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Old 25-09-2011, 10:36   #1
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AGM vs Sealed Lead Acid Battery

Im about to replace the service batteries, 2x 180ah . The current ones are AGM's the charger can be set for any, so is it worth using agms again or getting cheaper normal service batteries?
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Old 25-09-2011, 10:41   #2
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Re: Agm vs Sealed lead acid

There are lots of arguments about which is better--gel, AGM, or lead acid, but there is no argument that SEALED lead acid is about the worst thing you can get. They are susceptible to sulphation from undercharging and there is no way to replace the water if you overcharge them.
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Old 25-09-2011, 11:58   #3
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Re: Agm vs Sealed lead acid

The bottom line is the AGMs can be recharged faster than other lead-acid type batteries.
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Old 25-09-2011, 12:26   #4
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Re: Agm vs Sealed lead acid

If you're cruising and on the hook most of the time AGM's are the worst batteries as they will only last a season or two if they are not fully charged often. Most of the time on the hook it's difficult to fully charge batteries so you end up using the band between 50% and 85%. If you live in a marina or can fully charge them often they're fine. I went back to flooded batteries.
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Old 25-09-2011, 13:11   #5
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Re: Agm vs Sealed lead acid

steven, you're asking two different questions.

Conventional service batteries are UNSEALED wet lead batteries.

AGMs are one type of SEALED battery, often called a "valve regulated sealed battery"

A so-called "maintenance free" wet lead battery is often a plain wet lead battery that has been sealed, offering the worst of all worlds.

So what exactly are you looking for? Conventional wet lead batteries? They'll always be cheaper, often 30-50% cheaper.
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Old 25-09-2011, 16:29   #6
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Re: Agm vs Sealed lead acid

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Originally Posted by LakeSuperior View Post
The bottom line is the AGMs can be recharged faster than other lead-acid type batteries.
This is true, but I think moot in most cases on a boat. I'd be shocked if a boat has enough charge current capability to exceed the limits of non-AGM batteries. More often than not, boats have less charge current than is ideal.
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Old 25-09-2011, 17:30   #7
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Re: AGM vs Sealed Lead Acid Battery

AGMs, really dont offer any benefits to boaters, unless you can use their high charge acceptance. Otherwise they are easily damaged. Buy good quality open wet cells.

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Old 25-09-2011, 18:03   #8
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Re: AGM vs Sealed Lead Acid Battery

Here is the info on the three battery types. Flooded will have about 200 charge/discharge cycles, Gel will have about 1000, AGM will have about 300. In the charge acceptance rate - flooded will be 25% of Ah, gel will be 25% of Ah and agm will be about 40% of Ah. A flooded battery will self discharge at a rate of 6% per month if not on a charger, gel and agm will be about 3% per month. Flooded vents hydrogen gas, gel and agm do not. Price -A flooded dual purpose battery will run about 120, a gel will run about 280 and a agm will run about 190. For longevity a gel cell is best, a agm is a good compromise for saftey. Agm's have a 18 month free replacement - 5 year pro-rated, gel - 18 month free, 5 year pro-rated, flooded - 12 month free, 3 years pro-rated. My agm's have lasted no lest than 6 years on my live-aboard sailboat for the last 11 years.
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Old 25-09-2011, 18:13   #9
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Re: AGM vs Sealed Lead Acid Battery

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Originally Posted by clsailor View Post
Here is the info on the three battery types. Flooded will have about 200 charge/discharge cycles, Gel will have about 1000, AGM will have about 300. In the charge acceptance rate - flooded will be 25% of Ah, gel will be 25% of Ah and agm will be about 40% of Ah. A flooded battery will self discharge at a rate of 6% per month if not on a charger, gel and agm will be about 3% per month. Flooded vents hydrogen gas, gel and agm do not. Price -A flooded dual purpose battery will run about 120, a gel will run about 280 and a agm will run about 190. For longevity a gel cell is best, a agm is a good compromise for saftey. Agm's have a 18 month free replacement - 5 year pro-rated, gel - 18 month free, 5 year pro-rated, flooded - 12 month free, 3 years pro-rated. My agm's have lasted no lest than 6 years on my live-aboard sailboat for the last 11 years.
Curious clsailor, are you on a mooring, hook or connected to shore power?
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Old 25-09-2011, 18:50   #10
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Re: AGM vs Sealed Lead Acid Battery

