Most sustainable electrical setup

[john61ct]

Originally Posted by alansmith

is it true that true golf cart batteries (true deep cycle) can be discharged to 20% SOC without damaging them?

Sure if by "damage" you mean immediate.

The deeper your **average** draw the shorter their lifespan - all batteries.

For lead the guideline is

Stop discharging at 50% in normal cycling; only go lower for occasional exigencies.

If your setup needs the weight reduction, then go smaller and replace more frequently.

If you can carry more weight NP **and** replacing is a PITA, then size for shallower cycling.

[john61ct]

Originally Posted by alansmith

Dock head, FYI, I just bought two 6 volt 240amp/hr at 20 hours for 300 dollars on the nose. This is at Batteries Plus Bulbs in Richmond calif. That equals 1.25 per amp

The Duracell (Deka/EPM) FLA are great quality deep cycling, usually cheaper than that ~$200 a pair for well over 200Ah.

As good as Trojan T105 IMO.

[john61ct]

Originally Posted by Pizzazz

I stand corrected regarding the cycles... LifePO4 is really different from Li-Ion, 2000 vs. 400 cycles

And that 2000 is a very low estimate, more for stressful propulsion use than coddled House banks.

But stuff can happen that kills them early too, so a pretty risky bet compared to lead - in the NA market where good lead is so cheap.

[Dockhead]

Originally Posted by john61ct

And that 2000 is a very low estimate, more for stressful propulsion use than coddled House banks.

But stuff can happen that kills them early too, so a pretty risky bet compared to lead - in the NA market where good lead is so cheap.

Do you have data on that? What "stuff"?


I don't actually believe that LiFePo4 banks with a well designed BMS will EVER get killed prematurely. I've never actually heard of a case. Whereas lead with no safeguards at all can be killed in a day. So I would disagree with you on this -- I think the risk of killing a well set up LiFePo4 bank is orders of magnitude less than with lead.



We tend to think that BMSs are a lithium thing, but they would equally benefit lead battery banks and would prevent a lot of battery-murder. If I had a dollar for every lead-acid battery bank I killed during my cruising life . . . If I were to continue using lead, I would definitely set up some kind of HVC, LVC, and automatic cutoff in case of overheating.

[Dockhead]

Originally Posted by john61ct

The Duracell (Deka/EPM) FLA are great quality deep cycling, usually cheaper than that ~$200 a pair for well over 200Ah.

As good as Trojan T105 IMO.

In your opinion based on what?


I know a number of people who use these batteries and are happy with them as a good value, but no one who thinks they are equal to the premium Trojans.

[john61ct]

Originally Posted by Dockhead

What "stuff"?

I don't actually believe that LiFePo4 banks with a well designed BMS will EVER get killed prematurely. I've never actually heard of a case. Whereas lead with no safeguards at all can be killed in a day. So I would disagree with you on this -- I think the risk of killing a well set up LiFePo4 bank is orders of magnitude less than with lead.

We tend to think that BMSs are a lithium thing, but they would equally benefit lead battery banks and would prevent a lot of battery-murder. If I had a dollar for every lead-acid battery bank I killed during my cruising life . . . If I were to continue using lead, I would definitely set up some kind of HVC, LVC, and automatic cutoff in case of overheating.

The key phrase there is "well set up".

I see "a BMS" as a collection of functionality, which (should) include protections against:

temperature too high or too low
current too high, in or out
voltage too high or too low, pack level
vs individual cells, IOW too great an imbalance

Some sub-optimal cycling patterns or even "major events" outside those boundaries might only affect longevity, keeping you from getting the best value, high ROI over time

But really that is the least of your worries.

Some of them may render the bank **instant scrap**, and that can happen in the first season.

Some can even burn your boat down to the waterline, sure LFP is safer, **less** susceptible to thermal runaway than most other LI chemistries,

but it is not hard to turn them into an unquenchable ball of flame either.

That is all included in "stuff that can happen".

Having "a BMS" is by no means a guarantee it won't.

In fact relying on a single monolithic gadget too much is all too often **the cause** of stuff happening.

Yes of course an expensive lead bank can often benefit from better monitoring and protections, but most owners do just fine without, learning enough so that common sense is sufficient.

The other consideration is that a much cheaper lead bank is not such a big deal to replace if it's murdered in just a few years, rather than lasting a decade.

And, although yes lead batts can "explode" they do not burn like LFP can, fires more commonly start from shorts, wires melting, as can happen no matter the bank chemistry.

But back to LFP:

People spending say under a grand for their cells - and looking for a system they don't have to pay close attention to - often think that they are justified in spending under a couple hundred on the protective infrastructure, and expect "a BMS" to do the whole job.

Others may have $5-10K or even more invested, but do just fine without "a BMS", because they're willing to invest in a set of other discrete monitoring / protective / maintenance devices

as well as their ongoing **time & attention** to checklisted procedures, to gain the desired functionalities others expect from one OTS unit.

Electronic devices **all fail** eventually. Over a bank lifespan of maybe decades, it is pretty certain the electrickery bits will be the ones to start failing long before the cells do.

