AGM batteries for Pearson 36

[DCHunt]

I am looking at AGM batteries for my Pearson 36 sailboat with an original Atomic 4 from 1972. I have historically used wet cell lead acid batteries but I want to get away from the battery maintenance that is involved.

I read the AGM battery test report in Practical Sailor in the May 2015 issue. All those batteries are pretty expensive. We currently have Group 27 wet cell batteries in the boat. I was wondering if anyone had any experience with Optima Batteries such as the 8027-127 D27M battery. They weren't reviewed by Practical Sailor. I think that would be a replacement for what I have now.

Any thoughts?

Dan

[joe_db]

I do not like AGMs at all. My experience is that they have a shorter life than gels and cost just as much.
They also require really top notch charge controllers and battery chargers. Gels need good equipment, but are somewhat easier to handle than AGMs. In warm weather just setting the alternator for 14.1 volts is 95% of the battle right there.

[ndutton]

I tried the Optima yellow top and was very disappointed. The problem with my attempt was I threw the AGMs in the boat and ran with them without addressing the very different charging protocol required for good performance.

Ref: http://www.optimabatteries.nl/upl_files/File/DC5,0L.pdf

I decided I was not willing to redo the charging system and deal with its (higher voltage) effect on systems while underway just for the benefit of not having to check water. I can check water.

[roadnsky]

...I was wondering if anyone had any experience with Optima Batteries such as the 8027-127 D27M battery. They weren't reviewed by Practical Sailor. I think that would be a replacement for what I have now.

Any thoughts?

Dan-
Going against the grain a bit here...

I have TWO 8027-127 D27M Blue Tops.
One is 7 years old ('09) and the other is 2 years old.
Zero issues with them. Both are running strong and dependable.

I'm using a PRO MARINER 12•30 for charge/maintenance and have shore power.

Be advised though... they're NOT cheap!

[joe_db]

I found Deka literature online showing their gels with considerably longer lifespans (or charge cycles) than their AGMs.
If you do want AGMs after all, Sam's Club has relabeled Deka GRP 31s at a good price.

[DCHunt]

Thanks, everyone, for the info. Neil, thanks for the PDF reference on charging.

Jerry, the pictures and additional info really helped. What are the clear plastic things that are on top of the batteries in your pix? Are those fuses for the charger wires?

I have a Newmar PT25 charger that I believe has options for AGM and GEL. I would think that should work OK, no?

What about when the engine is running? I have the original alternator charging the batteries. Do I have to do something different if I am using AGM batteries?

Dan

[roadnsky]

Jerry, the pictures and additional info really helped. What are the clear plastic things that are on top of the batteries in your pix? Are those fuses for the charger wires?

Dan-
Yes those are Blue Sea Systems fusing for the charger. (Here's a better pic)

I have a Newmar PT25 charger that I believe has options for AGM and GEL. I would think that should work OK, no?

The key for charging these is having a charger capable of multi-stage charge rates. (See the link Neil posted)
Having a final stage of float/equalizing is important.

What about when the engine is running? I have the original alternator charging the batteries. Do I have to do something different if I am using AGM batteries?

The SHORT answer is most likely... no.
Especially if you have good shore power charging.
Before getting into the complicated answer, do you know what voltage your Alt is outputting when you're running at a decent cruise RPM? (1500-1700)

Having said all of that, I should point out that choosing a "proper" battery/charging SYSTEM is not a one-size-fit's-all deal.
It has quite a few variables based on how you use your boat and what your daily power consumption needs are.

AGM's are not the right choice for many sailors for various reasons. Some of them already posted here both in this string and others.

I am certainly not an expert in Marine DC systems.
I would defer to others who know waaaay more than I do.
(Neil comes immediately to mind on this forum)

But, as I said in my earlier post, the Optimas have worked very well and trouble free for my vessel.

