new batteries that will run for another 20 years.
We did that in Turkey with one bank of batteries that were about at the end of their life cycle(17 years). Plus lead batteries are well behaved and do not spring surprises on you, like going dead suddenly. Keep the fittings clean, water topped up, sealed away from all else, and strapped down in case your boat decides to do somersaults. Oh, and watch where you put your compass.

[Maine Sail]

Originally Posted by Sternwake

it is petulant when it does not get high amp recharged, or has to deal PSOC cycling for 4 or more cycles in a row.

Also after PSOC cycling for 4+cycles, it then takes tremendous amounts of time for amps to taper from 5 at 14.46v to 0.4 amps. Something like 8 hours at absorption voltage just to reset it to its maximum remaining capacity/performance. If I fail to give it enough time at absorption, then its performance is less than impressive, and cumulatively less so.

You are more observant than most and yes AGM & especially TPPL AGM batteries do like high current recharging but more importantly the Northstar's will do better in a PSOC environment at 14.6V -14.7V vs. 14.46V.

It is not uncommon for a lead acid battery to take considerably longer to fully charge after a period of PSOC cycling or when the battery is sulfated. Eight hours is not out of the norm to get to 0.5% acceptance. I stick used AGM batteries on my bench regularly that take in excess of 10 hours to fully charge, because they are sulfated..

FWIW Odyssey (Northstar is a splinter off product born out of Odyssey/EnerSys technology) prefers to use 0.3% if using the return current method of 100% SOC determination.

Below is a graph from Practical Sailor (May 2015) of a pretty typical "walk-down" you will see when PSOC cycling lead acid batteries. PSOC walk-down is the gradual loss of usable capacity as sulfation forms on the plates. Most folks would assume a 48.3A charge rate for 1 hour, on a 105Ah battery, in bulk, when starting from about 29% SOC (11.7V cut-off under the 20 hour discharge rate) would yield a 48.3Ah return. Bulk is very, very efficient, and and it nearly does yield that on cycle 1, and even perhaps cycle 2, but as the battery begins to sulfate, from PSOC use, the net usable capacity will walk-down even given the identical treatment on each cycle. This PSOC damage can be irreversible if the batteries go long enough between full re-charging or equalization (if applicable)..

These batteries were broken in, capacity tested, discharged to 11.7V at the 20 hour rate and then recharged at .46C for exactly 1 hour and again discharged back to 11.7V and charged at .46C for an hour. This repeated for 30 cycles. This battery started the test at 105.2Ah and ended at 93.67Ah after 30 PSOC cycles.

Image Courtesy of Practical Sailor

[roland stockham]

Simple answer. AGM's are PB batteries. 'Sealed for life' simply means when it runs out of water it is dead, like sealed bearing which last the life of the grease. If you don't want to do maintainance don't buy a boat!

[hellosailor]

Reed-
"Lead acid batteries are mostly foolproof, and if kept in sturdy, waterproof boxes will not be a problem burning anything."
I'd agree with you, but first someone must get the battery to the boat, usually in a car trunk or floor, without burning that trunk carpet or rear seat carpet, which can be pricey. And then into the launch or dockside, without burning your shirt or coat or pants. And then into the battery box, again not burning anything including any cabin sole. And then, play with the battery cells or hydrometer from time to time again, without burning anything.
I don't say that's impossible, I simply find that it is best done with lots of disposable liners and disposable clothes. Personally.

As to rebuilding batteries? In the States, unless you are using fork lift batteries or others with discrete 2,2V cells that are easily unbolted? Don't hold your breath, the battery shops and dealers that deal with the consumer market do NOT replace cells or rebuild batteries.

A couple of acid burns can be common, and make AGM's into a much cheaper competition, if you're not in the fork lift category here.



Roland-
AGM's are not simply sealed PB batteries. Back in the 70's Delco and others sold a lot of "maintenance free" wet acid batteries (in the entire GM car line, for example) and THOSE were simply sealed wet acid batteries. AGM is different, the "starved glass mat" separators also prevent precipitates from falling to the bottom of a cell and moving permanently off the plates. And they eliminate the 24-hour lag that it may take a wet lead battery's electrolyte to flow around and equalize the charge and the electrolyte itself.

[colemj]

Originally Posted by reed1v

Lead acid batteries are mostly foolproof, and if kept in sturdy, waterproof boxes will not be a problem burning anything. We vented them just like the fuel tanks. Secondly, almost anywhere around the world there are thousands of shops that will rebuild your batteries for very little money. So for about $200 bucks you can get a big used system, rebuild it for about $50 bucks, and have virtually brand new batteries that will run for another 20 years.

We did that in Turkey with one bank of batteries that were about at the end of their life cycle(17 years). Plus lead batteries are well behaved and do not spring surprises on you, like going dead suddenly. Keep the fittings clean, water topped up, sealed away from all else, and strapped down in case your boat decides to do somersaults. Oh, and watch where you put your compass.

What it's involved with "rebuilding"a battery? We certainly haven't been in those parts of the world where thousands of shops exist doing this. I have never seen a single place doing this, nor heard of one. And we have spent a lot of time in places where nothing gets thrown out unless it is truly worthless and can't be turned into something else - and batteries are always piled up in trash heaps in these places. Our batteries don't have any way to even open the cases, and I can't imagine that it would be cheaper to add new plates to them than buying new batteries, even if it was possible to get the cases open.

I'm calling B.S.

I don't think there is anything paramagnetic in a battery that would effect your compass.

Mark

[colemj]

Originally Posted by a64pilot

I am in a similar situation. I have a Lifeline AGM bank with Solar and a Diesel genset.
I plan on getting to 100% charge twice a week, I expect it will take 8 hours or so of generator running to get there, and when the batteries can accept it, I have 185 amps of charger to throw at them.
I'm looking , hoping for 5 years out of them, by that time I expect LifePo to be mature enough so that it's not a DIY job and or too expensive. My charge source are already LifePo capable, I think My outback 80 is ,but not sure.

From what I can gather, 10 years in a boat that doesn't live in a Marina isn't realistic for a an AGM bank, or any bank really, not counting Submarine batteries.
Where in the world can you get those things?

I went AGM due to sizing restrictions, those or maybe Gels are all that would fit in my box, I think Golf Cart batteries would have been much better, cost 1/3 as much so even if they only last half as long, your still ahead.

Didn't you just install 750 watts of solar? If so, then you won't be running your genset that often or that long, unless your usage is way out of normal.

You get submarine batteries from submarines. Those are common and for sale in thousands of shops on the planet that guy lives on. For the rest of us on planet earth, they just aren't a viable option.

Mark

[reed1v]

Two volt cells are available almost everywhere there are commercial fishing outfitters. Seen them on thirty foot sailboats. For those who have never sailed or cruised beyond their docks, most places like Turkey, India, Malaysia, and even in Chile will have shops that cut open the batteries, change plates, and reseal the cases. Not pretty but works.


Now, as far as babysitting your lead acid battery, there are modern chargers that will automatically deal with recharge rates to ensure appropriate conditioning. Practical Sailor has had articles on this so please read them. And as an aside, anyone going cruising really should subscribe to Practical Sailor for its wealth of information; join the SSCA for its enormous access to professional and experienced advice from its members like the Pardeys, and take some classes in basic engine, electronics, and rigging.

[Wotname]

Originally Posted by colemj

I don't think tmmhere is anything paramagnetic in a battery that would effect your compass.

Mark

The problem isn't the battery, its the magnetic field from current flow in the battery leads. Not normally a problem especially if the pos and neg leads are close together AND not near the compass or fluxvalve etc..