How Often Do You Check Your Water and How Low Is Too Low ?

[Highlander40]

Yeah,
While you have a large bank that will go a long time before charging.
You do not have any way to charge:
A. bulk rate of at least 200A @12V
OR
B: long enough to fully charge the bank to full float level.
Both requirements to get the full life from AGM's

So while it sounds like a good idea to have a huge house bank, it's not always so good..
The loads should be matched to the size of the bank and to the charging method used.

Realize that we are talking optimal procedures here, but optimal procedures will produce the longest life.
It's all about choices and how frugal you need to be.

Even using a generator your bank could take over four hours to charge.

You could use a smaller bank or stay with FLA batterys.

The thing is that for AGM's, wandering around at 60 to 70% will kill them quickly. There is no magic to AGM batterys unless you can charge them at a higher rate saving time or need to save a small amount of weight.
For me they have more power for the limited space on the boat.

Now if you need to have sealed batterys and very light weight, look at the LIFEPO4 stuff but that is cubic yards of money. That means a new generator and inverter and controls and maybe a whole electrical system.

For me that would make sense with a new build, planning everything around the batterys. You have to realize that a new technology is only good and wonderfull if you can reap the benefits.

A: longer life
B: greater safety, sealed system
C: Quicker charge
D: lighter weight (mostly LIFEPO4)

When you stick new cutting edge batterys into old antiquated control / charging (slow) systems, all you get is a huge waste of money.

Engineering is about matching apropriate components.

[witzgall]

Highlander;

I think you are not entirely correct about the statements below. LIFEPO4 can happily co-exist with MOST standard marine charging systems, if a proper Battery Management system is used to safeguard the cells. The one exception I think that is crutial is a good alternator with an EXTERNAL regulator, and an alternator temperature sensor. Because the cells can accept very high charge rates, you could easily cook a standard car-type alternator.

Of course, this holds true for AGM, Gel or Oddessy type batteries to an extent. If the poster cranks up his motor with a 50% charged AGM bank of a large size, that alternator will be trying to put it's maximum output into the bank for quite some time. If the alternator cannot handle the heat, and if the regulator cannot protect the alternator from excessive heat, then they will be short-lived.

Basically, you need to look at every component, and make sure the it is up to the task, the wiring sizes are correct,etc. But again, you would need to do that with any system, regardless of battery chemistry.


Chris

Originally Posted by Highlander40

Now if you need to have sealed batterys and very light weight, look at the LIFEPO4 stuff but that is cubic yards of money. That means a new generator and inverter and controls and maybe a whole electrical system.

For me that would make sense with a new build, planning everything around the batteries. You have to realize that a new technology is only good and wonderful if you can reap the benefits.

A: longer life
B: greater safety, sealed system
C: Quicker charge
D: lighter weight (mostly LIFEPO4)

When you stick new cutting edge batterys into old antiquated control / charging (slow) systems, all you get is a huge waste of money.

Engineering is about matching apropriate components.

[Highlander40]

Chris,
Thats the thing, without a charger that can put out a steady state charge of (50% or more?) A per AH of bank capacity, you only have half a system and threw away the extra cost of LIFEPO4 cells.

I think that systems designed from the ground up for LIFEPO4 are using DC generators to handle the huge charging loads.
Also where posible, using DC components or very large inverters.

Also Given a choice, wouldn't you have a higher voltage bank than 12 or 24V ? That cuts the current down and reduces wire size.

Getting back to the first statement. A 100 alternator with proper controlls would be fine for a LIFEPO4 bank of 200 AH? No way 800AH.

[witzgall]

I disagree with your last statement. LIFEPO4 cells actually prefer sitting at 50%-60% charge, so that if somebody wants a bigger bank, and can charge it fully only when motoring, or if the wind is steady/strong and they have a good wind gen, or, large alternator, then they can opportunity charge to take advantage of the larger bank when possible, and not hurt the cells otherwise. Would a larger alternator than 100a be better on a large LIFEPO4 bank? Certainly! But if we are comparing things using real world usage, then he would not be putting in a 800AH LIFEPO4 bank, but perhaps 400-600, and as long as the Alternator is heavy duty, it should be fine.

From my research, what LIFEPO4 cells do NOT like is to be floated at their max charge capacity. This won't happen on a boat, because the charging sources won't charge that high, and cruisers are always drawing the bank down anyways.

In my case, I am putting in a 200ah LIFEP04 bank, and have a 120a alternator, wind gen and solar. If the 200ah proves to be to small, then I can easily (and without penalty) add four 100-200ah cells to begin the bank up to 300-400ah.

Originally Posted by Highlander40

Chris,
Thats the thing, without a charger that can put out a steady state charge of (50% or more?) A per AH of bank capacity, you only have half a system and threw away the extra cost of LIFEPO4 cells.

I think that systems designed from the ground up for LIFEPO4 are using DC generators to handle the huge charging loads.
Also where posible, using DC components or very large inverters.

Also Given a choice, wouldn't you have a higher voltage bank than 12 or 24V ? That cuts the current down and reduces wire size.

Getting back to the first statement. A 100 alternator with proper controlls would be fine for a LIFEPO4 bank of 200 AH? No way 800AH.

[SV Demeter]

Wow this thread has hit all over the map eh? Im not going the LIFEPO4 route too expensive.

I am going with an 800ah bank however. Alternator right now is 100amp but will be carrying a spare/replacement that is bigger, probably 120-150 amp depending on what the engine mfg. has to say.

I started off asking about AGMs because I really would like sealed batteries and not to have to deal with watering. But it sounds like since my charging will predominantly come via solar and wind that the AGMs would not live long. Even if that solar is 540watts. One thought I have been having now though is would the AGMs be happy if say once a week they were fully charged back up by a decent amount of motoring, ie alternator charging? What if that only occured once a month? I am pretty much resolved to go the flooded route at this point but am going there kicking and screaming...Battery acid freaks me out.

[Highlander40]

Having used FLA and two sets of AGM's , my experience says NO! an ocasional charge at the dock to 100% or long motoring will not do.

The first set of AGM's was treated that way and lasted 3 years.

[SV Demeter]

Okay Im sold. Started making up the main cabling last night but ran out of 2/0 wire. Hydraulic crimper worked great. Hoping to get that side wrapped up this weekend and into distribution panels next week. So much fun working at my desk all day then on the boat all night. Thank god for heat...