LFP - Decline in charge acceptance rate with battery age

[tanglewood]

There are lots and lots of research papers from universities and large consumers (EV makers) showing life cycles, impact of over charging, impact of temperature, effects of different construction materials, etc. The performance and characteristics are very real, not made up.


But at the same time I completely agree that the supply chain is very immature. And the eco systems of products needed to build a full power system around an LFP pack is also very immature. But it's all classic early tech product breaking into a market, and it will take time.


From your comments, I think your assessment is right that it's not ready for you. That's fine. It's not ready for most people. There are very, very few people who I would recommend use LFP. In time I am convinced that will change. The technology is just too compelling for applications like boats. But until it has matured to a point where it's easy to implement, and mindless to operate, adoption will be constrained.


So rather than arguing that LFP sucks, perhaps argue that it's not ready for you.

[Delfin]

Originally Posted by hellosailor

"There is a reason why cars are better today than years past. In a world where everyone who is unhappy about a product can broadcast their unhappiness to the world via..."

Oh heck, even in the 80's before the public had access to what would become the internet and 300-baud board groups were an obscure thing...The Japanese were starting to kill Detroit based on word of mouth about "It ain't broke yet."

The wonderful thing about the internet is that there is SO MUCH trash and background noise there. 3-4 years ago the NYS attorney general's office did some research and concluded that something like 25% of all internet "reviews" were outright fraud. Shills and sour grapes and worse.

So when you consider the number of different players (is a BMS necessary to prevent explosions, as some big vendors have said? Or totally unneeded, as others say?) and the conflicting claims...Just take a look at YouTube and see how many people say you can resurrect a dead wet lead acid battery with alum, or epsom salts. Dozens of them and they all swear it works. Forever.
Think of all the money you wasted on new batteries! All those nice folks just couldn't be...well...lying, could they?

So, what are the URLs for all the manufacturer (prime, not just resellers) data showing actual tests and results? Where are all the warranties? Who has been in business for ten years, and still is in business?

Lithionics warranties their batteries for 2,000 cycles if you follow their charging advice. They've been around 8 years and have supplied product to the U.S. military. Their test results are available on their website.

[john61ct]

None of these markets are of any interest to the companies manufacturing LFP cells

1. individual consumers
2. the West
3. House bank / alternative energy
4. boating
5. campers / RVs

Absolutely no interest whatsoever

[Dev0n60]

Regarding the 'ageing' question mentioned in this thread: the diminishing charge acceptance with age>>
I did not read each & every post in the 7 pages so I'm sorry if someone else may have already mentioned this. Rod Collins of "Marine How To" has had a Winston 400ah pack (the same as ours) he has been running up and down on a bench top since 2009. He has been pushing these cells hard. Last I heard he is at about 800 pack cycles since 2009. He measures the available capacity using a lab grade load tester. From memory he started at about 445 ah capacity in 2009 (cycle 1). That is 45 ah over the manufacturer's rating!! After 9 years doing this he is still getting approximately 435 ah...
As Mr Collins points out, his testing is N=1. There are not any other people I have been able to find doing what he is.
For my part, after just 2.5 years and 186 cycles of cruising, fractional C usage, I notice no changes what so ever. The performance is truly awesome when compared to the AGMs.
We do use re-newables: Hydro-generator, Solar and Wind.... these are great at keeping the pack as charged as we want. I usually start dumping Amps when I am 85% SOC. We typically use about 150-200 Ah per day and put most of it back with renewables.
With the CanBus output from the Orion Jr BMS, we have been able to use a small, $50.00, Android tablet velcroed onto the bulkhead as a 24/7 monitor of parameters you choose (see photo).
The best thing for us is not running engines anymore to spin alternators. No more smell, noise, fuel costs.
After living aboard for almost 30 years now, we are really enjoying the performance difference in our stored energy.
It does require a lot of study before doing this to your cruising boat if you don't want to have a big hole in your wallet. I am NOT an expert by any means,..... just an enthusiast! At the 'rated' cycle life of these cells, At my age now, I hope to not ever need to replace the batteries again!! We'll see how it goes.

