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Old 13-06-2011, 16:30   #1
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Rolls versus AGM Batteries

1 of my house 4D wet cell batteries has lost the war and died. The house batteries are different ages and the dead one is definitley older but I don't know how old the good 1 is. So trying to decide if I should replace only the dead battery with another wet cell, or replace both with either wet cells or AGMs

The Rolls deep cycle wet cells are almost the same price as an AGM. Is this a case of high price making it appear that they are better (like a certain anchor). Or is the Rolls wet cell battery really close in performance to an AGM and worth the money?

And if I replace both house batteries with AGMs; is this going to be a problem to the wet cell start battery after I charge the Balmar alternator controller to charge an AGM? Or am I also going to have to replace a good start battery with an AGM at the same time?
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Old 13-06-2011, 16:44   #2
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Re: Rolls verse AGM batteries

Generally, it is not a good idea to replace only a portion of a battery bank, especially for wet cells. The "good" one does have wear and will bring down the potential of any "new" battery that replaces the bad one. So, by replacing just one, your are limiting the life/capacity of the entire bank from the get-go.

On mixing AGM house, and Wet starter batteries. Depends on how alternator charging is setup for the starter battery. If it is an echo-charge sorta thing? it should be fine. Battery combiner? No, dont do it. Battery isolator? No, don't do it.

Given differing sizes between house and starter, If your setup is either of the latter two (combiner or isolator), it is not good for ANY of your batteries, regardless of the chemistry.
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Old 13-06-2011, 17:05   #3
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Re: Rolls verse AGM batteries

Have an isolator but I don't think it is isolating anything. When the 1 house battery died I noticed that the start battery volatge went down to match the 2 house batteries. The only way from the electrical drawing in the boat manual I can see this happening is if the diodes in the isolator don't work.

As far as a new with the old wet cell, I know this isn't ideal. But I think the good battery is fairly new and the wet cells are cheap as far as a boat project goes (more the pain in the a.. to swap them out).
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Old 13-06-2011, 17:32   #4
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Re: Rolls verse AGM batteries

Yeah, I understand.

I once replaced two 6v golf cart flooded cell batteries and ran them for a couple months. Then I expanded the same bank by adding two more. That was six years ago and the batteries are still going strong. But, the two newer cells always boil off more electrolyte than the older two and the whole bank has difficulty coming to a full charge. I attribute that two mixing the two pair, even though one pair was only a couple months old with a few cycles on them. Its easier/cheaper to top up the electrolyte than replace all four cells.

On the isolator: been there, done that, got rid of it. Same with the combiner. With your balmar and smart charger, having combiner or isolator (esp with different battery sizes) can change the voltage sense and screw up the charge profile and limit the battery life/potential. For me the solution was an echo-charge between the house bank and starter battery. As the house bank tops off, the (barely discharged) starter battery tops off, but it doesn't alter the voltage 'appearance' to the smart regulator.

As for AGM or Rolls, with your current setup, it may be more costly in the long run. A less-than-adequate charging system will reduce the life of ANY battery system, regardless of chemistry or brand (you may just delay time of death). A properly designed charging system and cared for batteries can last almost forever. Again mine are cheap flooded cells at least six years old. I am amazed they have lasted this long.
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Old 13-06-2011, 17:45   #5
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Re: Rolls verse AGM batteries

I have all Group 31 AGM's now. When we got the boat there were 4 gelcells, to which I added two AGM's. Next year replaced 4 gelcells with 4 agms, and the next year added 2 more AGM's, for a total of 8 agm's and 880 ampere capacity.

It is not recommended to mix types, even though I did without any problems.

If I could I would use Odyssey batteries which are thin plate agm and accept charge more quickly. They are taller than standard group 31 AGM's and unfortunately won't fit.
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Old 13-06-2011, 17:48   #6
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Re: Rolls verse AGM batteries

I agree with Westsail 42 about not mixing old and new batteries, and about not mixing different types of cells.

