100AH lithium battery holds MORE power than 100AH lead acid??

[Simi 60]

Originally Posted by Baronkrak

You know it is possible to have more than one and charge them in turn.

If you like doing things the hard way I guess anything is possible.

[CaptainRivet]

Originally Posted by sailorboy1

It will charge it just fine. But the 13.8V is going to overcharge if you stay there long enough and that is a problem.

This is IMO, it matter not to me what people do. Especially if they do on purpose.

The 13.8V will overcharge your budget LFP with 5$ pure protection BMS but not a Victron Smart BMS, an Electrodacus or a REC BMS. Their end of charge parameter kicks in and cuts of the charge source before it can overcharge a cell.

[CaptainRivet]

Originally Posted by s/v Jedi

That’s not true, the reason they sell that is that there is a market demand for it. They are Dutch like me; the Dutch will sell anything when someone wants to buy it. During the 80-year war with the Spanish, the Dutch sold them canons because why let the opportunity to sell something slip away

Then please tell me what is the advantage of an MPPT that is partly fouled and doesn't even know the correct total voltage at the terminals be superior to decide to switch off charge compared to a BMS that can do that on precise cell voltage. An LFP is charging pretty much with all you throw at it, you don't need different phases and it can completely be without floating. So you can interrupt the charger anytime...its not lead where you have to follow the charge stages...

An MPPT cannot know that its floating a LFP to death but the BMS knows...

[s/v Jedi]

Originally Posted by CaptainRivet

Then please tell me what is the advantage of an MPPT that is partly fouled and doesn't even know the correct total voltage at the terminals be superior to decide to switch off charge compared to a BMS that can do that on precise cell voltage. An LFP is charging pretty much with all you throw at it, you don't need different phases and it can completely be without floating. So you can interrupt the charger anytime...its not lead where you have to follow the charge stages...

An MPPT cannot know that its floating a LFP to death but the BMS knows...

My rudder and prop have been fouled but never my MPPT

They know the exact voltage at the battery because the Cerbo GX is telling them after learning exact values from other sensors. It’s charge completion is precise to 5mV.

Have you even checked actual cell voltage against what your BMS reports it to be? I mean with a real precise voltmeter? What is the accuracy of that meter?

If you completely disable float mode then you either don’t have enough solar or you are wasting energy.

[sailorboy1]

Originally Posted by CaptainRivet

The 13.8V will overcharge your budget LFP with 5$ pure protection BMS but not a Victron Smart BMS, an Electrodacus or a REC BMS. Their end of charge parameter kicks in and cuts of the charge source before it can overcharge a cell.

I don't need anything to "kick in" and stop my charge.

I am already tired of this thread and going to go kick a wall or something

[kmacdonald]

There is a strong argument to not use a BMS. A lot of VERY EXPENSIVE failures were blamed on BMS failures. Usually from high end systems that were overthought but poorly designed and implemented. I've had no BMS interventions in over 5 years and no imbalance.

[wholybee]

Originally Posted by kmacdonald

There is a strong argument to not use a BMS. A lot of VERY EXPENSIVE failures were blamed on BMS failures. Usually from high end systems that were overthought but poorly designed and implemented. I've had no BMS interventions in over 5 years and no imbalance.

That is probably more of an argument against an overengineered system where a BMS controls everything. If all the BMS can do is open a contactor if something goes wrong, the BMS can't damage the batteries, but will protect if some other device fails.

[CaptainRivet]

Originally Posted by kmacdonald

There is a strong argument to not use a BMS. A lot of VERY EXPENSIVE failures were blamed on BMS failures. Usually from high end systems that were overthought but poorly designed and implemented. I've had no BMS interventions in over 5 years and no imbalance.

Nobody said your installation is bad...
There are different concepts and ways to achieve the same.
Eletrodacus is a well known open source BMS supported by Victron. Not overtought and actually very simple.
Again if you don't have a cerbo or even a victron MPPT your MPPT that should end charge dosn't even know the correct terminal voltage as its fouled by the voltage drop of the instatalltion cable,fuses..., it also doesn't know if a cell is peaking....so how should this MPPT know when to stop charging? Skilled installer measuering the difference and correcting the MPPT parameters accordingly but thats static and cannot adapt to changes over time.
And in case of ElectrodacusBMS if the BMS is not cutting the MPPT can still do its job, just one layer more security.

And my BMS was 180Euro, 2 other i bought used for 90 and 100Euro to have backup in case one breaks and will go onto the LTO's that replace lead starter as working spare.

Not running a BMS i did on LTO since 20years+ and on top notch winston since more then 10 years when(!!!) Its a 12V system, on LTO i had a NEEY active balancer if operated at >2C. Non one had a problem till today. Since 3 years i know electrodacus and always put that on above combo as cheap added securiity. At a 24V systems the internal resistance on 8S add up too much and always need a BMS in both cases.
On EVE,LIshen, Basen,Hisense budget cells even if grade A+ i always put a BMS, to much production devation as advise by my buddy who runs an NPO building powerwalls
with them and knows these cells inside out...

