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Old 11-20-2014, 03:03 PM   #41
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Originally Posted by ranger42c View Post
Hmmm... I often have trouble seeing things that are right in front of me...

But all I can see is wet and gels, not AGMs...

??

-Chris

Sorry...As I understand it, Gell Cell's behave similar to AGM types RE. Voltages. I may be wrong:

GEL: The Gel Cell is similar to the AGM style because the electrolyte is suspended, but different because technically the AGM battery is still considered to be a wet cell. The electrolyte in a Gel Cell has a silica additive that causes it to set up or stiffen. The recharge voltage on this type of cell is lower than the other styles of lead acid battery.
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Old 11-21-2014, 07:05 AM   #42
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Sorry...As I understand it, Gell Cell's behave similar to AGM types RE. Voltages. I may be wrong:

Ah. FWIW, I've been under the impression AGMs are more like FLAs for discharge rates. Our charger uses the same profile for those two. From that, I've guessed that the 50% discharge rule-of-thumb is also useful for AGMs, and our batteries reach that state of charge at 12.18V (well, when they were new, anyway).

Both Lifeline and Odyssey cite duty cycles down to 80% discharge... but I suspect that's more advertising than recommendation, especially since Lifeline's first citation (for GC2s) is to 50% SOC.... and their 80% citation might be only to compete with Odyssey

-Chris
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Old 11-21-2014, 07:08 AM   #43
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>but I suspect that's more advertising than recommendation,<

They do SELL batts , so a short service life is a good deal,,for them.
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Old 11-21-2014, 07:27 AM   #44
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>but I suspect that's more advertising than recommendation,<

They do SELL batts , so a short service life is a good deal,,for them.

Sure. But Lifeline says 1000 cycles to 50% for their 6V GC2 deep cycle AGM batteries, which doesn't seem too short.

They rate the same batteries at 550 cycles to 80% discharge, compared to Odyssey's 440 cycles to 80%, but the Odyssey in question is a 12V G31, deep cycle in advertising only, probably more accurately a pretty good dual purpose.

-Chris
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Old 11-21-2014, 10:10 AM   #45
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The big fear with a house only , no dedicated start is FLAT BATT..

Folks with an undervoltage alarm need to be aboard to start the recharge.

Leaving for a day trip , with a light on or a bilge pump stuck on can bring the house to dead in time.

The start batt for the engine solves the DEAD horror with little effort , no Sea Tow , batt cables .....
The "suspenders" in our case is an 8kw genset with a totally separate battery to start it. Fire it up, and it charges the big battery bank.
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Old 11-23-2014, 06:43 AM   #46
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>Fire it up, and it charges the big battery bank.<

Given enough TIME , and remember all batts do not like to be taken to near 0% SOC , and will usually need replacement afterwards.
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Old 11-23-2014, 09:26 AM   #47
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Can you get by without a separate engine start batttery, sure! Ditto:
  • A wrong type anchor
  • No inverter
  • No refrigerator
  • No AC if you live in FL
  • No heat if you live in the North
  • No fresh water flush for the head
  • No queen sized bed
  • No windlass
  • And many more
The above dittos could be called a sail boat or Willy, both perfectly acceptable for the many thousands of current owners. As the size, complexity and reliance upon ready amps of the vessel increase, so do the needs. Not to mention the potential requirement to quickly and safely raise anchor in the middle of a stormy night as the rocky shore approaches.
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Old 11-23-2014, 09:42 AM   #48
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What do think happens when the one batter in a parallel set up fails?

The voltage drops precipitously.

Exactly, and when that happens the other batteries dump all their charge into the failed battery and it overheats and sometimes spews acid.
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