Most sustainable electrical setup

[GoneDiving]

Originally Posted by Pizzazz

, easy to monitor and charge and if used in the bulk charge region, give comparable performance to lithium (ie efficient charging and discharging in the 20-80% state of charge range). If you abuse your batteries, they will last 400-500 cycles or two years if used every day, otherwise much longer.

Would you expand upon this please.

I'd agree that when designing a system where every AH is precious, charge/ discharge round trip efficiency would be an important consideration.

Everything I have read and been told has had Lead batteries having dramatically shortened service life if kept at the lower SOC where their charge/discharge efficiencies are highest. In contrast, Lithium has its greatest service life when operated at <80% SOC.


Thanks

"Partially discharged batteries should be re-charged as soon as possible. Damage is caused by leaving them in a partial state-of-charge …the lower the charge; and the longer a battery is left in a discharged condition – the greater the damage.

It is safe to cycle a battery between 50% SOC and 80% SOC – it is quite efficient to do so, too. But this kind of cycling cannot be continued for extended periods."

https://www.victronenergy.com/live/drafts:battery_life

[Pizzazz]

There are many sources on the web. Consider this reference, looks legit.



https://iopscience.iop.org/article/1...9/1/012134/pdf


Key points:
1. If you discharge 80-50%, you will get double the life vs. discharging 80-20%, other factors being equivalent.

2. Batteries really get murdered by high temperature (above 15C).

3. Lithium batteries also have a lifecycle limit, especially if they are driven at high charge/discharge rates.

My conclusions are:

It is so easy to murder batteries, just get the lowest capacity that meets your needs (in my case 20A current draw for I20 which means at least 400AHrs or 4 golf carts) and replace the batteries as often as needed.

The other approach is to convince yourself of a 10 year business case, invest huge amounts and hope you break even in year 8 or 12. I do not understand people who do that but if it makes them happy

[john61ct]

It is **lead** batteries that must get back to Full as often and quickly as possible.

That 80-20% range for LFP is way too conservative, if using true usable Ah capacity rather than guesstimating, sacrificing way too many expensive Ah for nothing.

Charge to 3.45Vpc and stop is very gentle and conducive to longevity.

Depending on your charge rate, you will be between 95 and 99% SoC.

Stop discharging well before the bank ends up at 3.0Vpc **at rest**

High C-rate loads can go lower, as long as upon stopping the sagging V bounces back above 3V

That will be between 10-15% SoC compared to the minimum V spec on the data sheet.

Assuming otherwise well cared for, gentle sub-C House usage, no fast charging etc

you might get 5000+ cycles, and only sacrificing what 20% of capacity.

Of course if you **do** end up cycling even more "in the middle" you may get even longer life, but that is not something worth planning for, for most owners.

[Pizzazz]

I don’t know much about lithium batteries but if you read the article above it says how difficult it is to estimate battery life accurately. So, when I hear 5,000+ cycles which will be equivalent to 15 years if cycled every day I feel skeptical. Consider phone lithium batteries. Typical discharge rates are around 20% capacity (phone lasts for 5 hours), typical charge rates are around 50% C (typical charge time is two hours) and the batteries are usually dead after 2 years (600 cycles). Usage on a sailboat will be similar (unless you oversized the lithium but then the economics will not work). And you are telling me that I should hope for a 15 year life when my phone can barely manage 2 years? It does not compute for me.

Also, regarding cycling, we can not cycle 99% to 1% on a sailboat with any battery system. A golf cart you can run dead on the course and then tow back to the garage. On a sailboat you need the reserve, so most people will only use 80-20.

[Pete7]

Originally Posted by Pizzazz

2. Batteries really get murdered by high temperature (above 15C).

There is no chance that batteries won't regularly exceed 15c on a yacht or motorboat.

On New Years day with water and air temperatures at 8c the battery temperature rose to 18c after 3 hours of gentle motoring despite being bitterly cold outside. Consider what happens during a long motor across the med or through the ICW in the height of summer.


Pete

[valhalla360]

Originally Posted by Mr O

As others have mentioned, forget the 3 way fridge..

As a monohull, propane fridges are not appropriate as they need to be reasonably level but on cats, they make for a great option.

No they aren't crazy expensive like marine fridges and a 20lb tank can keep it running for 3-4 weeks away from shore power.

Yes, they have to be installed properly and that should include a propane detector but if you have a propane stove, you already need that.

We had one for 10yrs (on a boat that was 12yrs old when we bought it, it was original manufacturers equipment and no problem passing survey/insurance). Worked great never gave us any problems...and no we didn't blow up.

