New AGMs to replace lead acid?

[btrayfors]

It's threads like this that make your head spin, at least until you knock it against the wall a few times.....hard :-)

1. AGMs are lead-acid batteries. So, too, are gelled batteries. So, the original query was AGMs vs. flooded lead-acid batteries (FLAs).

2. While AGMs and gels have greater charge acceptance than FLAs when at lower states-of-charge (SOC), all of them take many hours to reach full-charge, irrespective of charger size.

3. AGMs, in particular, can accept a heck of a lot of amperage in early charging stages, thus can be moved from, e.g., 50% to 80% SOC faster than, e.g., FLAs, given enough charging capacity.

4. It was correctly noted above that you cannot have too large a charger (and it was incorrectly stated in a couple of posts above that you can, or that you should not exceed 33% or capacity in charging current). Batteries will accept what they're going to accept, given correct voltage regulation. It doesn't matter if you have a 20-amp charger or a 2,000-amp charger, if you regulate the voltage correctly the batteries will accept EXACTLY THE SAME AMOUNT OF CURRENT.

5. That said, it generally is a good idea to fit a high-capacity charger or charging sources so that you are taking full advantage of battery acceptance capability. Think about it: you have a 100AH capacity AGM battery bank which is 50% depleted (50% SOC) and you want to recharge it as quickly as possible. What's better? A 20A charger? A 50A charger? or a 100A charger? Clearly the 100A charger has a slight edge because it will take advantage of the AGM's ability to accept a bit more than it's rated 100A at the beginning, but it quickly tapers off so the 50A charger wouldn't be too bad. The 20A charger would take considerably longer.

6. We still don't know enough about the OP's setup to comment fully. For example, how much actual charging capacity does he have with the 17kw genset running? Has he considered means to reduce his daily consumption? To me, running the generator 4 hours per day is completely zany. And, don't know if he's done the math but it's an extremely expensive way to charge batteries. Or to make hot water.

FWIW,

Bill

[a64pilot]

Originally Posted by rwells36

Refrigerator is 8 amps (doesn't run 24x7) mini freezer is 4 amps. These two appliances represent the power consumption outside of the genset running (4 hours for water-maker)

Rounding off to 10 amps (both appliances) x 120v = 1200 watts less 10% for DC-AC conversion means I'd need 1230 watts to break even.

In other words I'm taking out 10 amps per hour and replacing it with about 7.5 via 945 watts of 24v solar for a net loss of 2.5 amps per hour x 20 hour = 50 amps (accounting for 4 hours of genset time).

50 amp loss in 20 hours is low so I will estimate another 50 amps for other energy needs for a total deficit of 100 amps. Check my math guys; that doesn't seem like a lot to make up each day to me.

My take from this is your Solar is at a deficit, so it cannot charge, your charging is limited to generator on time.
You need to tell us what your charger (s) sizes are, however no matter how large they are, you need to increase Solar so that it can be a charge source too, or decrease consumption or of course both.
You need 5+ hours of charge time in a perfect world, yes you can get by with less but it will slowly degrade your batteries, which may not be terrible and may be the best thing to do, just don't go with high dollar AGM's in that case.
With six people aboard, I have to assume there is other electrical use other than refrigeration.

[john61ct]

Key question is: are you sure you can get to true 100% (not 98%) most days? That means lots of solar and sunny days.

If not, buy lowest cost per AH true deep cycle FLA, 2V or 6V, fewer cells the better.

If yes, get the same, but in a premium marque e.g. Rolls Surrette.

Or relying more on motor charging, less solar but still promising 100% go premium AGM for the faster charge acceptance rate, but give up the hydrometer, need a SmartGauge IMO for sure. Likely PSOC will murder them, or very high motor runtimes cost more than the bank.

Or if "no", a better if costly long-life and high CAR option, go Firefly Oasis, the only non-LFP that is OK with PSOC abuse, only rarely getting to 100%.

$500 per 100AH, but very likely to outlive anything but LFP (by years) in a partial SoC context.

LFP would be even better, but at 5x the investment, big risk there.

[rwells36]

Originally Posted by btrayfors

It's threads like this that make your head spin, at least until you knock it against the wall a few times.....hard :-)

1. AGMs are lead-acid batteries. So, too, are gelled batteries. So, the original query was AGMs vs. flooded lead-acid batteries (FLAs).

2. While AGMs and gels have greater charge acceptance than FLAs when at lower states-of-charge (SOC), all of them take many hours to reach full-charge, irrespective of charger size.

3. AGMs, in particular, can accept a heck of a lot of amperage in early charging stages, thus can be moved from, e.g., 50% to 80% SOC faster than, e.g., FLAs, given enough charging capacity.

4. It was correctly noted above that you cannot have too large a charger (and it was incorrectly stated in a couple of posts above that you can, or that you should not exceed 33% or capacity in charging current). Batteries will accept what they're going to accept, given correct voltage regulation. It doesn't matter if you have a 20-amp charger or a 2,000-amp charger, if you regulate the voltage correctly the batteries will accept EXACTLY THE SAME AMOUNT OF CURRENT.

5. That said, it generally is a good idea to fit a high-capacity charger or charging sources so that you are taking full advantage of battery acceptance capability. Think about it: you have a 100AH capacity AGM battery bank which is 50% depleted (50% SOC) and you want to recharge it as quickly as possible. What's better? A 20A charger? A 50A charger? or a 100A charger? Clearly the 100A charger has a slight edge because it will take advantage of the AGM's ability to accept a bit more than it's rated 100A at the beginning, but it quickly tapers off so the 50A charger wouldn't be too bad. The 20A charger would take considerably longer.

