Running the Battery to 0%

[MickeyAO]

At this point I’ve run my pack multiple times 100-5% (and below) and several times to 0% and will likely do so given that some stretches I drive just barely makes it with the available range for that leg.

I figure with the depreciation it becomes my primary home backup that can do Home Depot runs in a severe degradation situation…but based on what you’re seeing, how bad will it be?

Or is it just that below 20% the data is simply not all too reliable given the variations of the HPPC?

I'm sorry, but I do not have enough data to say what will happen to your pack. As far as the HPPC, I hope I have given enough hints on what concerns me without directly saying what I have found.

If you really want to see the data, convince your company (individuals cannot join directly) to sign up to the consortium. It only cost $75k a year, but at this point, you would need to pay for all 4 years to see the Lightning data. ($150k per year if you want the vehicle data also). New consortium starts in Sep 2024!

Or wait a year and you can buy a single year of previous data for only $80k!

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[Gimme_my_MME]

I'm sorry, but I do not have enough data to say what will happen to your pack. As far as the HPPC, I hope I have given enough hints on what concerns me without directly saying what I have found.

If you really want to see the data, convince your company (individuals cannot join directly) to sign up to the consortium. It only cost $75k a year, but at this point, you would need to pay for all 4 years to see the Lightning data. ($150k per year if you want the vehicle data also). New consortium starts in Sep 2024!

Or wait a year and you can buy a single year of previous data for only $80k!

What's the name of the consortium?

 

[Box Cat]

You might want to review some of my previous posts about observations from actual lab testing at the cell level. What the BMS and modules do? I don't care. But I know after 12 years of cell testing what the cells are doing (and currently testing the SK One E805A from an actual F150 Lightning that we dismantled after vehicle testing)

If you are monitoring your pack, you might want to find the PID for cell, module, or pack resistance to see my new concern.

Can you take it down to 0% rated? YES! Will I take mine below 20% SOC Actual? No.

Don't care to take what I say into account? You do you Boo! I just try to give hints about what I see in controlled cell level testing.

Please don't read any disrespect or attack against you into this post.

I respectfully disagree with your analysis and conclusion.

 

[MickeyAO]

I respectfully disagree with your analysis and conclusion.

I respect that, but may I ask what data you are basing your analysis on?

 

[Box Cat]

Mainly the fact that there is nothing wrong driving these cells down to a low state of charge.

Obviously, if one wants to maximize longevity you would not want to do it on a regular basis.

Granted, LFP is better than NMC in this perspective.

I do not have raw data quantifying degradation over a statistically meaningful number of charge/discharge cycles for different patterns, e.g. 20-80 90% of the time with 10% down to 0% and so on and so forth.

It would be interesting to run such experiments.

I do not know what exactly you are basing your statement regarding not wanting to drive your battery pack to a low state of charge ever, what experiments you ran, under what conditions, etc.

There will be a trade-off between degradation over time and battery depletion patterns. Not driving to less than 20% is somewhere in there towards less degradation, but driving to 0% or so occasionally is not that far too. If you go 100% to 0% every time you are at the other end with max degradation.

I do not do many miles a day so I typically stay 50%•80%, but on those occasional trips 100% to whatever down is ok. Practically speaking I would always plan to arrive to a charging station with some buffer anyway.

Perhaps LFP have better longevity but don’t do as well in cold weather.

Perhaps you may want to elaborate on why one event of driving this specific cell down to its lower SoC/Potential spec is so destructive.

 

[Grumpy2]

MickeyAO has sent me off on quite a bit of reading. It has become a puzzle.... I am struggling to understand what I am reading. But it is obvious why he can't spell it out.

As far as the HPPC, I hope I have given enough hints on what concerns me without directly saying what I have found.

I think the shape of the recovery pulses are the important aspect of the HPPC process. There must be thousands of recovery curves to be studied because the HPPC test is done at varying state of charge, and temperatures. I have read about various computer programs to help review these pulses.