[Dockhead]

Originally Posted by Pizzazz

I beg to differ. Lithium has advantages for sure but it is more expensive. We had a long thread a year ago, I remember a number approx. 7x more expensive for lithium vs. golf cart batteries. Some people claim a lower number. Golf cart batteries are cheap $1/AHr, easy to use, easy to monitor and charge and if used in the bulk charge region, give comparable performance to lithium (ie efficient charging and discharging in the 20-80% state of charge range). If you abuse your batteries, they will last 400-500 cycles or two years if used every day, otherwise much longer. When you are ready to replace, just plunk $400 and you have a decent size fresh bank.

Where do you get those numbers? In Europe, we pay €4.57 per nominal AH at 12v, for top notch Winston LiFePo4 cells. Trojan T105's cost €3.19. But if you factor in USABLE capacity, nominal * 80% vs nominal * 50%, then the cost per usable AH is €5.49 for lithium vs. €6.39 for golf car batts. That doesn't even get into the longer cycle life. And the comparison will be very different if you compare some kind of premium AGM or gels, too.


Lithium is definitely cheaper than lead, at least in Europe. Without even considering the longer cycle life.

[Dockhead]

Originally Posted by Pizzazz

There are many sources on the web. Consider this reference, looks legit.

https://iopscience.iop.org/article/1...9/1/012134/pdf
Key points:
1. If you discharge 80-50%, you will get double the life vs. discharging 80-20%, other factors being equivalent.

2. Batteries really get murdered by high temperature (above 15C).

3. Lithium batteries also have a lifecycle limit, especially if they are driven at high charge/discharge rates.

My conclusions are:

It is so easy to murder batteries, just get the lowest capacity that meets your needs (in my case 20A current draw for I20 which means at least 400AHrs or 4 golf carts) and replace the batteries as often as needed.

The other approach is to convince yourself of a 10 year business case, invest huge amounts and hope you break even in year 8 or 12. I do not understand people who do that but if it makes them happy

I think it's a valid approach, to consider batteries throwawy (since it is so easy to kill them), buy the cheapest, change often. If that's what you like to do, no one can tell you you're wrong.


HOWEVER, I think there is some mythology going on here. LiFePo4 is not actually more expensive even than cheap T105's. Also, using a proper BMS (something which lead would benefit from just as much), you are far less likely to kill them. That will allow you to realistically get the long cycle life they are capable of, or at least a fair shot. But even if they last only 400 cycles, you have come out ahead.


https://adammunich.com/lithium-has-b...han-lead-acid/

[john61ct]

All depends on the market.

In the US quality lead is $1/Ah and even second-hand LFP is getting 4x that on eBay, just for bare cells.

[Pizzazz]

I think there are facts and there are personal preferences. Golf cart batteries in the US cost $1/AHr and they are universally available. They are very tolerant to abuse, undercharging, temp, etc. The article I referenced (scientific vs. the opinion quoted a few posts later) clearly states that there is a certain amount of chemicals in a wet cell battery and if you discharge to 50% you will likely get 1,000 cycles. If you check with vendors (I have, they say the same thing). If you keep your batteries cool and we’ll ventilated they will last for 2-3 years but high temperatures will shorten their lives rapidly. All comparisons to lithium assume 30% useable capacity for wet cells vs 90% useable capacity for lithium and 400-500 cycles vs. 2,000. This is a logically incorrect comparison. You either need to assume 60% useable capacity for wet cells and 400 cycles or 30% useable capacity and 1,000 cycles. Then lithium is more expensive. A wet cell battery needs a good charger and no BMS. A lithium needs a BMS. How many times do we need to go over this?

There are good uses for lithium such as high current draw (rarely needed on a boat) or light weight. But cost is squarely in favor of wet cells by a huge margin.

Again if lithium could give you 80% capacity after 2,000 cycles, how come most phones batteries need replacing after 1-2 years (Max 500 cycles?). Anyway, I do not want to preach like others or other threads but either do the research yourself or believe me that nothing gets close to the cost effectiveness of golf cart batteries on a cruising sailboat.

SV Pizzazz

[Dockhead]

Originally Posted by Pizzazz

I think there are facts and there are personal preferences. Golf cart batteries in the US cost $1/AHr and they are universally available. They are very tolerant to abuse, undercharging, temp, etc. The article I referenced (scientific vs. the opinion quoted a few posts later) clearly states that there is a certain amount of chemicals in a wet cell battery and if you discharge to 50% you will likely get 1,000 cycles. If you check with vendors (I have, they say the same thing). If you keep your batteries cool and we’ll ventilated they will last for 2-3 years but high temperatures will shorten their lives rapidly. All comparisons to lithium assume 30% useable capacity for wet cells vs 90% useable capacity for lithium and 400-500 cycles vs. 2,000. This is a logically incorrect comparison. You either need to assume 60% useable capacity for wet cells and 400 cycles or 30% useable capacity and 1,000 cycles. Then lithium is more expensive. A wet cell battery needs a good charger and no BMS. A lithium needs a BMS. How many times do we need to go over this?

