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Old 30-07-2015, 09:29   #16
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Re: Switching from lead to AGM, anything to keep in mind?

My AGMs are about 8 years old and still going strong. However, I'm a weekend sailor not a cruiser, so I can charge them all the way up easily and frequently.

AGMs accept charge much faster than flooded batteries which is one of their great strengths, but can overheat some alternators if they don't have good internal protection. If you're just cruising locally, I'd just go for it and if your alternator can't handle it, it'll tell you and you can replace it.

Your alternator and prop charger (which is super cool, by the way) don't sound like they have an external 3 stage regulator. That's probably not such a big deal. If you hold your batteries at 14.4 for too long it can damage the batteries. In practice, people often have enough draw on the batteries and motor for short enough times that won't happen.

Older alternators were set around 13.8V anyways. That's good for battery life but terrible for charging. Check both and see where they're set and then we can give you some advice, depending on how you actually use the boat. It will probably be easiest just to go use the system for a while and see how it's behaving.

Worst case scenario, you may be able to turn off the alternator's field with a switch if you're motoring or sailing for long periods with full batteries.
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Old 30-07-2015, 12:13   #17
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Re: Switching from lead to AGM, anything to keep in mind?

I am envious of your new AGMs. We had AGMs in our Whitby and they lasted over 10 years, half of that full time cruising and half part time. I always kept them charged up and tried to never let them get below 50%. But I would do the same thing with flooded batts too.

You do need a bigger alternator for your AGMs. The reason being that the AGMs will take a higher amperage for a longer time than the wet batts. You could set your alternator regulator to a lower charge regimen and use it to limit the absorption phase but you would be getting rid of one of the major benefits of AGMs - faster recharge - and you would have to run the engine longer.

Wet cell batteries (new and old) develop a resistance to fast charging as you charge so will self-regulate how much the alternator can put out as you charge them. They will take a high amp rate at first and this will rapidly trail off. But you still have to replace the same number of amp-hours whether it is at 75A or at 120A. A rule of thumb is your alternator should be rated in amps one quarter of the amp hour (20hr deep cycle rating) of the batteries.

Can you get by with the smaller alternator - yes - if you customize the charging scheme with your (high quality programmable) regulator but you will have to run the motor longer. And in any case you need a good regulator and a good high quality alternator.
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Old 30-07-2015, 15:42   #18
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Re: Switching from lead to AGM, anything to keep in mind?

I have three new AGMs at 200 AH each. Just went to Kauai and, at anchor, they kept "everything" running for at least 12 hours without needing to be recharged. How often do you recharge your batteries and at what voltage level?
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Old 30-07-2015, 16:32   #19
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Re: Switching from lead to AGM, anything to keep in mind?

Its really about the charger. An 18 yr old charger is probably nort a "smart" charger that adjusts between Bulk, absorb and float levels of charge ( varying voltage input). And there are numerous good articles from the AGM manufacturers that explain how to use their products. They don't fail in two years if charged properly. See Lifelines web site and maybe Deka's manual etc. they do need to be recharged to 100% but not weekly; monthly. Mine ar e going on 7 years but I am a coastal sailor ( back to the dock every 2-3 days). If you are at sea you need to figure out how you charge them to 100%.
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Old 30-07-2015, 18:43   #20
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Re: Switching from lead to AGM, anything to keep in mind?

Couple of points to add. The critical thing with all sealed batteries is NEVER charge at more than 14.4v. If the batteries start to gas then you lose water and being sealed it can't be replaced so the batteries are a write off. this also means they can't be 'fast charged'. Although you can charge them at a good rate (above the rate for same size deep cycle ones) once you get to 75% the charge rate tapers off and it takes a long time at low current to get the last 25% in. This is not a problem if you regularly plug into mains and run a charger. If you have enough solar and in your case the shaft genny that may do the same. The other issue with AGM's is that you can't check if they are fully charged, nowhere to put the hygrometer. These issues may account for why some people find the don't last (they only have a life expectancy of about 3/4 the live of a good deep cycle anyway)
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Old 30-07-2015, 20:09   #21
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Re: Switching from lead to AGM, anything to keep in mind?

Well, the first question is, why change? AGMS are way more expensive and your charging systems cannot take advantage of the higher charge acceptance rate. Unless you need the "sealed" feature (eg. you frequently heel more than 45 degrees or you have lead acid batteries foolishly mounted in cabin space, there is really no advantage to switching.

That said, it sounds like someone unscrupulously sold you AGMS. (Anyone in the know would have asked about your charging systems and advised that unless you planned to significantly increase them, AGMS would be a waste.)

All that said, you will need to change your charge profile from lead acid wet cell to AGM to get the most out of them that you can with your existing charge system.

