Best 8d battery for full time liveaboard

[catalinajack]

Am I certain? Tell me how you become certain. As I understand battery science, it is all about replacing amps removed. In other words, when as many amps have been replaced as have been removed plus a few, then the batteries have become fully charged. Kindly re-education me if I am incorrect. In my case two days ago, it took 4.5 hours to fill my batteries back up with the same number of amps removed. Fact, after 4.5 hours my Magnum inverter-charger monitor indicated that the charger had moved on to the float stage, a pretty good indication that the batteries had been fully charged.

As for this 80%-50% "debate", think about this keeping in mind, in my case, that I have cycled my batteries to 50% and below 150 times in four years. A Trojan LA battery will last 1,000 cycles at 60%, 800 cycles at 70%, and about 700 cycles at 80% discharged. Now, someone please tell why I should be concerned about discharging my batteries below 50% fairly often which I don't anyway because my overnight power requirements are not such. Generally, we don't spend any more than three days without a full re-charge of the batteries so using them in the 50%- 90% range is also a non-factor. The bottom line for me, our use profile, is that I have no concern about flogging my batteries from time to time. Not doing so will not increase useful life to any degree I would care about. Really, is getting nine or ten years out of a set of batteries rather than eight years or even seven years a big deal? Not to this guy. Nor does running my generator for an extra hour or two bother me.

And, Simi 60, you are concerned about a premature failure? It's not like your batteries work one day and the next day they don't. No way would you ever be stranded by failed batteries.

Not a fixation as such but it is how it ended up
We have 8 x 250ah
6 X 250ah would have been borderline imho
There are no shops on the water so I don't want to rape them and have premature failure
Batteries are cheap, easier to get them in one go when its easy to get them.
If you lived aboard full time with no shore power like we do that would be more like 1450 cycles
How do you think they'd be holding up now?

.
Fully recharged?
Dont be to sure about that

It would be if all you relied on was genset or engine for charging, unless you run them right through the float cycle as well putting in minimal amps.


Quite possibly, they are an indicator imho, not truth

My victron says 100% SOC by midday yet solar appears to smash in amps for several more hours. On these days I wake up at 6am and voltage reads 24.3v and above 83% SOC
On days where there is little or no sun in the afternoon, so missing out on the "extra" even though the batteries SOC says 100% at 4pm the alarm is beeping at 6am and voltage reads around 23.1v but still above 80% SOC

 

[mvweebles]

But I have a hard time with the (ignorant)physics of LiFePO4 technology. Ultimately energy is heat.....or the other way around. It is hard to imagine 23 pounds absorbing the heat required of the task we are asking of them.

Things change, and battery technology has certainly changed a LOT over the last 25-years. See attached picture

OP: For full-time liveaboard, LFP batteries make financial sense. Consider:

1. FLA batteries for the most part have a max life of around 500-700 cycles. LFP 5000+
2. Depth of Discharge (DoD) on FLA should not go below 50%. LFP are fine down to 80% or more. That means fewer batteries are needed.
3. LFP batteries are smaller, lightweight, maintenance free, and can be mounted in any orientation. That means they can be moved to a lessor-used part of your boat opposed to consuming valuable engine room real estate.

So yea, LFP are 3x-4x more expensive, but they last 8x longer. Bad news is you may need to change your charger and of course cabling will be different.

But, to answer your original question on 8Ds......

When I bought Weebles, a sistership to your Willard 36 in 1998 (which I lived aboard for 5-years), she had a pair of 8Ds mounted between the stringers forward of the engine - arouond 450 AH capacity (225AH useable). A few years in, I replaced with three 8Ds which was a herculean effort even when I was young and in good shape.

After that, I went to six T105 6v batteries (600AH/300AH useable). The T105s are a little taller than the 8Ds, but generally fit in the same space. I built-up a replacement battery box to house them.

A goal of my inflight refit is to gain engine room space and make the machinery more accessible. Similar to Comodave, I am going LFP - I have seven 100AH LFP batteries that I've relocated to the aft Lazarette. So I have gone from roughly 600 AH of FLA (300AH usable) to 700AH LFP (600AH useable). I shed over 400 lbs of weight, and gained engine room space. Yes, carried a hefty price tag, but as Comodave says, good for a loooong time.

I'm hoping this is my final battery swap in Weebles. I've also installed 800W of solar and a new Magnum 3kw hybrid inverter/charger. I have a separate AGM start battery for my main engine, and a separate pair of AGMs for thruster/windlass/generator. Because of different battery chemistry, I have a DC-DC charger between the LFP house and the AGMs.