It would seem a full recovery from each small pulse across the entire spectrum of variables would be ideal. Under certain conditions, say less than 20% SOC perhaps the cells don't fully recover before the next pulse. If that is the case, would there be a permanent impact to the cell?

Can anyone here help me with this?

 

[Grumpy2]

It may not have much to do with the shape of the cycles.

The truck battery cathode uses 90 percent nickel, and just 5 percent each of manganese and cobalt. I don't know the actual lithium ion used in our cathodes, but these tests results are very interesting discovered thru HPPC testing:

The large capacity and power losses in this cell chemistry come mainly from increases in the bulk and/or interfacial impedance of the cathode.

www.osti.gov/servlets/purl/815355&ved=2ahUKEwiI-5yT_KiFAxVbLEQIHQJJA3wQFnoECCMQAQ&usg=AOvVaw3ZjVLhMW3d2RVIGzCFR_Xb

Conclusions The room temperature cycle performance and pulse power capability of lithium ion cells with graphite and LiNi0.8Co0.15Al0.05O2 were studied for different DOD cycling. Cycling this cell to 100%DOD, or 3.0V, leads to significantly faster rates of both capacity fade and impedance rise, compared to cells limited to 70% DOD. The cell cycled 1000 times at 100%DOD was unable to access 40% of the lithium between 3.0 and 4.1V even at a C/25 rate. The cell cycled 1000 times at 70% DOD showed only a 14% loss in high-rate capacity and only a 45% loss of power. The large capacity and power losses in this cell chemistry come mainly from increases in the bulk and/or interfacial impedance of the cathode.

 

[Grumpy2]

Abstract:

Twelve-cm2 pouch type lithium-ion cells were assembled with graphite anodes, LiNi0.8Co0.15Al0.05O2 cathodes and 1M LiPF6/EC/DEC electrolyte. These pouch cells were cycled at different depths of discharge (100% and 70% DOD) at room temperature to investigate cycle performance and pulse power capability. The capacity loss and power fade of the cells cycled over 100% DOD was significantly faster than the cell cycled over 70% DOD. The overall cell impedance increased with cycling, although the ohmic resistance from the electrolyte was almost constant. From electrochemical analysis of each electrode after cycling, structural and/or impedance changes in the cathode are responsible for most of the capacity and power fade, not the consumption of cycleable Li from sidereactions.

 

[Zprime29]

Haven't looked anything up yet, but based on what I've read here and can recall... I would hazard a guess that SOC under 20% drastically increases the crystalline structures that plague Li-Ion batteries. I'm not terribly worried about it since my use case means I will rarely go down into that range. I think I've done it maybe 2-3 in my 22k miles, and even then it was still upper teens.

I trust Mickey's advice and will actively try to maintain that going forward.

 

[invertedspear]

This thread is great. Watching people argue their anecdotal evidence against the guy who is currently testing these batteries in a lab is a riot. Even after seeing how the rest of us have already learned to just trust Mickey, through months to years of seeing his expert analysis, they persist in arguing based on "It didn't blow up when I did it". @MickeyAO I don't know how you've put up with all of us over all this time, but I appreciate you.

 

[MickeyAO]

Abstract:

Twelve-cm2 pouch type lithium-ion cells were assembled with graphite anodes, LiNi0.8Co0.15Al0.05O2 cathodes and 1M LiPF6/EC/DEC electrolyte. These pouch cells were cycled at different depths of discharge (100% and 70% DOD) at room temperature to investigate cycle performance and pulse power capability. The capacity loss and power fade of the cells cycled over 100% DOD was significantly faster than the cell cycled over 70% DOD. The overall cell impedance increased with cycling, although the ohmic resistance from the electrolyte was almost constant. From electrochemical analysis of each electrode after cycling, structural and/or impedance changes in the cathode are responsible for most of the capacity and power fade, not the consumption of cycleable Li from sidereactions.

