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

[Chotu]

Originally Posted by team karst

Yes, but the question as stated is “which has more power”. I still maintain the the LA likely can deliver 600 Amps at near 10V. 6kW of POWER. The Li cant. My 100Ah Li will trip out at around 200 A.

If people keep changing the question then any answer is possible. [emoji30]

That was due to the OP being careless about terminology, which he, at times is.

He meant energy, which can be seen by him continuously talking about watts and using W = V x A

Context should make it clear the title is bad. The whole premise is the higher voltage means more energy.

[team karst]

Dat be tru. [emoji1362]

[s/v Jedi]

The only thing that Ah should be used for is calculating the state of charge of a battery. The rest should all be done in Wh, kWh.

[CrispyCringle]

Originally Posted by smac999

If you fully discharge a 100ah lead acid battery which drops from 12.8v to 10.5v as you drain it.

And then you discharge a 100ah lith battery that holds 13.2v.

You made ~15% more energy (kwh) with same amount of ah with the lithuim

And watch this. In order to put that 100ah back into a battery. You charge at 14.4v. So you drained 100ah out at 12v and put 100ah back in at 14v. 20% more kwh was needed to put the same 100ah back in. Then was taken out.

Both batteries take 100ah out and 100ah in. They have the same ah. But not the same storage energy.

That’s why off grid houses use kwh and not ah to measure everything.

I whole heartedly agree. No one disputes the fact that a lithium battery holds more energy than a lead acid. Thats why this thread seems like much ado about nothing. There is no fresh "discovery" here.

[rpackard]

It seems to me that this discussion misses the point. Batteries are energy storage devices. So the important comparison would be (Watt hrs)/weight or per volume. As already said the 8% difference in available power is normally not important. The major energy usage is refrigeration to windlass use. The important consideration is how long can you operate your vessel at anchor without requiring use of the generator.

[Simi 60]

Originally Posted by rpackard

. The important consideration is how long can you operate your vessel at anchor without requiring use of the generator.

A lot longer on lifepo4 than AGM

[T1 Terry]

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

Basically, the first post is flawed because time was not added to the equation ... but that has already been mentioned a few times ....

Next problem, not all LFP batteries are created equal, the majority of the resellers fudge the figures.
The first distortion of the truth is the LFP 80% rule they created, it is just a fabrication, not a fact. They then add another 20% plus to the actual capacity to the claimed capacity ... i.e. the label says 100Ah but you can only have 80Ah if the apply the B/S 80% rule.
The next distortion all battery resellers use is the C rate the capacity is measured. A genuine manufacturer like Winston Battery https://en.winston-battery.com/ will show the discharge C rate and the discharge curve to validate their claims: https://en.winston-battery.com/stati...3577893499.pdf
The first page has the basics, the cell physical size, the "safe" operating voltages, meaning, stay inside these voltage constraints and you can expect the cycle life they show. The 80% and 70% cycle life means each and every cycle dropping to the list DoD and returned to 0% Dod or 100% SoC, they just mirror each other.
If you want more than 7,000 cycles between fully charged and the end of discharge, then build the battery pack to recharge every time the SoC drops to 30%, if 5,000 cycles min is good enough for you, then recharge every time the battery drops to 20% SoC ... but keep in mind, these two cycle life figures relate to you getting that 70% or 80% of the advertised capacity, at the advertised C load rating 0.5C, or 50% of the advertised capacity ... in this case, 50 amps constant.

Now let's get back to the first post, if you attempt to draw 10 amps from a C20 rated lead acid battery, you won't get half that 10 hrs, that 10 amp load is a C10 load and a 100Ah C20 rated battery is at best an 80Ah battery but in reality, probably closer to a 60Ah battery is it's not factory fresh having just had the acid fill and conditioning charge when you pick it up ... so not off the shelf.
So, the 50% discharge of the claimed 100Ah lead acid battery with a constant C10 load is, at best, 40Ah, more likely 30Ah.