6. We still don't know enough about the OP's setup to comment fully. For example, how much actual charging capacity does he have with the 17kw genset running? Has he considered means to reduce his daily consumption? To me, running the generator 4 hours per day is completely zany. And, don't know if he's done the math but it's an extremely expensive way to charge batteries. Or to make hot water.

FWIW,

Bill

Bill,

Thank you for the thoughtful post. Making fresh from sea water (not hot water) is the purpose of the genset. In addition to washer / dryer, meal prep and perhaps air conditioning.

[john61ct]

Then yes the gennie with a good high-amp charger, running for four hours *early in the day* will mean every nice sunny day should get you to 100% at 900w of panels.

No need to spend more on pricey and more finicky chemistries, a bank of monster Rolls Surrette FLA, as large/few 2v cells as possible, will last for many years, and allow for precise SoC tracking with a hydrometer.

Yes you need to check/replenish water, but ideally you can tune your charger to keep gassing to a minimum.

AGM gasses too, you just can't replace the water lost.

[admiralslater]

I am very happy with my firefly batteries ,but they may not fit . Their high acceptance and posc capabilities are why I chose them ,have not been attached to shore power for 3 weeks and ran engine only to come into harbour batteries hit 100 just about every day and I ran watermaker for 6 hours the other day.

[rwells36]

Originally Posted by admiralslater

I am very happy with my firefly batteries ,but they may not fit . Their high acceptance and posc capabilities are why I chose them ,have not been attached to shore power for 3 weeks and ran engine only to come into harbour batteries hit 100 just about every day and I ran watermaker for 6 hours the other day.

I considered FireFly but then found Outbacks Nano-Carbon batteries. Any comments on the Outbacks?

[admiralslater]

Originally Posted by rwells36

I considered FireFly but then found Outbacks Nano-Carbon batteries. Any comments on the Outbacks?

I only just heard of them so I have no imput

[StuM]

Originally Posted by a64pilot

GC2 is a wet cell 6V golf cart battery. Likely the most battery you can get for the money. There are better, but usually at a much higher cost, golf cart batteries are very widely available as well. Downside is you have to water them, although there are caps that will allow automatic or nearly so watering

Not so.

GC2 is a BCI battery Group Number, it has nothing to do with the technology.

GC2s can be found in Wet, AGM and Gel by different manufacturers.

[StuM]

Originally Posted by rwells36

Gel Cell is GC2?

That's like saying "yellow is round?". )

Battery technology and Group Size are two different things.

[a64pilot]

Originally Posted by john61ct

AGM gasses too, you just can't replace the water lost.

Within limitations, your don't have to.
Same company that makes Lifelines, makes the Concorde aircraft battery, it is a VR RG SLAB, that stands for valve regulated, recombinant gas, sealed lead acid battery. The Concorde and Lifeline appear to essentially be identical.
By some magical process that I know nothing about, it can recombine the hydrogen gas with oxygen and form water, I assume a catalyst is involved, but that is just a guess. However if you dead short the thing or shove ridiculous amounts of energy into it to create more gas than it can recombine, it will vent as opposed to explode, but I think under anything like normal use venting is rare.
I am sure too like everything else it's not perfect and in fact eventually I assume it will get short of water?

[a64pilot]

Originally Posted by StuM

Not so.

GC2 is a BCI battery Group Number, it has nothing to do with the technology.

GC2s can be found in Wet, AGM and Gel by different manufacturers.

OK however in this case I am sure what was meant was a wet cell golf cart battery. I am sure he was thinking GC meant Gel Cell, a logical conclusion

[StuM]

Originally Posted by rwells36

Refrigerator is 8 amps (doesn't run 24x7) mini freezer is 4 amps. These two appliances represent the power consumption outside of the genset running (4 hours for water-maker)

Rounding off to 10 amps (both appliances) x 120v = 1200 watts less 10% for DC-AC conversion means I'd need 1230 watts to break even.

In other words I'm taking out 10 amps per hour and replacing it with about 7.5 via 945 watts of 24v solar for a net loss of 2.5 amps per hour x 20 hour = 50 amps (accounting for 4 hours of genset time).

50 amp loss in 20 hours is low so I will estimate another 50 amps for other energy needs for a total deficit of 100 amps. Check my math guys; that doesn't seem like a lot to make up each day to me.

Several points.

1.Your units are all screwed up. Please learn the difference between Amps and Amp hours.

2. 1200 Watts plus 10% = 1320, not 1230

3. Even if your fridge + freezer draw 10 Amps when running (that sounds very high), they won't run all the time. So lets be a bit more realistic - your very high consumption fridge+freezer at a 50% duty cycle would require about 16000 Watt hours. (I still find that figure hard to believe)

4. You won't have 945W of solar for most of those 20 hours. Realistically, 945W of solar will give you about 4500 Watt hours.

5. Your 100 Amp hour per day estimated deficit at 120V is huge. That's 1000 Ah of 12 volt battery capacity. That means that you are going to need a huge battery bank and charging system.

I think you need to check your real power consumption and make sure that you are not mixing Amps an 12V with Amps at 120V.

[KISS]

To give a highly truncated answer w/out explanation (because I'm lazy):

No, I would stick with traditional lead-acid.

Cheaper, more readily available, just as good/better for most purposes.

[john61ct]

Originally Posted by a64pilot

OK however in this case I am sure what was meant was a wet cell golf cart battery.

As for me, I just meant the form factor implying true deep cycling, getting away from starter sizes which usually aren't but deceptively marketed as if they are.

Chemistry is indeed a separate issue, which decision-value flow logic I posted above, starting with

> Key question is: are you sure you can get to true 100% (not 98%) most days? That means lots of solar and sunny days.

Not worth spending big bucks on AGM or even premium FLA, unless that's a "yes".

Unless jumping up to the PSOC tolerant chemistries.