AGM vs Flooded House batteries

[KP44]

Originally Posted by Dehler 25

I currently have six flooded Crown 6v golf cart batts in series parallel with primary recharge from 720 watts of newly replaced solar. My down side is that I have them as a single house bank and not split in two. It would have required the banks not to be balanced and while some may point out that on "both" it should not matter I would be on "both" at all times anyway. I wanted to go to eight batts but space was exhausted. I would like to have the two banks so that if a battery failed I could isolate the bad bank but wonder if a rewire is worth it. I noticed after going from 210 tired watts of solar to the 720 I am charging a lot hotter at 14.5 which causes me to watch the flood level a lot closer as bubble bubble boil to trouble! Opinions?

It is better for your batteries to have a single house bank because the batteries are never drawn down as far. Keep an engine starting battery(s) in a separate bank but use all your house batteries as a single house bank.

The worst thing for batteries is drawing them down to half or less. A large bank can give you much more power before your batteries are getting low.

[Firehoser75]

Sorry I am a little late to the party.
Most boaters "murder" their batteries due to PSOC (not fully regularly recharging) operation of their batteries. If you fall into that category (and you probably do) then the best dollar value is to buy inexpensive (flooded lead acid) golf cart batteries, probably from Sam's Club, Costco, etc. and just replace them more often.
As stated by others, there are some advantages to other types like AGM but you will pay quite a bit more money for them, and will probably "murder" them just as quickly or maybe even more so. Firefly batteries (much more initial cost) will tolerate PSOC operation, but you may also incur additional costs to ensure your charging setup will optimize for Fireflies (so probably not really in the discussion).
The only way to regularly recharge your batteries to 100% charge regularly is by plugging into shore power regularly (so basically travelling dock to dock), running under power for long runs most days for 6 plus hours (with a good alternator with external regulation and temp sensors), having a good solar array optimized for the size of your house bank and electrical use (if you anchor out alot), or running a generator around 6-7 hours most days to fully recharge. Unless you have solar, the majority of boaters don't achieve this (full recharge) and are therefore not obtaining the best life possible from their batteries due to the PSOC damage they are doing.
Another point, is depth of discharge. With a larger bank, you will not regularly (daily) discharge your bank as low as you would with a smaller (amp hour) bank. Shallower discharges can equate to more cycles before the battery "packs it in" hence longer life.

So, dollar for dollar you will be better off with flooded lead acid. However, they are not without their downsides. You do have to keep them topped off with distilled water, equalize them occasionally, and ensure they have some ventilation. They also have to be mounted "upright" and secured in battery boxes. Unless you install a good solar system, also be prepared to replace them (especially if you buy the cheaper brands) every few years.
Lots to think about.

[MAJICDAN]

Have two house banks. One with 9 group 31 sams deep cycle batteries. The other with ten same golf cart batteries. We live aboard and travel the Caribbean six months of the year. We check the water levels and specific gravity for bad cells every month. I always buy lead acid so I can check the batteries without unwiring them to check them each month. The golf cart batteries were new the spring of 2017 and are all in all seem to work as good as new. The original group 31 batteries were new at the same time. None of the originals are left. Several of the batteries have been replaced twice. I always carry four spare group 31 batteries with me when I leave the states for the Caribbean. If you can, always buy the golf cart batteries.

[Dave9111]

If you can fit flooded golf cart batteries in place, that is the best bang for your buck. If you can fit group 27's, I have found Interstate Group 27 Deep cycles to be very good. Much better than any group 27's I've used before. Self discharge over the entire winter was almost zero. I didn't know flooded batteries could be this good. Costco sells Interstate at a good price.

[DHHerndon]

I have been using four size 31 AGMs (3 for my house bank and 1 for my starter) on my Fisher motorsailer for the last 20 years. I got 11 years from my first set and I am now in my 9th year for my current set - they are still going great. The long life and maintenance-free qualities are well worth it for me. Dave Herndon

[tkeithlu]

Earlier in this conversation it was determined that I will go with flooded size 27s Duracell batteries from Sam's, that 6v golf cart batteriews are about 1" too tall for my under the sole battery bank, and that yes, I've got two sophisticated (more so than me, when it comes to batteries) charging systems. Those new batteries have been in place for a week now.

Along the way I've learned a bunch about batteries from your very informative posts. Thank you.

Late note: There are now 6v golf cart batteries in size 27 cases. Next time I'll try them.

[sailjumanji]

Originally Posted by tkeithlu

Earlier in this conversation it was determined that I will go with flooded size 27s Duracell batteries from Sam's, that 6v golf cart batteriews are about 1" too tall for my under the sole battery bank, and that yes, I've got two sophisticated (more so than me, when it comes to batteries) charging systems. Those new batteries have been in place for a week now.

Along the way I've learned a bunch about batteries from your very informative posts. Thank you.

Late note: There are now 6v golf cart batteries in size 27 cases. Next time I'll try them.

I think that Duracell battery is actually made by East Penn. EP is the company that made my Deka AGMs that lasted 12 years.

[Mauruuru]

Let me just say that hard lessons are not the best teaching method. Here's why I say yes AGM is worth every penny of the difference:
I had a bow thruster installed on the boat and it was supposed to have its own AGM battery along with a combiner for charging (since it was up in the bow under the bed)......I thought I checked it when the work was done but obviously must not have been careful enough because one day the bow thruster just stopped working and all I could get was a click of the contactor trying to turn on......investigation revealed the battery to be dead. Hmmmm I thought it must be the combiner gone bad-its been three years since it was installed. Nope, combiner fine. When I uncovered the battery I found to my displeasure that it was a flooded-not AGM-battery! While I paid for an AGM, I got a cheapo flooded cell battery and of course for three years I never checked the water levels.....bone dry.
And that wasn't the worst of it. The acid that boiled off with the water had collected on things near and far......including the fins on the air conditioner and yep you guessed it ate the aluminum until the freon leaked (two years later)......
so yes Sealed, maintenance free, AGM battery is worth every penny of the difference!

[Normanskier]

I had the duramax flooded which required maintenance. If you remember to do it. They lasted 3 years. I replaced them with the AGM. For the little difference in cost go for the glass Matt batteries. There is an assortment of discussions concerning the potential problem of overcharging them and shortening their life. I have had no problems with that. And most of the discourse thinks there really is no problem.
Interestingly I was all set to get the same 27 duramax from a different supplier. By sheer happenstance I came across Sams Club pricing. Some fifty dollars less, per battery.
If you go for the 31, check your space as mine just fit. The 32s are dimensionally bigger.