My AGM epiphanies

[rslifkin]

As the battery bank gets bigger, voltage sag becomes less of a problem. A 100 amp load won't sag a 1200ah bank nearly as badly as a 600ah one. So depending on factors like that and how often you can get the batteries topped off, the benefits of LiFePO4 will vary depending on the situation. In some cases, just the increased space and weight density makes them worthwhile, as you can fit more battery capacity (but that isn't a limiting concern on many boats).

 

[mvweebles]

So, lithium battery proponents, please explain to me, and others similary situated, how lithium would be life-changing.

I do not pretend to believe you can be pursuaded (I note there is no question mark at the end of what seems to be a question). I respect your opinion and understand your position. All I can tell you is that the combination of solar and LiFePO4 has fundamentally changed my power calculus. Gone are concerns about usage, ability to recharge, etc. Much more even and consistent infrastructure. Worrying about DoD/SoC are now nerd-out things, not really a concern.

14-16 hours to 50% DoD is not even close to what I would be comfortable with - my goal is net-zero so power becomes a non-issue. At 50% DoD, with a standard alternator, it can take 6-10 hours to recharge a 6x6vGC FLA bank. So you need beefed-up alternators and/or a generator - suddenly the $1200 in 6V batteries is an incomplete expense.....unless running half the day to recharge the batteries is normal.

I'm not buying the argument that a FLA battery has a fixed number of AH to give, and that (within reason) how those AH are expended (i.e. many shallow discharges vs few deep discharges) have little effect on the overall reservoir of total AH available.

Peter

 

[sunchaser]

Peter
For your cruising style of living on the hook in Mexico your battery setup sounds pretty ideal given today’s choices. CJ is in a different location with a different cruising regimen thus a sea change in ready electron thinking doesn’t appeal to him.

We currently are in a large marina dominated by commercial fishing craft. Dollars to doughnuts not one of them has Li batteries or solar panels. But several cruising boats nearby have setups like yours. Even though necessity is the mother of invention, one’s requirements tends to seep in to this subject.

 

[twistedtree]

It seems to me that the life-changing experiences are those of extreme users, those who put inordinate demands on their systems. For most boaters, the issues talked about here simply do not exist, at least they do not for me.

Inordinate is a relative term. There have been a number of discussions about when LFP is more/less beneficial, and not everyone's usage patterns benefit the same. Is my usage "inordinate"? Maybe to some, but I would call it "convenient".

I have eight flooded golf car batteries. We generally cruise from anchorage to anchorange. Occasionally, we stay two nights, rarely three, in one place. Our luddite house bank easily last 14-16 hours before reaching 50% DOD and that's with two 4.2 cf fridges, a 7 cf chest freezer, two TVs plugged in full-time, and a SAT-TV dome and receiver on full-time. And, yet, in the morning we can brew coffee and use the microwave or toaster with no discernible decrease in performance (the effects of voltage sag). At times we even plug in a portable induction cooktop to cook breakfast although not all of the 120VAC implements at the same time. My batteries are five years old and test to 97% of original capacity.

You, and many others have run like this for decades.

So, lithium battery proponents, please explain to me, and others similary situated, how lithium would be life-changing.

In your case, the benefit would be shorter generator run times. Does that matter to you? At this point it would seen not, which is fine.

As for longevity of batteries, twistedtree has explained the science. All batteries have a limited ability to deliver electrons. Cycles are meaningless. What counts is the number of electrons utilized. The tank is of limited capacity. So, what does that mean for the heavier users who have adopted lithium. It means that your profligate use of electrons will result in a battery bank that will not last nearly as long as you think it will based on a flawed concept of battery life being determined by cycles.

Cycles aren't meaningless or a flowed concept. They are just an incomplete metric for lifespan. FLA/AGM published cycle life is always based on a DOD, typically 50%. More complete specs will plot cycle life vs DOD, and that's the more complete story showing the range of usage available, and showing that 50% DOD is just one usage pattern, not the only usage pattern.


LFP is no different. 2500 cycles at 100% DOD has been proven over and over again for about 20 years now. And that's under much more abusive operation that any house battery bank will ever see. That's already about 5x the lifespan of lead, and only grows with more gentle use.