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Old 31-07-2015, 04:50   #22
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Re: Switching from lead to AGM, anything to keep in mind?

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I went to AGMs a few years ago. They lasted two seasons. Unless you can fully charge them frequently, AGMs are not the way to go for a cruising boat. I'm back to flooded now. Lots of posts on this issue. Do a search.
My AGM batteries are getting on for 13 years old and going strong. They are always on solar. If an AGM is completely flattened it needs another charged battery (any L.A. of same V ) in parallel to start the charging process. There is an explanation online regarding Optima batteries ( which I have). It is suggested that people sometimes discard flattened AGM batteries not knowing this. It is due to the very low internal resistance of an AGM meaning they are open circuit when flat. I also have an Exide AGM in a car which flattened when I left the lights on. It refused to start charging on a charger until I parralled another charged battery to start the process
Google "charging completely flat Optima AGM batteries" for a more complete explanation than I can write. This applies to any make of AGM. Generally they are more robust than flooded cell L.A. They are of course non spill and could be installed upside down. Im sure someone will debate all that though.

On the other hand GEL batteries require a lower charging voltage than AGM or flooded cell. GEL batteries will eventually fail if the charge rate is not adjusted down.

Yes I am a fan boy of AGM for good resson due to good experience. Keeping any type of L.A. correctly charged is key to long battery life.
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Old 31-07-2015, 05:14   #23
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Re: Switching from lead to AGM, anything to keep in mind?

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If an AGM is completely flattened it needs another charged battery (any L.A. of same V ) in parallel to start the charging process. There is an explanation online regarding Optima batteries ( which I have). It is suggested that people sometimes discard flattened AGM batteries not knowing this. It is due to the very low internal resistance of an AGM meaning they are open circuit when flat. I also have an Exide AGM in a car which flattened when I left the lights on.
You can read all sorts of misguided advice on-line. This really has nothing to do with the internal resistance or the battery going open circuit and everything to do with lawyers & safety....

Newer chargers simply will not charge a very low voltage battery because they are programmed not to and are essentially assuming the battery is internally shorted and is simply too dangerous to charge.

This is a safety feature of the charger (lawyers/law suits etc.) and has nothing to do with the battery not accepting a charge. When you parallel in another battery it "accepts a charge", an old school dumb charger will do the same, if you have one, and either will raise the voltage to the lawyer safe chargers minimum voltage level. Raising the voltage with another battery or an old school "dumb" charger allows the smarter charger to continue charging the battery...
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Old 31-07-2015, 05:19   #24
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Re: Switching from lead to AGM, anything to keep in mind?

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You can read all sorts of misguided advice on-line. This really has nothing to do with the internal resistance or the battery going open circuit and everything to do with lawyers & safety....

Newer chargers simply will not charge a very low voltage battery because they are programmed not to and are essentially assuming the battery is internally shorted and is simply too dangerous to charge.

This is a safety feature of the charger (lawyers/law suits etc.) and has nothing to do with the battery not accepting a charge. When you parallel in another battery it "accepts a charge", an old school dumb charger will do the same, if you have one, and either will raise the voltage to the lawyer safe chargers minimum voltage level. Raising the voltage with another battery or an old school "dumb" charger allows the smarter charger to continue charging the battery...
Yes indeed you can read dumb advice. As I said "someone will debate all that"
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Old 31-07-2015, 05:28   #25
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Re: Switching from lead to AGM, anything to keep in mind?

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Yes indeed you can read dumb advice. As I said "someone will debate all that"
I just wanted to clarify that there is no magic dust thing going on with a dead AGM vs.say dead GEL or a dead flooded battery. Dead is dead regardless of which lead acid technology we are using...

Newer smart chargers won't charge them for safety reasons. It is actually good that you brought this up because so few are aware of how these chargers work or don't in certain situations and, as you said, otherwise still operable lead acid batteries may still work but the charger just won't charge them...

I currently have four dead as door nails Optima's sitting in my shop and I can put any one of them on my shop chargers and they will charge. Plug them into any of my consumer grade "smart chargers" and they won't. Not a battery specific thing but rather a charger specific issue..
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Old 31-07-2015, 09:57   #26
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Re: Switching from lead to AGM, anything to keep in mind?

We bought Deka, Model 904D, AGM Batteries in late October of 2007 to replace the original, 2 year old, Gel Cell batteries that came with our boat. Per the Deka instructions, I set our Xantrex inverter charger and our Balmar Max Charge MC-612 to the AGM Charging Profile. Today, 15,000 miles and 7-1/2 years later, these AGM's still show "like new" characteristics when checked on an electronic battery analyzer. The key to longevity is in the charging profile. Under NO circumstances (other than a life saving emergency) charge an AGM as if it were a Led/Acid or Gel Cell Battery.

