Deep Cycle AGM Batteries

[WASP18]

I'm about to purchase two AGM batteries from Cabelas (private label - manufact unknown). There are four group sizes: 22, 24, 27 and 30. I'm leaning toward the size 24. The customer product reviews are mostly five star. A common complaint is the shortness of the terminal posts. Has anyone had to purchase some kind of extender for the posts? If so, where did you find them? Is this battery suitable for our Mac needs? Which one would "you" buy?

http://www.cabelas.com/marine-deep-cycl ... s.shtml#sf

[Wind Chime]

We have three of the "Group 24" size.
Two of them on a West Marine "Combiner", and the third on its own wired for A/C charging only (back-up).
No 3-way switch.
A double circut A/C step charger.
We also have an "emergency start" portable cell.

[06HARLEYULTRA]

Look on the forms for "musings with maine sail", or do a google search. His postings will save you time, headache, and $$$$.
Most batteries are only manufactured by a few companies, and then labeled with that brand. Sam's has good/better pricing than most, for the exact same battery. I would bet Cabela's has labeled a standard battery and then jacked up the price.

Just my 2 cents......

[RobertB]

Concerning short terminals - not sure why this could be an issue -

If terminals seem short, probably have too many wires attached. I have solved this by using a bus bar with 5/16 inch terminals for the grounds and a terminal fuse block on the battery terminals (the cables to the battery then hook to the fuse holder). Therefor, only one item per battery terminal.

[Divecoz]

Checking your link versus Sams Website.. Cabelas is about for now $16 cheaper and a little more powerful

[Matt19020]

I have those batteries in my boat...So far so good!
Here are some previous post:
http://www.macgregorsailors.com/forum/v ... t=+battery
http://www.macgregorsailors.com/forum/v ... t=+battery
http://www.macgregorsailors.com/forum/v ... ry+battery

[seahouse]

Hey WASP18!

The short answer is that AGM batteries will cost more than lead-acid batteries both in the long and short term. All current mass-market battery technologies cost more in both the long and short term than lead acid batteries. Lead-acid batteries have not yet been knocked off the podium and continue to provide the best bang for the buck on a lifetime basis.

So why buy an AGM battery?

In exchange for the extra money you get low maintenance (you never have to, nor can you, add water), no acid spilling when you tip or break them, no off-gassing and they will withstand lower temperatures (freezing) without damage. AGM’s can charge and discharge at higher amperage rates than lead-acid, and their internal discharge rate (such as during seasonal storage) is lower.

If these features are important to you, then pay extra for an AGM. If not, then a lead acid battery is a better choice.

If you're using deep-cycle batteries, I would suggest that you upsize them somewhat if you are going to use them as starting batteries, although modern outboards do not require the starting current that older outboards did, so this is not as necessary as it once was.

Regards- Brian.

[Retcoastie]

I second Brian. The main reason I have AGMs is some one else bought them. If I were buying I would get lead-acid. I see the greatest need for AGM batteries is for a boat that stays on a mooring ball or a slip for long periods of time.

Ken

[WASP18]

Thanks everyone!

[yukonbob]

I've run agm (specifically optima's) in all my vehicles and now my boat, and I love them. I tend to discharge them rather deep and they always bounce back. No adding distilled water, no worrying if there's gonna be holes in my clothes or back berth cushions when I take them out, no explosive gas in the bilge (rather unlikely either way). I specifically like the optima's as they can be mounted completely upside down with no problems. Take them out in the winter and just throw them back in the summer.

[Hamin' X]

Both types are lead-acid batteries. AGM stands for: Absorbed Glass Mat, where the acid solution is soaked into a fiberglass mat. Standard batteries are called: Flooded Wet Cell. Some of the advantages of AGM have been covered, but there are a few more. The AGM will still be putting out full voltage, even when under water, such as when the boat is swamped. Wet cells will dilute and stop functioning. AGM cells will still function to full capacity, even when the boat has capsized, where the flooded cell will drain corrosive acid throughout the interior of your boat and fail. Also, due to decreased internal resistance, a "deep cycle" AGM battery may be used as a starting battery, whereas with a wet cell, you have to compromise with a starting/deep cycle "marine" battery. The latter will not tolerate as many deep cycle discharge/charge cycles. For my type of use, the AGM type will last twice as many seasons as the wet cells, thus saving money.

AGM batteries are the only type that I now use on remote mountaintop communication sites, due to their ability to survive many complete discharge/charge cycles, mounting/handling options and the ability to ship the via UPS as non-hazardous. For non communications uses, they are very rugged and shock resistant. YMMV.

~Rich

[Catigale]

Pricing comparison May 2012

At West Marine a group 24 AGM sells today at 215 USD - I can get a Group 24 deep cycle battery for about 90 USD, so the capital cost advantage is about 2x ish for the flooded cell type. Lifetime of the battery will obviously depend heavily on usage patterns etc, so each boater has to make this call individually - there is no 'right answer' on the cost issue.
Ive replaced my flooded cell Group 24 once since 2002 - and that was more because I let them sit discharged one winter.

You do not need a starter battery with the outboards on Macs - especially with an EFI engine, where crank time is minimal.

[yukonbob]

Wow I picked mine up for $114 ea t costco

[RobertB]

One other issue to consider is that AGM batteries are much more sensitive to overcharging than flooded cell batteries. Recommned you have a quality charger - especially if you plan to leave hooked up for long periods such as I do when the boat is in the driveway (installed charger maintains batteries and acts as house power). This is a sensitive issue since West Marine has now given me two repacement batteries (AGM group 24) .

[bartmac]

There's another good reason to use AGM batteries.....there's a flood of second hand ones available usually used in very sensitive well maintained facilities....kept on factory recommended float chargers and seldom used.Fire fighting, emergency lighting/power,computer UPS setups in high rise buildings.These setups have mandatory maintenance and testing requirements which in Australia lead to replacement of batteries quite often after only 2-3 years...easier to replace than test and the companies which service these setups can assure customers that every thing is A1....mind you the service companies make good money out off replacement.I have purchased about 10 of these high quality batteries and do charge and discharge tests to batch them as I like the bank to have similar age and condition batteries if connected.So far our 26X has had 4 x 100Ha (since replaced with 2 x 186ha Geltech batteries again used... in an aircraft power back up situation) fitted and our camper 6 x 100Ha...more than enough and at reasonable cost....BUT all fitted with very specific staged chargers (both mains and solar) because as earlier mentioned you can cook these types of batteries overnight...once the electrolite is not in contact with the plates ...all over red rover...stuffed....anchors....sinkers...... ie dead