Many BMS and their FETs / contactors "failure modes" do not leave the bank / system in a safe state. It is up to the designer of the overall system to plan for all contingencies and ensure redundancy in the critical protections.

[john61ct]

Originally Posted by Dockhead

I know a number of people who use these batteries and are happy with them as a good value, but no one who thinks they are equal to the premium Trojans.

Trojan in general as a company has not been getting stronger in their balancing of "quality vs marketing".

And I did not say compared to the premium lines like RE.

Plain old regular T-105s, often available locally on sale for within 15% of the Dekas, sometimes even cheaper.

Sure all their FLA lines are dead solid, but I personally would not pay over 20% of a premium compared to the Duracell FLAs.

[Q Xopa]

Originally Posted by john61ct

Trojan in general as a company has not been getting stronger in their balancing of "quality vs marketing".

And I did not say compared to the premium lines like RE.

Plain old regular T-105s, often available locally on sale for within 15% of the Dekas, sometimes even cheaper.

Sure all their FLA lines are dead solid, but I personally would not pay over 20% of a premium compared to the Duracell FLAs.

Interesting opinions and conjecture. Some of them may even be correct.

It certainly is easy for anyone to make any old WAG unfounded statements.

But in the interest of posts here being as credible as possible. Lets try and deal in verifiable facts, or at least as close to them as possible, as previously requested if you could provide some facts/ studies/ credible sources, etc that has led you to your conclusions that would be much appreciated.

Or maybe your intuition?

Thanks.

[Dockhead]

Originally Posted by john61ct

. . . Sure all their FLA lines are dead solid, but I personally would not pay over 20% of a premium compared to the Duracell FLAs.

On the basis of what? What is your source for this information? Have you seen a cycle life chart for the Duracells? I think you haven't because Interstate or whoever makes them doesn't even publish one, the hallmark of a cheap battery producer. The golf cart guys who operate fleets of golf carts report getting 40% to 50% more cycles out of the Trojans which is why they are so often used in fleets despite the extra cost, in an application where every penny counts.


Sometimes, granted not always, you get what you pay for.

[john61ct]

Why would you put Interstate in the same sentence as the Duracells? Chalk and cheese that's a Deka/EPM brand, an excellent vendor for both FLA and GEL.

Interstate is not even a manufacturer, most if not all their relabelled batts are made by Johnson / JCI, not a true deep cycling batt in there anywhere afaic.

I stand by what I said, the Deka GCs are just as good value as T-105s, $/Ah/year, and usually a fair bit lower up front.

But if the Trojans are only 15-20% more, then I reckon it's six of one, half dozen the other.

[Dockhead]

Originally Posted by john61ct

The key phrase there is "well set up".

I see "a BMS" as a collection of functionality, which (should) include protections against:

temperature too high or too low
current too high, in or out
voltage too high or too low, pack level
vs individual cells, IOW too great an imbalance

Some sub-optimal cycling patterns or even "major events" outside those boundaries might only affect longevity, keeping you from getting the best value, high ROI over time

But really that is the least of your worries.

Some of them may render the bank **instant scrap**, and that can happen in the first season.

Some can even burn your boat down to the waterline, sure LFP is safer, **less** susceptible to thermal runaway than most other LI chemistries,

but it is not hard to turn them into an unquenchable ball of flame either.

That is all included in "stuff that can happen".

Having "a BMS" is by no means a guarantee it won't.

In fact relying on a single monolithic gadget too much is all too often **the cause** of stuff happening.

Yes of course an expensive lead bank can often benefit from better monitoring and protections, but most owners do just fine without, learning enough so that common sense is sufficient.

The other consideration is that a much cheaper lead bank is not such a big deal to replace if it's murdered in just a few years, rather than lasting a decade.

And, although yes lead batts can "explode" they do not burn like LFP can, fires more commonly start from shorts, wires melting, as can happen no matter the bank chemistry.

But back to LFP:

People spending say under a grand for their cells - and looking for a system they don't have to pay close attention to - often think that they are justified in spending under a couple hundred on the protective infrastructure, and expect "a BMS" to do the whole job.

Others may have $5-10K or even more invested, but do just fine without "a BMS", because they're willing to invest in a set of other discrete monitoring / protective / maintenance devices

as well as their ongoing **time & attention** to checklisted procedures, to gain the desired functionalities others expect from one OTS unit.

Electronic devices **all fail** eventually. Over a bank lifespan of maybe decades, it is pretty certain the electrickery bits will be the ones to start failing long before the cells do.

Many BMS and their FETs / contactors "failure modes" do not leave the bank / system in a safe state. It is up to the designer of the overall system to plan for all contingencies and ensure redundancy in the critical protections.

The key phrase "well set up" applies to any onboard system. If the oil pump goes out on your diesel engine, the engine will be ruined. Of course we presume that it's well set up.



