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Lead Acid vs AGM battert change

cmaumus

Junior Member
I'm the 3d or 4th owner of an '82 E-25+ that I can only guess has the original electrical system (or most of it) in it. I currently use two Group 24 Dual Purpose lead-acid batteries to start the Yanmar 1GM diesel and to run the cabin and running lights. (I always start with battery 1 and only use battery 2 as the house battery-- until I have to switch to "Both" to get the engine going which is where I am again today.) I've gotten 3 years out of my most recent pair. However I've been thinking about making the move from the flooded batteries to the newer AGM type. But I've read in various magazines that altho in many cases the recharging system for the lead batteries works well with the AGM batteries, in some cases it does not. The gal at West today told me the newer rechargers even have separate setting for lead, mat and gel. Has anyone had any experience with swapping over using the OEM charging equipment? Should I just keep going with the lead-acid batteries and play it safe? Thanks for any input.
 

rwthomas1

Sustaining Partner
You really are not giving us enough information to help you. Are you on a dock or a mooring? How are the batteries charged?

A stock alternator will not keep up the batteries charged completely unless you motor very very frequently and for long periods of time.

If you have a shore power battery charger and it is not a modern unit that is selectable for the different battery chemistries then likely you are already not charging the batteries correctly.

If you are on a dock and do not regularly use the boat in such a way that depletes the batteries to 50% or so and you need to recharge away from the dock, then a high output alternator/regulator is probably not worth your money. Spend it on a high quality shore charger instead. If you plug the boat in after a weekend and the charger has the week to top off the batteries before the next use, that is ideal.

Battery chemistry is more about application than anything else. If you need a battery that accepts a high charge rate, can be mounted in any position, without venting, then an AGM or even a Gel is preferred. If you don't mind periodically checking water levels, are mindful of not abusing the batteries with very deep discharges and can live with a little longer recharging times lead acid is very hard to beat for the cost.

I just replaced 3 group 31 lead acids that make up my house bank. The batteries were on the boat when I purchased it and were marked "2000" That is 10 years of use and I cannot complain about that. They were very well cared for, pretty good charging system and not abused. I went with lead acid again for this reason.

RT
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
A related consideration is the fact that lead acid/wetcell batteries discharge hydrogen gas while charging and should be vented. On some of our boats, the house batteries are enclosed in a battery compartment located under the quarterberth. Not only is there no opportunity to vent the batteries in this location, but if the quarterberth is used for sleeping while plugged into shorepower at the dock, the hydrogen gas would not be good for the person in that berth. I suspect that most boats have enough openings for adequate ventilation as long as no one is sleeping in the quarterberth. Others may not agree.... Any thoughts on this are welcome.

Frank
 

rwthomas1

Sustaining Partner
That is an interesting observation Frank. I have wondered about the venting issue as well. Most "good old boats" like the Ericsons we know and love do not have any battery ventilation whatsoever, at least not that I have seen. My boat was originally equipped with 2 group 31's. Now it has 4 in the basically the same location. If is not vented any more now than it was when it was built. There is no practical way to relocate the batteries and the only option would be to add some vents to the cabinetry. Easy, but is that enough?

I expect the ABYC has a standard now for venting battery boxes in modern boats. I would also question how many times has battery venting been an issue in older boats? Is this something to really be concerned about? AFAIK, hydrogen is lighter than air. I assume that it simply escapes through the cracks in the battery box cover? Yes this in under the quarterberth but the cabinetry is less than airtight regardless.

I do not as a rule have the batteries charging if someone is sleeping in the quarterberth and this seems like a good idea.

I would love to hear some input on this topic.

RT
 

Tom Metzger

Sustaining Partner
Huh?

I am reluctant to get into discussions like this, but I want everybody to know that hydrogen is mixed with oxygen for breathing while deep diving to avoid the bends.

I will also add that charging with a 3 step charger releases minimal amounts of hydrogen. That's why you do not have to fill batteries frequently.

Has anyone considered that maybe we should quit breathing air because it contains nitrogen that has been shown to cause the bends, asphyxiation, and other problems? :rolleyes:

Sorry, but I have become sensitive to people trying to save me from non-dangers.

On topic, AGMs cost twice as much as flooded cell batteries. If treated correctly flooded cells will last several years.

As Loren would say, YMMV.
 

Emerald

Moderator
On topic, AGMs cost twice as much as flooded cell batteries. If treated correctly flooded cells will last several years.

As Loren would say, YMMV.

I just got a solid 5+ years out of my pair of group 27 flooded batteries. Always kept them on float with a 3 stage charger while in the water. I know my electrical use is simple compared to many, but I feel like this is a pretty good track record by just keeping a good quality battery healthy and never tanking them and leaving them discharged for any extended period. They were by Dekar, and I am currently using Interstate, which are going fine in year two of service.
 

Randy Rutledge

Sustaining Member
Do any of you have a 1968 to 1982 corvette? The battery is in the passenger compartment behind the driver’s seat, earlier cars had batteries with vent caps with tubes that went out of the passenger compartment but replacement batteries were not equipped with this venting tube on the caps and the mid 1970’s up had no vent tubes from the factory . That is a much tighter compartment and higher rate of charge than the maintenance charge most of our batteries are getting.

This is as Tom says, battery ventilation is not a health risk and little chance of a flash fire under heavy charge and an open flame.

Save me from myself but not the fear mongers fantasies
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
I'm not big on fearmongering or unnecessary regulations either (have cursed both on occasion :) but the survey done on my boat prior to my purchase by an American surveyor in California did comment negatively on the lack of venting of our house batteries in that location--even though I have gel cell batteries which apparently don't vent like the wet cell one do.

