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Old 02-06-2010, 17:28   #1
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AGM or Gel Batteries ?

Well, I've been told its time to replace the house battery bank. But what should I replace them with: Gel or AGM 4D's? Opinions please?
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Old 03-06-2010, 13:12   #2
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Does your charging system support Gel or AGM or is lead-acid limited? That would be a consideration for me. Pricing/life would be the other. The last time I looked the cost of lead-acid was considerably less than either Gel or AGM and the life cycle about the same.

While I'd like to eliminate the task of checking levels and like the fact that sealed batteries don't out-gas and work under water, I'm still sailing with deep cycle 6V lead-acid batteries.
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Old 03-06-2010, 13:18   #3
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Charging system

My system accepts all three types and money is no object for house batts So what type should I get for ocean travel
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Old 03-06-2010, 13:33   #4
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I previously had a set of gel 4Ds that were 180 Ah apiece. The AGM 4Ds I just installed are rated at 210 Ah apiece. AGMs are more rugged, charge more efficiently, and will probably last longer than gels. What's not to like about that?
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Old 03-06-2010, 13:44   #5
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Gels can be ruined by a one time charge at the wrong rate/voltage. For me, gels are just too fragile for use on a boat. AGM's are about three times the cost of lead acid batteries and, FWIH, don't live up to their service life claims. Sure you want AGM??
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Old 03-06-2010, 14:03   #6
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AGMs and Gels ARE lead-acid batteries! They're just not flooded, i.e., don't have a liquid electrolyte.

Which type to use depends on your electrical setup, on planned usage and, to some extent, on your wallet. You said that money is no object and that you plan to do "ocean sailing".

AGMs surely have a lot to recommend them but, unfortunately, longevity and reliability aren't among their best traits. Some have had excellent experience with them, have treated them right, and they've lasted a relatively long time. Others have had sudden and catastrophic failures with them, including one poor chap who was several hundred miles from the Azores. For ocean cruising, this would be a cautionary note for me. Their ability to take a huge charging current is great, but you must have sufficient onboard charging capability to realize the benefits. Fitting AGMs to boats with standard alternator setups often leads to burning up the alternator.

Gels are an excellent choice for boats which spend most of their time in a marina plugged in. I have some gelled golf carts in my basement which spent the first 10 years on such a sailboat -- only doing weekend trips and the occasional longer trip -- and have spent the past four years in testing. They still test at over 90% capacity...very, very good, indeed. However, as was mentioned, gels can be killed by overcharging as well as undercharging. AGMs are a bit more tolerant for sure.

Most robust is the standard flooded battery. Typical longevity is about 3-5 years, but some who treat their batteries well have gotten more. At the top end of the flooded battery chain are the very excellent batteries made by Rolls/Surette. These heavy duty deep cycle batteries typically last more than 10 years, and sometimes 15 years or so. They can take more abuse than AGMs or gels, and are a proven design. However, they must be maintained by keeping clean and by ensuring that the water level stays above the plates (HydroCaps or WaterMiser Caps help a lot in this respect).

So....given your parameters of "cost no consideration" and "ocean sailing", I'd choose Rolls/Surette every time. At least for the present, until something provably better comes along.

In this respect, I and others had high hopes for Firefly Technologies (a Caterpillar spinoff). After a long gestation period, they finally came to limited production of group 31 batteries for the military and trucking industries, but recently filed for bankruptcy. Damn!

Other technologies are on the way, but I think the watchword should be "any time now" :-)

Bill
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Old 03-06-2010, 16:02   #7
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To me, lead acid batteries require regular checking of the liquid level in order to prolong their life. Technically you are correct.

AGM is preferred when a high burst of amps may be required. In most cases recharge can be accomplished by using a good quality standard battery charger or engine alternator. The life expectancy; measured as cycle life or years remains excellent in most AGM batteries if the batteries are not discharged more than 60% between recharge.

Gel cell batteries are typically a bit more costly and do not offer the same power capacity as do the same physical size AGM battery. The Gel Cell excels in slow discharge rates and slightly higher ambient operating temperatures. One big issue with Gel Batteries that must be addressing is the CHARGE PROFILE. Gel Cell Batteries must be recharged correctly or the battery will suffer premature failure.

To answer the posters question, I'd go with the AGMs. If I had less deep pockets I'd go with a bunch of 6V "liquid electrolyte" batteries. That way I could replace a 6V and not lose the whole 12VDC, I don't have to rent a crane or break my back pulling a 4D out, and if I had the height I could go with the tall 6V batteries and get some real capacity.

On my current boat the emergency batteries are 8D AGMs but the engine and genstart batteries are the old lead acid variety. The UPSs are gels as well.
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Old 03-06-2010, 16:45   #8
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I recently installed an LiFePO4 battery and so far it is great.

