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Old 10-13-2016, 09:22 PM   #41
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Originally Posted by Pilou View Post
Thanks for clear and precise explanation.
Then if Ah capacity stays the same what is the good of having 6 x 6v batteries wired in series (actually my service battery bank) instead of 3 x 12v batteries wired in parallel?
The guy that answered this is not correct! 6 volt deep cycles are better because they weigh as much or more than a 12v. The weight comes from the amount of lead in the plates, the more lead the longer the battery will last.

And those saying the Ah rating stays the same are correct!
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Old 10-14-2016, 12:09 AM   #42
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When you wanna get serious, put these in.
Agreed! Had them on my last boat. One other plus is that they come in 2,4,6,8, & 12 volt packaging configurations. It's like using Legos to build your battery banks.
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Old 10-14-2016, 05:30 AM   #43
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When you wanna get serious, put these in.
It looks as it's doing very well. 20 hours rate is 820, warranty is 10 years, first 36 months are full replacement, next 84 months are prorated which is very good and a guarantee of quality.

318 LBS, I know that SY47 has higher E/R but how do you move them ?
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Old 10-14-2016, 07:31 AM   #44
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Originally Posted by ssousa View Post
The guy that answered this is not correct! 6 volt deep cycles are better because they weigh as much or more than a 12v. The weight comes from the amount of lead in the plates, the more lead the longer the battery will last.

And those saying the Ah rating stays the same are correct!
Yes more lead or thicker plates often means longer life but this not always the case and the construction is also different between 12V marine batteries and golf or industrial batteries. Plate separators are better, grids are thicker the paste is different etc. etc..

Compare a pair of 6V Trojan T105's (GC-2) and a pair of 12V SCS-225's (G-31) for a 225Ah bank and a 260Ah.

Two 12V SCS-225's weigh 132 pounds and will deliver 260Ah's and 600 lab cycles to 50% DOD

Two 6V T105's weigh 132 pounds and will deliver 225Ah's and 1200 lab cycles to 50% DOD

Both banks weigh the same but the G-31 12V bank will deliver more ampere hours of capacity yet only half the lab cycles 600 lab cycles to 1200 lab cycles.

The problem is that consumers most often buy batteries based on Ah capacity or cost per Ah while totally ignoring cycling ability. The G-31's weigh the same as the T105's and deliver 35 more ampere hours so they must be better right? No, wrong..

If we look at the East Penn line and compare batteries of identical case sizes and only vary them the type of battery.

East Penn 12V G-31 AGM - 300 Lab Cycles to 50% DOD - 69 Pounds
East Penn Flooded 12V G-31 - 350 Lab Cycles to 50% DOD - 60 Pounds
East Penn GEL 12V G-31 - 1000 Lab Cycles to 50% DOD - 70 Pounds

East Penn Flooded 6V GC-2 - 1000 Lab Cycles to 50% DOD - 64 Pounds

As can be seen a 1 pound difference in weight yields 700 more cycles between AGM & GEL. Nine pounds less weight yields 50 more cycles for the flooded battery over the AGM? It is the construction and battery type that really define cycle life. Within the flooded category construction varies too.

Weight can not be the only determination of expected durability or cycle life. Heck two G-31 Trojans weigh the same as two T105's and can deliver 35 more ampere hours of capacity but they will only do so for half as long in the lab. Equal weight boxes, more ampere hour capacity out of two of the 12V batteries, but half the lab cycles. The Trojan golf car 12V T1275 at 150Ah's can also do 1200 lab cycles but the 12V G-31 (automotive case) can only do 600. If you were buying a 12V battery with 130Ah to 150Ah's which one makes the better choice, the one designed for golf car duty or the one that is an adapted automotive battery with a "marine deep-cycle" sticker? Considering that boats usually need more than 1 battery why spend money on cheap short lived 12V automotive type batteries when you can install batteries that can yield considerably better service life?

The design, intended purpose and construction of the battery play a large role in how it cycles and while weight & plate thickness plays a roll it does not have the impact people often think it does..

Again these are not my words but the words of a battery manufacturer who actually produces all the types of batteries being discussed.

Senior Battery Engineer - Major US Battery Manufacturer:

"Yes, for packs of equivalent energy content (voltage * capacity) the Golf Car types and L16's are 2-3 times better than the DC automotive sizes (24, 27 and 31)."

Note how he used the word "automotive sizes" when stating they were 2-3 times lesser a battery than golf car or L-16 type battery....

