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Thread: AGM vs. Lead Acid Batteries

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    Default AGM vs. Lead Acid Batteries

    Does anyone have any experience with using an AGM vs. lead acid battery for their boat?

    I like the idea of no maintenance, faster charging, and lower rates of discharge during storage for the AGM, but I have no actual experience with them. I currently have 2 lead acid batteries (1 house; 1 starting) that are charged with Blue Seas ACR, and am considering replacing the lead acid house battery with an AGM. Based on discussions with Blue Seas, there should not be any problem with charging. I have a Honda 225 outboard.

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    Member Akgramps's Avatar
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    A AGM is still a lead acid battery, the agm stands for absorbent glass mat, which is the material between the plates.
    They are expensive but excellent batteries, particularly so for a seasonal use item such as boat motorcycle, etc. A particular advantage here in AK is they are unaffected by the cold, in other words they dont lose their charge over the course of the winter. So the likely hood of them freezing is next to none, as long as there is no draw on them. What convinced me was the 12 year life I got out a motorcycle battery, which in the past I would be lucky to get two seasons out of. I bought two for my riverboat maybe 5 years ago, I use to remove them in the fall bring them inside and put on a maintenance type charger, alternating from time to time. In any case the last two years I left them in the boat all winter, -40 and all that, about a month ago I pulled the boat in to swap out a bilge pump. I checked the voltage on the batteries, one was 12.66 and the other was 12.7.

    The other advantage is most AGM type batteries are suitable for both starting and house, so dual service in the sense of being able to deliver high amps fast for starting and still endure deep cycling events routinely.

    I spent close to 600 bucks for two batteries and that can be hard to swallow, if they give me 10-12 years w/o trouble then I think its worth it.
    There is nothing worse than battery issues when out on the water. can ruin a trip rather quickly. As far as mixing and matching, I would be hesitant to do that as a typical lead acid and AGM can require different rates of charge. And like any dual battery system , truck or boat you should replace both, especially if both batteries are being charged by the same alternator as most rec boat are. And for reasons more complex than I can explain here. But the short story is a old battery with a new battery can potentially over charge the new battery as it is has less resistance to charge than the old battery.
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    I have the exact same setup... Blue Seas ACR and 2 AGM batteries with an Etec 225. It has worked great. The second time I put in with the new wiring set up, the positive lead had come off of the starting battery and it had drained all the way down to nothing. I put the battery selector to "combine" or whatever it's called (not off, not on, but essentially both) and the main fired right up off the house battery. Drove around for awhile, trolled for awhile, and then stopped to jig. When I went to start the main again (having put the battery switch back to "on" after starting it the first time - isolating the batteries again) it fired up like a champ off the starting battery. My house battery is an optima, but after doing a bunch of research I went with the Cabelas AGM for my starting battery. I guess I'll reserve my judgement until I run an entire season with it, but since it was on sale for $129 I can probably get a new one every year (although I hope not to) and still come out money ahead. We'll see how it holds up.
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    Quote Originally Posted by kodiak_hunter View Post
    Does anyone have any experience with using an AGM vs. lead acid battery for their boat?

    I like the idea of no maintenance, faster charging, and lower rates of discharge during storage for the AGM, but I have no actual experience with them. I currently have 2 lead acid batteries (1 house; 1 starting) that are charged with Blue Seas ACR, and am considering replacing the lead acid house battery with an AGM. Based on discussions with Blue Seas, there should not be any problem with charging. I have a Honda 225 outboard.
    kodiak_hunter;,,,, FWIW, this is a "No" Brainer,,, AGM or Gell-type, do it, and don't look back.

    "TG"
    [ Retired and Living the "Dream" in Alaska, Semper-Fi ]

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    Thanks for the great feedback. In reviewing the Blue Seas ACR documents, it looks like the maximum battery bank is group 27, which may limit the options a bit - I think I'll get the optima for the starting, and then a group 27 AGM deep cycle. I will call Blue Seas for options to increase to a group 31. Appreciate your input.

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    Member Akgramps's Avatar
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    Before you jump on the Optima bandwagon, think about what a battery is made of, mostly lead and acid with a plastic case, a group 27 battery with 6 round cells will weigh 10 to 15 pounds less than a rectangle battery, like a Trojan, Northstar or Odyssey..... less lead, less acid and cost less to make and has less capacity..... I know they look cool..... and I am not trying to incite of inflame as they may be good batteries, there is just less material in one and personally I think its all marketing......





    Which Blue Seas ACR do you have?
    “Nothing worth doing is easy”
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    Incite inflame - no way, I appreciate your input and very good point on the Optima - they are a lot lighter!

    I must have read an earlier or older model of the ACR that indicated a limit to group 27. For the ACR, I have the 120 AMP, model 7610, which does not show any limitation for battery size bank.

    Do you see any problem with different group sizes between the house and starting battery (i.e. would it be okay for a group 31 AGM for the house, and say a group 27 AGM for the starting? I need 800 CCA for starting.

