Lead acid, agm, or gel batteries? - SailNet Community

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Old 03-25-2006
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Lead acid, agm, or gel batteries?

I'm living aboard full time and trying to decide if I want to go with 6-volt golf cart batterries or some type of gel battery. Are gel or agm worth the investment in the long run. Which type has the most number of charge cycles and amp hours???????
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Old 03-25-2006
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The main problem with 6V batteries, is if one cell goes bad, your whole system is kaput, because you no longer have 12V. How probable that is, I don't know, just know it's a concern. Many people swear by golf cart batteries.

Flooded batteries will give you more cycles, IF charged properly, than gel or agm. The gel and agm's though are maintaince free, and not affected by heeling and other cause of going off level.

The primary factor in battery life is proper charging and usage. Nigel Calder covers the subject in depth in his Boatowner's Mechanical and Electrical Manual. A worthwhile book to have.

FWIW I'm going to agm's on my boat, mainly due to placement.
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Old 03-25-2006
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I only have experience with flooded batteries. I use 4 golf cart batteries in a series-parallel configuration for house batteries. I have a good monitoring/charging system and am careful about the use. With that I get excellent lifetimes (in 14 yrs I have replaced batteries twice, I think the original batteries were about 12 yrs old when I got the boat).
My understanding is that you can get about the same lifetimes out of all the technologies. However you do have to be more careful about the discharge/ recharge cycling for wet cells. The newer technologies will take higher charge rates which translates to shorter charging times and less engine usage just to charge batteries (assuming you have the higher output alternators).
In my evaluation, the cheapness of the lead acid batteries wins, but then I am a real cheapskate.
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Old 03-25-2006
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AGM's apparently need to be regulated, are expensive and fussy. Do more research. Search www.ssca.org and www.boatered.com
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Old 03-26-2006
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I do not find the AGM's at all "fussy"..Indeed, they are likely to keep on going in circumstances where wet cell would boil off and curl up their little leaden toes.
A classical example of this for us was with a starter battery. The ignition switch failed in a special and unhappy way, in that it kept feeding power to the starter motor even after the you let go of the key. Not enough power to crank the motor, but enough to keep the solenoid engaged. So the starter motor was acting like some deranged unregulated generator that fed back into the battery....

By the time that all of this was discovered, the starter was toast...and the AGM battery was doing its best to look spherical. I kid you not , the casing had literally inflated, the only thing holding it "in" were the battery clamps...which made for an interesting shape once everything was removed for repair. The thing is, the battery STILL works. It looks decidedly odd, and we have taken it out of the boat, but it did not burst or leak and is currently doing sterling service as the battery of my 4wheel drive. It has been doing this for a little over four motnhs now with no problems at all.

So I will stick with the "finisky" AGM's and also tell people to watch out for "peculiar" and expensive little electrical glitches with their boat starter systems. I had a couple of small salt crystals, inside a $14ignition switch do a little over $900 of damage in 15 hours of motoring.

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Old 03-26-2006
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AGM's have one asspect missed. It takes less input to charge them. They do have tighter regulation requirements but them a good regualtor is required for any serious use no matter what you use. If you swap an AGM for a flood and don't change the regualtor then you are screwed. They don't swap out without changing the regulation settings. That is why they often get a bad rap that is undeserved.

I had 3 banks using 6 Trojan 6 Volt golf carts. They lasted a long time and do work well and are cheap. They also out gas and 4 were destryoying my AC heat exchanger and 2 were under the main electrical panel. The out gas eats aluminum and most other metals.

Flood batteries need venting and can't hanlde heeling well at all. You have to watch them for low water and one bad cell trashes the whole bank - hence my having had three banks. You can't group them more than 2 per bank and be safe. I now have one starting battery and one bank of 2 Lifeline AGM 4D's. Cost is higher but it's a simpler, easier to use, with more power and less weight that recharge faster with no maintence. The cost was about $100 more. I was able to reset all my regulation and charging systems for AGM from Flood. I'm starting my third season and so far they are fine.

A link 10 batter=y monitor is a great thing to have for any type of bank. It really helps you know how you really use your power and you are alrted to trouble when you discharge too low.
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