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Originally Posted by clsailor View Post
Here is the info on the three battery types. Flooded will have about 200 charge/discharge cycles, Gel will have about 1000, AGM will have about 300. In the charge acceptance rate - flooded will be 25% of Ah, gel will be 25% of Ah and agm will be about 40% of Ah. A flooded battery will self discharge at a rate of 6% per month if not on a charger, gel and agm will be about 3% per month. Flooded vents hydrogen gas, gel and agm do not. Price -A flooded dual purpose battery will run about 120, a gel will run about 280 and a agm will run about 190. For longevity a gel cell is best, a agm is a good compromise for saftey. Agm's have a 18 month free replacement - 5 year pro-rated, gel - 18 month free, 5 year pro-rated, flooded - 12 month free, 3 years pro-rated. My agm's have lasted no lest than 6 years on my live-aboard sailboat for the last 11 years.
True but misleading

AGMs and in particular GELS offer really nothing extra to the average boaters. Firstly you cant use their ( AGMS) supposed high charge acceptance rate , if you look at the data, you have to be careful not to cause outgassing.

GELs are very sensitive to overcharging and as a result are alomost always cronically uncharged,the self discharge rates are irelevent for most boat uses. They have no place on a boat IMHO.

Good quality flooded cells offer a good compromise. But if you want to save money just buy cheap open cell batteries, They will give you 4-6 years of life if looked after, then dump them.

see Sterling Power Products: What is the best battery to use for an auxiliary charging system? for a good opinion

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Old 25-09-2011, 19:19   #11
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Re: AGM vs Sealed Lead Acid Battery

I can share my experience. While in the Florida Keys last winter, the batteries began dying. They were great until I was on hook for several weeks at a time. I pulled all six Lifeline AGM batteries and discovered they were 10 years old! When the dealer asked what brand I wanted I quickly said Lifeline AGM...don't want to do this again for another 10 years.

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Old 25-09-2011, 19:41   #12
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Re: AGM vs Sealed Lead Acid Battery

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I can share my experience. While in the Florida Keys last winter, the batteries began dying. They were great until I was on hook for several weeks at a time. I pulled all six Lifeline AGM batteries and discovered they were 10 years old! When the dealer asked what brand I wanted I quickly said Lifeline AGM...don't want to do this again for another 10 years.

Bill

All that indicates is that until before you "went on the hook", teh shore system was disguising the fact that the AGMS were probably dead years ago, Its not any indication that they lasted 10 years. In fact I would say from my experience AGMs last less.

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Old 25-09-2011, 21:25   #13
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Re: AGM vs Sealed Lead Acid Battery

This is another story of it all depends. If you are in a marina most of the time, a relatively cheap unsophistcated system will be fine for the few times you go cruising. Just make sure you have a smart charger toprevent over charging, the biggest killer of all batteries.

In my case the batteries are under a seat in the main saloon. I use AGM's, 660 amps with the same footprint as Golfcart batteries. The big advantage on the hook is you can throw a huge charge at them. I have given them well over 100 amps for an extended time. What they don't like is overvoltage and are probably the the most sensitive battery sytem for this. A good regulator and battery monitor are a must. I use a Xantrex smatr regulator and a Link 2000.

Someone mentioned topping up the charge. I do this with a solar system that outputs over 30 amps at midday. I go from bulk to acceptance usually around noon and to float before 2pm.
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Old 26-09-2011, 00:26   #14
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Re: AGM vs Sealed Lead Acid Battery

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Originally Posted by goboatingnow View Post

GELs are very sensitive to overcharging and as a result are alomost always cronically uncharged,the self discharge rates are irelevent for most boat uses. They have no place on a boat IMHO.
I have had a very good life from Gels. 16 years on my previous boat and 10-13 on this one (with some difficult conditions from a PO for much of their life).
This long life is their main advantage and can make them cost effective. There is also the benefit and added safety of very little gassing and no acid to spill. Low self discharge is a help if you leave the boat for long periods and no maintenance means more time to enjoy the cruising life.
With good regulators available for solar, wind and AC charges there is no excuse for poor charging practice these days.
If you do go for gel batteries get good ones, mine are Sonnenschein.
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Old 26-09-2011, 00:52   #15
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Re: AGM vs Sealed Lead Acid Battery

If you are water sailing">blue water sailing and live on the hook, gels are one of the best options. They are very tolerant of undercharging and won't drip acid on you when you take a knockdown. Mine have lasted on average about 7 years of constant daily cycling.
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