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    I was actually thinking along the same lines as Akgramps. Optima is a bit of hype. I had both Optima and Trojan AGM batts and the Trojans were by far better. They are hard to find local up here but well worth it if you want to go with AGMs.

    That all being said, why do you need a sealed AGM battery vs a traditional battery. Traditional lead acid batts typically have more of everything, particularly amp hours, and they cost less. Compare a high quality traditional battery such as Trojans with their AGM of the same series. The traditional battery is typically better in most categories and costs considerably less. My experience has been, if you take care of them, traditional batteries are a much better deal and last as long. That being said, if you want don't want to worry about taking care of them, mount them at a weird angle, ship them non-hazmat, or beat them around then AGM is the way to go. Otherwise, save your money and buy a good quality standard battery. I've owned boats for years and bought both types. Wish I'd never have spent the extra money for AGMs.

    Just my 2 cents.

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    Quote Originally Posted by Akgramps View Post
    Before you jump on the Optima bandwagon, think about what a battery is made of, mostly lead and acid with a plastic case, a group 27 battery with 6 round cells will weigh 10 to 15 pounds less than a rectangle battery, like a Trojan, Northstar or Odyssey..... less lead, less acid and cost less to make and has less capacity..... I know they look cool..... and I am not trying to incite of inflame as they may be good batteries, there is just less material in one and personally I think its all marketing......





    Which Blue Seas ACR do you have?
    Quote Originally Posted by patrickL View Post
    I was actually thinking along the same lines as Akgramps. Optima is a bit of hype. I had both Optima and Trojan AGM batts and the Trojans were by far better. They are hard to find local up here but well worth it if you want to go with AGMs.

    That all being said, why do you need a sealed AGM battery vs a traditional battery. Traditional lead acid batts typically have more of everything, particularly amp hours, and they cost less. Compare a high quality traditional battery such as Trojans with their AGM of the same series. The traditional battery is typically better in most categories and costs considerably less. My experience has been, if you take care of them, traditional batteries are a much better deal and last as long. That being said, if you want don't want to worry about taking care of them, mount them at a weird angle, ship them non-hazmat, or beat them around then AGM is the way to go. Otherwise, save your money and buy a good quality standard battery. I've owned boats for years and bought both types. Wish I'd never have spent the extra money for AGMs.

    Just my 2 cents.
    After 40 years in the telephone industry working with large and small power plants i have to agree! Buy standard lead acid and maintain them and you will be money ahead and have more cca for lots less money. If you want to mount them sideways go with AGM. I still have the original batteries in the boat!
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    I used to work in the battery business for 10 years, and always told customers the same thing...

    AGM are amazing batteries, but i only really recommended them for starting purposes. They have more power, are more reliable, have a life span longer than normal acid batteries.

    Regarding deep cycle use (as in your house battery on a boat), i would recommend a lead acid battery and just be sure to pull it out and maintain it in the off season. AGM deep cycles are stupid expensive and generally have the same amount of power. Their lifespan on average is less than double, while the price is more than double. When it comes to deep cycle use, your "minutes reserve" is what you can about, and AGM generally do not offer more. The BEST bang for your buck are two golf cart 6V batteries, assuming you have the room for them in your compartment. they are 2-3 times the power of a pair of 12V ones.

    There are definitely benefits of AGM batteries, but in my opinion, the price outweighs them when regarding deep cycle batteries.

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    Kodiak hunter, how many years of service are you getting out of your batteries now. Also at the end of the year do you do any battery maintenance such as topping off or equalizing

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    Quote Originally Posted by kodiak_hunter View Post
    Do you see any problem with different group sizes between the house and starting battery (i.e. would it be okay for a group 31 AGM for the house, and say a group 27 AGM for the starting? I need 800 CCA for starting.
    The alternator doesnt care if two different size batteries are connected to the system, the ACR will regulate the charge. the important thing is the motor runs long enough to charge the battery back up. There are many good points made here about the cost VS value of AGM. I have been considering using two 6V golf cart batteries for the house battery on the GP I am rebuilding. Its hard to argue with a $100.00 battery cost even if they only last 3 years..... its expensive to get the same amp hours out of a AGM battery. I dont have any personal experience with the GC batteries and price there can vary as well. Maybe some one on here will chime in as to how long the ones from Costco last as that seems to be the source for low cost.

    Ideally you should determine what your amp hour (AH) load will be between charging cycles (typically overnight), then you can determine what size battery you need to do the job. remember you realistically only use 30% of the AH capacity of a battery. two 6V GC batteries will be rated at ~220 amp hours, so actual AH available will be ~ 70 AH. Reason is the battery should typically be discharged to 50% and charged back up to 80%. This is the range where the battery will give you the most life and be reasonable to operate. It would be great to recharge a battery to 100% all the time. Its usually not practical as it will take a while to do this and most rec boats charging systems dont run long enough to accomplish this. This is a general statement as I am sure there are some that are making long trips and maybe have a well thought out electric system.