The bottom line for me is that my dumb old flooded batteries give me everything I need, every day, every cruise with no compromise of utility and/or convenience. So, five years from now I will have to spend $1,300 at today's prices for a replacement bank of Trojan T-105s. Works for me.

And that's all good.

 

[DDW]

As for longevity of batteries, twistedtree has explained the science. All batteries have a limited ability to deliver electrons. Cycles are meaningless. What counts is the number of electrons utilized.

Lead acid chemistries WILL deliver less total AH over their life if deeply discharged. Just that the difference is not as precipitous as many have supposed. Lithium batteries too, but with lithium the difference is negligible. And the total AH delivered by lithium is many times that of any lead acid chemistry, more than recovering their extra cost. This was even true a few years ago, and with the drop in price of lithium, is doubly true now. So regardless of operational advantages, lithium is the cheap choice - if you are keeping the boat for very long.

 

[mvweebles]

Peter
For your cruising style of living on the hook in Mexico your battery setup sounds pretty ideal given today’s choices. CJ is in a different location with a different cruising regimen thus a sea change in ready electron thinking doesn’t appeal to him.

We currently are in a large marina dominated by commercial fishing craft. Dollars to doughnuts not one of them has Li batteries or solar panels. But several cruising boats nearby have setups like yours. Even though necessity is the mother of invention, one’s requirements tends to seep in to this subject.

Yes, my use-case is at the outer edges, but my guess is there are a lot of people that don't want to be awakened by low-voltage alarms in the morning. That said, LiFePO4 and solar would help a boat like CJs, but running multiple fridges, freezers, TVs, and electronics full-time is likely beyond the reach of even a robust energy system. He might be able to double/triple his off-grid time, but in the end, the power demands are just too high to view a battery bank as anything other than a temporary bridge between generator/engine run-time; or being connected to shore power. Going from 12-16 hours to 50% DoD on FLA to 36 hours to 80% DoD on LiFePO4 isn't going to move the needle much.

Peter

 

[twistedtree]

I'm not buying the argument that a FLA battery has a fixed number of AH to give, and that (within reason) how those AH are expended (i.e. many shallow discharges vs few deep discharges) have little effect on the overall reservoir of total AH available.

Peter

This is probably a good time to talk about this some more, because although the fundamental concept is shown in battery specs, there are other factors at play. So let's talk about the warts and imperfections...



First, the whole concept of having a lifetime number of Ah that you can cycle through the battery is more like 90% true, not 100% true. Again, just look at the published specs. But the notion that there is exponential decline if you use more then 50% DOD is 100% untrue.


Second, the concept breaks down more if you operate at the DOD extremes. Again, look at the published specs. But house battery use seldom, if ever operates that way.


Third, heavy loads have a disproportionate impact on lead batteries via the Peukert effect. Heavy loads draw down more Ah than their face value. Linking this back to the notion of running a smaller battery bank harder, and for a shorter life, the Peukert effect will be more pronounced. With half the bank size, any given load is proportionally twice as large with a subsequent larger Peukert degradation. So for any given load, Peukert hits you harder with a small bank vs a big bank, and that one IS an exponential relationship. It's not a big exponent, but it's not one either.


Fourth is the human factor, primarily operating at partial SOC and consequent permanent sulfation buildup over time. The longer we own and operate a battery bank, the more likely we make our own contribution to shortening their life.

 

[CMS]

Apologies in advance if this is common knowledge but I just figured it out.

I've got a house bank of 1000 Ah of Rolls AGM batteries which means 500 Ah usable. I don't let the batteries go below 50% but it is a pain when the batteries approach this figure at the end of a day. What to do? Run the generator a couple hours (most expensive electricity ever) or let the batteries go below 50% (and shorten their lives) and just charge them from the main on the next days run?

I stumbled on a post suggesting that pulling the batteries below 50% wasn't that big a deal - https://tab-rv.vanillacommunity.com/discussion/9940/agm-battery-depth-of-discharge-myth-busted I then dug into the Rolls data sheets.