[ndutton]

I am certainly not an expert in Marine DC systems.
I would defer to others who know waaaay more than I do.
(Neil comes immediately to mind on this forum)

It's very nice of Jerry to think of me that way but my experience with batteries other than conventional wet cells is extremely limited. All I could do is read up on internet sources and repeat the information back to you. 'Tis far more honorable to admit my limitations and not pretend to be an expert.

However, from a practical point of view I'd assess what the AGM's or Gel's are going to cost, add the cost of a new charging system for both shore power and alternator and probably a much higher output alternator. Then decide if the perceived benefits are truly worth it. Consider too that underway you may be producing a higher voltage than your electrical components are used to so you'll have to deal with that as well.

Make an honest assessment of your expectations and what they're going to cost.

[DCHunt]

Thanks, guys. I'll reconsider the AGMs. I really like the fact that they are self contained though. Getting to the batteries during the summer to add water is a pain. We use the boat about 95% of the time for day sails and it is almost always plugged into shore power for the night.

I'm not sure the cost is all that different though between the Optima AGM and Wet Cells. Group 27 Wet Cell batteries on Amazon are running between $160 and $339. The Optima 8027-127 D27M is $193.39.

I'll check with Numar to see if there are any issues with the charger and and AGM batteries like the Optima.

Thanks again,

Dan

[Wrsteinesq]

Alternate AGM Source

Just wanted to note that if AGM's are the choice, you should look at sears diehard platinum marine batteries. The specs on Diehard group 31s are virtually identical to those of the Odyssey 2150s. It certainly appears that the group 31 diehards are in fact made by the same people as make the Odyssey 2150s. Of course, Sears batteries go on sale far more often and there's a lot more places to take them for any replacements.

[edwardc]

Go onto Sailboatowners.com and read Mainsail's extensive and knowledgable comments on batteries and charging, especially Gels vs AGMs.

I just had to replace batteries, and was considering switching from Gels to AGMs. After looking at the lifetime cycling numbers, I stuck with the Gels. I had two group-31 Seakawk's (relabeled Deka's), and I got 12 years (!) out of the last set by paying attention to proper charging protocols. I replaced them with a pair of G-31 Gel-Tech's (also relabeled Deka's). I paid about $250 ea for them (included sales tax but no shipping). Well worth it if I get another 12 years!

[ndutton]

A word of caution

While certain AGM analyses and presentations are certainly knowledgeable, I have seen first hand where the advice can add up to over three grand worth of new stuff that the adviser would be happy to sell you. Keep the calculator close at hand as you read up on the subject.

I'd relocate my batteries for ease of maintenance and treat myself to new sails before I'd drop that kind of dough on a battery/charging system. In fact, that was pretty much the analysis I made for my 39 year old sailboat.

Remember, it's only a freakin' battery.

[edwardc]

Neil,

I think we're all in agreement. Everyone I've talked to, including Mainsail, says that flooded batteies are far and away your best bang for the buck IF you are religiously diligent about keeping them topped off.

AGMs can make sense if you have a high current consumption application, and have a alternator capable of pounding the Amp-Hours back in at a high rate. Gels can't quite discharge and charge at the rate that AGM's can, but have a much higher number of lifetime charging cycles between 50% and 80% State-of-Charge (SOC) which is where sailboat house batteries usually operate. (if they're not being abused by discharging below 50%).

[ndutton]

Roger that Ed. I'm only trying to present the practical side of the issue. Speaking as a cheapskate, spending $3K on a battery system for a boat that only cost $5K in the first place (yep, I bought mine for $5K) is IMO foolishness.

Of course, buying a 30 foot sailboat for $5K is foolishness itself, isn't it?

[hanleyclifford]

Roger that Ed. I'm only trying to present the practical side of the issue. Speaking as a cheapskate, spending $3K on a battery system for a boat that only cost $5K in the first place (yep, I bought mine for $5K) is IMO foolishness.

Of course, buying a 30 foot sailboat for $5K is foolishness itself, isn't it?

You got off cheap: