Dealing With AGM Battery Sensitivity

[Evergreen]

Hello:

I just learned that we need new batteries on our CD36. Currently I believe we have the original stock setup as far the engine and batteries are concerned. We have a Perkins 4-108 with a single unit alternator/regulator and two group 24 lead acid batteries. We also have a Tru-Charge 20 battery charger with three stage regulator.

We have been doing some reading regarding our options and are particularly interested in AGM batteries. However, we are very concerned about the sensitivity of AGM batteries to overcharging!

Question: Would a stock combination alternator/regulator be prone to overcharging AGM batteries? Would I have to purchase a separate more sophisticated regulator to insure that I don't have problems when charging with the engine?

Thanks for you input.

Philip & Sharon "Evergreen"

[Russell]

Yes, you definately want a modern regulator for AGM batteries. The issue wont be overcharging, but actually undercharging leading to sulfating.

[Steve Laume]

I did the whole alternator, multistage regulator thing last year. The AGMs were in my boat for a while before I bought her. I don't think the old set up did them justice. If you are satisfied with the output of your current regulator a good auto electric shop can set you up to use an external regulator. I found a brand new AR-3 or 4 on E-bay at a reasonable price. I think that puts me one step behind the state of the art on regulators. I really like the concept of AGM batteries, Steve.

[Anthony P. Jeske]

Hi:
I would strongly suggest you look into gel batteries instead of AGM. Gel batteries are much more resistant to overcharging and similar abuse. Their recharge cycle is very similar to a wet cell cycle, so you don't have to replace your on board wet cell based charger, etc.
I used to work for Offshore Systems, a San Diego based distributor and installer of marine generators, heating systems, refrigeration, navigation systems, etc. We always recommended gel batteries to our customers.
Good Luck,
Tony Jeske
CD-28 #365
NO REGRETS
San Diego

[Jeff Barnes]

Philip and Sharon

I replaced the batteries on my CD036 a few years ago with 4 6-volt AGMs. With a little more than 400AH total capacity, this has been adequate, even with the Super Cold Maching frig. (current hungry little devil). I upgraded to a 75A alternator (a little larger wouldn't be a bad idea), and a three stage regulator wit adjustable voltages for accept and float stages. This is important with AGMs. (Also measure voltages when adjusting at the battery terminals). Most modern chargers (yours included) should have a switch to slect battery type. I have placed these batteries under the stbd salon seat (the small L-shap portion). These things have been great, trouble free for 4 years and have required no service/removal during the winter in Cape Cod, MA. (although the bpoat is stored inside all winter, but no heat).

Regards,

Jeff

[Russell]

]I have placed these batteries under the stbd salon seat (the small L-shap portion).

So you were able to fit four 6v there? I thought long and hard about that as a battery location, but wasnt sure I could fit four 6v (which is what I was using at the time). Installing them there certainly you should keep to gels or agms of course. Did you have to cut the opening up more to install them? You must have, especially to fit the last battery.

I have 5 group 31 AGMs for my house bank (plus 2 group 27s for start and 1 group 31 for windlass in other spots), I ended up putting them the only place I could fit them all and keep them in one place, the starboard cockpit locker. That locker is now dedicated to batteries, hated to give up the storage, but few places exist on the CD36 for large battery banks.

[Jeff Barnes]

Russell,

I had to slightly enlarge the opening and make a new cover, but that was all. There is just enough room down there (after making the opening bigger) for 4 6-volt AGMs (mien are Lifelines). It sounds as though you have greater AH requirements than average, and thus all the juice in the stbd locker (I have my CNG tanks in there). I have a windlass as well (Sprint 1000) and still run that of my AGMs, as well as the frig which uses about 50 AH per day (and thats with lots of additional insulation). I just use one group 27 for starting the old 4-108.

All teh best,

Jeff

[Mark Yashinsky]

What are your power requirements on the boat and how will you replenish them (dock or engine). Sounds like the dock might be covered, but what is the output of your alternator? AGM's are nice because the will recharge quickly, IF you can supply the amps. They do not like high charging voltage, but they are more tolerant than Gels. The high charging current could overheat your alternator. At least start with a high quality 3 stage external regulator that has specific programs for your battery type and see if it has provisions for temperature sensors (alternator!! and maybe the batteries).
Since you will have at least two batteries, how are you going to keep both charged? There are charge combiners that will combine the batteries for charging, but not discharging. You dont have to start doing the odd/even days for which battery to use. You could then get into the battery monitors. And with a CD36, what about a separate starting battery? Need to keep that charged, which there are devices to do just that.

[Dean Abramson]

Philip and Sharon, if it's any consolation, I find the subject of batteries to be totally cosmic, and I really wish that the experts would all get together and get their stories straight.