My Rolls AGMs list an expected life of ~1200 cycles at 50% depth of discharge. That translates to 1000 * .5 * 1200 = 600K Ah. At a routine 80% DOD the expected cycles drop from ~1200 to ~675 cycles - almost a 50% decrease. However, the usable Ah in this case are 1000 * .8 * 675 = 540K Ah. That is just 10% less than the 50% DOD number. Looking at total Ah available rather than cycles suggests that going below 50% DOD occasionally - or maybe regularly - isn't that big a deal.

Another conclusion I've reached from this is I spend too much time worrying about the batteries. I'm just going to use them as I want (within limits) and replace them when needed.

The models they use for those projections are purely mathematical... that is why 50% seems to be the same throughput as lower DoD's..A once in a blue moon discharge to 80% DoD is ok but recharge to 100% ASAP..

 

[Mako]

Ah, I miss the good o' days when I had a big bank of eight 8D's connected to a huge 3kW transformer inverter from (I'm guessing) either WW2 or the Crusades. I ran the heck out of it, barely watered them, and just had a ball.

Ignorance is so wonderful sometimes!

 

[OldDan1943]

West marine 4D batteries are made by West Penn mfg.
Opinion?
https://www.westmarine.com/buy/west...m-battery-198-amp-hours--15020266?recordNum=2

 

[rslifkin]

East Penn generally makes good batteries. Their 12v "deep cycle" AGMs aren't particularly heavy duty deep cycles, but they're not bad batteries by any means. I've had them last many years as starting batteries.

 

[Bacchus]

I've used many East Penn battys in different configurations and been satisfied for the price point.,yes you can butb"better" quality battys but at 1.5X - 2X $$ I don't find them a better economical alternative.
My 3 AGM 8Ds are in their 9th season and still doing well.
I put 8 AGM Duracell 6V GCs in my motorhome and doing well but only a few years use do far.
I do pay attention to recharge after depleting and use maintainers in storage when possible.
Boat is stored for winter with no power available. My AGMs are typically at 12.5-12.7 V after 6 mos storage.
I have seen note from CMS that he has seen issues with East Penn andcI value his experience. So far I'm very satisfied but I would NEVER pay West Marine price for them.
NAPA 8D AGM by EP is 100$ less than WM for more batty.
https://www.napaonline.com/en/p/BAT...qYAhbj45JVlpE947vhoCYKsQAvD_BwE&gclsrc=aw.ds&

 

[O C Diver]

I switched to Fireflys last fall in part because of their 1,000 cycle 80% discharge rating. Not having to recharge them 100% each time is also attractive. Normal usage is a less than 50% discharge and 100% recharge on any day the boat is under way.

Ted

 

[BruceK]

...So, lithium battery proponents, please explain to me, and others similary situated, how lithium would be life-changing...

It might be truly life changing for a bipolar battery user, lithium carbonate being a prescribed mood stabilizer.

Seriously though, a well managed bank of LA, flooded, sealed or better still in AGM, can be an excellent easily managed economic storage source. I`ll happily make the AGM transition but Lithium is a big step. Fortunately we are finding more of it in Australia, prices and demand are rising, it`s not without attractions.

 

[Simi 60]

Seriously though, a well managed bank of LA, flooded, sealed or better still in AGM, can be an excellent easily managed economic storage source.. .

Yeah but it's not.
Have you tried pricing up a decent sized AGM bank in Oz recently?

It's why we went Lifepo4,
Double the useable amp hours in LFP for less coin than 8 X 220ah replacement AGM

I`ll happily make the AGM transition but Lithium is a big step

Actually, it was pretty easy.
Prior research was essential

 

[CMS]

FWIW when I discuss batteries, how they last perrform etc. it is all based on many years of testing marine and RV batteries to BCI testing standards..My business was perhaps the first marine electrical business to invest in discharge testers..It has allowed me to see first hand how depth of discharge affects battery life..



For example a 105Ah East Penn AGM 4/2018 date code tested on 11/2018 t at just 67.42Ah...Owner estimates 25 deep cycles to 50%..This was on a GB32 trawler not a sailboat..

For those wondering about LiFePo4 this is the testing of my 400Ah cells at year 13 and 2000+ cycles most to at least 80% DoD...I built that bank in 2009 for just about 2k...

 

[DDW]

CMS - you have to come spoil all those marvelous opinions with cold facts .

