EVE MB31 discharge rates clarification, Higee comparison and longevity considerations.

[Luk88]

I'm reading EVE MB21 datasheet and I'm a bit confused about this:

Specifically, why is Max Continuous Discharging Power the same as "Standard Discharging Power". It seems very curious. If the max continuous discharge power is the same as standard are they essentially constantly running at max power in standard use and if so, is it like for example running a Higee cell with a datasheet like this:

At 1C all the time?

I mean, are these cells getting stressed in standard conditions at 0.5C/P? And if not, why are they unable to provide 1C? Or is EVE just trying to make their 10K cycles claim more realistic?

Which brings me to the next question. Is this all just to be able to use essentially similar construction and bump cycle numbers to 10K? I essentially consider this 10K at 70% equivalent to 6K at 80%. Then if it had Max Continuous Discharging Power at 1P they would probably have to say 4K cycles at 80%? Does this seem logical?

Now, I'm oversizing my battery banks so my discharge rate will rarely approach 0.5C/P, but still I'd feel much better knowing I could go there if necessary. Is Higee with their Max 1C continous discharge rate and 6K+ cycle numbers (at 80%) telling us their cells are better for high current applications? Also EVE doesn't specify peak brief discharge current (Higee 3C for up to 30s).

While actual testing of DC internal resistance shows a month old EVE MB30/MB31 as a lot more robust than a year old (but very low cycle count) Higee cells. So is essentially Higee talking bs? Or is EVE overcautious? Can someone please make sense of this?

 

[zcskywire2]

I'm reading EVE MB21 datasheet and I'm a bit confused about this:
View attachment 226244
Specifically, why is Max Continuous Discharging Power the same as "Standard Discharging Power". It seems very curious. If the max continuous discharge power is the same as standard are they essentially constantly running at max power

Some of the wierdness is probably just the standardization of formatting for cell datasheets. Standard Charge and discharge rates are what the cell is designed around for cycle life testing. In the case of the EVE MB31 it is the same but often as you see it is different for other cells. If you look carefully in the Higee 280ah datasheet, the cycle life is rated at standard charge and discharge or 0.5c

I mean, are these cells getting stressed in standard conditions at 0.5C/P? And if not, why are they unable to provide 1C? Or is EVE just trying to make their 10K cycles claim more realistic?

As I have learned from much more knowledgeable members on the forum, These large capacity cells are made with thick film coting on the internal layers. This allows them to pack much more energy in the same volume at the trade off of discharge and charge rates. Above 0.5C rates on the thick film storage cells it gets way harder on the battery to provide the power. The EVE cell being a good be denser in the same volume likely has thicker film construction on the internal layers than the Higee meaning that it struggles more above 0.5C

Which brings me to the next question. Is this all just to be able to use essentially similar construction and bump cycle numbers to 10K? I essentially consider this 10K at 70% equivalent to 6K at 80%. Then if it had Max Continuous Discharging Power at 1P they would probably have to say 4K cycles at 80%? Does this seem logical?

No you can not. There are many new techniques to improve cell cycle life with no real external differences. On of the big new ones is p
re-Lithinating the cell. Basically doping the cell with special compounds to add extra consumable lithium to a cell as one of the decay factors is a consumption of lithium from the cells electrodes during cycling. This is why you now can have two 314ah cells of the same shape and size from the same manufacturer and get vastly different cycle life's. I'm using Cornex PF173-314A and PF173-314B cells for the example here but others like CALB have done similar. The only cycle life equivalent I have seen is 6K to 80% = 8K to 70%. I received two different datasheets from a cell manufacturer with different cycle life ratings for the same cell.

Now, I'm oversizing my battery banks so my discharge rate will rarely approach 0.5C/P, but still I'd feel much better knowing I could go there if necessary. Is Higee with their Max 1C continous discharge rate and 6K+ cycle numbers (at 80%) telling us their cells are better for high current applications? Also EVE doesn't specify peak brief discharge current (Higee 3C for up to 30s).

Yes, this isn't to much of a surprise. The original main use for the 280Ah sized cells was in large electric vehicles like trucks and busses before energy storage.

While actual testing of DC internal resistance shows a month old EVE MB30/MB31 as a lot more robust than a year old (but very low cycle count) Higee cells. So is essentially Higee talking bs? Or is EVE overcautious? Can someone please make sense of this?

AC and DC Cell impedance are very sensitive to the state of charge of the cell. Cycling and age of cells will also increase play a large effect. It would be very easy for the Higee cells to have a way different impedance due to these factors.