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skrenz
Captain

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USA
351 Posts

Initially Posted - 02/20/2012 : 17:18:05

Its that time again. Time to replace the house battery. Well, actually, on my boat, the only battery. I had been using a standard lead acid battery that came with the boat from a previous owner and it has died over the winter layup.
I want to replace it with an AGM battery but have several questions about AGM batteries verses lead acid ones:
1. My battery is charged mostly from the outboard alternator. Reading around it appears that AGM batteries are more sensitive to charging that lead acid batteries, do I need to somehow manage the charging current from the engine while running so as not to over charge the battery?
2. This is probably a subjective question but just how many amp hours are adequate for a Catalina 25 with standard lighting and essentially minimal demands?
3. Is one barand of AGM battery better than another? If so, what brand is a good one?
4. An of course, does anyone have any suggestions on where to get a good price on AGM batteries?

This should keep the forum hopping for a few days.

Thanks

Steve Krenz
`Elan
1978 SR/SK #482
Santa Fe, New Mexico

Edited by - on

Joe Diver
Master Marine Consultant

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USA
1218 Posts

Response Posted - 02/20/2012 : 17:44:14

While not a specific answer to your questions (sorry), last year I was faced with replacing the heart of my DC system....and all things considered, I just went down to Academy and bought 2 matched, group 27 marine deep cycles giving me 210 aH in the bank, plus a nice Guest charger. Couldn't be happier and can easily get through the weekend (Friday night to Sunday evening) out on the lake and on the hook.

I can't remember what I paid...like $125 each for the batteries and $99 for the charger, but it was a good deal (sale prices) and one of the best things I've done for the boat so far.....I would have spent 3x or 4x on AGM's I think, and after doing alot of research on them, just didn't see it for what I needed. Don't think they're all that and a bag of chips.

Edited by - on

islander
Master Marine Consultant

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USA
4018 Posts

Response Posted - 02/20/2012 : 17:46:49

Yep must be Feb. A lot depends on how you use the boat, Day sail, overnight etc. If you just daysail a single group 27 or like me a group 31 with an amp rating of around 85-110 will do. Personally I don't see the advantage to the AGM battery outside of no maintenance for the substantial extra cost but that is your choice. 1) The engine won't overcharge your battery. The rectifier controls this. 2)As many as you can get. 3)Debatable to no end. Is Ford better than GM? 4) You have to shop around.My recommendation is to get a wet DC battery and with the money you saved get a small 5-10 watt solar panel to finish charging the battery after you shut the engine off unless you plug into shore power and have an onboard charger.

Edited by - islander on 02/20/2012 18:18:00

Stu Jackson C34
Admiral

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844 Posts

Response Posted - 02/20/2012 : 17:56:15

I would strongly caution against AGM batteries. They are quite sensitive to proper and full recharging.

http://forums.sbo.sailboatowners.com/showthread.php?t=124973

Edited by - on

Lee Panza
Captain

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USA
465 Posts

Response Posted - 02/20/2012 : 19:52:08

Stu, could you check that link? I just tried it and it timed-out. Thanks.

Edited by - on

NautiC25
Admiral

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USA
957 Posts

Response Posted - 02/20/2012 : 20:03:20

I killed two WM batteries. I wanted batteries that would store a lot of power, but fit in the factory battery box. So I went with two Interstate group 29's with 210 min reserve. They're the biggest I found to fit, are still kicking, and provide all night lighting, radio, led tv, phone charging....... And they're charging on a small 9w solar panel.
They were priced very well at $118, and have a great warranty with local representation. Got them from the local Interstate dealer. Model # SRM-29.

Edited by - NautiC25 on 02/21/2012 06:14:06

blanik
Navigator

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Canada
210 Posts

Response Posted - 02/20/2012 : 20:58:31

there are a lot of variables about your electrical setup, do you have a VHF? a GPS? are they on all the time? or just lights? for a basic light setup AGM batteries are overkill, they are so expensive, for the same amount of money i would get two lead/acid batteries and put LEDs light everywhere...