[CatNewBee]

The manufacturer (Winston) does testing. But you don't accept their results. So do your own tests or stay away from LFP instead of trolling all the time!

The cells are industrial grade, used to store large amount of energy in various applications including massive renewable energy storages for grid applications, submarine propulsion, public transportation, electric vehicles, boats, also in OEM batteries like Mastervolt, Victron and others. We can be happy to have access to this technology as private users without paying premiums for re-branding or being forced to buy proprietary systems to get a grip on the cells.

The largest cells they produce at the moment are 10000Ah. No other manufacturer yet has the technology ready to do this, even 1000Ah cells are not yet available from the competition. Winston is a pioneer in LiFeYPO4 technology and does have a significant leap ahead to his competitors.

BTW they dont care if a single end-user trolls around, they do mass production in GW capacities and are sold out ahead. They deliver container wise and are well known and appreciated in the industry.

You may not be ready for the technology, but the technology is already there and in mass production and use around the globe in various toys, scooters, cars, busses, in stationary applications at communication companies, power grid operators, off-grid storages, military applications, ups applications for public buildings / hospitals etc. and other critical infrastructures.

If you feel too overwhelmed, or have no idea, what we are talking about, stick with your good old FLA setup, that's ok.

You can contact the references on their web site for details and visit the battery show

https://thebatteryshow.com

http://en.winston-battery.com

[Maine Sail]

Originally Posted by Dev0n60

Rod Collins of "Marine How To" has had a Winston 400ah pack (the same as ours) he has been running up and down on a bench top since 2009. He has been pushing these cells hard. Last I heard he is at about 800 pack cycles since 2009. He measures the available capacity using a lab grade load tester. From memory he started at about 445 ah capacity in 2009 (cycle 1). That is 45 ah over the manufacturer's rating!! After 9 years doing this he is still getting approximately 435 ah...

Despite this pack being for my own educational purposes, the pack is not just used on a bench in the lab. We use it in-board the boat for about 6 months each year and we try to let almost every cycle go to 80% DOD before we consider recharging. Course if an opportunity exists to charge fast and we are only at 70 DOD, we charge... Early on I burned a ton of electricity cycling the bank and it is tedious and boring and the results were the same over, and over, and over..... The bank is now approaching 1100 cycles and is still exceeding 400Ah's of capacity. I am still capacity testing, to 0% SOC, every 50 cycles.

Originally Posted by Dev0n60

As Mr Collins points out, his testing is N=1.

Bingo... n=1 data does not make for good science..

I have seen a lot of destroyed LFP packs so just because my bank is doing fine, don't count on all of them doing fine. With the way some users wish to treat them like lead by over absorbing, floating and continually keeping them in the upper SOC ranges I suspect many would be quite surprised if they ran a capacity test.. Owners will only ever know the condition of their LFP bank by running controlled and repeatable capacity tests.

[john61ct]

Originally Posted by Maine Sail

Owners will only ever know the condition of their LFP bank by running controlled and repeatable capacity tests.

I assume the 20-hour protocol spelled out in your Adjusting Battery Monitor article is pretty close?

Do you also use the 10.5V point for 0% SoC / 100% DoD, same as with lead?

I have not dared go that low,

while 2.63Vpc is above where many cheap BMS cut out, I've used 2.8V as my last-ditch final layer of LVD,

in practice rarely get below 2.9Vpc and that's only with heavy amps, resting bounces back.

My day-to-day house loads have their own LVD cutoffs above 12V.

[Maine Sail]

Originally Posted by john61ct

I assume the 20-hour protocol spelled out in your Adjusting Battery Monitor article is pretty close?

Do you also use the 10.5V point for 0% SoC / 100% DoD, same as with lead?

