Wet Cell or AGM

[sarbog]

After nearly 5 years, my stbd battery bank is going bad. I plan to replace all four batteries in the next month (of course this has to happen around Christmas!). I currently have wet cell batteries and they have given me no problems in five years, rare to even need water added, maybe twice that I can recall. I don't use them hard, i.e., very little extended anchoring out on just my batteries. Usually in marinas when we cruise. Occasional night out on the hook but more common is just out for the day.
I have always thought about going to AGMs but the fact is they are going to be at least twice as expensive. Thus, the AGMs would have to last at least twice as long just to break even cost wise. Is there some other advantage that I am missing. Otherwise just on cost I am inclined just to go with a top quality wet cell. Am I missing something?

 

[paulswagelock]

I get 5-7 years out or deka wet cells for $120 each. Never been able to justify spending 2x as I would not entertain 10-12 year old batteries in my boat.

 

[Jimmy Buoy]

I get 5-7 years out or deka wet cells for $120 each. Never been able to justify spending 2x as I would not entertain 10-12 year led batteries in my boat.

+1 to that!

 

[JV II]

Bubbling hydrogen gas out of a wet cell battery in an enclosed engine room increases oxidation of metals. +1 to AGM.

 

[juggernaut1]

AGM's main advantage is that they are deep cycle battery and can be run further into a discharge state than a wet cell. So you can run more stuff for longer before needing recharging. They also have a much higher charge acceptance rate than a wet cell meaning they will recharge faster. AGM's can also be recharged many more times than a wet cell and hence have a longer lifespan.

Given that you've had 5 years out your existing batteries then I would say that your use is suiting your current wet cell battery setup. If needed you could always add an extra wet cell battery for more capacity if space permits.

 

[trit21]

I have 5 Sears AGM, same ones I think that Scott has, and 4 of them are 7 yrs old, one of them 5 yrs old. My old SeaRay only had 4 batts so I had to buy 1 more for the Tiara. They are going stong knock on fiberglass. I also had a problem with my wet cell batts in the SeaRay boil over and the noxious fumes in the ER was enough for me to make the switch. Wet cell batts should not be used in a confined space for the reason JVII and my experience has proven. AGM's are truly maintenance free batts.

 

[Wylie_Tunes]

Sarbog,

There can be some advantages to AGM's, especially for a house bank. They tend to take deeper and more frequent cycles with better recovery as compared to wet cell. With good maintenance and a proper size house bank, wet cells can give many years of good service at a cost effective investment.

One thing to consider with making a swap from wet cell to AGM, is your current charger. You will need a charger that will service AGM's.

 

[dpmulvey]

Based on your usage and longevity stats, AGM would be a waste of money for you.

 

[northern]

I use 4 deep cycle group 27. All four are used as start batteries 2 per engine with one engine set used a house batteries for 12 volt items. I had the same set up on the 28 footer. Used wet cell and they seem to last. I replaced 2 this year that still started the engine but seemed to not provide as much house power. They were 2009 vintage. I have been staggering replacement by 2 years. The other set is 2011. I intend to replace them in 2017. Costco seems to have good prices on them. For 120 volt inverter I have 10 six volt golf cart batteries and the first set lasted from 2006 to 2014.

 

[SmilingMonkey]

I'm struggling with this exact same decision too. My batteries are 5 years old, and I need to replace at least one of them. I've found that group 31 AGM's can be bought for just under $200 each. Compared to $120-150 for group 27 "wet" batteries, I think it's worth the difference.

The one question I do have is, how do I know if my charger is ok for AGM batteries? I just bought the boat 2 weeks ago and didn't think to check what charger I have. The boat is a 2010 330DA.

 

[SmilingMonkey]

Any modern charger will charge AGM batteries fine. AGM batteries are classified as lead acid batteries. Gel Batteries are the ones that require a special charger setting.

By modern, I mean any charger built after, say, 1990's (generalization)....btw. I did end up replacing my functioning inteli-power PD2040 with the PD2150 for more capacity, and it does have an AGM setting. From what I understand, the AGM setting allows the batteries to receive just a little more top charge, possibly giving them a small percentage more reserve capacity than a regular charger. Basically that means they will have their full rated capacity when fully charged. However, a charger without an AGM setting will work fine with AGM batteries.

Thanks! Looks like I'll be doing AGM.

 

[Almightys]

Since most are on winter layup, I'd just be subscribing to pep boys and advanced auto parts email spam list to be aware when they offer the 30-50% off coupon codes and get things for dirt cheap just my $0.02