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AGM vs. Lead

Old 03-23-2007, 05:51 PM
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Default AGM vs. Lead

I have searched, but cannot find my answer.

I am going to be getting new batteries. I am going with Group 27's. What is the advantage of the AGM's over regular lead? I know they are maintenance free, and will last longer. I also know they are higer CCA and MCA, but not RC. I really don't mind having to add some distilled water every now and then. And I like the fact that the Lead batteries are cheaper and lighter. The only real difference I can see is the CCA's and the MCA's. But if my old Group 24's started my motors ok, the new 27's should be even better. Is there any real advantage to the higher CCA and MCA?
Thanks,
Jim
Old 03-23-2007, 06:13 PM
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Default Re: AGM vs. Lead

email me and I'll send you a FAQ on lead vs gel vs agm - then you decide...agm's may not be what you want to do...agreed....I like the fact that I never have to check them for warter, they do not discharge when I'm not on the boat and they always have more power than I'm gonna need.....if you are one who can check water and don't need reserve power, then flooded will work fine - and I'm not trying to be sarcastic...but offshore I like more power than I need...
glen@veradoclub.com
Old 03-23-2007, 06:24 PM
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Default Re: AGM vs. Lead

Email sent Glen thanks.
Old 03-23-2007, 09:20 PM
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Default RE: AGM vs. Lead

Where did you get the idea that an absorbent glass mat battery would last longer than a flooded cell lead-acid battery? There is a reason that most AGM batteries have short warranty periods--they don't last as long as a flooded cell lead-acid battery.
Old 03-23-2007, 09:43 PM
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Default Re: AGM vs. Lead

Glen E, thanks !! I am lookin to replace my Batts. and have researched the technology, I'm goin with the optima bluetop 34. In your expierence, would you agree?? I have the RM full system Nav. and constant V. is very important with this system. I've read you're responses and value you're advice as although i'm mechanically sound, i'm puter stupid. I appreciate any help you may have in this matter. Standin by, ch. 06.....
Old 03-24-2007, 08:39 PM
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Default Re: AGM vs. Lead

My AGM's have a 5 year warranty?
Old 03-25-2007, 12:29 PM
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Default Re: AGM vs. Lead

The Cabela's AGM battery that is so often touted on this forum has only a one-year warranty. In contrast, a high-quality lead-acid flooded cell battery often has a 7- to 10-year warranty. You have to wonder why a manufacturer would give their product a one-year warranty if it was supposed to last longer than a competitor's product which has a 10-year warranty.

AGM batteries have a lot of nice qualities, but it is completely misleading to make a general statement that an AGM battery will last longer than a lead-acid flooded cell battery.
Old 03-25-2007, 08:18 PM
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Default Re: AGM vs. Lead

I have never seen a Group 24, 27 or 31 lead acid battery with more than one year warranty. I'm not saying they're not out there, but I have never seen one in these categories with anywhere close to 7 to 10 year warranty. What manufacturer offers this?
Old 03-25-2007, 09:06 PM
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Default Re: AGM vs. Lead

I have never used an AGM battery, but change the lead cell batterys in my boats every 3 years. I maintain and keep the old lead batterys and use them in my warehouse for my forklifts. I have to be honest and say that I have lead cell batterys being used everyday in forklifts working with in excess of 1200-1500 lbs that are minimum 6-9 yrs old. granted they are not using radar etc, but never a problem, and i always have plenty of replacements.
Old 03-25-2007, 11:27 PM
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Default Re: AGM vs. Lead

ZX2050 - 3/25/2007 8:18 PM

I have never seen a Group 24, 27 or 31 lead acid battery with more than one year warranty. I'm not saying they're not out there, but I have never seen one in these categories with anywhere close to 7 to 10 year warranty. What manufacturer offers this?
Rolls and Surrette offer marine lead-acid flooded cell batteries with 7 to 10-year warranties.