[CaptainRivet]

Originally Posted by wholybee

That is probably more of an argument against an overengineered system where a BMS controls everything. If all the BMS can do is open a contactor if something goes wrong, the BMS can't damage the batteries, but will protect if some other device fails.

Mostly its unexperienced (think they are very experienced) installer that install a complex high end system. The more you can adjust the more you can screw up.
The reason i hardly modify electrodacus adavanced parameters and if i consult the creator Dacian and ask for his advice on it before doing it.
My system on my boat is now in 3rd iteration, i run it for some time see whats going well and what can be improved. You simply cannot think about all use cases and boats are that individual that some you just realize after some time operating it or extensive stress tests.
As i am on the limits of Electrodacus steering inputs i am testing run 2 Electrodacus in parallel, (1 is master) and monitor very closly and till known they are identical to last digits. Plan is to use one for charge side and one for load side steering, desaster done by both.
Would justify upgrade to a TAO BMS but thats 1000+ and has a different logic means i would have to re-concept and reinstall the whole steering side new.

[tanglewood]

Originally Posted by s/v Jedi

The BMS should never cut off a charge source because the charge source should stop charging well before the BMS would do anything about it.

Only during disasters, like a battery with failing cells, should it be necessary for the BMS to take any such action. For “normal” out of balance cell issues, the BMS may enable a balancer: again this has nothing to do with cutting off chargers.

I think BMS control of chargers and loads, for example by DVCC, ATL, ATC, etc) is a perfectly legitimate architecture. But controlling chargers is not the same thing as disconnecting the battery. The later is an action of last resort, where the former is just a different way of doing charge control.

[T1 Terry]

Wow, so much "knowledge" from some posters here that have never actually set up a battery built from individual cells and monitored the voltage of each cell group as the battery charges and discharges.

All battery chemistries experience some type of Peukerts factor losses, nothing is perfect and there is no such thing as power unity, there will always be losses.
The negligible Peukerts factor is referring to the discharge rates the LFP cells experience when used as house batteries. Even a 1C, a quality 100Ah LFP battery will deliver 100 amps for 1 hr ..... but a 1 hr energy storage device isn't practical for house battery use.

The time factor I mentioned in my previous post was referring to the advertised capacity delivered over what time period. The Winston LYP cells are rated at a full capacity discharge over 2 hrs, yet hold the cell voltage above the 2.8v mark while under load. They will deliver the full capacity over 1 hr and still hold all the cell voltages above 2.8v while under load, so the advertised capacity is under rated so expectations are always met, there aren't many lithium battery manufacturers or sellers that can claim anything close to that.

I once attempted to discharge a 100Ah LYP battery at a C20 rate, time constants beat me, after 24 hrs it was still showing 3.2v in each cell while under load .... naturally, the SoC meter showed 0% SoC, but that was because the capacity was set at the C2 rate because that is the known and advertised capacity, not the C20 rate I was testing the battery. The battery would not have been at the fully discharged point until the cells showed 2.8v under load.
Unfortunately, I needed both the test rig and the battery, the battery to go in one of my river pump systems at home and the load testing equipment for paying customer work.

Sadly, I can't even share the data log of the discharge curve, it was on my computer that I lost in the workshop fire.

The whole lithium battery nonsense about anything with lithium in the name will explode or burst into flames etc has p*ssed me off so much I've finished with using them as the gold standard for energy storage .... just too much unfounded nonsense being spread by anyone who has something to gain by creating a massive hype about their dangers.

Will LFP or LYP cells catch fire, in a fire, yes, the plastic will burn and the electrolyte is flammable if heated enough, can an LFP, LYP or LTO chemistry lithium battery explode into flame, no, there is no oxygen generated inside these chemical mix cells, you need cobalt or water to be able to generate oxygen when heated .... superheated water will separate into hydrogen and oxygen, so will passing an electrical current through it, that is why over charged lead acid battery explode, the internal short eventually creates a spark and ignites the two parts hydrogen and one part oxygen (H2O) and that gas cloud goes off big time ......

Can a drop in lithium battery catch fire, yes, the circuitry that makes up the internal BMS can fail and create a short circuit, catching the plastic case on fire and that heat would be enough to get the electrolyte up to a flammable temperature ... but it would still require the oxygen from the surrounding air to actually burn .......
You should never see a lithium battery that contains cobalt or lead acid battery with an internal BMS, that is just a bomb waiting to go off ......

T1 Terry

[T1 Terry]

Originally Posted by Putt-Putt

Although I agree with a lot of what T1 Terry said in post #67, I have difficulty with this statement.