Our cycle life testing is normally 3 different temperatures (25C, 45C, and 55C) and 3 different delta SOCs centered around 50% SOC (30%, 60%, and 90% delta). After 12 years of testing many types of chemistries, this is why I harp on the delta per charge (see previous posts)

However, what we found in the thermal stability test (see SAE J2464), we will not use 55C and instead we are debating the next best temperature to use (some want 0C, some want 35C)

Still not selling my truck on all this information as my use case fits nicely in these parameters, but make sure you don't let the temperature get too high

 

[Yellow Buddy]

This thread is great. Watching people argue their anecdotal evidence against the guy who is currently testing these batteries in a lab is a riot. Even after seeing how the rest of us have already learned to just trust Mickey, through months to years of seeing his expert analysis, they persist in arguing based on "It didn't blow up when I did it". @MickeyAO I don't know how you've put up with all of us over all this time, but I appreciate you.

I mean in fairness, it DIDN'T blow up when I did it. I’ve been trying to get @MickeyAO to tell me it will but he won’t, and I think that’s an important distinction.

Based on what I’ve gathered, it’s a bit like bacon. Bacon has never stopped me dead in my tracks.

Is it likely clogging my arteries? Yes.
Will it someday kill me? Likely.
Will I know when it’ll happen? Not likely.
Will I change my habits? Maybe when it’s too late.
Will my Dr and @MickeyAO still be right?Yes.

…but I’ll probably still run my truck below 20% while I eat my bacon. I’ll just be more informed while I do it.

 

[Maxx]

Abstract:

Twelve-cm2 pouch type lithium-ion cells were assembled with graphite anodes, LiNi0.8Co0.15Al0.05O2 cathodes and 1M LiPF6/EC/DEC electrolyte. These pouch cells were cycled at different depths of discharge (100% and 70% DOD) at room temperature to investigate cycle performance and pulse power capability. The capacity loss and power fade of the cells cycled over 100% DOD was significantly faster than the cell cycled over 70% DOD. The overall cell impedance increased with cycling, although the ohmic resistance from the electrolyte was almost constant. From electrochemical analysis of each electrode after cycling, structural and/or impedance changes in the cathode are responsible for most of the capacity and power fade, not the consumption of cycleable Li from sidereactions.

Thanks for great posts. I think some people (including myself) get a bit confused on level of impact of each of these. The tests often compare these DODs in a large number of cycles. People are told you are suppose to charge to 100% and go to low SOC once in a while (some do it monthly) so your BMS knows what is what and can guess better. Then they are told keep the DOD to minimum. I am hovering between 40%-60% SOC most of the time. Rarely go outside 30%-70% except occasional trips but my battery health ( guessing it is cell impedance) is dropping faster than most. It is nice to know the degree of impact of each of these. So people may like to know should I park the truck in the shade half mile away and walk in a 120F degree sunny day but may be not when it is 90F? Everything being absolute is not as helpful as knowing how much of an impact each of these parameters have. It is always "never do that" or "you will be just fine"

 

[Box Cat]

You need to re-read post 30.

There is really not much to read in post 30, or are you referring to other posts?
It is just a statement that is not backed up by data (or at least the data is not available).
If these cells are so much worse than others at low depth of charge it would be nice to know a little more.
The fact that running too low or too high has worse degradation is already known.
What would be useful is to quantify the impact on the real SoC over time.
I have driven my truck down to close to 0% (two miles left) and recharged it and the battery stats I can pull from the truck are the same.
What would be the impact if I did that more frequently? How much capacity would I lose after a year for instance? etc., etc.

 

[Maquis]

There is really not much to read in post 30, or are you referring to other posts?
It is just a statement that is not backed up by data (or at least the data is not available).
If these cells are so much worse than others at low depth of charge it would be nice to know a little more.
The fact that running too low or too high has worse degradation is already known.
What would be useful is to quantify the impact on the real SoC over time.
I have driven my truck down to close to 0% (two miles left) and recharged it and the battery stats I can pull from the truck are the same.
What would be the impact if I did that more frequently? How much capacity would I lose after a year for instance? etc., etc.

You can have the data he uses to arrive at his conclusions. See post 46. He’s trying to be as helpful as he can within the constraints of legal agreements of his employer. Anyone is free to disagree / disregard the advice given.

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