Diver - the only problem with Fireflys is they are no longer available.

 

[ranger58sb]

Diver - the only problem with Fireflys is they are no longer available.

FWIW, the note on Ocean Planet's website suggests the Victron Energy Super Cycle batteries may offer features similar to Firefly.

-Chris

 

[catalinajack]

Inordinate is a relative term. There have been a number of discussions about when LFP is more/less beneficial, and not everyone's usage patterns benefit the same. Is my usage "inordinate"? Maybe to some, but I would call it "convenient".





You, and many others have run like this for decades.





In your case, the benefit would be shorter generator run times. Does that matter to you? At this point it would seen not, which is fine.




Cycles aren't meaningless or a flowed concept. They are just an incomplete metric for lifespan. FLA/AGM published cycle life is always based on a DOD, typically 50%. More complete specs will plot cycle life vs DOD, and that's the more complete story showing the range of usage available, and showing that 50% DOD is just one usage pattern, not the only usage pattern.


LFP is no different. 2500 cycles at 100% DOD has been proven over and over again for about 20 years now. And that's under much more abusive operation that any house battery bank will ever see. That's already about 5x the lifespan of lead, and only grows with more gentle use.





And that's all good.

And TT, that is pretty much what I have been trying to say all along. Lithium makes sense for some folks and not so for others. But, I think there are many more boaters who cruise in the manner in which we do rather than those folks who stay out for extended periods of time. And, yes, I understand the benefits of solar and less generator run time. I just don't care. The fact is that lithium would not change my life in any significant way but I do understand that, for others, lithium does. What I object to is definitive statements that something IS when, in fact, the answer is more likely "it may be". It all depends, does it not?

 

[rslifkin]

And TT, that is pretty much what I have been trying to say all along. Lithium makes sense for some folks and not so for others. But, I think there are many more boaters who cruise in the manner in which we do rather than those folks who stay out for extended periods of time. And, yes, I understand the benefits of solar and less generator run time. I just don't care. The fact is that lithium would not change my life in any significant way but I do understand that, for others, lithium does. What I object to is definitive statements that something IS when, in fact, the answer is more likely "it may be". It all depends, does it not?

It also depends on the boat. For some, reduced space and weight for batteries is enough of an advantage. For others, it doesn't really matter.

 

[EngNate]

60% is not a big change from 50%. The Rolls site has a graph. If you calculate total Ah delivered over the service life there is little difference between 50 and 70% discharges. If you're trying to make one bank last as long as possible the less discharge the better. But if you're looking at the ongoing long term cost per Ah used, a higher discharge comes out better figuring in that fewer batteries are used.

 

[CarlF]

I think what’s being lost in this discussion is the special problem of PSOC (partial state of charge) sulfation ONLY in AGM’s used for a house bank. This is not a significant problem in flooded or even gels. It’s only a an issue for deep discharged AGM’s (AGM’s make great start batteries since the aren’t deep discharged)

As Rod says, AGM’s can be “murdered” in less than a year by PSOC. This isn’t minor gradual capacity loss but 80%+ capacity loss. It is unmistakable. I’ve had it happen twice to a two year old house bank despite never discharging below 50% and meticulously following the manufacturers recommendations.

If you plug into a marina almost every night you won’t ever experience this. It happens if you regularly anchor out for 3-4 days. Neither solar, genset, or alternators provide enough hours of float to prevent PSOC (unless you run your genset all night or run your engines 6+ hours between anchorages)

As this is the kind of cruising I do, I gave up on AGM’s as a house bank. I went to gels and was very happy. With my new boat I used LFP and am even happier.

 

[Bmarler]

I think what’s being lost in this discussion is the special problem of PSOC (partial state of charge) sulfation ONLY in AGM’s used for a house bank. This is not a significant problem in flooded or even gels. It’s only a an issue for deep discharged AGM’s (AGM’s make great start batteries since the aren’t deep discharged)

As Rod says, AGM’s can be “murdered” in less than a year by PSOC. This isn’t minor gradual capacity loss but 80%+ capacity loss. It is unmistakable. I’ve had it happen twice to a two year old house bank despite never discharging below 50% and meticulously following the manufacturers recommendations.