Now let's look at a quality lithium battery built with quality cells, I'll use the Winston 100Ah LYP cells as the comparison example:
100Ah @ 0.5C is the same as a 2C load rating, 100% of the capacity at a constant 50 amp load for 2 hrs till the battery is at 0% SoC, not zero volts, more likely to be better than 12v under the 50 amp load if the battery was correctly condition charged and had not been pushed too often past the "safe" cell voltages ......
This also says, without putting in print, the capacity @ a 0.1C or C10 load, would be more than 100Ah.
This means the actual capacity would need to be measured at a constant 10 amp load before the cell/s dropped below 3v will still under load ... only from there would you know how many Ah was the 50% SoC point at a C10 load ....

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

That is the true way to compare one energy storage device to another, you need to know the load over time you expect the storage device to be capable of supplying that load.
Just because the sticker says "100Ah" is meaning less until the time factor is included to tell you over how many hrs it can deliver the energy demand you require, drop in lithium batteries are the worst when it comes to fudging the numbers .....

Now you'll all have to wait until I've completed the testing on the sodium ion cells that will arrive by the end of the mth, then, at least you will have a comparison of one premium brand LYP battery as a comparison to use as a bench mark

T1 Terry

[Chotu]

^ Unfortunately you should have read a little more of the thread. Time was included.

It’s not the greatest leap in the world intellectually to use W = V x A over time, turning Watts to KWh

[Baronkrak]

Originally Posted by smac999

That’s why off grid houses use kwh and not ah to measure everything.

I would guess that off grid houses uses Alternating Current.

Originally Posted by Simi 60

A lot longer on lifepo4 than AGM

Yours undersized AGM was a poor choice.

Originally Posted by T1 Terry

The first distortion of the truth is the LFP 80% rule they created, it is just a fabrication, not a fact.

It is a fact that each time my Victron LFP approaches the 80%, a low cell disconnect will occur.

It remain that:

Originally Posted by StuM

(FWIW, I wouldn't put too much faith in advice from sources which can't even get the basic units right)

[Putt-Putt]

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

Originally Posted by T1 Terry

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

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?

[Simi 60]

Originally Posted by Baronkrak

.


Yours undersized AGM was a poor choice.

What makes you think it was undersized?
The AGM was 880ah @ 24 vs 840ah @ 24 for lifepo4

It is a fact that each time my Victron LFP approaches the 80%, a low cell disconnect will occur

That sounds more a Victron BMS setting issue not a cell issue
Where are you getting the 80% used/20% left reading from?

I ask because our Victron battery monitor, which reads a combination of 3 batteries, 24 cells combined is not as accurate as the actual Bluetooth monitor on the BMS that reads individual cells,

[Mr. Kevin]

But what is your metachlorian count?? Just kidding, this is a great discussion.

[wholybee]

Originally Posted by Baronkrak

I would guess that off grid houses uses Alternating Current.


Yours undersized AGM was a poor choice.


It is a fact that each time my Victron LFP approaches the 80%, a low cell disconnect will occur.

It remain that:

Off grid houses use LFP, and LFP are DC. For alternating current we introduce VA (Volt Amps) but that is another discussion.

If you get a low cell disconnect, at any SoC other than 0% Soc (or maybe has high as 3% Soc) then either your SoC meter isn't calibrated correctly (thus you really are at 0%), or your cells are out of balance.

I get 330Ah from my 300Ah battery. I can take it all the way to 0%, and still not get a disconnect.

[noelex 77]

The point that the capacity of lithium in AHrs can be directly compared to lead acid is not appropriate. The higher voltage of lithium during discharge is correct, but this is a minor consideration, especially that during charge the voltage of lead acid will typically be higher.

Of more significance is that lithium can be safely discharged to lower levels, although in an emergency both lead acid and lithium can be discharged to a similar SOC. Unfortunately unlike lead acid lithium is not generally charged to 100%.

Overall, I think we can replace lead acid with around 50-75% capacity if changing to lithium. So perhaps 600 Ahrs of lead can be replaced with 400 Ahrs of lithium for the same net effect. These differences in should be factored in when costing new batteries.

[Chotu]

I think this is incorrect to say that lithium is absorbing less energy during the charging phase due to a lower voltage. because it can take anything you throw at it. The voltage might be 13.8, but the amps are like 100.

or in other words, 1C to 3C charge rates on lithium. It’s absorbing energy like crazy compared to lead. And no Peukert effect. The coefficient is nearly 1.

They truly are storing more energy for the same AH business