Best plan might be to hold onto the three remaining 4Ds until they too are ready to be replaced, and then get a whole new bank out of whatever floats your boat at that point.
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Old 13-06-2011, 18:05   #7
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Re: Rolls verse AGM batteries

Throw out the isolator!! USE A RELAY!!
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Old 13-06-2011, 18:36   #8
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Re: Rolls verse AGM batteries

So back to the Rolls batteries; are they worth the extra cost?
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Old 13-06-2011, 18:50   #9
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Re: Rolls verse AGM batteries

Yes, they are - but with any batteries you can only buy the ones that will fit into your battery compartments unless you are willing to dramatically change the interior of the boat.
- - Any battery that is as expensive as AGM's or Rolls beg some really good battery management. State of the art regulators and combiners/echo chargers.
- - If you don't want to spend on the type of charging system/regulators needed to keep things properly maintained, then go with the old fashioned liquid lead acid like Trojans or other mass produced batteries. They accept a large amount of abuse and are cheap enough to be replaced every couple/three years.
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Old 13-06-2011, 18:52   #10
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What is the intended duty? Partial or slow charges , solar or wind charging call for a wet cell battery ,no matter the brand.
Rapid charging to full or float state or beyond call for AGM .

The best price depends on matching the battery type to the use.

On a related topic can anybody recommend a portable charger to use for equalizing at 15.5V. ?
That's what Lifeline calls for.

Thanks,
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Old 13-06-2011, 19:22   #11
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Re: Rolls verse AGM batteries

Comparing Rolls performance to a good AGM battery is like comparing old Edison carbon filament bulbs to LED lights. Rolls batteries have very high internal cell resistance compared to an "equavalent" (as if there is one) AGM battery which has very low cell resistance. The terminal voltage under the same load will be MUCH lower for a Rolls than an AGM.

Rolls batteries are good for running anchor lights for long periods of time, not good for heavy long loads like AGM batteries will do.
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Old 13-06-2011, 19:52   #12
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Re: Rolls verse AGM batteries

Quote:
Originally Posted by osirissail View Post
- - If you don't want to spend on the type of charging system/regulators needed to keep things properly maintained, then go with the old fashioned liquid lead acid like Trojans or other mass produced batteries. They accept a large amount of abuse and are cheap enough to be replaced every couple/three years.
What he said. Rolls are very high quality batteries, but you can kill them just as easily as a cheap Trojan if your charging system is not tuned for optimal performance.

If you can get by with your remaining house cells, maybe stick with them until you are ready to replace the entire lot.
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Old 13-06-2011, 19:58   #13
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Re: Rolls verse AGM batteries

Quote:
- - Any battery that is as expensive as AGM's or Rolls beg some really good battery management. State of the art regulators and combiners/echo chargers.
Batteries are a total package from charger to alternator to to load requirements. Banks too large never get recharged and failure to fully recharge will be the sooner path to failure. Too small and the severe deep discharge reduces the lifespan as well. You manage batteries over a lifespan and you charge then in the same manner. The better you do that the longer they last and the less money you spend.
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Old 13-06-2011, 20:01   #14
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Re: Rolls verse AGM batteries

I like basic deep cycle wet cells. Their lower cost make replacing them an easier decision. And new batteries of any kind are far superior to aged batteries of any kind.
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Old 13-06-2011, 20:05   #15
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Re: Rolls verse AGM batteries

If you are like many cruising sailors and discharge your batteries to 50% then recharge to 80-90%, the information you want from the manufacturer is the "number of cycles" (to a certain discharge level). I expect you'll find those Rolls are rated for a higher number of cycles than the AGM's you're considering.

You still might want to consider the AGM's if you don't (or can't) check the water in the flooded battery. You also might like the AGM's if you have large alternators that that can charge very quickly due to AGM's better "charge acceptance".

AGM's seem to have shortened life if they are not recharged to 100% once a week or so. This usually requires an overnight charge from shore power. If your boat stays in a marina this obviously isn't a problem.

Finally, there is are some new AGM's out (one brand is Odyssey) that claim a lot more cycles than most AGM's. The jury is still out on this.

For engine start, a fully charged AGM is just about ideal. It delivers a huge amount of amps very quickly and doesn't discharge while sitting around. But if your current start battery is fine, why mess with it.

The problem with mixing types (or ages) of batteries in one bank is one battery ends up carrying a large share of the load but the charger only sees the bank average. This tends to greatly shorten the life of the heavier discharged battery.

I agree you should get rid of the isolator. Relays are fine but I've never met anyone who didn't like their Echo charger (or the similar Duo-charge from Balmar) for the start battery.

Carl
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