AGM or GEL batteries

Jan 12, 2011
930
Hunter 410 full time cruiser
It doesn't matter what type of batteries you get. If just depends on how well you take care of them.
 

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
AGM or GEL batteries, and why? is there a way to tell if an existing inverter is appropriate for these batteries. I have a heart interface, original to boat 1997. And is there a good place on line to order these batteries?
  1. To compare AGM and gelled electrolyte, deep discharge batteries, I recommend starting with batteryuniversity.com. Here's the article on gel: http://batteryuniversity.com/learn/article/bu_201b_gel_lead_acid_battery And, here's the article on AGM: http://batteryuniversity.com/learn/article/absorbent_glass_mat_agm. I think gels are better, but they are considerably more expensive, when I shopped (nearly 75% more than equivalent AGM).
  2. If you can adjust the acceptance voltage and the float voltage, you can use your charger. The problem with many older "smart" chargers is that they employ a timed acceptance charge; what you really want it is a charger that will hold the acceptance voltage until a programmable current level is reached, preferably 0.5% of the bank Ah capacity. Note that this could take a long, long time to reach!
  3. I bought my flooded batteries at Wal-Mart, and my AGMs via Amazon Prime. Online a big issue will be shipping charges. You want the freshest batteries available, so an advantage of WalMart is that you can examine the date code on the batteries - not even obscured anymore, it will state month and year of manufacture. You also want all batts in a bank to be preferably not only the same date code, but the same lot, if possible, so the likelihood they "match" is very good.
 

SG

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Feb 11, 2017
1,670
J/Boat J/160 Annapolis
JVISS wrote: Regarding your comments on AGM, I would like to see a reference that supports that. What I have read from authoritative sources is in contradiction, specifically, that AGM charge faster, and go to 80% depth of discharge for the same life cycle as flooded taken to 50%.
  • You say "forever." Can you be more quantitative, please? I haven't seen in the literature that it takes 'forever' to put back the last 7%, and - compared to what technology?
  • You say you increase the likelihood of sulfating if you don't charge them up frequently, yet, AGM are known to have better storage characteristics, and lower self-discharge than flooded.
  • The paragraph that starts "When we go to beyond 60%," doesn't make any sense to me at all. There's a lot of qualitative criticism, like "a lot," "declining," and "painful," but nothing one can really go on. Perhaps you can elaborate?
I've had three sets of Lifelines 4D AGM's over the last 19 years. The first set (with a Heart 2500 Combi lasted 8 years). The second, 4 years; and, the third two years; and the fourth, 1 year. Between the second and the third sets, I upgraded to more robust MasterVolt (nominal 200 AMP) Combi unit. I almost always charge the batteries to "full" from the generator or at shore power.

With both the Heart (now, Xantrex) and the Mastervolt, I have personally watched the acceptance voltage through the recharging cycles carefully. The Mastervolt is easier to tweak the voltages and monitor the amps in and out than the less robust (nominal) 130 amp "advertised" Heart's capacity.

However, if you watch to see what happens with the real world acceptance voltage, you'll see the declining curve of actual amp hours into the battery as you move to increased charge levels. That's when the batteries are fresh "out of the box".

To get the batteries up to 95% takes a long time (which you measure in hours, not minutes) even if you have 130 amps of actual "real world" charging capacity available to get to the batteries. (The 2500 Xantrex, though rated at a nominal 130 Amps never really puts out much more than 65 or amps to the house load after it gets settled down, for example.)

I recharged my Lifelines at 14.4+/-Volts (At the battery terminals in Bulk Mode). The batteries just have naturally slower acceptance rates as they move up the charge "curve".

I've consulted with two sets of marine electrical "experts" and others comments. In calls to Lifeline, they have said over the years, in essence, "that's just normal".

It's faster in cooler 55-60 degree water than 80 degree water, but the real world acceptance rate is lower. If you don't charge the AGM's back up very regularly, you'll be sorry.

JViss: How would you chart your acceptance rate from a 50% through 100% recharge? How many hours does it take to get your batteries back up to above 95% when under shore power and at with what equipment. When you're under way, with an alternator, what's been your measured experience?