If you plug into a marina almost every night you won’t ever experience this. It happens if you regularly anchor out for 3-4 days. Neither solar, genset, or alternators provide enough hours of float to prevent PSOC (unless you run your genset all night or run your engines 6+ hours between anchorages)

As this is the kind of cruising I do, I gave up on AGM’s as a house bank. I went to gels and was very happy. With my new boat I used LFP and am even happier.

Interesting. What brand of agms were you using?
I’ve had very good luck with agms on previous boats and am thinking of using them to replace the aging fla Trojans I’m running now. Since a need 16 batteries I’m taking the decision seriously. If my bank only lasted two years I’d be extremely unhappy.
I do the same 2-4 days out at a time, and monitor my batteries continuously. I’m eventually going to install solar on the pilothouse roof to help keep them topped off.
I was thinking two 400 watt panels for starters.

 

[LargeMarge]

2003, we installed eight Concord Lifeline 105ah AGMs.
Our photovoltaic -- six 305-Watt, a total of 1,830-Watts.
.
We boondock exclusively.
We never saw much need for a genset.
.
Early on, we realized we have more juice than we need.
We accomplished this two ways:
* eliminating wasters
* using juice during mid-day sun, mostly by-passing the bank.
.
One of our brainiac chums calculated our draw.
Apparently, we rarely pull more than three percent (3%) from our bank.
.
We cook with induction hot-plates.
We heat water with electricity.
.
At no point are we 'doing without'.
We have everything we need, we just need less of it.
.
Our AGM bank is nearing its second full decade of full-time live-aboard.
In all those years, our only time of concern was near the Arctic, the sun low on the horizon for twenty-three hours every day.

 

[Simi 60]

2003, we installed eight Concord Lifeline 105ah AGMs.
Our photovoltaic -- six 305-Watt, a total of 1,830-Watts.

.
One of our brainiac chums calculated our draw.
Apparently, we rarely pull more than three percent (3%) from our bank.
.
We cook with induction hot-plates.
We heat water with electricity.
.
.

8 X 105 and using induction and electric hot water yet still only using 3%?
Something doesn't sound right but I could be wrong.

We had 8 X 220ah and 2500w of solar in sub tropical climates
Had electric hot water but NO induction and used a lot more than 3% - closer to 20%
We do have big refrigeration.

 

[LargeMarge]

8 X 105 and using induction and electric hot water...using 3%?
Something doesn't sound right...

.
Excellent point.
.
Semi-retired welder-fabricator here.
Home-built, we are rigged *significantly* different than something from a factory.
.
We heat water using one of our 'sous vide' circulation heaters (we carry two for resilience).
We heat water in a dedicated three-gallon Torpedo keg, plenty for a shower.
Figure around 900-Watts for ten minutes, tapering to around 400-Watts as it nears the set-point.
At the set-temperature, it cycles at around 80-Watts.
.
And remember, we schedule our draw for mid-day, so much of our juice is straight out of the sky.
.
Our Torpedo keg is part of our extensive keg system:
For drinking and worshing water, we use stainless-steel five-gallon retired Pepsi kegs manufactured by the Cornelius Company.
These kegs are popular with home-brewers of beer and kombucha.
The Torpedo is a miniature version of the standard 'Corny keg'.
.
As we see it, this water system offer advantages over a yuge tank:
* modular -- our typical load is seven kegs, a total of 35-gallons... and we can add several dozen more.
* isolation -- if one gets stanky, the others stay in service... and are used to clean the problem-child.
* loanable -- a keg can go to somebody short on drinking water.
* portable -- a keg can go to the campfire or picnic-table or fish-cleaning board.
.
Corny kegs are engineered to be pressurized.
For us, a quick puff from a 12vdc bicycle-tire compressor, and water flows from the sink-sprayer designed for a stand-still house kitchen.
.
.
After a half-century of making-do in lesser factory 'mobile homes', our current full-time live-aboard is a culmination of everything we need but nothing else.

 

[ronobrien]

True unless running (alts), long gen runs ( for A/C?), solar or visiting a dock once / week.

I was going to suggest that the gen when at anchor for the bulk charge and solar (if equipped obviously) for the float charge. So basically, what he said.