Resting voltage after charging cell with 0.5P/C and terminate at 3.65V?

[Sonne]

This would result in over charge as the cells specify a 0.05C cut off at 3.65V. Is the manufacturer wrong?

Perhaps the “standard charge” Eve rate their LF280k v3 to 8,000 cycles lifespan is not in fact 100% SOC defined chemically? This, if I understood correctly, is when there’s almost no lithium remaining in the LFP lattice.

If I were a cell manufacturer who has to back their product with a warranty, I probably would not encourage users to charge to the point where any further charging will oxidise and reduce the electrolyte at the electrodes. Better to define a “full charge” which still has some headroom.

Ps.. I know there a few versions of LF280k datasheet floating around, but the one I just consulted makes reference to 280Ah of charge as “100% SOC”, so clearly it’s a term which can mean different things to different people according to context! I think RCinFLA’s context was full to the point where you can’t get more charge in. But hopefully he will reply to you, I love to see posts which develop our understanding of these batteries.

 

[sunshine_eggo]

Perhaps the “standard charge” Eve rate their LF280k v3 to 8,000 cycles lifespan is not in fact 100% SOC defined chemically? This, if I understood correctly, is when there’s almost no lithium remaining in the LFP lattice.

Therein lies my speculation that there's a difference in theory and practice.

If I were a cell manufacturer who has to back their product with a warranty, I probably would not encourage users to charge to the point where any further charging will oxidise and reduce the electrolyte at the electrodes. Better to define a “full charge” which still has some headroom.

Exactly, so projecting the theoretical position may be counterproductive and misleading on a practical basis.

In other worse, "fully charged resting voltage of 3.43 or higher" may actually be detrimental to batteries.

Ps.. I know there a few versions of LF280k datasheet floating around, but the one I just consulted makes reference to 280Ah of charge as “100% SOC”, so clearly it’s a term which can mean different things to different people according to context! I think RCinFLA’s context was full to the point where you can’t get more charge in. But hopefully he will reply to you, I love to see posts which develop our understanding of these batteries.

I generally don't expect to come out on top if I disagree with @RCinFLA

 

[RCinFLA]

Chemistry is complicated and requires a long discussion. Comments below barely scratch the surface of the topic.

LFP is a very strong cathode material. Its strength comes from iron providing the LFP positive electrode lattice support far superior to other lithium-ion chemistries when 99.9% of lithium-ions have left the positive electrode lattice at full SoC. Not really a problem with LFP cathode with regard to full charge being 99.9% of lithium-ions leaving the cathode.

Yes, there are things that can degrade LFP cathode, but they are not really worth worrying about. You may have heard about iron migration to negative anode. It is the result of secondary damage that will kill the cell first, so I don't consider it a significant issue to worry about.

You really do not need to fear fully charging a LFP battery like nickel-based EV lithium-ion batteries.

LFP cell longevity is dominantly determined by negative graphite anode and electrolyte degradation.

Graphite and electrolyte damage mostly happens when lithium-ions have a hard time finding a safe parking spot (intercalation) in the graphite during charging. This happens to a higher degree near full charge and cooler temperatures. It is also aggravated by thick electrode lithium-ion cells which have the most capacity for smallest volume, weight, and cost (most prismatic cell designs). This shows up with higher overpotential voltage.

High cell temperatures and high SoC accelerate electrolyte damage, but it is usually second place to graphite anode degradation. Cell manufactures give LFP cells 10-20% more graphite than matching LFP cathode capacity to allow for some graphite degradation and give spare lithium-ion 'parking spots' in the graphite negative anode.

Constant rebuilding of Solid Electrolytic Interface protective shell around graphite eats up free lithium and electrolyte. It is the cell aging process you cannot avoid.

I have been beating the drum on how important understanding overpotential voltage is. It is a strong indicator of cell state of health. High overpotential in lithium-ion battery is like a person having high blood pressure.

The higher the overpotential for given cell current, the more out of equilibrium balance the electrolyte becomes. The more the electrolyte is out of equilibrium balance the more vulnerable electrolyte is to secondary detrimental irreversible chemical decomposition. Electrolyte is the conveyor belt for lithium-ion migration between positive and negative electrodes. Electrolyte decomposition in lithium-ion batteries is like a person having clogged arteries along with high blood pressure.

 

[cj0]

Therein lies my speculation that there's a difference in theory and practice.

Regarding practice.

The iCharger manufacturer doesn't specify p-p voltage ripple.

Have you ever measured (preferably with a scope up to 20 Mhz) the amount of voltage ripple that the iCharger 4010 Duo signal has at its outputs, near the change-over point between CC and CV when charging a single cell?

 

[sunshine_eggo]

Regarding practice.

The iCharger manufacturer doesn't specify p-p voltage ripple.

Have you ever measured (preferably with a scope up to 20 Mhz) the amount of voltage ripple that the iCharger 4010 Duo signal has at its outputs, near the change-over point between CC and CV when charging a single cell?

Nope.