http://www.rollsbattery.com/

http://www.surrette.com/
Old 03-26-2007, 06:25 AM
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Default Re: AGM vs. Lead

I just replaced two surrette batteries a week ago, after 7+ years.
Old 03-26-2007, 09:43 AM
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Default RE: AGM vs. Lead

Jim31 - 3/23/2007 5:51 PM

...And I like the fact that the Lead batteries are cheaper and lighter....
It is misleading to make a general statement that flooded cell lead-acid batteries are lighter than VRLA AGM batteries. In my experience, just the opposite is true. One of the appeals of an VRLA AGM battery is that it is generally smaller and lighter than a flooded cell lead-acid battery of similar ratings.

If a decision is to be made on the relative merits of a valve-regulated lead-acid absorbent glass mat battery and a flooded cell lead-acid battery, it is important that the basis of that decision be made on reasonably accurate observations and not on pure inventions of "facts."
Old 03-26-2007, 12:40 PM
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Default Re: AGM vs. Lead

jhebert - 3/25/2007 11:27 PM

ZX2050 - 3/25/2007 8:18 PM

I have never seen a Group 24, 27 or 31 lead acid battery with more than one year warranty. I'm not saying they're not out there, but I have never seen one in these categories with anywhere close to 7 to 10 year warranty. What manufacturer offers this?
Rolls and Surrette offer marine lead-acid flooded cell batteries with 7 to 10-year warranties.

http://www.rollsbattery.com/

http://www.surrette.com/
Prices look relatively high, and none of the 24's nor 27's meet the CCA specifications of my outboards...
Old 03-26-2007, 01:06 PM
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Default Re: AGM vs. Lead

With AGM's when you pull an amp hour out it takes an amp hour to charge... for the full life of the battery. With Lead as the battery ages it takes as march as 4 to 1 on the recharge ratio. You can kill an AGM and recharge it without any longterm damage... this is bad for a lead... Glens AGM FAQ sheet will talk about this...

AGM, or Absorbed Glass Mat Batteries
A newer type of sealed battery uses "Absorbed Glass Mats", or AGM between the plates. This is a very fine fiber Boron-Silicate glass mat. These type of batteries have all the advantages of gelled, but can take much more abuse. We sell the Concorde (and Lifeline, made by Concorde) AGM batteries. These are also called "starved electrolyte", as the mat is about 95% saturated rather than fully soaked. That also means that they will not leak acid even if broken.

AGM batteries have several advantages over both gelled and flooded, at about the same cost as gelled:
Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage.

Nearly all AGM batteries are "recombinant" - what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost.

The charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. The Concorde (and most AGM) batteries have no charge or discharge current limits.

AGM's have a very low self-discharge - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries. The Concorde batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged.

AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM's will cost 2 to 3 times as much as flooded batteries of the same capacity. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs these features.

Old 03-26-2007, 01:13 PM
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Default Re: AGM vs. Lead

Certainly depends on your usuage - if I had one of the new gen Merc/Yam/Zuke motors and was rack stored with no charger going to the batts, I would have no question an AGM. There is simply more of your batt left when you come back after a few weeks.

If I was on a lake and had a nice smaller boat on a lift and had 3 stage charger on a easliy accessable flooded batt, that would do fine.

But for offshore, I will have nothing but an AGM unitl the next great technology comes along. The can take much more vibration, don't discharge, come back faster when they are discharged and are maint free. That seals it right there. Not worried about the warranty, never read here of a cabella going bad yet. I have (4) 27 months old and they read like the day I bought them.
Old 03-26-2007, 06:00 PM
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Default Re: AGM vs. Lead

I am thinking I may just use the Interstate Group 27 SRM-27B's. I used the Group 24's in my other boats and they always lasted 3 years. I use distilled water, remove them in the winter, and charge them up before they go back into the boat. I have used them for going offshore, and never a problem. Also, I have added shore power this year, so this should help too. Oh, and my engines are 96' Mercury 150 carbed outboards.

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