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

[CaptainRivet]

Originally Posted by smac999

it depends if the load draws less amps at 13v then at 12v. if the load current is the same you don't gain anything. and still consumes the same ah.

some loads probalby will and some won't

either way it's still 100ah. but it might have more wh

Wrong the efficiency of a LFP compared to lead is about 80-85% in AH and 65-70% in WH
You roughly need 118AH to charge a lead to 100AH while around 101AH for 100AH on LFP.
Usage due to Peukert effect the same, the higher the load you draw the bigger the gap between them and on the typical 200A range for induction cooking this impact is big and also reduces the lifespan of a lead massively while no impact on LFP. The load is also higher on the lead due to its much higher internal resistance compared to a LFP and then even more current due to plumbing further the longer the load is applied means significant more losses

[Baronkrak]

Load 60W = 60VA

LFP 12.8V nom...60/12.8 = 4.69A......100Ah /4.69 = 21.32h

LA 12.0V nom....60/12 = 5.00A.........100Ah /5 = 20h

Now, I have Victron LFP and they will never reach an 80% discharge before a low cell disconnects the load.

Usable capacity using Victron LFP:......80Ah/ 4.69 = 17.06h

Then one needs to account for the LFP BMS use of energy, in my case, 3Ah per day (24h) and I have Genasun MPPT. Night consumption 0.9mA.

[dfelsent]

Originally Posted by HeywoodJ

This is just not that complicated. An Ah is an Ah. It represents a current of one Ampere flowing for a period of one hour. It is a somewhat useful measurement with batteries (on which another recent thread expended far too many electrons).

The amount of energy represented by that Ah depends entirely on the voltage. One Amp, for one hour, at 24V is 24Wh. The same Ah at 12V is 12Wh.

Chotu is correct that the amount of usable energy in LFP for a given Ah is generally greater than the average energy in a LA Ah because the average voltage is higher. This is not magic, and doesn’t make a huge difference. The voltage curve of LFP is very flat (one of the things we all like about it), when you take energy out the biggest part comes out with a voltage of ~3.2V/cell or 12.8V (“12V” nominal system). There’s some energy that will come out at higher (and lower) voltages, but the bulk will come out between about 12.6 to 13.2V (around that 3.2V/cell). With LA the average V is much more dependent on SoC. If you are a 20% DoD user with return to “full” every cycle you actually probably withdraw closer to 13V, at least at low currents. A more typical user probably withdraws at 12.4 to 12.6V, and therefore LFP wins, but only by about 8% or so.

Whether or not you can do anything useful with that difference in energy depends on what you are using it to do.

This is spot on.

[Chotu]

Originally Posted by dfelsent

This is spot on.

Truly. It’s baffling anyone can argue against facts they simply don’t understand. It’s not an opinion or something political. It’s the natural of reality. Quite an eye opener. Instead of evaluating or learning, they argue based on feelings. Lol

A foreign concept to me

[dfelsent]

Originally Posted by Chotu

Truly. It’s baffling anyone can argue against facts they simply don’t understand. It’s not an opinion or something political. It’s the natural of reality. Quite an eye opener. Instead of evaluating or learning, they argue based on feelings. Lol

A foreign concept to me

Some people don’t understand that they don’t understand. I’ll give them that much credit. [emoji1]

[CaptainRivet]

Originally Posted by dfelsent

This is spot on.

Yep but with DIY or low budget drop in are allready on a price of a good AGM thats still a nobrainer. And having such a somple system you need a dc2DC for the alternator and thats it.
Cannot wait to get rid of my lead starter...
All these hardcore lead guys never had an LFP, if they would they will never look back to stoneage...

[K1MGY]

Originally Posted by Chotu

...
I think that makes a 100 amp hour lead acid battery and a 100 amp hour lithium battery not equivalent in terms of their ability to return energy. We never talk about this. We talk about amp hours.

A correct statement. Same capacity. Different ability to deliver the capacity.

Discharge characteristics do not, in my opinion, result in more power delivered to a load over time. I believe any differences (and there are many between lead-acid and Li), won't produce more power for equivalent ratings as I believe you suggest.