There are good uses for lithium such as high current draw (rarely needed on a boat) or light weight. But cost is squarely in favor of wet cells by a huge margin.

Again if lithium could give you 80% capacity after 2,000 cycles, how come most phones batteries need replacing after 1-2 years (Max 500 cycles?). Anyway, I do not want to preach like others or other threads but either do the research yourself or believe me that nothing gets close to the cost effectiveness of golf cart batteries on a cruising sailboat.

SV Pizzazz

Don't compare phone batteries -- that's a different chemistry with very different characteristics. The cycle life of LiFePo4 is well documented -- see MaineSail's tests. He got over 90% after 2000 cycles IIRC. They ought to be basically good for the life of your boat.


My comparison showing lithium to be cheaper by usable capacity assumed 50%, not 30% usable capacity for lead. But the last 10% - 15% is not actually so much usable with lead if you are off grid, so the way I compared artificially favors lead.


You keep saying "quality lead costs $1 per AH". I am not in the U.S. and haven't bought batteries there, but I have not seen T-105's for less than $125 each, and that is on sale. And that's not $1.19 per AH because that is a 6v battery. Two of them is $250, and that is $2.38. That is clearly more expensive than LiFePo4 by usable capacity and EVEN if you assume you can use 50% of the nominal capacity of your T105's, which you often can't on a cruising sailboat off the grid.



I'm not trying to talk you out of your preference -- you have the right to like what you like. But I don't want incorrect information to be left unanswered.


Lead batteries do really make sense where your boat is already set up for them (converting the electrical system to use lithium cells does cost some money) and you are anyway getting 4 or 5 years out of them according to the way you sail, and you don't really need the other advantages of lithium. But for some other people, the case is compelling, as it works better, and it's cheaper for a heavy user.

[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.

Heh, fellas, is it true that true golf cart batteries (true deep cycle) can be discharged to 20% SOC without damaging them? I see conflicting info. Waddya think?

[Dockhead]

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.

Heh, fellas, is it true that true golf cart batteries (true deep cycle) can be discharged to 20% SOC without damaging them? I see conflicting info. Waddya think?

Yes, there are certainly cheaper choices, but we were talking about "quality lead".


Concerning your other question -- we had a huge discussion about this last year. You can find in the archives. You can discharge to 20% but you don't want to do it often, and you will want to be sure to do a good finish charge afterwards. I think that's a fair summary of what we concluded.

[Pizzazz]

I stand corrected regarding the cycles... LifePO4 is really different from Li-Ion, 2000 vs. 400 cycles. In this case, there seems to be no business case for AGM batteries as they cycle really bad. In my calculations the lifetime cost seems to be 1x for golf cart batteries, 3x for AGMs and 3-4x LifePO4, all things being considered. Wow, interesting... another project, convert to LifePO4 eventually.

Thanks @dockhead.

SV Pizzazz

[Dockhead]

Originally Posted by Pizzazz

I stand corrected regarding the cycles... LifePO4 is really different from Li-Ion, 2000 vs. 400 cycles. In this case, there seems to be no business case for AGM batteries as they cycle really bad. In my calculations the lifetime cost seems to be 1x for golf cart batteries, 3x for AGMs and 3-4x LifePO4, all things being considered. Wow, interesting... another project, convert to LifePO4 eventually.

Thanks @dockhead.

SV Pizzazz

Cheers. I was surprised myself when I dug into it.


I agree with your conclusion -- no case whatsoever nowadays for AGM or Gel batts. My other conclusions -- hardly any case for lead batteries on a new-built boat, or a boat which is getting a new electrical system. Good case for golf cart batteries on a boat with existing lead-oriented system, and where the boat is mostly in marinas and not off grid much (which admittedly may be a majority of cruising boats). Very compelling case for LiFePo4 for other situations.


Note that I am talking about using LiFePo4 CELLS, not drop-in lithium batteries. These are very different cases. With drop-in lithium batteries, you are making the BMS and a bunch of the infrastructure into a consumable, and you are paying a lot of money for someone else to configure it in a way where it can be used in a lead-oriented boat without modifications. I don't think that makes sense. Even if you are getting away without installing a BMS and low and high voltage cutoffs (which is trivial), you still have to deal with the charging sources, which in most cases will need to be upgraded and configured.



That's a good reason right there to stick with lead -- LiFePo4 simply functions differently, and will need significant modifications to take full advantage of this functional difference. For use cases where you don't really need the cycle life or the other advantages, all that much, then you won't find it worthwhile to convert over.


I would not be converting my boat, if I could easily fit golf cart batts. That is because I will probably not still own this boat more than another couple of years. But I can't fit golf cart batts, and my use case (months off grid sometimes) cries out for the advantages of LiFePo4 anyway.