Open apology to @Steve_S

[snoobler]

@Steve_S,

Please accept my apologies for so aggressively challenging you with regards to voltage "settling" of LFP cells. My experience with rapid settling of 40Ah CALB cells did not translate to the 280Ah Eve cells.

My Eve cells obtained from Amy experienced dramatically lower settling rates.

Cell 1: 3.46 after 5.5 hours (also the lowest capacity, 2.6% lower than the others)
Cell 2: 3.52 after 23 hours
Cell 3: 3.50 after 22.5 hours
Cell 4: 3.53 after almost 4 hours
Cell 5: 3.52 after 22 hours
Cell 6: 3.50 after 22 hours
Cell 7: 3.53 after 4 hours
Cell 8: 3.52 after 3.5 hours
Cell 9: 3.51 after 4 hours

After sitting for almost 4 days, I ran the bolded ones through another 20A to 3.65V charge (already full). They all terminated at 2A within 2-3 minutes. The amount of charge accepted across the 5 varied by 180mAh (.06%).


Here's a plot of one of the settlings:



You were right.

I was wrong.

 

[toms]

Good on you Snoobler ?

 

[Steve_S]

Thank You you but it really is not necessary my friend.
It is all a learning experience and sharing our lessons with each other helps us all benefit.
As for CALB vs EVE or CATL or any other "Brand" for that matter, there is always a wildcard and that is the "Chemistry Stew" which varies between every manufacturer... You might even say, they all have their special "Magic Potions" which are always a mystery.

 

[toms]

A gracious response Steve, and yes - thanks to all that contribute. It’s easier to criticise than to jump in and offer up information.

 

[Steve_S]

I know that sometimes my responses "Annoy" some but I try to approach every response with a more complete answer (too much detail) but I am always thinking of the reader who comes along later & may not know as much or understand something. I've been "smacked" a few times for "backfilling" incomplete answers left by some... seems they feel it's a slam on them or something, no idea why... I guess maybe it's part of the general "angst" people are feeling now and as such, they have to lash out at something. Luckily, I can count them on one hand and still have fingers left. I do have a small list of "ignored" though, because I don't need silly. (being a bit PC there...)

 

[snoobler]

Had to be done/said. For me, data rules all. I can be pretty insistent when it comes to supporting data. That's another way of saying I can be a dick sometimes.

 

[Steve_S]

Ohh I dunno, your pretty mellow. There are a few though (there always is) but that's what Ignore is for.
Your all good !

 

[HaldorEE]

So I have been bloviating in a very related thread all morning. Here is the thread.

Electronic Loads

I have been reading discussions about top balancing cells and I realized I need to be a bit more organized about this. So as part of that I think I will design a constant current, electronic load. I am thinking about using one of the L2 family of Linear N channel MOSFETs from IXYS (Littlefuse)...

diysolarforum.com

I found your thread about charging a single cell to be very interesting if somewhat confusing (as in contradictory advice from people who's opinion I respect).

Here is what I think is a good plan for charging a single cell to as close to 100% SOC as is practical:

First of all, use a 3.65V CV supply combined with a CC controller like is described in my thread.

Single stage charge process. This has the disadvantage of taking longer, but it simpler to do. I can do this entirely in analog circuitry

• Set CC rate to 0.05C
• Start charging and monitor charge current
• When charge current drops to 0.01C, disconnect charger.

Multi-stage charging process. This is going to be faster, but will be more complicated (definitely going to be easier to do with a microcontroller managing the process)

• Set CC rate to max (0.2C)
• Start charging and monitor cell voltage
• When cell voltage rises to 3.5V, change CC rate to 0.05C
• Monitor charge current
• When charge current drops to 0.01C, disconnect charger.

What do you guys think about this. Is the middle stage in the multi-stage charge process unnecessary? Can I just set CC to 0.15C or 0.2C and then disconnect the charger when the charge rate drops to 0.01C or is there value in finishing the charge at 0.05C?

 

[HaldorEE]

Please don't start with the "" comments.



I are not completely dumb. I did graduate from the 3rd grade and everything.

 

[snoobler]

I tend to test to specs when I can. Full is 0.05C @3.65V. Max charge is 0.5C. Stay inside that envelope, and it doesn't matter what you do.

I used "smart" LFP chargers that default to a 10% cut-off from the initial charge current. My initial charge current was 20A (max), so it terminated at 2A by default, so I violated the 0.05C, but that was due to convenience. For giggles, I resumed the charge at 2A, which forced the cut off at 200mA. They took on another whopping 110mAh.

Looking at the chart data, less than 400mAh was taken on between the taper from 14A (0.05C) to the cut off of 2A

I don't regard either as a significant violation of the cell specs.

That's not a direct answer to your question other than everything you propose is either within that envelope and/or does not violate it in a meaningful way. You're simply changing the time it takes to charge.

 

[snoobler]

Please don't start with the "" comments.

View attachment 33552

I are not completely dumb. I did graduate from the 3rd grade and everything.

I had to look up bloviating. Who's the dummy now?

 

[grizzzman]

I had to look up bloviating. Who's the dummy now?

Well.....you weren't the only one