[moseriw]

simple answer of course... YES because it is possible to empty the LiFePo4 until the batterie shuts down at < 5%. Lead acid should not be discharged below 60% where - depending on the battery:

100% = 12,65V
90% = 12,5V
80% = 12,3V
75% = 12,2V
60% = 12V
50% = 11,8V = EMPTY!

So... where is the interesting thing in the question?

[wholybee]

You have demonstrated why Ah isn't a real measurement of stored energy, but Wh is. Wh is what you get when you include Voltage in the unit.

[Andrew Lippman]

First, it is incorrect to say that a battery "holds power." It "holds" energy. You care about the usable energy you can get from it. Lithium seems to provide more usable energy due to internal efficiency and lower (useful) discharge limit.

Second, Ah is an arbitrary measure. It is good for comparison when the voltage is the same, for example different 12v batteries. My last boat had a 24v system, so my 300Ah bank had about twice as much energy as a 12v bank with that Ah rating.

Lots of electronics and LEDs are agile and can operate from 10-32volts. I'm pretty sure they draw about the same power, and over time use the same net energy. There may be some residual loss in the internal voltage conversion but not a whole lot. I don't know whether other gear just dissipates as heat the difference between 12 and 13 volts. A windlass will run a little faster and incandescent bulbs will be a little brighter. You might notice this when you start the engine and the alternator voltage goes above 13 volts.

But I wouldn't want to live on the difference. Mostly I just sail until it's time to charge, then I start up the engine. Even efficient devices won't alter my time by all that much. If you're fastidious, you might notice slightly lower amp readings on your meters with the new, higher voltage lithiums.

I love lithium. Its a great chemical, like vinegar, useful for lots of things. You can color fireworks, power electric devices, and if you're depressed eat it (in some forms...). No doubt it is in my future when my batteries die. I like the way they are becoming integrated with other systems and smarter. My only concern is that my laptop never gets the life we see advertised, so I am a watcher for now.

[wholybee]

Originally Posted by moseriw

simple answer of course... YES because it is possible to empty the LiFePo4 until the batterie shuts down at < 5%. Lead acid should not be discharged below 60% where - depending on the battery:

100% = 12,65V
90% = 12,5V
80% = 12,3V
75% = 12,2V
60% = 12V
50% = 11,8V = EMPTY!

So... where is the interesting thing in the question?

You misunderstood the question. Given an LFP and an AGM battery. Both 12V, and both 100Ah. Charge them both to 100%. Then discharge them both the same amount, to 50%. The LFP will have done more work, pulled the chain in further or however you want to measure it. 50Ah will have been consumed in each case, and the LFP will have released more stored energy, despite both having spent 50Ah or 50% of the battery. This is because LFP maintains a higher voltage, and thus more *Wh* are stored in the LFP.

[smac999]

Originally Posted by CrispyCringle

How does Watt=V x A prove that 100AH lithium battery holds MORE power than 100AH lead acid? Makes no sense. For one thing, they aren't the same units. You arent comparing the same thing.

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.

[Chotu]

Originally Posted by wholybee

You misunderstood the question. Given an LFP and an AGM battery. Both 12V, and both 100Ah. Charge them both to 100%. Then discharge them both the same amount, to 50%. The LFP will have done more work, pulled the chain in further or however you want to measure it. 50Ah will have been consumed in each case, and the LFP will have released more stored energy, despite both having spent 50Ah or 50% of the battery. This is because LFP maintains a higher voltage, and thus more *Wh* are stored in the LFP.

Well put and absolutely correct

[Chotu]

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.

And this is why it’s time for us to do the same. We are using antiquated lead thinking from back when there was only one battery chemistry.

It’s time for the AH to go as a measure of a battery’s capacity.

[team karst]

Originally Posted by Andrew Lippman

First, it is incorrect to say that a battery "holds power." It "holds" energy. You care about the usable energy you can get from it. Lithium seems to provide more usable energy due to internal efficiency and lower (useful) discharge limit.



.

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]