    To discharge beyond 50% is detrimental on the battery and battery life. And if operating in the 50-80 area its a good idea to bring it back up occasionally with a full charge
    “Nothing worth doing is easy”
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    I had three 8 D's on my boat in Whittier for 15 years and agree with the above comments on lead acid batteries. I used to get 5-6 years on a set at least and got them pretty cheap at Costco once they opened up here. Keeping them maintained and keeping them from too deep a discharge is key and for you guys living on the hook for a few days or week at a time like I used to do, a good primer is "Living on 12 Volts" by David Smead. High output alternators, smart 3-step regulators, battery monitors, inverters, isolators, etc. all come into play and David has a way of explaining easily how to set up your system so that it works well. I'm not sure what your options are with outboards for some of these goodies and you may be limited. My experience has been with inboards which accept high output alternators and the two belt pulleys necessary. You can really get carried away on this stuff and spend a ton of money on toys that charge, monitor and keep your house and start batteries in good shape - there's always a project on a boat and what's better to spend the money on to make life on the water more enjoyable?

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    QUOTE=kodiak_hunter;1472145]
    I like the idea of no maintenance, faster charging, and lower rates of discharge during storage for the AGM, but I have no actual experience with them. I currently have 2 lead acid batteries (1 house; 1 starting) that are charged with Blue Seas ACR, and am considering replacing the lead acid house battery with an AGM. Based on discussions with Blue Seas, there should not be any problem with charging. I have a Honda 225 outboard.[/QUOTE


    Of the three advantages you mention AGM batteries have, faster charging is the only one that is worth paying for. If the alternator cannot supply enough current to take advantage of the fast charging after supply all the loads on your boat your wasting money.

    When Blue Seas said there no problem charging, I think he meant using there ACR not that the Honda 225 is capable of supplying all the current you need. There always problems keeping a battery charge on outboards engines

    If you did a electrical audit it would answer a lot of questions. It could also find out what you need to do to increase battery life.


    QUOTE=kodiak_hunter;1472261]
    Do you see any problem with different group sizes between the house and starting battery (i.e. would it be okay for a group 31 AGM for the house, and say a group 27 AGM for the starting? I need 800 CCA for starting.[/QUOTE]

    I just don't see the advantage of mixing the two battery when they are bought AGM. Deep Cycle AGM batteries have very low internal resistance making them a good starting battery.

    If you want to use a starting and deep cycle batteries I suggest you stay with the same brand just to be sure there no difference that your not aware of that could cause problems.

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    14 years ago I installed 2 group 34 Optima AGM's for starting the boat's VP KAD44 diesel, and a house bank of 2 g31 East Penn Deka AGM's. The starting bank lasted through 7 summers, and the house bank through 11 summers. Optima AGM's lasted 10 years in my Cummins truck, which sits outside all winter. Optimas have less AH per pound or per dollar than you would want for house use, but they are fine at pumping out cranking amps for starting.

    Deka's are quality USA batts, and can be bought from an industrial battery supplier for less than you might think - maybe 1/3 less than from a marine supplier. They're sold under several different brand names. If you find a g31 AGM with model number 8A31DTM, it's probably an East Penn Deka.

    These days I have 2 Sears Platinum g34 AGM's for starting, and 2 g31 Platinum AGM's for house.

    With AGM's I like having no maintenance, no spilling/corrosion, and very low self-discharge compared to flooded lead acid batts when sitting over the winter.

    Gels you don't want - they require special lower charging voltages.
    Richard Cook
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    I have minimal power needs on my Tolman. I run a West Marine AGM as that was what I could find when I was ready to launch for a starting battery. a very expensive option but after 2 years of building I wanted to go. I have used that battery for 7 years. I took it out the first 3 years. Forgot about it years 4 and 5, and year 6 I remembered about February and brought it in. When I put the charger on it each year before going out it was fully charged. I used a couple of standard batteries for the house battery and they would last a couple or 3 years before giving trouble. If I forgot about them they would be discharged in the spring. I picked up a AGM from Cabala's last year. I am going with AGM as my batteries are in the cabin and I was concerned with outgassing. Granted my cabin is far from airtight but it seemed a good idea. I use an ACR for charging my house battery. Alternator goes to the starting battery, when it is fully charged the ACR sends the charge to the house battery. I do not have the 2 batteries connected. I have a jump wire that I can use to physically tie the 2 batteries together in case I need a jump for the starting battery. I do not have to remember to turn my switches on or off as I have a switch for each battery. If I can't start the boat it means I forgot to switch it on. If I can't turn on my chart plotter it means I forgot the switch to the house battery. Kind of idiot proof which is what I need. I do carry a jump box most trips but I am not sure it will actually start my outboard but it will raise the motor. I have no science backing my method bit it works for me now. Ken

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    i remember when tubless tires came out and so many said its so much better to have a tube and why pay more for tubeless.

    same with batteries. soon enough there will be no regular lead acid batteries only agm or the next generation of batteries.
    saving a hundred bucks when going out on the ocean on a battery isnt my idea of saving.

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