For your convenience, I've attached a Deka Battery Comparison Guide, in PDF format. It's very informative and accurate.

Enjoy You New AGM's!

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File Type: pdf Battery Selection.pdf (32.8 KB, 46 views)
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Old 31-07-2015, 13:55   #27
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Re: Switching from lead to AGM, anything to keep in mind?

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The critical thing with all sealed batteries is NEVER charge at more than 14.4v.
Our Odyssey manual recommends between 14.1-14.7V for our PC-2150s (G31s) with a minimum 40-amp charger, and warns to not exceed 15.0V.

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Old 31-07-2015, 14:18   #28
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Re: Switching from lead to AGM, anything to keep in mind?

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Our Odyssey manual recommends between 14.1-14.7V for our PC-2150s (G31s) with a minimum 40-amp charger, and warns to not exceed 15.0V.

-Chris
Yep and Odyssey / Enersys prefers to see you in the higher end of that range or 14.7V on their TPPL AGM batteries. They also have the data to back up significantly better cycle life at these higher charging voltages. Higher voltages, if allowed by the manufacturer, and some don't allow them, helps keep the plates better cleaned of sulfation especially on sailboats where PSOC operation is the norm.. Keep in mind these voltage suggestions are always based on temp compensated charging. If you are not temp compensating, and are in a warm climate, a lower max absorption voltage will be necessary.

Deka suggests 14.6V for their AGM's, Firefly 14.4V, and Lifeline 14.4V.

Sulfation/undercharging is what is killing most AGM's, not drying them out. I have torn into boat loads of dead AGM batteries and have yet to find but a couple that were dried out and those were caused by controller-less solar regularly exceeding 15V nearly every day........
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Old 31-07-2015, 16:03   #29
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Re: Switching from lead to AGM, anything to keep in mind?

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Originally Posted by Maine Sail View Post
I just wanted to clarify that there is no magic dust thing going on with a dead AGM vs.say dead GEL or a dead flooded battery. Dead is dead regardless of which lead acid technology we are using...

Newer smart chargers won't charge them for safety reasons. It is actually good that you brought this up because so few are aware of how these chargers work or don't in certain situations and, as you said, otherwise still operable lead acid batteries may still work but the charger just won't charge them...

I currently have four dead as door nails Optima's sitting in my shop and I can put any one of them on my shop chargers and they will charge. Plug them into any of my consumer grade "smart chargers" and they won't. Not a battery specific thing but rather a charger specific issue..
Each of us can only write from our own experience. I have what I'm sure you would call a small dumb portable mains charger. It has Boost or Auto as settings. That is self explanatory as Auto simply floats the charge after initial charging.

That Dumb charger will charge a completely flat flooded LA but it won't charge a completely flat AGM whether Optima or Exide unless I parallel another LA. I don't think the Optima Battery manufactures would provide misguided advice.

I first became aware of Optima AGM s when I was making a video documenting the construction of 2 Volvo round the world race yachts. They were each fitted with a huge bank of as I remember between 12 and 20 Optima AGMs. That was at a world class boatbuilder that built amongst many others, Americas Cup monohull yachts. Talking to the electrician I realised the advantages so bought some for my boat. That was 13 years ago. I still have them going strong apart from a blue top starting battery I replaced 2 years ago. I do use a Next Step alternator charger and solar. Like I said use the correct charging procedures for whatever type of batteries you decide on.
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Old 31-07-2015, 17:17   #30
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Re: Switching from lead to AGM, anything to keep in mind?

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Originally Posted by Capn_G View Post
We bought Deka, Model 904D, AGM Batteries in late October of 2007 to replace the original, 2 year old, Gel Cell batteries that came with our boat. Per the Deka instructions, I set our Xantrex inverter charger and our Balmar Max Charge MC-612 to the AGM Charging Profile. Today, 15,000 miles and 7-1/2 years later, these AGM's still show "like new" characteristics when checked on an electronic battery analyzer. The key to longevity is in the charging profile. Under NO circumstances (other than a life saving emergency) charge an AGM as if it were a Led/Acid or Gel Cell Battery.

For your convenience, I've attached a Deka Battery Comparison Guide, in PDF format. It's very informative and accurate.

Enjoy You New AGM's!

Capn_G.
The 5 year old Exide AGM in one of my cars goes just fine without any adjustment to the normal car type regulator. Just charges at 13.8 v and the current according to the battery state. I'm sure there is an ideal charge profile for any battery but AGM s are pretty robust. That's one of their advantages.
Because that car has aftermarket security fitted, when I leave it at an airport for often a month any battery would be flattened by the security drain so I have a 20 w solar panel I stick on the dash and plug it to a fixed cable to a cheap charge controller near the battery.
Just keeps on going much like the Energiser Man.
I can see now that batteries are much like religion.
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