My boat had had gels when we bought it, but they were shot, so I went down to West Marine to buy two new gels. I cannot remember exactly what the story was, but I had an issue with one of the new gel batteries right away. When I brought it back to West, the manager says, "Dean, we get more returns of gel batteries than anything else we sell," and he took back both gels and proceeded to sell me two AGMs, at slightly LESS than the cost of the gels. Go figure. The thing he said was best about AGMs is that they were not real fickle about how they wanted to be charged, particularly in comparison to gels.

So we have done one season with the AGMs so far and they seemed fantastic. But that's not much of a story, is it?

Yesterday, in preparation for putting them back into the boat, I put one of them on my so-called "smart charger." (Wal-Mart, 29 bucks. Black & Decker.) The battery had last been charged in the fall before I put it away. The LED display on the charger said it was charging at the 2V rate for about one minute, then it said it was fully charged, then after a minute, I got an error code which means "Internal Open Cell/Sulfated Condition."

After battling momentary depression (these are not cheap batteries), I took my multimeter and found the battery was at about 12.5 volts. Then I rigged up some wire and made a light bulb burn really bright.

So today, I schlepped it down to the boat, where we worked all afternoon. It powered our stereo for several hours, and it powered our water pressure pump for several cycles of filling/draining the hot water heater and flushing with fresh water. I am fairly attuned to the sound of that pump, and my take is that the battery is as healthy as a horse.

I am not sure what the moral of this story is, but my tentative decision is to buy a new charger...

Good Luck!!!

Dean

[Oswego John]

Dean,

My first thought is that if you suspect any trouble this season with one of the batteries, don't wait too long.

If it's under warrantee/guarantee for X amount of months, by the end of the second season, it may have expired. Go on record early about suspected trouble.

Rigging up a bright bulb is not much of a heavy load test. Powering a stereo isn't a heavy load, either. The pump is somewhat of a load, but not a true stress test.

What you might do is take the battery(ies) to an independent automotive electric shop (not WM) and let them test it(them) under a carbon pile load. They have the equipment to do a proper test. If anything is going on, or about to, it will bring the trouble to the forefront. They will know what to look for.

Here's wishing you a good season coming.
O J.

[Mark Yashinsky]

Never took my AGMs home nor charged them during the winter and they have had no problem bring the beast to life in the spring.
Another advantage w/ AGM's, they self discharge at a much slower rate. Just make sure they are charged when putting the boat to sleep in the fall.

[Dean Abramson]

Thanks, OJ. I am definitely mindful of the warranty; it is 18 months. And I agree that was hardly a scientific test.

Russell, or anyone: what would be the symptoms of a sulfated condition?

[Oswego John]

Hi Mark,

Awaking the iron wind. That's a good term, never heard it before. I've heard of the iron gennie, (I guess genoa) and a few others, but not iron wind. Have to try to remember that saying.

I haven't a clue as to what the parameters are for testing a given size amp/hour battery. From what I understand, there is not only a high amperage but also a time dwell period involved.

I would guess that the starter would be close to a sufficient amp load, but it is used for a brief period when starting. I would suppose that an anchor winch would be more suitable for testing the battery under load for a sustained period.

But like I said, I really don't know. I've always taken batteries to an auto electric shop. They have the specs and all the answers. If there is a dead or failing cell, they'll pick up on it . And the test is while you wait. It's very short.

Larry DeMers, where are you when we need you? Larry is our in-house engineer, maven, guru, expert when it comes to batteries.

Best regards,
O J

[Evergreen]

Hello:

I wish to thank everyone for their replies.

Sounds like AGMs are a good way to go as long as the charging is regulated by a sophisticated regulator.

Apparently I have the shoreside charging covered. However, I gather from what everyone says I need to replace my stock alternator/regulator with a alternator and an independent advanced regulator that can be set for AGM charging. I'm seeing lots of $ signs but I want it to be done right so that it is reliable. I'll look into it.

Thank again, Philip & Sharon "Evergreen"

[Boyd]

Hi All:

I had a set of those over priced AGM's. After about 2 years they just quit. NO WARNING what so ever, despite the fact that I kept them on a Xantrex 3 stage charger the whole time. They would hold small amperage loads just fine but not start the engine. The resting voltage was in the 12.5 volt range. Took a while for me to figure it out. For a while I though my starter was bogus. There is no way to tell if they are failing short of a load test, another disadvantage.

The event ruined my New Years cruise. Every tried finding batteries on New Years Day?

Now I have 4 Trojan T-105's (6 volt golf cart batteries) These things are tough, cheap, and very easy to find. Four years on this batch and no sign of them quitting. The nice thing is you can use an automotive alternator. No need for a fancy 3 stage charge controller on the alternator. They are so cheap that if I even get suspicious they are starting to fail I will just get new ones. I can check them with a standard hydrometeor.

I suspect your Walmart charger is not designed for AGM's and uses the wrong charging voltages which will toast them. It also probably doesn't know that AGM's have much less internal resistance than liquid electrolyte batteries so it is mistakenly reading a sulfated condition.

Boyd
s/v Tern
CD30 MkII
Fort Lauderdale, Fla.