Why is this something which makes it more likely that lithium banks will get killed than lead banks? A lithium bank can be run without a BMS or other protections just like a lead bank can, and many people do this. Adding a BMS (to either lead or lithium) massively reduces the risk of killing the bank. The small chance that the BMS fails does not make that setup worse than a plain lead bank with no BMS.



And what "checklisted procedures" are you talking about? One of the beautiful things about lithium is that it is far simpler to manage than lead. You don't have different charging phases and you don't care about partial state of charge. All you have to do is keep an eye on voltages and temperatures to verify that everything is going the way it should, something most of us already do with lead batteries (and we have to, without a BMS).



And lastly why do you think all of the basic protections need redundancy? The BMS by itself has massively reduced the risks. I will not be making any redundant protections on my system -- it's not needed and it's overcomplication, which brings its own drawbacks. Don't get carried away with all this -- my lithium bank, usable amp hour for usable amp hour, will cost no more than a bank of Trojan T105's, €2736 to be exact, for premium consecutive serial numbers fresh Winston cells from the premier European supplier. Why would I spend thousands and hundreds of hours of engineering time to mitigate a 1 in a 1000 risk of a BMS failure plus simultaneous charging source failure killing that bank? That's the cost of two tanks of fuel, for goodness sake -- that's a risk I can take with those odds.



You do understand, don't you, that a BMS failure by itself, will not kill the bank? You would have to have a BMS failure which you don't notice (most of them give an alert when they fail) PLUS a failure of a charge source, at the same time. The risk of this is vanishingly small. Charging source failure will kill a lead bank just like it will a lithium bank, and 99% of cruisers out there with lead have zero protection against this other than keeping an eye on voltage, including those with expensive premium AGM and gel batteries which are far more expensive than lithium. The BMS is a whole extra layer of protection just by itself; there is no need to make it more complicated than that.

[john61ct]

People talk about getting the BMS to regulate the charge source(s)

which is when redundancy becomes important.

Obviously there is no one black and white here, just degrees of investment and aversion to risk, on most points we agree.

This all started from someone asking "what could possibly go wrong?" to prevent an ROI that will take 20+ years.

I think that got answered at least from my POV.

Your rig your choices!

[Dockhead]

Originally Posted by john61ct

People talk about getting the BMS to regulate the charge source(s)

which is when redundancy becomes important.

Obviously there is no one black and white here, just degrees of investment and aversion to risk, on most points we agree.

This all started from someone asking "what could possibly go wrong?" to prevent an ROI that will take 20+ years.

I think that got answered at least from my POV.

Your rig your choices!

But I think controlling the charge source from the BMS may also be a reasonable approach, although that's not what I will be doing. The better BMSs like Batrium fail safely, shutting down charge source and giving an alarm, in case of failure. The risk of some bank-killing event with a device like that is vanishingly small.



And how do you get 20+ years ROI? If it costs the same per usable AH of capacity, then the ROI is 0. If you kill all the cells in 5 years you will still be ahead of the game, compared to 4 years you would normally get with lead. If a pack of LiFePo cells cost $50,000, I might understand some of your reasoning, but they don't cost like that. The don't cost more than quality lead batteries. In my case, they cost the price of two tanks of fuel. More or less pocket change in the context of the cost of running a boat like this.



I think it is not right to overthink this. Lithium power is not actually rocket science. It's merely different from lead, requiring changing some habits of thought.

[john61ct]

You are not in the NA market are you

[Dockhead]

Originally Posted by john61ct

You are not in the NA market are you

Correct, but I seriously doubt that it is much different there.


In Europe, it looks like this:



The cost per usable AH is based on 80% usable (rather conservative) for lithium vs 50% usable for Trojan.

The comparison is a little complicated because you do have some emergency reserve below 50% SOC with lead, which you don't have with lithium. On the other hand, when off grid you will rarely be getting up to 100% so your usable power may actually be 35%, not 50%.

You could bring in some el-cheapo golf cart batteries like the Sam's Club ones and that will look somewhat cheaper on a usable AH basis but that is not a reasonable comparison -- cycle life will be much less and resistance to accidents much less -- we are comparing brand new fresh serially numbered premium LiFePo4 cells.


Another point on the economics of lithium, and maybe the most important point -- due to the high charge acceptance and total lack of inefficient absorption charge you will save a ton of generator hours with lithium. It costs me about €4/hour to run my generator including fuel, maintenance, and amortization. That actually dwarfs the cost of amortization of the batteries -- one cycle of use of a 300 amp lithium bank costs €0.86 (based on 2000 cycle life) whereas it will cost about €8 to produce the power to charge it. To charge a lead bank to 100% takes hours and hours of generator use, which is why you don't do it, consciously killing the batteries with PSOC cycling -- because killing the batteries is cheaper (and more pleasant) than all those generator hours.



This issue doesn't exist ONLY for those who have a vast abundance of solar power which significantly outproduces the daily power needs. It's possible to have this on a catamaran, or on a mono where you don't care about upwind sailing ability so you don't mind putting on a huge arch. But even in such cases, you're not saving any money with quality lead vs. lithium, at least not in Europe.