LEDs with a small 20W solar panel with it's controller should be enough to never worry about electricity all summer on a mooring... (no access to shore power) (just check the water level once a month in the batteries)

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/21/2012 : 09:15:49

One flooded cell 27 is fine for day sailing and an occasional overnight, especially with LED's. I have two 27's and sometimes spend several nights out. Other battery designs have some advantages, but they aren't worth the price in my application.

Edited by - on

OLarryR
Master Marine Consultant

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USA
3440 Posts

Response Posted - 02/21/2012 : 10:16:56

Agree with most others that have posted. I have 2 flooded batteries onboard. The PO had these batteries for at least a year before I bought the boat and I have now had the boat since Fall'05. I have a 20 watt solar panel for handling the recharging which is only of light loads (fishfinder and occasional use of nav/stm lights, very infrequent for my mini-boombox when not using it's own batteries). The batteries are still okay but may need changeout this next season - (I keep trending voltage readings on my solar panel controller when my panel is not in the charging mode.)

Given that the batteries have been in operation for a minimum of 7 years, I see no reason to go with a different battery choice when these batteries eventually need to be changed out. The floode batteries are less expensive than other types and I do not mind checking/adding water infrequently.

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 02/21/2012 : 11:08:55

I like my one AGM as I've used doubles in the past and love having only one to deal with now. I feel like less is more. ( yep.. more money) I don't draw anything much right now, and only charge with a solar panel.

Can't give you any experience, as it is new.

Edited by - on

Stu Jackson C34
Admiral

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844 Posts

Response Posted - 02/22/2012 : 10:05:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Lee Panza
 Stu, could you check that link? I just tried it and it timed-out. Thanks.
<hr height="1" noshade id="quote"></blockquote id="quote">

Lee, I just tried it and it works. Might want to try again.

Edited by - on

skrenz
Captain

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USA
351 Posts

Response Posted - 02/23/2012 : 17:37:03

I read the article Stu, but there are several things to consider. The authors of this article use a lot of electricity and thus are discharging their system almost every day. The real piece of information I got out of this was the need to "Equalize" or Condition" your batteries quite often. The authors seem to be doing this at least once a month. Further reading from other sources indicate that you should do equalization with ALL types of batteries, including typical wet cell batteries. Ref: http://www.progressivedyn.com/battery_basics.html

Unfortunately, equalization is not in the cards for me. Although I have little demand (LED lights, VHF, Hummingbird depth and GPS), my dock hook up does not have AC power available. Therefore there is no way to run an equalization cycle any time the boat is tied up using a battery charger. The only thing I have available is a solar cell and the outboard alternator, neither of which could be set up to do an equalization cycle.

On the other hand, I'm probably not ever going to be discharging my battery as much as the author of the articles. So it looks like for me it will be a process of keeping the batteries topped up with the solar cell during the week, using the charge in the battery over the weekend and perhaps equalizing the battery once or so a season. I still like AGM batteries and the article does not really scare me off. But given my lack of available shore power and the additional cost of AGM cells I will probably go with a flooded cell.

Edited by - on

Stu Jackson C34
Admiral

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844 Posts

Response Posted - 02/23/2012 : 18:27:46

Steve, that was a good analysis. But don't get drawn into the "they have bigger boats" syndrome. The ISSUE is always the batteries themselves and the care and maintenance of same. After all, we're all buyin' the same $$ piece of lead and plastic, and want them to last as long as possible. Sometimes, the smaller the boat the tighter the budget.

Same goes for the type of battery. I think you made a wise choice. If you keep them charged, don't over-discharge them, and don't draw them down (even to 50%), then you should be fine. If you've done an energy budget and this is case the, that sound just fine.

I learned about energy budgets this way: two nights out of Monterey on the way to San Francisco in our C25, one 90ah gel cell battery. 'Bout dawn of the second morning the running lights dimmed! Good thing the sun was coming up!

Edited by - on

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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.