I have not dared go that low,

while 2.63Vpc is above where many cheap BMS cut out, I've used 2.8V as my last-ditch final layer of LVD,

in practice rarely get below 2.9Vpc and that's only with heavy amps, resting bounces back.

My day-to-day house loads have their own LVD cutoffs above 12V.

These are not lead acid batteries thus a 20 hour discharge rate is not required and you can go with a higher discharge rate so it does not take 20 hours. Also there is no need to use a lead cut off voltage as that just puts you pretty deep into the lower knee yet yields very, very little extra capacity. Just not worth going there.

Some manufacturers rate capacity at 1C, .5C, .3C and some at .1C. As far as I can tell there seems to be no standardized discharge rate for LFP so I use a rate that is multiples more than our average house loads. At our average discharge rates the bank might yield another .5Ah of capacity but, that is not what I am after with this testing. I do this to determine SOH / storable energy capacity changes and a repeatable test, with good repeatable accuracy, is key..

With LFP the discharge rate is not really as important as it is with lead but repeatability is important if you want to know where your bank stands compared to the last test.. These days I use a 30A constant current discharge rate for capacity testing of the bank which is much higher than the average loads we use on-board.

The cut off I use, and have been using since about cycle 550 or so, is 12.0V or 3.0VPC for a 12.8V nominal bank. 3.0VPC is at the top of the vertical part of the lower knee so there is no sense, nor capacity worth going after, in discharging below this point.

[john61ct]

Originally Posted by Maine Sail

These days I use a 30A constant current discharge rate for capacity testing of the bank which is much higher than the average loads we use on-board.

The cut off I use, and have been using since about cycle 550 or so, is 12.0V or 3.0VPC for a 12.8V nominal bank.

Excellent, thanks, yes repeatable standardization is what I'm after,

and yes very happy to not go below 3Vpc.

So my previous usual-for-lead .05C rate would then give an overly optimistic measure of capacity?

Or the fact the Peukert exponent is insignificant at sub-C rates, likely using a fixed rate like 30A with various sized banks will make little difference?

Definitely a bonus getting a quicker test.

[rgleason]

DevOn60 uses an Orion Jr BMS $425 with an android tablet to monitor.
https://www.electriccarpartscompany.com/Orion-Jr-BMS


BMS Overview https://www.electriccarpartscompany....iew_p_490.html


PCB for smaller batteries https://www.electriccarpartscompany....agement-System

Read the bottom of this page. It may be hard to diagnose things.
Also chargers need to be for Lithium or MOS will be damaged.


Without a BMS or PCB balencing the cells you could loose 10-20% of capacity and shorten life.

[john61ct]

Oops dupe

[john61ct]

Why this thread? OP has never provided relevant data, better to start a new one IMO.

What is a DevOn60?

That vendor is one vendor, one-man operation afaik, and oriented to EV usage, completely different care profiles as the mobile House bank.

Balancing "live" is very controversial, IMO adds complexity with little advantage, as long as you avoid the shoulders.

As I've said no charger I've seen marketed "for lithium" is anything I'd let near mine.

May well work fine adopting that approach, but IMI will mean shorter lifespan, higher risks and higher costs.

[Dev0n60]

Dev0n60 is my Cruisers Forum user's name.... Very similar to how you use 'john61ct'. One could ask what is a 'john61ct'.
I am just trying to participate in the forum. I am not disparaging anyone.
We have lived on our Valiant 40 for 30 years cruising the world. We are based in New Zealand presently.
Our post is based on real experience using the LFP technology after years & years of Lead Acid.
I had hoped this would be useful information for others. I have NO investment what-so-ever in advocating for this technology.

[rgleason]

DevOn60, John was challenging my post, and probably did not realize Devon60 was a User. It would be very helpful if you could describe what you have done! I'm trying to figure this technology out.

[john61ct]

Thanks for clarifying, found posts upthread now more clear