This same manufacturer slaps the same "deep-cycle" label on G-24, 27 & 31's as they do L-16's, GC-2's, GC12V's etc.. Fair? Given what they stated above I'd say it's far from fair to the consumer..

Unfortunately we can't simply buy batteries based on Ah's to $$, as many, many consumers do, we also need to look at the manufacturers projected lab data to determine how they rate it for cycling compared to other batteries within their own brand. Trojan rates the 12V G24, 27 & 31 at just 600 lab cycles and the GC-2, GC12's, J185's, L16's etc at 1200 lab cycles, East Penn is similar...
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Old 10-14-2016, 08:40 AM   #45
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Do the above statements hold true for comparable AGM's?

e.g. 2- GC2-AGM's in series a better choice than a 8D-AGM
(from a life standpoint - I realize there is a small difference in AH capacity)
Not necessarily but in some cases yes. For example the 4D & 8D AGM's from East Penn cycle life is very slightly longer than their G24, 27 & 31 AGM's but their AGM product in general is a poor PSOC cycling design and is really a dual purpose battery not a deep-cycle product. If you want an excellent cycling product from East Penn their GEL batteries are the way to go. Their AGM product is best used for starting, thruster or windlass loads not cycling..

With premium AGM's such as Odyssey, Northstar, Lifeline, Firefly etc. the case size makes little to no difference in lab cycle life because the plates are just scaled larger or smaller losing or gaining Ah capacity but not cycle life. With flooded batteries the manufacturers can save tons of money by making a cheaper product but the cost to build AGM's makes this nowhere near as worthwhile in an AGM or GEL product so they just scale the same plate design in physical dimension. For example a G-24 Lifeline deep cycle has the same lab cycle rating as their 6V GPL-4CT

Within the AGM brands however quality varies widely. Trojan has a new AGM out but we have no idea where it will land quality wise. Crown is in development of a new AGM but again we really know nothing about it. Most of the Chinese stuff is utter rubbish with the exception of Full River..

Right now the lead acid battery to beat, not just AGM, is the Firefly Carbon Foam battery. This is an amazing battery for marine PSOC use.

Until the industry and BCI impose a PSOC cycle rating on deep cycle batteries the consumer is at the will of the marketing mavens who spout lots of misleading information....

For more info on how AGM's fare under PSOC use, see the May 2015 Practical Sailor - Fighting Sulfation in AGM's as well as the August 2015 Practical Sailor - AGM Batteries Test Update issue.
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Old 10-14-2016, 09:28 AM   #46
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6 volt deep cycles are better because they weigh as much or more than a 12v.
Only because most 12 volt batteries are not true deep cycle, or do not have the same AH capacity. If you get a 12 volt battery that is truly equivalent to the 6 volt battery--both in terms of capacity and deep cycling ability--then each of the 6 volt batteries will weight a bit more than half the weight of the 12 volt.

This is simply because, in reality, what we call a "12 volt battery" is a bank of six, 2-volt cells, connected in series, and put into a single case. A "six volt battery" is a bank of three, 2-volt cells, connected in series, and put into a single case. If the 2-volt cells are equivalent in terms of capacity and deep cycling ability, then they MUST weigh approximately the same. (Assuming, obviously, that we're not comparing different types of batteries--like wet cell to AGM.) If they do not weigh approximately the same, then they CANNOT be equivalent in capacity and deep cycling ability.
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Old 10-14-2016, 09:33 AM   #47
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Which battery made my bananas go black
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Old 10-14-2016, 10:07 AM   #48
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Which battery made my bananas go black
Bananas on a boat? I'm appalled!
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Old 10-14-2016, 10:14 AM   #49
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Bananas on a boat? I'm appalled!
Really? I find bananas quite appeeling.
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Old 10-14-2016, 12:02 PM   #50
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Originally Posted by Pilou View Post
It looks as it's doing very well. 20 hours rate is 820, warranty is 10 years, first 36 months are full replacement, next 84 months are prorated which is very good and a guarantee of quality.

318 LBS, I know that SY47 has higher E/R but how do you move them ?
I suppose I'll find out, when these crap out. But as I get older, I've learned to appreciate youths ability to accomplish heavy lifting for the right price.

I've been told I have "Pesonality" ! LOL
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Old 10-14-2016, 01:47 PM   #51
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I've learned to appreciate youths ability to accomplish heavy lifting for the right price.

I've been told I have "Pesonality" ! LOL
Hahaha ! Good point, great idea. It is knowing how to put in place a strategy that works, people who want to solve the major issues must have their hands free to take the initiative and delegate to specialists.
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