Peter

 

[catalinajack]

Mister Weebles, your statement that "FLA batteries for the most part have a max life of around 500-700 cycles" is at odds with Trojan's data sheets. Their FLAs are projected to last 1,500 cycles at 40% Depth of Discharge, 1,200 cycles at 50%, and 700 cycles at 80% DOD. Obviously, useful life is dependent upon DOD. So, even if one would flog their batteries consistently down to 30 or 20% one hundred times per year, which is far more than that for many boaters, the batteries would still last from five to seven years. LFP batteries make financial sense only for those who plan to keep their boat for at least fifteen years. LFPs also make sense for the space-challenged.

Things change, and battery technology has certainly changed a LOT over the last 25-years. See attached picture

OP: For full-time liveaboard, LFP batteries make financial sense. Consider:

1. FLA batteries for the most part have a max life of around 500-700 cycles. LFP 5000+
2. Depth of Discharge (DoD) on FLA should not go below 50%. LFP are fine down to 80% or more. That means fewer batteries are needed.
3. LFP batteries are smaller, lightweight, maintenance free, and can be mounted in any orientation. That means they can be moved to a lessor-used part of your boat opposed to consuming valuable engine room real estate.

So yea, LFP are 3x-4x more expensive, but they last 8x longer. Bad news is you may need to change your charger and of course cabling will be different.

But, to answer your original question on 8Ds......

When I bought Weebles in 1998, she had a pair of 8Ds mounted between the stringers forward of the engine - arouond 450 AH capacity (225AH useable). A few years in, I replaced with three 8Ds which was a herculean effort even when I was young and in good shape.

After that, I went to six T105 6v batteries (600AH/300AH useable). A goal of my inflight refit is to gain engine room space and make the machinery more accessible. Similar to Comodave, I am going LFP - I have seven 100AH LFP batteries that I've relocated to the aft Lazarette. So I have gone from roughly 600 AH of FLA (300AH usable) to 700AH LFP (600AH useable). I shed over 400 lbs of weight, and gained engine room space. Yes, carried a hefty price tag, but as Comodave says, good for a loooong time. I'm hoping this is my final battery swap in Weebles. I've also installed 800W of solar and a new Magnum 3kw hybrid inverter/charger. I have a separate AGM start battery for my main engine, and a separate pair of AGMs for thruster/windlass/generator. Because of different battery chemistry, I have a DC-DC charger between the LFP house and the AGMs.

Peter

View attachment 111063

 

[mvweebles]

Mister Weebles, your statement that "FLA batteries for the most part have a max life of around 500-700 cycles" is at odds with Trojan's data sheets. Their FLAs are projected to last 1,500 cycles at 40% Depth of Discharge, 1,200 cycles at 50%, and 700 cycles at 80% DOD. Obviously, useful life is dependent upon DOD. So, even if one would flog their batteries consistently down to 30 or 20% one hundred times per year, which is far more than that for many boaters, the batteries would still last from five to seven years. LFP batteries make financial sense only for those who plan to keep their boat for at least fifteen years. LFPs also make sense for the space-challenged.

Well, Trojan's data sheets are at odds with one another.

Here's a link that states 1600 duty cycles at 50% DoD.

Here's a link for Trojan that states 1200 cycles at 50% DoD.

And here's a Golf Cart review site that states 750 cycles.

If anyone thinks they are getting 1200 cycles (or even 750) out of set of 6V FLA batteries, they should be all means get them. All I can tell you is that as a full-time liveaboard and as an occasional cruiser, I ended up changing after 4-5 years, and that was only because I procrastinated for at least a year (maybe two). They really needed to be replaced long before, it's just such a pain in the ass with those heavy suckers that I waited.

Peter

 

[catalinajack]

Peter, all I can tell you is this. We are full-time liveaboards and are way more than occasional cruisers. We completed the Great Loop, 5,500 miles, a year ago or so. Our eight Deka FLA golf car batteries are nearly fours years old and are still going strong even though these batteries have been abused from time to time. I fully expect to get three or four more years out of them but, even if it is fewer, I care not. For about one boat unit I will have a new bank good until I am well over 80 years old (70yo now) and for another boat unit, approaching 90yo. Why would I spend three or four times that amount for LFPs? Bad investment. LFPs make sense for some, but not many at today's prices.

Well, Trojan's data sheets are at odds with one another.

Here's a link that states 1600 duty cycles at 50% DoD.

Here's a link for Trojan that states 1200 cycles at 50% DoD.

And here's a Golf Cart review site that states 750 cycles.

If anyone thinks they are getting 1200 cycles (or even 750) out of set of 6V FLA batteries, they should be all means get them. All I can tell you is that as a full-time liveaboard and as an occasional cruiser, I ended up changing after 4-5 years, and that was only because I procrastinated for at least a year (maybe two). They really needed to be replaced long before, it's just such a pain in the ass with those heavy suckers that I waited.