Usable capacity is double the lead batteries.
Charge is more efficient.
Weight is half of lead batteries.

Two downsides are cost and a mechanism to prevent discharge. (If your charging system can do more than 16v, you would also want to prevent overcharge).

There is a comprehensive thread not to far down...
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Old 04-06-2010, 07:31   #9
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Originally Posted by xxuxx View Post
My system accepts all three types and money is no object for house batts So what type should I get for ocean travel
If cost is not the main concern the very best batteries you can buy are LiFePO4 due to double the energy density of lead acid/AGM/gel batteries.
There are many other benefits also.
You can read more about LiFePO4 batteries here-
http://www.cn20090810.p-client.net/w...Technology.pdf
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Old 04-06-2010, 07:43   #10
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If cost is not the main concern the very best batteries you can buy are LiFePO4 due to double the energy density of lead acid/AGM/gel batteries.
Even though these batteries don't have a big history at sea they seem to have some interesting features. If you do decide to use them, please keep us informed as to how they are working out for you and the cost benefits they are providing.
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Old 04-06-2010, 08:33   #11
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My system accepts all three types and money is no object for house batts So what type should I get for ocean travel
You're talking my language... When I installed the batteries "7 years ago" I wanted a worry free system, no gassing off, No filling batteries, and No Leakage..
A system that would run the boat, Off the grid, and not have to worry about what the wife was using while I had the inverter running..
Opperating under the wind charger and solar pannels and to take whatever I put them trru..
I bought Lifeline 4ds, service free AGMs...
We have 10 of them on the boat, and expect them to last for ANOTHER 10 to 12 YEARS..
Our 4ds have an algarythm (sp) of being fully charged at 12.8 and 50% charge at 12.2.. ours have never been below 12.6..
The reason behind the number of batteries is that we now have over 2000 amp hours of storage.. about half of that being usefull as you never discharge below 50%.. Being ours are working in the high upper end of the charge cycle, the life expected is much higher.. they have NEVER been through a full cycle..
Two weeks ago, I pulled each battery and let it settle for 48 hours and then checked it.. All of them were above 12.8..
AGMs are a higher price, but charged properly, Just might have an unlimmited lifespan.........
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Old 04-06-2010, 14:46   #12
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You're talking my language... When I installed the batteries "7 years ago" I wanted a worry free system, no gassing off, No filling batteries, and No Leakage..
A system that would run the boat, Off the grid, and not have to worry about what the wife was using while I had the inverter running..
Opperating under the wind charger and solar pannels and to take whatever I put them trru..
I bought Lifeline 4ds, service free AGMs...
We have 10 of them on the boat, and expect them to last for ANOTHER 10 to 12 YEARS..
Our 4ds have an algarythm (sp) of being fully charged at 12.8 and 50% charge at 12.2.. ours have never been below 12.6..
The reason behind the number of batteries is that we now have over 2000 amp hours of storage.. about half of that being usefull as you never discharge below 50%.. Being ours are working in the high upper end of the charge cycle, the life expected is much higher.. they have NEVER been through a full cycle..
Two weeks ago, I pulled each battery and let it settle for 48 hours and then checked it.. All of them were above 12.8..
AGMs are a higher price, but charged properly, Just might have an unlimmited lifespan.........
You have my respect sir.

Mike
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Old 04-06-2010, 15:11   #13
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if will be nice when we have a LOT of field experience with the LiFePO4 batteries. So far I have very few field reports. Interesting technology should it work out to be long- term viable.
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Old 07-06-2010, 18:44   #14
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Appreciate everyones suggestions......

Thanks to everyone. MY ultimate goal is to have 1000 amp hr house bank with wind and solar inputs,
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Old 07-06-2010, 19:22   #15
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Seriously consider the benefits of using a LiFePO4 house bank. It will have a design life of 20 years and a full factory warranty of up to 5 years (depending on the manufacturer).
For your planned 1000Ah AGM bank you would have the same effective capacity by running 500-600Ah LiFePO4 bank and at about one third of the weight.
Also look at the charging efficiency since you will be charging from solar and wind.
Lead acid / AGM batteries are typically 70% - 80% charge efficient at best while LiFePO4 are 95% - 99% efficient which means that almost every ounce of generated solar and wind energy is stored as useable power in the batteries with next to no wastage due to the much more efficient chemical conversion process while charging.

If you want to be able to monitor all wind and solar power energy generated and stored in your batteries you might want to look into fitting a "solar/wind energy bank". All the information is at hand from the user interface touch screen.
Attached Files
File Type: pdf LiFeTech Energy Solar &Wind Energy Bank 051210.pdf (282.5 KB, 258 views)
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