[By the way, I have been a proponent of the AGM technology. The Lifelines had a stellar reputation and I've supported them. However, ask yourself: Why, with the same batteries, do you they recommend that you EQUALIZE them regularly -- even if you charge them back up to over 95% almost always; and store them at near 100% capacity on a very controlled system)? Something has changed in their manufacturing process. I've read the same materials that you've cited.]
 

jviss

.
Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
To get the batteries up to 95% takes a long time (which you measure in hours, not minutes) even if you have 130 amps of actual "real world" charging capacity available to get to the batteries.
The maximum current available form the charger does not matter when you are in acceptance mode, unless, of course, your battery bank can absorb that maximum current at the acceptance voltage, which is liekly only with an enormous house bank, like for a submarine.
I recharged my Lifelines at 14.4+/-Volts (At the battery terminals in Bulk Mode).
At 14.4V you are not in bulk mode, you are in acceptance mode, or just about to enter it. Bulk is a max current charge stage, acceptance is a constant voltage charge stage.
However, if you watch to see what happens with the real world acceptance voltage, you'll see the declining curve of actual amp hours into the battery as you move to increased charge levels. That's when the batteries are fresh "out of the box".
This is true, by definition; since acceptance is a constant voltage stage, and because of lead-acid battery chemistry, current will decline as charge on the batteries increases, "fresh out of the box," or not.
How many hours does it take to get your batteries back up to above 95% when under shore power and at with what equipment.
I don't know, I'm never there when it happens. I'm on a mooring, and have solar. I have a Morningstar Sunsaver controller and 240W of panels.
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
and why? is there a way to tell if an existing inverter is appropriate for these batteries. I have a heart interface, original to boat 1997. And is there a good place on line to order these batteries?
GEL Batteries:
GEL batteries are some of the longest cycling batteries I see in the marine environment. My friend Bruce we around the globe twice on a set of Prevailer GEL batteries TWICE!! The only two GEL batteries I would touch are the Deka/East Penn made GEL or the Sonnenschein Prevailer products. These are the gold standard GEL batteries and they deliver fantastic cycle life if installed, used and charged correctly.

GEL Warning: Gel batteries must be properly charged to get optimal cycle life. GEL batteries need to be installed using a system approach. It's not just a battery that you need you also need the proper charging system. Currently I have four sets of GEL batteries out there in excess of 12 years, with one of them at 17 years. One of my cruising customers (nine months per year full-time cruising), who's also a forum member here, has exceeded 10 years on their GEL house bank and this is with a system that could arguably use some tweaking. None of these banks charges at any more than 14.2V and even then the 14.2V is short duration, like a Balmar regulators BV setting, then dropping to 14.1V for absorption. Over charge these batteries and they will die quickly. No stock alternators need apply for this job.

AGM Batteries:
Like GEL there is a wide variation of quality in AGM batteries. The premium AGM's, suitable for deep cycle use on boats, include Lifeline, Northstar, Odyssey and Firefly. The new Trojan AGM's are yet to be proven in the real world but may also be good.. The ONLY Chinese made AGM's I would touch would be Fullriver or Rolls (the Rolls AGM's are made in China). Unlike their GEL batteries, which are fantastic, you could not pay me to install an East Penn made AGM for deep cycle use. These are best used as starting batteries and perform poorly in a PSOC use application.

Be aware that a LOT of people murder their AGM's and only wind up with a bigger hole where their wallet used to be when compared to a flooded product.. Flooded deep cycle, Golf Car grade or better, (see; What is a Deep Cycle Battery) are still a tremendous value. If you can get 7-12 years out of flooded deep cycle battery bank then you are a good candidate for AGM or GEL. If you can't get 7-12 years out of flooded batteries, fix your system and then buy AGM or GEL when you can treat them properly. Course if you have excess money burning a hole in your wallet then just install a set of GEL or AGM, as a "drop-in replacement" for flooded, and cross your fingers...

Flooded Batteries:

For most boat owners who are unwilling to take a "system approach" to AGM or GEL batteries, deep cycle flooded battery banks are almost always the best value for the money. The vast majority of boats out there are still using flooded batteries as are the RV community and off-grid solar. Again if you can't get a solid 7+ years out of flooded deep cycles then AGM or GEL are going to chew through your money a lot faster...

The following articles address battery buying decisions:

Fighting Sulfation In AGM Batteries - Practical Sailor May 2015

AGM Battery Test Update - Practical Sailor August 2015

AGM Batteries - Making the Choice - Musings with Maine Sail

What is a Deep Cycle Battery - MarineHowTo.com
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
The ONLY AGM batteries I would recommend regularly discharging to 80% DOD is the Firefly Carbon foam. $$$$ but it really does what it claims.. Do this with other AGM's, including the premium deep cycle products from Odyssey, Northstar, Lifeline etc. and you'll be kicking yourself in the rear end. If you talk to any of the quality AGM makers they will tell you not to regularly cycle below 50% SOC. Cycle a non-premium AGM (tons of them out there) to 80% DOD and they will be dead very, very quickly.

The occasional dip to 80% DOD is fine with a premium AGM provided they are followed up with a 100% SOC recharge ASAP.
 
Jun 15, 2012
694
BAVARIA C57 Greenport, NY
Just purchased 3, 8D Deka Gel batteries from Remy Battery. Installed last month, so far working well.