Peter

 

[twistedtree]

I am no fan of 8Ds. But I have a hard time with the (ignorant)physics of LiFePO4 technology. Ultimately energy is heat.....or the other way around. It is hard to imagine 23 pounds absorbing the heat required of the task we are asking of them. Again....totally ignorant observation on my part.

I can help a bit with this. The LFP battery actually generates LESS heat, not more.


The heat generated by a battery depends on it's efficiency, not it's capacity or physical size. With an ideal battery, if you put 100Ah into it while charging, you could pull 100Ah out of it, and it would generate zero heat.


But of course batteries aren't ideal. A LA battery is roughly 85% efficient. If you charge it with 100Ah, you can only take out 85Ah. The difference becomes heat generated within the battery, some while charging, and some while discharging. In this example, the lost 15Ah at 12V would be 180W to be dissipated by the battery.


In contrast, an LFP battery is 98% efficient. So if you put in 100Ah, you can pull out 98Ah, and only 2Ah at 12, or 24W of heat is generated and needs to be dissipated.

 

[Woodland Hills]

Rolls brand flooded lead acid batteries from Pascoe in Maryland.

 

[Simi 60]

Am I certain? Tell me how you become certain.

This is how I became certain.
As mentioned, on a cloudy or no sun day I can run the genset, see the charge go from 100+ amps @80% SOC down 30 amps @ 100% SOC and full ah replacement but is that fully charged?


If it is, how come on solar I get to see it going from 100+ amps @80% SOC down to 30 amps @100% SOC yet continue pushing amps in until the battery's are finally only accepting a couple of amps?
That to me suggests they are now fully charged.

That and the fact that on genset days, the next morning a 23v alarm is beeping and on solar days in the morning the batts still read 24+v tells me that 100% is not necessarily 100%

And, Simi 60, you are concerned about a premature failure? It's not like your batteries work one day and the next day they don't. No way would you ever be stranded by failed batteries.

I have had start batteries that started the engine, lifted the anchor, let me motor 2 miles to a fuel dock yet 1 hour later wouldn't start the engine.

There's an example of stranded by failed batteries

On the house bank if I had a borderline sized bank and ran it down to 50% and the next day it was raining and I had a genset issues and could not start it to charge batteries, whilst not stranded I would have refrigeration and freezers shutting down soon after losing several months of supplies and horror of horrors, warm beer.

At least with an oversized battery bank (I prefer to think of it as correctly sized) I can squeeze an extra day and hopefully get sun or genset on the next.

 

[cks]

IMO, Lifeline are the best 8D’s

 

[fgarriso]

Does cost come into this anywhere?

 

[Baker]

I can help a bit with this. The LFP battery actually generates LESS heat, not more.


The heat generated by a battery depends on it's efficiency, not it's capacity or physical size. With an ideal battery, if you put 100Ah into it while charging, you could pull 100Ah out of it, and it would generate zero heat.


But of course batteries aren't ideal. A LA battery is roughly 85% efficient. If you charge it with 100Ah, you can only take out 85Ah. The difference becomes heat generated within the battery, some while charging, and some while discharging. In this example, the lost 15Ah at 12V would be 180W to be dissipated by the battery.


In contrast, an LFP battery is 98% efficient. So if you put in 100Ah, you can pull out 98Ah, and only 2Ah at 12, or 24W of heat is generated and needs to be dissipated.

The only thing I was getting at was the whole E=MCsquared thing. Maybe the LFP equation changes the "C"...but usually it is heat.

 

[catalinajack]

Wire your house bank to start your engines then you won have a failure.

This is how I became certain.
As mentioned, on a cloudy or no sun day I can run the genset, see the charge go from 100+ amps @80% SOC down 30 amps @ 100% SOC and full ah replacement but is that fully charged?


If it is, how come on solar I get to see it going from 100+ amps @80% SOC down to 30 amps @100% SOC yet continue pushing amps in until the battery's are finally only accepting a couple of amps?
That to me suggests they are now fully charged.

That and the fact that on genset days, the next morning a 23v alarm is beeping and on solar days in the morning the batts still read 24+v tells me that 100% is not necessarily 100%



I have had start batteries that started the engine, lifted the anchor, let me motor 2 miles to a fuel dock yet 1 hour later wouldn't start the engine.

There's an example of stranded by failed batteries

On the house bank if I had a borderline sized bank and ran it down to 50% and the next day it was raining and I had a genset issues and could not start it to charge batteries, whilst not stranded I would have refrigeration and freezers shutting down soon after losing several months of supplies and horror of horrors, warm beer.

At least with an oversized battery bank (I prefer to think of it as correctly sized) I can squeeze an extra day and hopefully get sun or genset on the next.