It may be much ado about nothing, and there may be much more important stuff to worry about on most boats, but I mentioned it above simply as a consideration, not being sure myself how significant it is or isn't.

Frank
 

Randy Rutledge

Sustaining Member
Battery gasses have been proved to cause cancer in rats in California, as has air, diet drinks and PIZZA.

Sorry the devil made me do it!!!
 

Rocinante33

Contributing Partner
White lab rats cause cancer. As a laboratory professional, I can vouch for the veracity of this comment.;)
 

Tom Metzger

Sustaining Partner
...by an American surveyor in California did comment negatively on the lack of venting of our house batteries in that location--even though I have gel cell batteries which apparently don't vent like the wet cell one do.
Frank - You should know better than to deal with the "Great Satan".
 

Maine Sail

Member III
I'd stick with standard wet cell batteries. If you want to do a better job at battery maintenance, and install a system that can take advantage of the AGM's benefits, then you can consider them but three years service life points to bad battery maintenance habits. In my experience I have not yet known anyone to get any longer service life out of AGM batts than wets despite the makers claims. They would likely suffer the same three year fate as wets if treated the same yet you would pay as much as three times as much for them.

You should easily get five years, even from the least expensive wet cell deep cycle batts, if you are not deeply discharging them below 50% state of charge, and are not letting them sit discharged for days or weeks on end and you use a good shore side charger. My friend Kai is on his 6th season on Sam's Club deep cycle batteries and they still tested at 92% of new CA spec. He uses a standard alternator with no fancy charging system but he does have a battery monitor and never discharges the bank below about 55% state of charge.

I have also seen multiple instances where a bank of AGM's toasted existing alternators due to the high rates of charge they can accept by running the alt at or near max output for far to long and literally cooking it. In one case the customer bought the identical alternator and it too fried in about three weeks. That same fried alt was re-built and converted to external regulation, with temp sensing, and is still going 4 years later. A good system deigned for AGM batts would have both battery and alternator temperature sensing to prevent this from happening. Personally, I would never install a large house bank of AGM's without temp sensing which requires external regulation.

Replacing a bank of wets with AGM's, especially a house bank, is not always as easy as a few connections. I vote to stick with wets..
 

cmaumus

Junior Member
I am dockside with shore power. But I really don't know what sort of a recharging system I have. I assume I have a standard alternator with my Yanmar. I use the boat weekly motoring about 10 mins each way in and out of the harbor. Since I mainly day sail, I put very little strain on the house battery. And most of the time the engine kicks over with minimal stress on the starting battery.

I have been using 2 dual purpose batteries which I understand to be a compromise battery. Would there be any advantage to using a starter battery and an deep cycle battery together or is that a no-no? :confused:
 

Emerald

Moderator
This is one of those topics that can illicit very strong opinions. So, with that said, I think your combination batteries are just fine. It's all I've been using for years now, and they have done well for me and my little Yanmar.

Regarding your charger, you have homework before we can answer your question. Next you're at the boat, take a look and jot down the make and model. Just for a seat of the pants assessment, if you have multiple LEDs on the charger, it is probably multi-stage. Typically, I've seen 3 LEDs, marking bulk charge, absorption and float. Any chance you can remember what it looks like? Once you've verified you have a decent charger, the next step is to make sure you keep the batteries topped with distilled water. A little simple maintenance should give you long life with the use you describe.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Good advice as usual David. I would add a tiny bit of trivia -- in searching for a new bottle of distilled water, I find that I have to read the label carefully at the store. "Distilled" water is often on the bottom shelf, and some kind of filtered or purified (?) water is more prominently displayed. Same gallon plastic jug, and they all look about the same as you walk up the aisle.
For my batteries, I tend to believe that actual distilled water is best.

LB
 

Tom Metzger

Sustaining Partner
Would there be any advantage to using a starter battery and an deep cycle battery together or is that a no-no? :confused:

No real advantage one way or the other for your setup.

That said, you should get more than three years out of your batteries. Oops, let's back off a moment. You are in Louisiana where it gets very warm. I think like a northerner. Do other people down there get consistently longer life from their batteries? Heat can reduce life.

One thing you should check is that your battery connections are tight. I am a fan of replacing wing nuts with hex nuts. You can get 5/16"-18 thread stainless hex nuts at any hardware or marine store. really tighten down on them. BTW, there should be a flat washer under the nut.

Do you have a shore power charger? Not a problem if you don't, but you should run your engine for at least 10 minutes at cruising rpm when going in & out of your marina with the battery switch on both. Idling the engine or running at low speed doesn't count in the time. Don't forget to switch off of both when you shut down the engine.

If you have a shore power charger it may be overcharging your batteries. You might want to turn it off when you are away from the boat. Twenty minutes a day on the engine should be enough for the way you describe your usage. Overcharging would be evidenced by low water levels in the batteries.

Do you check to see if you have enough water in the batteries? You should check every month or two and add distilled water if the level in any cell is below the sight ring in the fill holes. The cells are separated so you have to add water to each cell that needs it. If your batteries are "maintenance free" the caps will not come off and the batteries die when you run out of water.

Learning to use a voltmeter with your batteries is the easiest way to monitor their health.
 

Touchrain

Member III
It's my understanding that the primary issues on venting are that: the battery gases are corrosive, particularly for sensitive electronics such as inverters and a volatility risk, very slight or medium, depending on who you talk to. Never have heard of a direct health risk.

That said, I have two substantial banks of gels from 2000, and they seem to be going quite fine because they have not been cycled hard. Deep discharges are the killers, and I try limit discharge to about 1/3, not even the 50 percent that many folks recommend. Nigel Calder has some good discussions of the issues and relative longevity in some of his writings.

When it is time to replace, I will have to make a decision. Hopefully battery science/technology will have continued to advance.
 
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