Delta Voltage (OCV) And Any Significance To Li-ion mV Self-Discharge

This thread is for a certain ES member to either trash it's Title, trash talk the OP, assume ownership, give it his best effort or ignore altogether.

For me to first offer my 2 cents worth may only encourage his brash disconcerting comment(s) which he seems to relish. Especially when it comes to offering his opinion on a thread i post as far as its usefulness or lack thereof of any meaningful lithium-ion acceptable amount of self-discharge and significance thereof.

On the other hand for him to first offer his interruption of the title of this thread may result in me agreeing with him; which he forbide me from ever doing. So, he may just ignore this thread unless i first offer up my take on the title of this thread. Thus giving him opportunity to do what comes across to me as a little subtle trolling to discredit me instead of some encouraging support which would be a breathe of fresh air.

Don't see much in here about the title? Looks like a rant from your other threads.

ZeroEm said:

Don't see much in here about the title? Looks like a rant from your other threads.

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I'm offering him the opportunity to takeover this thread and give us his prospective of Delta Voltage as it may or may not relate to measuring the difference between acceptable and unacceptable self-discharge of high energy dense lithium-ion cells like say VTC6 and 30Q.

You previously told me you didn't at first grasp the concept i was putting forth in another thread, but said you now understood the concept. Don't be so quick to write of the Title of this thread as something too difficult to grasp. Yes, the phrasing may not be the best, but john61ct is certainly knowledgeable enough to explain Delta Voltage (OCV) when it comes to what mV/time is acceptable and not acceptable when it comes to Self-Discharge of high energy dense cells.

We know that high energy dense cells rated at 15 -20 amps MCD are more prone to self-discharge.

It was my understanding from spinningmagnets that i could block john61ct from my thread. However, this is apparently not an option ... so yes i have every right to rant when his intrusion/motive on a thread i start is suspect after more than a few intrusions for a couple years.

So instead i'm giving him first option to takeover this thread being that he is knowledgeable of Delta Voltage and explain any significance to measuring acceptable vs unacceptable millivolt Delta Voltage when it comes to Self-Discharge with cells like VTC6 and 30Q.

Not all that long ago he called Samsung's 30Q cell "junk" soon after spinningmagnets had just replied that it was a cell he'd recommend to the OP. So any disparage of 30Q's usefulness may relate to measuring its Delta Voltage of acceptable versus unacceptable Self-Discharge (mV/time) of high energy dense Li-ion cells. It would be helpful if john61ct would tell us his basis for calling 30Q "junk".

If you can ask your question clearly I will try to answer best I can.

From what you wrote above I have no clue what the topic is. No idea what you think you mean by the term "delta voltage" for exampld.

The term "self-discharge" means, with cells isolated and at rest, losing energy over time. It means only that. I have inferred from your past posts you are using that term for some other phenomena.

30Q has been proven to have QC issues where some percentage of cells from each production run suffer from excessive self-discharge. Apparently this issue has not been fixed over time.

That percentage might be low enough that it rarely causes problems with packs composed of a small number of cells.

But as soon as you use them to build larger packs with dozens of cells, the risk of one or more bad ones causing problems goes up exponentially.

"Delta" is sometimes used in engineering to denote the letter D, as in Whiskey Tango Foxtrot. If "V" is being used to denote voltage, then DV might refer to differential voltage.

If someone wants to parallel several cells, and you recommend that they all have a voltage that is within 0.1V of each other, you might say "Ensure the DV is within 0.1V before connecting the cells in parallel".

Yes, just means gap or "difference", but depends on context.

In the context of balancing a pack, I recommend a target delta of no less than ~10-20mv (.01V -. 02V) of one another.

Start-balance setpoint of at least 50mv (.05V).

But really depends on how bad the imbalance problem is, how often balancing maintenance is performed, what type of gear used what the balance current rate is, etc

But no idea if the question here is about balancing.

spinningmagnets said:

"Delta" is sometimes used in engineering to denote the letter D, as in Whiskey Tango Foxtrot. If "V" is being used to denote voltage, then DV might refer to differential voltage.

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Delta has many variations of usage ... Delta Covid, Delta Dental, Delta Airfoil, Delta Dawn (referring to early dawn over the trianglular shaped delta at the mouth of a large river) and others like "Delta OCV".

What do you think about calling a copper clad triangular ebike pack ... "Delta Tri"

The specific defintion i'm referring to is found in most any 1970s Webster Collegiate Dictionary. Don't have it with me now, but if my memory serves me right it has something to do with the "escaping ions of electrons". Will report back later with exact Webster 1970s wording unless someone else beats me to the exact punch line first :thumb:

spinningmagnets said:

If someone wants to parallel several cells, and you recommend that they all have a voltage that is within 0.1V of each other, you might say "Ensure the DV is within 0.1V before connecting the cells in parallel".

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Believe i said that ideally (JMO) p-groups be within at least 0.01V of each other p-group (not p-string :wink: )

john61ct said:

If you can ask your question clearly I will try to answer best I can.

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It will be clearer than fog if you would carefully read and digest this Electronic Design article ... https://www.electronicdesign.com/technologies/test-measurement/article/21808344/keysight-technologies-measure-selfdischarge-using-ocv-on-lithiumion-cells ... (take note to digest the following quote) ...

Determining self-discharge involves making just two open-circuit voltage measurements, but one must consider relaxation and voltmeter accuracy when grading cells. Delta-OCV is the tried-and-true method, but quicker options are emerging.

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This is basically what Darren2018 and i discussed (and every manufacturer should do with every high energy dense cell) on my Self-Discharge UPDATE On 30Q 141 Cells thread. Appreciate if john61ct wouldn't post on that thread or be blocked/deleted if he does as he once said 30Q cells are "junk". From previous interference he'd find some way to misinterpret, misrepresent, occasional disinformation and otherwise disrupt and derail. This would result in my request to lock the thread as there would be no more reporting and sharing of my ongoing 30Q 10S3P split-pack experimenting.

Whereas i would welcome spinningmagnets input/insight as he favors 30Q 141 & 30Q K cells ... with appropriate pre-testing before build as well as appropriate build consideratons as well as its usage, balancing, care, etc along its lifelong journey :thumb:

Excuse me..
You were both told to stop talking to each other twice now. Both given warnings.
Both of you were also told to use the ignore function.

eMark is getting a 14 day timeout for being the instigator and starting this thread to bait john into it.
I do not want to see the behavior continued afterwards.