It is pretty well known that LFP discharge curves for various loads are all relatively flat except at both ends and generally when you reach 2.8V (SOC 0%) regardless of the rate of discharge, the battery has delivered close to it's nameplate rated Ahs.

The Winston LYP100 AHA discharge curve (in T1's link) under normal? temperature shows that if the discharge current is 3CA (= to 300 amps) the battery at 2.8V has delivered about 104% of it's capacity or 104 Ahs.
If the discharge rate is 0.5CA, only 50 amps, the battery at 2.8V has delivered 114% of it's capacity or 114 Ahs. About 10% more, fair enough.
So much for a Peukert exponent of zero with LFP.

So how does discharging the 100 Ah LFP battery at 0.1CA, 10 amps for 50 hours (totalling 500 Ahs discharged) result in a SOC of 50%?

That would mean you must have started with a 1000 Ah battery.

Perhaps T1 typed one too many zeros. 5 hours seems correct to me and compares about right to the 4+ hours T1 assigned to the lead battery.
Afterall, and Ah is and Ah regardless of the chemical reaction that effectively stored it.

The other issue is why the 50% SOC cut off with LFP, just to seem to be fair to the lead? Why? How many cycles beyond 7000 do you expect to be around for?

The issue here is the thinking is stuck in the lead acid world, 50% SoC in a lead acid battery is easily measure by voltage, LFP, LYP and LTO lithium batteries can only use voltage as measurement toll for fully charged or fully discharged, now where in between.
The 100Ah lithium house battery would need to be discharged at the 10 amp rate from fully charged, all cells holding above 3.5v after a 12 hr rest, down to 2.8v while under load, that would give a 100% capacity at a 10 amp continuous load. Then divide that by 2 and you would know where the 50% SoC point was reached .......

T1 Terry

[Putt-Putt]

Originally Posted by T1 Terry

I have to admit, I only got about 1/2 way through the second page before I gave up ..

So, this is what I mean by adding the time into the equation:

The Lead acid deep cycle C20 rated 100Ah battery
a constant 10 amp load would supply the load for around 4 hrs at best before the 50% SoC was reached.

The Winston LYP C2 100Ah battery
a constant 10 amp load would still be supplying that 10 amps for more than 50 hrs before the 50% SoC point was reached

T1 Terry

Although my boat packs around enormous amounts of lead, my mind is able to be lead free most of the time.

My issue was your last statement in the above quote, 100Ah LFP supplying a 10 amp load for 50 hours (that would be 500 Ahs delivered to the load) before the 50% SoC is reached. Really?

Please explain as to how that works, I'm new to LFP.

It's interesting to note that when you added my quote to your response in your post #162, your quote of 10 x 50 = 100/2 which was originally included in my quote, is missing. Humph, wonder if it will happen this time?

[CaptainRivet]

Originally Posted by Putt-Putt

Although my boat packs around enormous amounts of lead, my mind is able to be lead free most of the time.

My issue was your last statement in the above quote, 100Ah LFP supplying a 10 amp load for 50 hours (that would be 500 Ahs delivered to the load) before the 50% SoC is reached. Really?

Please explain as to how that works, I'm new to LFP.

It's interesting to note that when you added my quote to your response in your post #162, your quote of 10 x 50 = 100/2 which was originally included in my quote, is missing. Humph, wonder if it will happen this time?

Well he will most likely ment 5h but possibly its 10h at 50% because Winston
A) is extremely conservative with their ratings and normally be around 20% above and
B) the rating given is at 0.5C of capacity, means a 100AH cell is rated with 50A discharge=c50 is in reality a 115-120Ah cell and a C10 discharge with a Winston 100AH cell is realistically at 160 till 200AH capacity.

Thats what you get when you pay around 450Euro for a 300AH cell while an EVE 304AH is about 150-180Euro depending on source and grade.

[Putt-Putt]

Cptn. Rivet

I think T1 likely meant to type 5 hours as well and said so at the time, but he typed 50 not 5. When I asked for clarification I was told I was stuck in the lead world. No wonder my feet feel heavy.

If Winston is extremely conservative and their ratings are indeed 20% low, that does not explain how you can get 500 Ahs. out of a 100 Ah. battery and still have it sit at 50% SOC. Thats 1000% conservative.

If indeed a Winston 100 Ah cell under a 10 Amp load can actually deliver something like 160 to 200 Ahs without ever being close to 0% SOC like you say, I'm dumbfounded. Now in all fairness there could be a language or my interpretation issue here, tough to tell.

In the meantime I will put aside that perpetual motion machine I've been playing with as LFP with its charge efficiency and energy return profile shows way more promise.
Just think, you charge at 0.5 CA and according to the Winston chart that T1 linked, your battery is 115% charged when it reaches 4.0V, so its now a 115 Ah battery, not far off of Captn Rivet's 20%. Then when you discharge at 10 Amps according to Captn Rivet you get about 180 Ahs back. Whoopee...free energy......Magic. Where do I sign up?